src/regexp.c

/* vi:set ts=8 sts=4 sw=4 noet:
 *
 * Handling of regular expressions: vim_regcomp(), vim_regexec(), vim_regsub()
 *
 * NOTICE:
 *
 * This is NOT the original regular expression code as written by Henry
 * Spencer.  This code has been modified specifically for use with the VIM
 * editor, and should not be used separately from Vim.  If you want a good
 * regular expression library, get the original code.  The copyright notice
 * that follows is from the original.
 *
 * END NOTICE
 *
 *	Copyright (c) 1986 by University of Toronto.
 *	Written by Henry Spencer.  Not derived from licensed software.
 *
 *	Permission is granted to anyone to use this software for any
 *	purpose on any computer system, and to redistribute it freely,
 *	subject to the following restrictions:
 *
 *	1. The author is not responsible for the consequences of use of
 *		this software, no matter how awful, even if they arise
 *		from defects in it.
 *
 *	2. The origin of this software must not be misrepresented, either
 *		by explicit claim or by omission.
 *
 *	3. Altered versions must be plainly marked as such, and must not
 *		be misrepresented as being the original software.
 *
 * Beware that some of this code is subtly aware of the way operator
 * precedence is structured in regular expressions.  Serious changes in
 * regular-expression syntax might require a total rethink.
 *
 * Changes have been made by Tony Andrews, Olaf 'Rhialto' Seibert, Robert
 * Webb, Ciaran McCreesh and Bram Moolenaar.
 * Named character class support added by Walter Briscoe (1998 Jul 01)
 */

/* Uncomment the first if you do not want to see debugging logs or files
 * related to regular expressions, even when compiling with -DDEBUG.
 * Uncomment the second to get the regexp debugging. */
/* #undef DEBUG */
/* #define DEBUG */

#include "vim.h"

#ifdef DEBUG
/* show/save debugging data when BT engine is used */
# define BT_REGEXP_DUMP
/* save the debugging data to a file instead of displaying it */
# define BT_REGEXP_LOG
# define BT_REGEXP_DEBUG_LOG
# define BT_REGEXP_DEBUG_LOG_NAME	"bt_regexp_debug.log"
#endif

/*
 * The "internal use only" fields in regexp.h are present to pass info from
 * compile to execute that permits the execute phase to run lots faster on
 * simple cases.  They are:
 *
 * regstart	char that must begin a match; NUL if none obvious; Can be a
 *		multi-byte character.
 * reganch	is the match anchored (at beginning-of-line only)?
 * regmust	string (pointer into program) that match must include, or NULL
 * regmlen	length of regmust string
 * regflags	RF_ values or'ed together
 *
 * Regstart and reganch permit very fast decisions on suitable starting points
 * for a match, cutting down the work a lot.  Regmust permits fast rejection
 * of lines that cannot possibly match.  The regmust tests are costly enough
 * that vim_regcomp() supplies a regmust only if the r.e. contains something
 * potentially expensive (at present, the only such thing detected is * or +
 * at the start of the r.e., which can involve a lot of backup).  Regmlen is
 * supplied because the test in vim_regexec() needs it and vim_regcomp() is
 * computing it anyway.
 */

/*
 * Structure for regexp "program".  This is essentially a linear encoding
 * of a nondeterministic finite-state machine (aka syntax charts or
 * "railroad normal form" in parsing technology).  Each node is an opcode
 * plus a "next" pointer, possibly plus an operand.  "Next" pointers of
 * all nodes except BRANCH and BRACES_COMPLEX implement concatenation; a "next"
 * pointer with a BRANCH on both ends of it is connecting two alternatives.
 * (Here we have one of the subtle syntax dependencies:	an individual BRANCH
 * (as opposed to a collection of them) is never concatenated with anything
 * because of operator precedence).  The "next" pointer of a BRACES_COMPLEX
 * node points to the node after the stuff to be repeated.
 * The operand of some types of node is a literal string; for others, it is a
 * node leading into a sub-FSM.  In particular, the operand of a BRANCH node
 * is the first node of the branch.
 * (NB this is *not* a tree structure: the tail of the branch connects to the
 * thing following the set of BRANCHes.)
 *
 * pattern	is coded like:
 *
 *			  +-----------------+
 *			  |		    V
 * <aa>\|<bb>	BRANCH <aa> BRANCH <bb> --> END
 *		     |	    ^	 |	    ^
 *		     +------+	 +----------+
 *
 *
 *		       +------------------+
 *		       V		  |
 * <aa>*	BRANCH BRANCH <aa> --> BACK BRANCH --> NOTHING --> END
 *		     |	    |		    ^			   ^
 *		     |	    +---------------+			   |
 *		     +---------------------------------------------+
 *
 *
 *		       +----------------------+
 *		       V		      |
 * <aa>\+	BRANCH <aa> --> BRANCH --> BACK  BRANCH --> NOTHING --> END
 *		     |		     |		 ^			^
 *		     |		     +-----------+			|
 *		     +--------------------------------------------------+
 *
 *
 *					+-------------------------+
 *					V			  |
 * <aa>\{}	BRANCH BRACE_LIMITS --> BRACE_COMPLEX <aa> --> BACK  END
 *		     |				    |		     ^
 *		     |				    +----------------+
 *		     +-----------------------------------------------+
 *
 *
 * <aa>\@!<bb>	BRANCH NOMATCH <aa> --> END  <bb> --> END
 *		     |	     |		      ^       ^
 *		     |	     +----------------+       |
 *		     +--------------------------------+
 *
 *						      +---------+
 *						      |		V
 * \z[abc]	BRANCH BRANCH  a  BRANCH  b  BRANCH  c	BRANCH	NOTHING --> END
 *		     |	    |	       |	  |	^		    ^
 *		     |	    |	       |	  +-----+		    |
 *		     |	    |	       +----------------+		    |
 *		     |	    +---------------------------+		    |
 *		     +------------------------------------------------------+
 *
 * They all start with a BRANCH for "\|" alternatives, even when there is only
 * one alternative.
 */

/*
 * The opcodes are:
 */

/* definition	number		   opnd?    meaning */
#define END		0	/*	End of program or NOMATCH operand. */
#define BOL		1	/*	Match "" at beginning of line. */
#define EOL		2	/*	Match "" at end of line. */
#define BRANCH		3	/* node Match this alternative, or the
				 *	next... */
#define BACK		4	/*	Match "", "next" ptr points backward. */
#define EXACTLY		5	/* str	Match this string. */
#define NOTHING		6	/*	Match empty string. */
#define STAR		7	/* node Match this (simple) thing 0 or more
				 *	times. */
#define PLUS		8	/* node Match this (simple) thing 1 or more
				 *	times. */
#define MATCH		9	/* node match the operand zero-width */
#define NOMATCH		10	/* node check for no match with operand */
#define BEHIND		11	/* node look behind for a match with operand */
#define NOBEHIND	12	/* node look behind for no match with operand */
#define SUBPAT		13	/* node match the operand here */
#define BRACE_SIMPLE	14	/* node Match this (simple) thing between m and
				 *	n times (\{m,n\}). */
#define BOW		15	/*	Match "" after [^a-zA-Z0-9_] */
#define EOW		16	/*	Match "" at    [^a-zA-Z0-9_] */
#define BRACE_LIMITS	17	/* nr nr  define the min & max for BRACE_SIMPLE
				 *	and BRACE_COMPLEX. */
#define NEWL		18	/*	Match line-break */
#define BHPOS		19	/*	End position for BEHIND or NOBEHIND */


/* character classes: 20-48 normal, 50-78 include a line-break */
#define ADD_NL		30
#define FIRST_NL	ANY + ADD_NL
#define ANY		20	/*	Match any one character. */
#define ANYOF		21	/* str	Match any character in this string. */
#define ANYBUT		22	/* str	Match any character not in this
				 *	string. */
#define IDENT		23	/*	Match identifier char */
#define SIDENT		24	/*	Match identifier char but no digit */
#define KWORD		25	/*	Match keyword char */
#define SKWORD		26	/*	Match word char but no digit */
#define FNAME		27	/*	Match file name char */
#define SFNAME		28	/*	Match file name char but no digit */
#define PRINT		29	/*	Match printable char */
#define SPRINT		30	/*	Match printable char but no digit */
#define WHITE		31	/*	Match whitespace char */
#define NWHITE		32	/*	Match non-whitespace char */
#define DIGIT		33	/*	Match digit char */
#define NDIGIT		34	/*	Match non-digit char */
#define HEX		35	/*	Match hex char */
#define NHEX		36	/*	Match non-hex char */
#define OCTAL		37	/*	Match octal char */
#define NOCTAL		38	/*	Match non-octal char */
#define WORD		39	/*	Match word char */
#define NWORD		40	/*	Match non-word char */
#define HEAD		41	/*	Match head char */
#define NHEAD		42	/*	Match non-head char */
#define ALPHA		43	/*	Match alpha char */
#define NALPHA		44	/*	Match non-alpha char */
#define LOWER		45	/*	Match lowercase char */
#define NLOWER		46	/*	Match non-lowercase char */
#define UPPER		47	/*	Match uppercase char */
#define NUPPER		48	/*	Match non-uppercase char */
#define LAST_NL		NUPPER + ADD_NL
#define WITH_NL(op)	((op) >= FIRST_NL && (op) <= LAST_NL)

#define MOPEN		80  /* -89	 Mark this point in input as start of
				 *	 \( subexpr.  MOPEN + 0 marks start of
				 *	 match. */
#define MCLOSE		90  /* -99	 Analogous to MOPEN.  MCLOSE + 0 marks
				 *	 end of match. */
#define BACKREF		100 /* -109 node Match same string again \1-\9 */

#ifdef FEAT_SYN_HL
# define ZOPEN		110 /* -119	 Mark this point in input as start of
				 *	 \z( subexpr. */
# define ZCLOSE		120 /* -129	 Analogous to ZOPEN. */
# define ZREF		130 /* -139 node Match external submatch \z1-\z9 */
#endif

#define BRACE_COMPLEX	140 /* -149 node Match nodes between m & n times */

#define NOPEN		150	/*	Mark this point in input as start of
					\%( subexpr. */
#define NCLOSE		151	/*	Analogous to NOPEN. */

#define MULTIBYTECODE	200	/* mbc	Match one multi-byte character */
#define RE_BOF		201	/*	Match "" at beginning of file. */
#define RE_EOF		202	/*	Match "" at end of file. */
#define CURSOR		203	/*	Match location of cursor. */

#define RE_LNUM		204	/* nr cmp  Match line number */
#define RE_COL		205	/* nr cmp  Match column number */
#define RE_VCOL		206	/* nr cmp  Match virtual column number */

#define RE_MARK		207	/* mark cmp  Match mark position */
#define RE_VISUAL	208	/*	Match Visual area */
#define RE_COMPOSING	209	/* any composing characters */

/*
 * Magic characters have a special meaning, they don't match literally.
 * Magic characters are negative.  This separates them from literal characters
 * (possibly multi-byte).  Only ASCII characters can be Magic.
 */
#define Magic(x)	((int)(x) - 256)
#define un_Magic(x)	((x) + 256)
#define is_Magic(x)	((x) < 0)

    static int
no_Magic(int x)
{
    if (is_Magic(x))
	return un_Magic(x);
    return x;
}

    static int
toggle_Magic(int x)
{
    if (is_Magic(x))
	return un_Magic(x);
    return Magic(x);
}

/*
 * The first byte of the regexp internal "program" is actually this magic
 * number; the start node begins in the second byte.  It's used to catch the
 * most severe mutilation of the program by the caller.
 */

#define REGMAGIC	0234

/*
 * Opcode notes:
 *
 * BRANCH	The set of branches constituting a single choice are hooked
 *		together with their "next" pointers, since precedence prevents
 *		anything being concatenated to any individual branch.  The
 *		"next" pointer of the last BRANCH in a choice points to the
 *		thing following the whole choice.  This is also where the
 *		final "next" pointer of each individual branch points; each
 *		branch starts with the operand node of a BRANCH node.
 *
 * BACK		Normal "next" pointers all implicitly point forward; BACK
 *		exists to make loop structures possible.
 *
 * STAR,PLUS	'=', and complex '*' and '+', are implemented as circular
 *		BRANCH structures using BACK.  Simple cases (one character
 *		per match) are implemented with STAR and PLUS for speed
 *		and to minimize recursive plunges.
 *
 * BRACE_LIMITS	This is always followed by a BRACE_SIMPLE or BRACE_COMPLEX
 *		node, and defines the min and max limits to be used for that
 *		node.
 *
 * MOPEN,MCLOSE	...are numbered at compile time.
 * ZOPEN,ZCLOSE	...ditto
 */

/*
 * A node is one char of opcode followed by two chars of "next" pointer.
 * "Next" pointers are stored as two 8-bit bytes, high order first.  The
 * value is a positive offset from the opcode of the node containing it.
 * An operand, if any, simply follows the node.  (Note that much of the
 * code generation knows about this implicit relationship.)
 *
 * Using two bytes for the "next" pointer is vast overkill for most things,
 * but allows patterns to get big without disasters.
 */
#define OP(p)		((int)*(p))
#define NEXT(p)		(((*((p) + 1) & 0377) << 8) + (*((p) + 2) & 0377))
#define OPERAND(p)	((p) + 3)
/* Obtain an operand that was stored as four bytes, MSB first. */
#define OPERAND_MIN(p)	(((long)(p)[3] << 24) + ((long)(p)[4] << 16) \
			+ ((long)(p)[5] << 8) + (long)(p)[6])
/* Obtain a second operand stored as four bytes. */
#define OPERAND_MAX(p)	OPERAND_MIN((p) + 4)
/* Obtain a second single-byte operand stored after a four bytes operand. */
#define OPERAND_CMP(p)	(p)[7]

/*
 * Utility definitions.
 */
#define UCHARAT(p)	((int)*(char_u *)(p))

/* Used for an error (down from) vim_regcomp(): give the error message, set
 * rc_did_emsg and return NULL */
#define EMSG_RET_NULL(m) return (emsg((m)), rc_did_emsg = TRUE, (void *)NULL)
#define IEMSG_RET_NULL(m) return (iemsg((m)), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG_RET_FAIL(m) return (emsg((m)), rc_did_emsg = TRUE, FAIL)
#define EMSG2_RET_NULL(m, c) return (semsg((const char *)(m), (c) ? "" : "\\"), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG3_RET_NULL(m, c, a) return (semsg((const char *)(m), (c) ? "" : "\\", (a)), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG2_RET_FAIL(m, c) return (semsg((const char *)(m), (c) ? "" : "\\"), rc_did_emsg = TRUE, FAIL)
#define EMSG_ONE_RET_NULL EMSG2_RET_NULL(_("E369: invalid item in %s%%[]"), reg_magic == MAGIC_ALL)


#define MAX_LIMIT	(32767L << 16L)

static int cstrncmp(char_u *s1, char_u *s2, int *n);
static char_u *cstrchr(char_u *, int);

#ifdef BT_REGEXP_DUMP
static void	regdump(char_u *, bt_regprog_T *);
#endif
#ifdef DEBUG
static char_u	*regprop(char_u *);
#endif

static int re_mult_next(char *what);

static char_u e_missingbracket[] = N_("E769: Missing ] after %s[");
static char_u e_reverse_range[] = N_("E944: Reverse range in character class");
static char_u e_large_class[] = N_("E945: Range too large in character class");
static char_u e_unmatchedpp[] = N_("E53: Unmatched %s%%(");
static char_u e_unmatchedp[] = N_("E54: Unmatched %s(");
static char_u e_unmatchedpar[] = N_("E55: Unmatched %s)");
#ifdef FEAT_SYN_HL
static char_u e_z_not_allowed[] = N_("E66: \\z( not allowed here");
static char_u e_z1_not_allowed[] = N_("E67: \\z1 - \\z9 not allowed here");
#endif
static char_u e_missing_sb[] = N_("E69: Missing ] after %s%%[");
static char_u e_empty_sb[]  = N_("E70: Empty %s%%[]");
static char_u e_recursive[]  = N_("E956: Cannot use pattern recursively");

#define NOT_MULTI	0
#define MULTI_ONE	1
#define MULTI_MULT	2
/*
 * Return NOT_MULTI if c is not a "multi" operator.
 * Return MULTI_ONE if c is a single "multi" operator.
 * Return MULTI_MULT if c is a multi "multi" operator.
 */
    static int
re_multi_type(int c)
{
    if (c == Magic('@') || c == Magic('=') || c == Magic('?'))
	return MULTI_ONE;
    if (c == Magic('*') || c == Magic('+') || c == Magic('{'))
	return MULTI_MULT;
    return NOT_MULTI;
}

/*
 * Flags to be passed up and down.
 */
#define HASWIDTH	0x1	/* Known never to match null string. */
#define SIMPLE		0x2	/* Simple enough to be STAR/PLUS operand. */
#define SPSTART		0x4	/* Starts with * or +. */
#define HASNL		0x8	/* Contains some \n. */
#define HASLOOKBH	0x10	/* Contains "\@<=" or "\@<!". */
#define WORST		0	/* Worst case. */

/*
 * When regcode is set to this value, code is not emitted and size is computed
 * instead.
 */
#define JUST_CALC_SIZE	((char_u *) -1)

static char_u		*reg_prev_sub = NULL;

/*
 * REGEXP_INRANGE contains all characters which are always special in a []
 * range after '\'.
 * REGEXP_ABBR contains all characters which act as abbreviations after '\'.
 * These are:
 *  \n	- New line (NL).
 *  \r	- Carriage Return (CR).
 *  \t	- Tab (TAB).
 *  \e	- Escape (ESC).
 *  \b	- Backspace (Ctrl_H).
 *  \d  - Character code in decimal, eg \d123
 *  \o	- Character code in octal, eg \o80
 *  \x	- Character code in hex, eg \x4a
 *  \u	- Multibyte character code, eg \u20ac
 *  \U	- Long multibyte character code, eg \U12345678
 */
static char_u REGEXP_INRANGE[] = "]^-n\\";
static char_u REGEXP_ABBR[] = "nrtebdoxuU";

/*
 * Translate '\x' to its control character, except "\n", which is Magic.
 */
    static int
backslash_trans(int c)
{
    switch (c)
    {
	case 'r':   return CAR;
	case 't':   return TAB;
	case 'e':   return ESC;
	case 'b':   return BS;
    }
    return c;
}

/*
 * Check for a character class name "[:name:]".  "pp" points to the '['.
 * Returns one of the CLASS_ items. CLASS_NONE means that no item was
 * recognized.  Otherwise "pp" is advanced to after the item.
 */
    static int
get_char_class(char_u **pp)
{
    static const char *(class_names[]) =
    {
	"alnum:]",
#define CLASS_ALNUM 0
	"alpha:]",
#define CLASS_ALPHA 1
	"blank:]",
#define CLASS_BLANK 2
	"cntrl:]",
#define CLASS_CNTRL 3
	"digit:]",
#define CLASS_DIGIT 4
	"graph:]",
#define CLASS_GRAPH 5
	"lower:]",
#define CLASS_LOWER 6
	"print:]",
#define CLASS_PRINT 7
	"punct:]",
#define CLASS_PUNCT 8
	"space:]",
#define CLASS_SPACE 9
	"upper:]",
#define CLASS_UPPER 10
	"xdigit:]",
#define CLASS_XDIGIT 11
	"tab:]",
#define CLASS_TAB 12
	"return:]",
#define CLASS_RETURN 13
	"backspace:]",
#define CLASS_BACKSPACE 14
	"escape:]",
#define CLASS_ESCAPE 15
    };
#define CLASS_NONE 99
    int i;

    if ((*pp)[1] == ':')
    {
	for (i = 0; i < (int)(sizeof(class_names) / sizeof(*class_names)); ++i)
	    if (STRNCMP(*pp + 2, class_names[i], STRLEN(class_names[i])) == 0)
	    {
		*pp += STRLEN(class_names[i]) + 2;
		return i;
	    }
    }
    return CLASS_NONE;
}

/*
 * Specific version of character class functions.
 * Using a table to keep this fast.
 */
static short	class_tab[256];

#define	    RI_DIGIT	0x01
#define	    RI_HEX	0x02
#define	    RI_OCTAL	0x04
#define	    RI_WORD	0x08
#define	    RI_HEAD	0x10
#define	    RI_ALPHA	0x20
#define	    RI_LOWER	0x40
#define	    RI_UPPER	0x80
#define	    RI_WHITE	0x100

    static void
init_class_tab(void)
{
    int		i;
    static int	done = FALSE;

    if (done)
	return;

    for (i = 0; i < 256; ++i)
    {
	if (i >= '0' && i <= '7')
	    class_tab[i] = RI_DIGIT + RI_HEX + RI_OCTAL + RI_WORD;
	else if (i >= '8' && i <= '9')
	    class_tab[i] = RI_DIGIT + RI_HEX + RI_WORD;
	else if (i >= 'a' && i <= 'f')
	    class_tab[i] = RI_HEX + RI_WORD + RI_HEAD + RI_ALPHA + RI_LOWER;
#ifdef EBCDIC
	else if ((i >= 'g' && i <= 'i') || (i >= 'j' && i <= 'r')
						    || (i >= 's' && i <= 'z'))
#else
	else if (i >= 'g' && i <= 'z')
#endif
	    class_tab[i] = RI_WORD + RI_HEAD + RI_ALPHA + RI_LOWER;
	else if (i >= 'A' && i <= 'F')
	    class_tab[i] = RI_HEX + RI_WORD + RI_HEAD + RI_ALPHA + RI_UPPER;
#ifdef EBCDIC
	else if ((i >= 'G' && i <= 'I') || ( i >= 'J' && i <= 'R')
						    || (i >= 'S' && i <= 'Z'))
#else
	else if (i >= 'G' && i <= 'Z')
#endif
	    class_tab[i] = RI_WORD + RI_HEAD + RI_ALPHA + RI_UPPER;
	else if (i == '_')
	    class_tab[i] = RI_WORD + RI_HEAD;
	else
	    class_tab[i] = 0;
    }
    class_tab[' '] |= RI_WHITE;
    class_tab['\t'] |= RI_WHITE;
    done = TRUE;
}

#define ri_digit(c)	(c < 0x100 && (class_tab[c] & RI_DIGIT))
#define ri_hex(c)	(c < 0x100 && (class_tab[c] & RI_HEX))
#define ri_octal(c)	(c < 0x100 && (class_tab[c] & RI_OCTAL))
#define ri_word(c)	(c < 0x100 && (class_tab[c] & RI_WORD))
#define ri_head(c)	(c < 0x100 && (class_tab[c] & RI_HEAD))
#define ri_alpha(c)	(c < 0x100 && (class_tab[c] & RI_ALPHA))
#define ri_lower(c)	(c < 0x100 && (class_tab[c] & RI_LOWER))
#define ri_upper(c)	(c < 0x100 && (class_tab[c] & RI_UPPER))
#define ri_white(c)	(c < 0x100 && (class_tab[c] & RI_WHITE))

/* flags for regflags */
#define RF_ICASE    1	/* ignore case */
#define RF_NOICASE  2	/* don't ignore case */
#define RF_HASNL    4	/* can match a NL */
#define RF_ICOMBINE 8	/* ignore combining characters */
#define RF_LOOKBH   16	/* uses "\@<=" or "\@<!" */

/*
 * Global work variables for vim_regcomp().
 */

static char_u	*regparse;	/* Input-scan pointer. */
static int	prevchr_len;	/* byte length of previous char */
static int	num_complex_braces; /* Complex \{...} count */
static int	regnpar;	/* () count. */
#ifdef FEAT_SYN_HL
static int	regnzpar;	/* \z() count. */
static int	re_has_z;	/* \z item detected */
#endif
static char_u	*regcode;	/* Code-emit pointer, or JUST_CALC_SIZE */
static long	regsize;	/* Code size. */
static int	reg_toolong;	/* TRUE when offset out of range */
static char_u	had_endbrace[NSUBEXP];	/* flags, TRUE if end of () found */
static unsigned	regflags;	/* RF_ flags for prog */
static long	brace_min[10];	/* Minimums for complex brace repeats */
static long	brace_max[10];	/* Maximums for complex brace repeats */
static int	brace_count[10]; /* Current counts for complex brace repeats */
#if defined(FEAT_SYN_HL) || defined(PROTO)
static int	had_eol;	/* TRUE when EOL found by vim_regcomp() */
#endif
static int	one_exactly = FALSE;	/* only do one char for EXACTLY */

static int	reg_magic;	/* magicness of the pattern: */
#define MAGIC_NONE	1	/* "\V" very unmagic */
#define MAGIC_OFF	2	/* "\M" or 'magic' off */
#define MAGIC_ON	3	/* "\m" or 'magic' */
#define MAGIC_ALL	4	/* "\v" very magic */

static int	reg_string;	/* matching with a string instead of a buffer
				   line */
static int	reg_strict;	/* "[abc" is illegal */

/*
 * META contains all characters that may be magic, except '^' and '$'.
 */

#ifdef EBCDIC
static char_u META[] = "%&()*+.123456789<=>?@ACDFHIKLMOPSUVWX[_acdfhiklmnopsuvwxz{|~";
#else
/* META[] is used often enough to justify turning it into a table. */
static char_u META_flags[] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/*		   %  &     (  )  *  +	      .    */
    0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 0,
/*     1  2  3	4  5  6  7  8  9	<  =  >  ? */
    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1,
/*  @  A     C	D     F     H  I     K	L  M	 O */
    1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1,
/*  P	     S	   U  V  W  X	  Z  [		 _ */
    1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1,
/*     a     c	d     f     h  i     k	l  m  n  o */
    0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
/*  p	     s	   u  v  w  x	  z  {	|     ~    */
    1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1
};
#endif

static int	curchr;		/* currently parsed character */
/* Previous character.  Note: prevchr is sometimes -1 when we are not at the
 * start, eg in /[ ^I]^ the pattern was never found even if it existed,
 * because ^ was taken to be magic -- webb */
static int	prevchr;
static int	prevprevchr;	/* previous-previous character */
static int	nextchr;	/* used for ungetchr() */

/* arguments for reg() */
#define REG_NOPAREN	0	/* toplevel reg() */
#define REG_PAREN	1	/* \(\) */
#define REG_ZPAREN	2	/* \z(\) */
#define REG_NPAREN	3	/* \%(\) */

typedef struct
{
     char_u	*regparse;
     int	prevchr_len;
     int	curchr;
     int	prevchr;
     int	prevprevchr;
     int	nextchr;
     int	at_start;
     int	prev_at_start;
     int	regnpar;
} parse_state_T;

/*
 * Forward declarations for vim_regcomp()'s friends.
 */
static void	initchr(char_u *);
static int	getchr(void);
static void	skipchr_keepstart(void);
static int	peekchr(void);
static void	skipchr(void);
static void	ungetchr(void);
static long	gethexchrs(int maxinputlen);
static long	getoctchrs(void);
static long	getdecchrs(void);
static int	coll_get_char(void);
static void	regcomp_start(char_u *expr, int flags);
static char_u	*reg(int, int *);
static char_u	*regbranch(int *flagp);
static char_u	*regconcat(int *flagp);
static char_u	*regpiece(int *);
static char_u	*regatom(int *);
static char_u	*regnode(int);
static int	use_multibytecode(int c);
static int	prog_magic_wrong(void);
static char_u	*regnext(char_u *);
static void	regc(int b);
static void	regmbc(int c);
#define REGMBC(x) regmbc(x);
#define CASEMBC(x) case x:
static void	reginsert(int, char_u *);
static void	reginsert_nr(int op, long val, char_u *opnd);
static void	reginsert_limits(int, long, long, char_u *);
static char_u	*re_put_long(char_u *pr, long_u val);
static int	read_limits(long *, long *);
static void	regtail(char_u *, char_u *);
static void	regoptail(char_u *, char_u *);

static regengine_T bt_regengine;
static regengine_T nfa_regengine;

/*
 * Return TRUE if compiled regular expression "prog" can match a line break.
 */
    int
re_multiline(regprog_T *prog)
{
    return (prog->regflags & RF_HASNL);
}

/*
 * Check for an equivalence class name "[=a=]".  "pp" points to the '['.
 * Returns a character representing the class. Zero means that no item was
 * recognized.  Otherwise "pp" is advanced to after the item.
 */
    static int
get_equi_class(char_u **pp)
{
    int		c;
    int		l = 1;
    char_u	*p = *pp;

    if (p[1] == '=')
    {
	if (has_mbyte)
	    l = (*mb_ptr2len)(p + 2);
	if (p[l + 2] == '=' && p[l + 3] == ']')
	{
	    if (has_mbyte)
		c = mb_ptr2char(p + 2);
	    else
		c = p[2];
	    *pp += l + 4;
	    return c;
	}
    }
    return 0;
}

#ifdef EBCDIC
/*
 * Table for equivalence class "c". (IBM-1047)
 */
char *EQUIVAL_CLASS_C[16] = {
    "A\x62\x63\x64\x65\x66\x67",
    "C\x68",
    "E\x71\x72\x73\x74",
    "I\x75\x76\x77\x78",
    "N\x69",
    "O\xEB\xEC\xED\xEE\xEF\x80",
    "U\xFB\xFC\xFD\xFE",
    "Y\xBA",
    "a\x42\x43\x44\x45\x46\x47",
    "c\x48",
    "e\x51\x52\x53\x54",
    "i\x55\x56\x57\x58",
    "n\x49",
    "o\xCB\xCC\xCD\xCE\xCF\x70",
    "u\xDB\xDC\xDD\xDE",
    "y\x8D\xDF",
};
#endif

/*
 * Produce the bytes for equivalence class "c".
 * Currently only handles latin1, latin9 and utf-8.
 * NOTE: When changing this function, also change nfa_emit_equi_class()
 */
    static void
reg_equi_class(int c)
{
    if (enc_utf8 || STRCMP(p_enc, "latin1") == 0
					 || STRCMP(p_enc, "iso-8859-15") == 0)
    {
#ifdef EBCDIC
	int i;

	/* This might be slower than switch/case below. */
	for (i = 0; i < 16; i++)
	{
	    if (vim_strchr(EQUIVAL_CLASS_C[i], c) != NULL)
	    {
		char *p = EQUIVAL_CLASS_C[i];

		while (*p != 0)
		    regmbc(*p++);
		return;
	    }
	}
#else
	switch (c)
	{
	    /* Do not use '\300' style, it results in a negative number. */
	    case 'A': case 0xc0: case 0xc1: case 0xc2:
	    case 0xc3: case 0xc4: case 0xc5:
	    CASEMBC(0x100) CASEMBC(0x102) CASEMBC(0x104) CASEMBC(0x1cd)
	    CASEMBC(0x1de) CASEMBC(0x1e0) CASEMBC(0x1ea2)
		      regmbc('A'); regmbc(0xc0); regmbc(0xc1);
		      regmbc(0xc2); regmbc(0xc3); regmbc(0xc4);
		      regmbc(0xc5);
		      REGMBC(0x100) REGMBC(0x102) REGMBC(0x104)
		      REGMBC(0x1cd) REGMBC(0x1de) REGMBC(0x1e0)
		      REGMBC(0x1ea2)
		      return;
	    case 'B': CASEMBC(0x1e02) CASEMBC(0x1e06)
		      regmbc('B'); REGMBC(0x1e02) REGMBC(0x1e06)
		      return;
	    case 'C': case 0xc7:
	    CASEMBC(0x106) CASEMBC(0x108) CASEMBC(0x10a) CASEMBC(0x10c)
		      regmbc('C'); regmbc(0xc7);
		      REGMBC(0x106) REGMBC(0x108) REGMBC(0x10a)
		      REGMBC(0x10c)
		      return;
	    case 'D': CASEMBC(0x10e) CASEMBC(0x110) CASEMBC(0x1e0a)
	    CASEMBC(0x1e0e) CASEMBC(0x1e10)
		      regmbc('D'); REGMBC(0x10e) REGMBC(0x110)
		      REGMBC(0x1e0a) REGMBC(0x1e0e) REGMBC(0x1e10)
		      return;
	    case 'E': case 0xc8: case 0xc9: case 0xca: case 0xcb:
	    CASEMBC(0x112) CASEMBC(0x114) CASEMBC(0x116) CASEMBC(0x118)
	    CASEMBC(0x11a) CASEMBC(0x1eba) CASEMBC(0x1ebc)
		      regmbc('E'); regmbc(0xc8); regmbc(0xc9);
		      regmbc(0xca); regmbc(0xcb);
		      REGMBC(0x112) REGMBC(0x114) REGMBC(0x116)
		      REGMBC(0x118) REGMBC(0x11a) REGMBC(0x1eba)
		      REGMBC(0x1ebc)
		      return;
	    case 'F': CASEMBC(0x1e1e)
		      regmbc('F'); REGMBC(0x1e1e)
		      return;
	    case 'G': CASEMBC(0x11c) CASEMBC(0x11e) CASEMBC(0x120)
	    CASEMBC(0x122) CASEMBC(0x1e4) CASEMBC(0x1e6) CASEMBC(0x1f4)
	    CASEMBC(0x1e20)
		      regmbc('G'); REGMBC(0x11c) REGMBC(0x11e)
		      REGMBC(0x120) REGMBC(0x122) REGMBC(0x1e4)
		      REGMBC(0x1e6) REGMBC(0x1f4) REGMBC(0x1e20)
		      return;
	    case 'H': CASEMBC(0x124) CASEMBC(0x126) CASEMBC(0x1e22)
	    CASEMBC(0x1e26) CASEMBC(0x1e28)
		      regmbc('H'); REGMBC(0x124) REGMBC(0x126)
		      REGMBC(0x1e22) REGMBC(0x1e26) REGMBC(0x1e28)
		      return;
	    case 'I': case 0xcc: case 0xcd: case 0xce: case 0xcf:
	    CASEMBC(0x128) CASEMBC(0x12a) CASEMBC(0x12c) CASEMBC(0x12e)
	    CASEMBC(0x130) CASEMBC(0x1cf) CASEMBC(0x1ec8)
		      regmbc('I'); regmbc(0xcc); regmbc(0xcd);
		      regmbc(0xce); regmbc(0xcf);
		      REGMBC(0x128) REGMBC(0x12a) REGMBC(0x12c)
		      REGMBC(0x12e) REGMBC(0x130) REGMBC(0x1cf)
		      REGMBC(0x1ec8)
		      return;
	    case 'J': CASEMBC(0x134)
		      regmbc('J'); REGMBC(0x134)
		      return;
	    case 'K': CASEMBC(0x136) CASEMBC(0x1e8) CASEMBC(0x1e30)
	    CASEMBC(0x1e34)
		      regmbc('K'); REGMBC(0x136) REGMBC(0x1e8)
		      REGMBC(0x1e30) REGMBC(0x1e34)
		      return;
	    case 'L': CASEMBC(0x139) CASEMBC(0x13b) CASEMBC(0x13d)
	    CASEMBC(0x13f) CASEMBC(0x141) CASEMBC(0x1e3a)
		      regmbc('L'); REGMBC(0x139) REGMBC(0x13b)
		      REGMBC(0x13d) REGMBC(0x13f) REGMBC(0x141)
		      REGMBC(0x1e3a)
		      return;
	    case 'M': CASEMBC(0x1e3e) CASEMBC(0x1e40)
		      regmbc('M'); REGMBC(0x1e3e) REGMBC(0x1e40)
		      return;
	    case 'N': case 0xd1:
	    CASEMBC(0x143) CASEMBC(0x145) CASEMBC(0x147) CASEMBC(0x1e44)
	    CASEMBC(0x1e48)
		      regmbc('N'); regmbc(0xd1);
		      REGMBC(0x143) REGMBC(0x145) REGMBC(0x147)
		      REGMBC(0x1e44) REGMBC(0x1e48)
		      return;
	    case 'O': case 0xd2: case 0xd3: case 0xd4: case 0xd5:
	    case 0xd6: case 0xd8:
	    CASEMBC(0x14c) CASEMBC(0x14e) CASEMBC(0x150) CASEMBC(0x1a0)
	    CASEMBC(0x1d1) CASEMBC(0x1ea) CASEMBC(0x1ec) CASEMBC(0x1ece)
		      regmbc('O'); regmbc(0xd2); regmbc(0xd3);
		      regmbc(0xd4); regmbc(0xd5); regmbc(0xd6);
		      regmbc(0xd8);
		      REGMBC(0x14c) REGMBC(0x14e) REGMBC(0x150)
		      REGMBC(0x1a0) REGMBC(0x1d1) REGMBC(0x1ea)
		      REGMBC(0x1ec) REGMBC(0x1ece)
		      return;
	    case 'P': case 0x1e54: case 0x1e56:
		      regmbc('P'); REGMBC(0x1e54) REGMBC(0x1e56)
		      return;
	    case 'R': CASEMBC(0x154) CASEMBC(0x156) CASEMBC(0x158)
	    CASEMBC(0x1e58) CASEMBC(0x1e5e)
		      regmbc('R'); REGMBC(0x154) REGMBC(0x156) REGMBC(0x158)
		      REGMBC(0x1e58) REGMBC(0x1e5e)
		      return;
	    case 'S': CASEMBC(0x15a) CASEMBC(0x15c) CASEMBC(0x15e)
	    CASEMBC(0x160) CASEMBC(0x1e60)
		      regmbc('S'); REGMBC(0x15a) REGMBC(0x15c)
		      REGMBC(0x15e) REGMBC(0x160) REGMBC(0x1e60)
		      return;
	    case 'T': CASEMBC(0x162) CASEMBC(0x164) CASEMBC(0x166)
	    CASEMBC(0x1e6a) CASEMBC(0x1e6e)
		      regmbc('T'); REGMBC(0x162) REGMBC(0x164)
		      REGMBC(0x166) REGMBC(0x1e6a) REGMBC(0x1e6e)
		      return;
	    case 'U': case 0xd9: case 0xda: case 0xdb: case 0xdc:
	    CASEMBC(0x168) CASEMBC(0x16a) CASEMBC(0x16c) CASEMBC(0x16e)
	    CASEMBC(0x170) CASEMBC(0x172) CASEMBC(0x1af) CASEMBC(0x1d3)
	    CASEMBC(0x1ee6)
		      regmbc('U'); regmbc(0xd9); regmbc(0xda);
		      regmbc(0xdb); regmbc(0xdc);
		      REGMBC(0x168) REGMBC(0x16a) REGMBC(0x16c)
		      REGMBC(0x16e) REGMBC(0x170) REGMBC(0x172)
		      REGMBC(0x1af) REGMBC(0x1d3) REGMBC(0x1ee6)
		      return;
	    case 'V': CASEMBC(0x1e7c)
		      regmbc('V'); REGMBC(0x1e7c)
		      return;
	    case 'W': CASEMBC(0x174) CASEMBC(0x1e80) CASEMBC(0x1e82)
	    CASEMBC(0x1e84) CASEMBC(0x1e86)
		      regmbc('W'); REGMBC(0x174) REGMBC(0x1e80)
		      REGMBC(0x1e82) REGMBC(0x1e84) REGMBC(0x1e86)
		      return;
	    case 'X': CASEMBC(0x1e8a) CASEMBC(0x1e8c)
		      regmbc('X'); REGMBC(0x1e8a) REGMBC(0x1e8c)
		      return;
	    case 'Y': case 0xdd:
	    CASEMBC(0x176) CASEMBC(0x178) CASEMBC(0x1e8e) CASEMBC(0x1ef2)
	    CASEMBC(0x1ef6) CASEMBC(0x1ef8)
		      regmbc('Y'); regmbc(0xdd);
		      REGMBC(0x176) REGMBC(0x178) REGMBC(0x1e8e)
		      REGMBC(0x1ef2) REGMBC(0x1ef6) REGMBC(0x1ef8)
		      return;
	    case 'Z': CASEMBC(0x179) CASEMBC(0x17b) CASEMBC(0x17d)
	    CASEMBC(0x1b5) CASEMBC(0x1e90) CASEMBC(0x1e94)
		      regmbc('Z'); REGMBC(0x179) REGMBC(0x17b)
		      REGMBC(0x17d) REGMBC(0x1b5) REGMBC(0x1e90)
		      REGMBC(0x1e94)
		      return;
	    case 'a': case 0xe0: case 0xe1: case 0xe2:
	    case 0xe3: case 0xe4: case 0xe5:
	    CASEMBC(0x101) CASEMBC(0x103) CASEMBC(0x105) CASEMBC(0x1ce)
	    CASEMBC(0x1df) CASEMBC(0x1e1) CASEMBC(0x1ea3)
		      regmbc('a'); regmbc(0xe0); regmbc(0xe1);
		      regmbc(0xe2); regmbc(0xe3); regmbc(0xe4);
		      regmbc(0xe5);
		      REGMBC(0x101) REGMBC(0x103) REGMBC(0x105)
		      REGMBC(0x1ce) REGMBC(0x1df) REGMBC(0x1e1)
		      REGMBC(0x1ea3)
		      return;
	    case 'b': CASEMBC(0x1e03) CASEMBC(0x1e07)
		      regmbc('b'); REGMBC(0x1e03) REGMBC(0x1e07)
		      return;
	    case 'c': case 0xe7:
	    CASEMBC(0x107) CASEMBC(0x109) CASEMBC(0x10b) CASEMBC(0x10d)
		      regmbc('c'); regmbc(0xe7);
		      REGMBC(0x107) REGMBC(0x109) REGMBC(0x10b)
		      REGMBC(0x10d)
		      return;
	    case 'd': CASEMBC(0x10f) CASEMBC(0x111) CASEMBC(0x1e0b)
	    CASEMBC(0x1e0f) CASEMBC(0x1e11)
		      regmbc('d'); REGMBC(0x10f) REGMBC(0x111)
		      REGMBC(0x1e0b) REGMBC(0x1e0f) REGMBC(0x1e11)
		      return;
	    case 'e': case 0xe8: case 0xe9: case 0xea: case 0xeb:
	    CASEMBC(0x113) CASEMBC(0x115) CASEMBC(0x117) CASEMBC(0x119)
	    CASEMBC(0x11b) CASEMBC(0x1ebb) CASEMBC(0x1ebd)
		      regmbc('e'); regmbc(0xe8); regmbc(0xe9);
		      regmbc(0xea); regmbc(0xeb);
		      REGMBC(0x113) REGMBC(0x115) REGMBC(0x117)
		      REGMBC(0x119) REGMBC(0x11b) REGMBC(0x1ebb)
		      REGMBC(0x1ebd)
		      return;
	    case 'f': CASEMBC(0x1e1f)
		      regmbc('f'); REGMBC(0x1e1f)
		      return;
	    case 'g': CASEMBC(0x11d) CASEMBC(0x11f) CASEMBC(0x121)
	    CASEMBC(0x123) CASEMBC(0x1e5) CASEMBC(0x1e7) CASEMBC(0x1f5)
	    CASEMBC(0x1e21)
		      regmbc('g'); REGMBC(0x11d) REGMBC(0x11f)
		      REGMBC(0x121) REGMBC(0x123) REGMBC(0x1e5)
		      REGMBC(0x1e7) REGMBC(0x1f5) REGMBC(0x1e21)
		      return;
	    case 'h': CASEMBC(0x125) CASEMBC(0x127) CASEMBC(0x1e23)
	    CASEMBC(0x1e27) CASEMBC(0x1e29) CASEMBC(0x1e96)
		      regmbc('h'); REGMBC(0x125) REGMBC(0x127)
		      REGMBC(0x1e23) REGMBC(0x1e27) REGMBC(0x1e29)
		      REGMBC(0x1e96)
		      return;
	    case 'i': case 0xec: case 0xed: case 0xee: case 0xef:
	    CASEMBC(0x129) CASEMBC(0x12b) CASEMBC(0x12d) CASEMBC(0x12f)
	    CASEMBC(0x1d0) CASEMBC(0x1ec9)
		      regmbc('i'); regmbc(0xec); regmbc(0xed);
		      regmbc(0xee); regmbc(0xef);
		      REGMBC(0x129) REGMBC(0x12b) REGMBC(0x12d)
		      REGMBC(0x12f) REGMBC(0x1d0) REGMBC(0x1ec9)
		      return;
	    case 'j': CASEMBC(0x135) CASEMBC(0x1f0)
		      regmbc('j'); REGMBC(0x135) REGMBC(0x1f0)
		      return;
	    case 'k': CASEMBC(0x137) CASEMBC(0x1e9) CASEMBC(0x1e31)
	    CASEMBC(0x1e35)
		      regmbc('k'); REGMBC(0x137) REGMBC(0x1e9)
		      REGMBC(0x1e31) REGMBC(0x1e35)
		      return;
	    case 'l': CASEMBC(0x13a) CASEMBC(0x13c) CASEMBC(0x13e)
	    CASEMBC(0x140) CASEMBC(0x142) CASEMBC(0x1e3b)
		      regmbc('l'); REGMBC(0x13a) REGMBC(0x13c)
		      REGMBC(0x13e) REGMBC(0x140) REGMBC(0x142)
		      REGMBC(0x1e3b)
		      return;
	    case 'm': CASEMBC(0x1e3f) CASEMBC(0x1e41)
		      regmbc('m'); REGMBC(0x1e3f) REGMBC(0x1e41)
		      return;
	    case 'n': case 0xf1:
	    CASEMBC(0x144) CASEMBC(0x146) CASEMBC(0x148) CASEMBC(0x149)
	    CASEMBC(0x1e45) CASEMBC(0x1e49)
		      regmbc('n'); regmbc(0xf1);
		      REGMBC(0x144) REGMBC(0x146) REGMBC(0x148)
		      REGMBC(0x149) REGMBC(0x1e45) REGMBC(0x1e49)
		      return;
	    case 'o': case 0xf2: case 0xf3: case 0xf4: case 0xf5:
	    case 0xf6: case 0xf8:
	    CASEMBC(0x14d) CASEMBC(0x14f) CASEMBC(0x151) CASEMBC(0x1a1)
	    CASEMBC(0x1d2) CASEMBC(0x1eb) CASEMBC(0x1ed) CASEMBC(0x1ecf)
		      regmbc('o'); regmbc(0xf2); regmbc(0xf3);
		      regmbc(0xf4); regmbc(0xf5); regmbc(0xf6);
		      regmbc(0xf8);
		      REGMBC(0x14d) REGMBC(0x14f) REGMBC(0x151)
		      REGMBC(0x1a1) REGMBC(0x1d2) REGMBC(0x1eb)
		      REGMBC(0x1ed) REGMBC(0x1ecf)
		      return;
	    case 'p': CASEMBC(0x1e55) CASEMBC(0x1e57)
		      regmbc('p'); REGMBC(0x1e55) REGMBC(0x1e57)
		      return;
	    case 'r': CASEMBC(0x155) CASEMBC(0x157) CASEMBC(0x159)
	    CASEMBC(0x1e59) CASEMBC(0x1e5f)
		      regmbc('r'); REGMBC(0x155) REGMBC(0x157) REGMBC(0x159)
		      REGMBC(0x1e59) REGMBC(0x1e5f)
		      return;
	    case 's': CASEMBC(0x15b) CASEMBC(0x15d) CASEMBC(0x15f)
	    CASEMBC(0x161) CASEMBC(0x1e61)
		      regmbc('s'); REGMBC(0x15b) REGMBC(0x15d)
		      REGMBC(0x15f) REGMBC(0x161) REGMBC(0x1e61)
		      return;
	    case 't': CASEMBC(0x163) CASEMBC(0x165) CASEMBC(0x167)
	    CASEMBC(0x1e6b) CASEMBC(0x1e6f) CASEMBC(0x1e97)
		      regmbc('t'); REGMBC(0x163) REGMBC(0x165) REGMBC(0x167)
		      REGMBC(0x1e6b) REGMBC(0x1e6f) REGMBC(0x1e97)
		      return;
	    case 'u': case 0xf9: case 0xfa: case 0xfb: case 0xfc:
	    CASEMBC(0x169) CASEMBC(0x16b) CASEMBC(0x16d) CASEMBC(0x16f)
	    CASEMBC(0x171) CASEMBC(0x173) CASEMBC(0x1b0) CASEMBC(0x1d4)
	    CASEMBC(0x1ee7)
		      regmbc('u'); regmbc(0xf9); regmbc(0xfa);
		      regmbc(0xfb); regmbc(0xfc);
		      REGMBC(0x169) REGMBC(0x16b) REGMBC(0x16d)
		      REGMBC(0x16f) REGMBC(0x171) REGMBC(0x173)
		      REGMBC(0x1b0) REGMBC(0x1d4) REGMBC(0x1ee7)
		      return;
	    case 'v': CASEMBC(0x1e7d)
		      regmbc('v'); REGMBC(0x1e7d)
		      return;
	    case 'w': CASEMBC(0x175) CASEMBC(0x1e81) CASEMBC(0x1e83)
	    CASEMBC(0x1e85) CASEMBC(0x1e87) CASEMBC(0x1e98)
		      regmbc('w'); REGMBC(0x175) REGMBC(0x1e81)
		      REGMBC(0x1e83) REGMBC(0x1e85) REGMBC(0x1e87)
		      REGMBC(0x1e98)
		      return;
	    case 'x': CASEMBC(0x1e8b) CASEMBC(0x1e8d)
		      regmbc('x'); REGMBC(0x1e8b) REGMBC(0x1e8d)
		      return;
	    case 'y': case 0xfd: case 0xff:
	    CASEMBC(0x177) CASEMBC(0x1e8f) CASEMBC(0x1e99)
	    CASEMBC(0x1ef3) CASEMBC(0x1ef7) CASEMBC(0x1ef9)
		      regmbc('y'); regmbc(0xfd); regmbc(0xff);
		      REGMBC(0x177) REGMBC(0x1e8f) REGMBC(0x1e99)
		      REGMBC(0x1ef3) REGMBC(0x1ef7) REGMBC(0x1ef9)
		      return;
	    case 'z': CASEMBC(0x17a) CASEMBC(0x17c) CASEMBC(0x17e)
	    CASEMBC(0x1b6) CASEMBC(0x1e91) CASEMBC(0x1e95)
		      regmbc('z'); REGMBC(0x17a) REGMBC(0x17c)
		      REGMBC(0x17e) REGMBC(0x1b6) REGMBC(0x1e91)
		      REGMBC(0x1e95)
		      return;
	}
#endif
    }
    regmbc(c);
}

/*
 * Check for a collating element "[.a.]".  "pp" points to the '['.
 * Returns a character. Zero means that no item was recognized.  Otherwise
 * "pp" is advanced to after the item.
 * Currently only single characters are recognized!
 */
    static int
get_coll_element(char_u **pp)
{
    int		c;
    int		l = 1;
    char_u	*p = *pp;

    if (p[0] != NUL && p[1] == '.')
    {
	if (has_mbyte)
	    l = (*mb_ptr2len)(p + 2);
	if (p[l + 2] == '.' && p[l + 3] == ']')
	{
	    if (has_mbyte)
		c = mb_ptr2char(p + 2);
	    else
		c = p[2];
	    *pp += l + 4;
	    return c;
	}
    }
    return 0;
}

static int reg_cpo_lit; /* 'cpoptions' contains 'l' flag */
static int reg_cpo_bsl; /* 'cpoptions' contains '\' flag */

    static void
get_cpo_flags(void)
{
    reg_cpo_lit = vim_strchr(p_cpo, CPO_LITERAL) != NULL;
    reg_cpo_bsl = vim_strchr(p_cpo, CPO_BACKSL) != NULL;
}

/*
 * Skip over a "[]" range.
 * "p" must point to the character after the '['.
 * The returned pointer is on the matching ']', or the terminating NUL.
 */
    static char_u *
skip_anyof(char_u *p)
{
    int		l;

    if (*p == '^')	/* Complement of range. */
	++p;
    if (*p == ']' || *p == '-')
	++p;
    while (*p != NUL && *p != ']')
    {
	if (has_mbyte && (l = (*mb_ptr2len)(p)) > 1)
	    p += l;
	else
	    if (*p == '-')
	    {
		++p;
		if (*p != ']' && *p != NUL)
		    MB_PTR_ADV(p);
	    }
	else if (*p == '\\'
		&& !reg_cpo_bsl
		&& (vim_strchr(REGEXP_INRANGE, p[1]) != NULL
		    || (!reg_cpo_lit && vim_strchr(REGEXP_ABBR, p[1]) != NULL)))
	    p += 2;
	else if (*p == '[')
	{
	    if (get_char_class(&p) == CLASS_NONE
		    && get_equi_class(&p) == 0
		    && get_coll_element(&p) == 0
		    && *p != NUL)
		++p; /* it is not a class name and not NUL */
	}
	else
	    ++p;
    }

    return p;
}

/*
 * Skip past regular expression.
 * Stop at end of "startp" or where "dirc" is found ('/', '?', etc).
 * Take care of characters with a backslash in front of it.
 * Skip strings inside [ and ].
 * When "newp" is not NULL and "dirc" is '?', make an allocated copy of the
 * expression and change "\?" to "?".  If "*newp" is not NULL the expression
 * is changed in-place.
 */
    char_u *
skip_regexp(
    char_u	*startp,
    int		dirc,
    int		magic,
    char_u	**newp)
{
    int		mymagic;
    char_u	*p = startp;

    if (magic)
	mymagic = MAGIC_ON;
    else
	mymagic = MAGIC_OFF;
    get_cpo_flags();

    for (; p[0] != NUL; MB_PTR_ADV(p))
    {
	if (p[0] == dirc)	/* found end of regexp */
	    break;
	if ((p[0] == '[' && mymagic >= MAGIC_ON)
		|| (p[0] == '\\' && p[1] == '[' && mymagic <= MAGIC_OFF))
	{
	    p = skip_anyof(p + 1);
	    if (p[0] == NUL)
		break;
	}
	else if (p[0] == '\\' && p[1] != NUL)
	{
	    if (dirc == '?' && newp != NULL && p[1] == '?')
	    {
		/* change "\?" to "?", make a copy first. */
		if (*newp == NULL)
		{
		    *newp = vim_strsave(startp);
		    if (*newp != NULL)
			p = *newp + (p - startp);
		}
		if (*newp != NULL)
		    STRMOVE(p, p + 1);
		else
		    ++p;
	    }
	    else
		++p;    /* skip next character */
	    if (*p == 'v')
		mymagic = MAGIC_ALL;
	    else if (*p == 'V')
		mymagic = MAGIC_NONE;
	}
    }
    return p;
}

/*
 * Return TRUE if the back reference is legal. We must have seen the close
 * brace.
 * TODO: Should also check that we don't refer to something that is repeated
 * (+*=): what instance of the repetition should we match?
 */
    static int
seen_endbrace(int refnum)
{
    if (!had_endbrace[refnum])
    {
	char_u *p;

	/* Trick: check if "@<=" or "@<!" follows, in which case
	 * the \1 can appear before the referenced match. */
	for (p = regparse; *p != NUL; ++p)
	    if (p[0] == '@' && p[1] == '<' && (p[2] == '!' || p[2] == '='))
		break;
	if (*p == NUL)
	{
	    emsg(_("E65: Illegal back reference"));
	    rc_did_emsg = TRUE;
	    return FALSE;
	}
    }
    return TRUE;
}

/*
 * bt_regcomp() - compile a regular expression into internal code for the
 * traditional back track matcher.
 * Returns the program in allocated space.  Returns NULL for an error.
 *
 * We can't allocate space until we know how big the compiled form will be,
 * but we can't compile it (and thus know how big it is) until we've got a
 * place to put the code.  So we cheat:  we compile it twice, once with code
 * generation turned off and size counting turned on, and once "for real".
 * This also means that we don't allocate space until we are sure that the
 * thing really will compile successfully, and we never have to move the
 * code and thus invalidate pointers into it.  (Note that it has to be in
 * one piece because vim_free() must be able to free it all.)
 *
 * Whether upper/lower case is to be ignored is decided when executing the
 * program, it does not matter here.
 *
 * Beware that the optimization-preparation code in here knows about some
 * of the structure of the compiled regexp.
 * "re_flags": RE_MAGIC and/or RE_STRING.
 */
    static regprog_T *
bt_regcomp(char_u *expr, int re_flags)
{
    bt_regprog_T    *r;
    char_u	*scan;
    char_u	*longest;
    int		len;
    int		flags;

    if (expr == NULL)
	EMSG_RET_NULL(_(e_null));

    init_class_tab();

    /*
     * First pass: determine size, legality.
     */
    regcomp_start(expr, re_flags);
    regcode = JUST_CALC_SIZE;
    regc(REGMAGIC);
    if (reg(REG_NOPAREN, &flags) == NULL)
	return NULL;

    /* Allocate space. */
    r = (bt_regprog_T *)lalloc(sizeof(bt_regprog_T) + regsize, TRUE);
    if (r == NULL)
	return NULL;
    r->re_in_use = FALSE;

    /*
     * Second pass: emit code.
     */
    regcomp_start(expr, re_flags);
    regcode = r->program;
    regc(REGMAGIC);
    if (reg(REG_NOPAREN, &flags) == NULL || reg_toolong)
    {
	vim_free(r);
	if (reg_toolong)
	    EMSG_RET_NULL(_("E339: Pattern too long"));
	return NULL;
    }

    /* Dig out information for optimizations. */
    r->regstart = NUL;		/* Worst-case defaults. */
    r->reganch = 0;
    r->regmust = NULL;
    r->regmlen = 0;
    r->regflags = regflags;
    if (flags & HASNL)
	r->regflags |= RF_HASNL;
    if (flags & HASLOOKBH)
	r->regflags |= RF_LOOKBH;
#ifdef FEAT_SYN_HL
    /* Remember whether this pattern has any \z specials in it. */
    r->reghasz = re_has_z;
#endif
    scan = r->program + 1;	/* First BRANCH. */
    if (OP(regnext(scan)) == END)   /* Only one top-level choice. */
    {
	scan = OPERAND(scan);

	/* Starting-point info. */
	if (OP(scan) == BOL || OP(scan) == RE_BOF)
	{
	    r->reganch++;
	    scan = regnext(scan);
	}

	if (OP(scan) == EXACTLY)
	{
	    if (has_mbyte)
		r->regstart = (*mb_ptr2char)(OPERAND(scan));
	    else
		r->regstart = *OPERAND(scan);
	}
	else if ((OP(scan) == BOW
		    || OP(scan) == EOW
		    || OP(scan) == NOTHING
		    || OP(scan) == MOPEN + 0 || OP(scan) == NOPEN
		    || OP(scan) == MCLOSE + 0 || OP(scan) == NCLOSE)
		 && OP(regnext(scan)) == EXACTLY)
	{
	    if (has_mbyte)
		r->regstart = (*mb_ptr2char)(OPERAND(regnext(scan)));
	    else
		r->regstart = *OPERAND(regnext(scan));
	}

	/*
	 * If there's something expensive in the r.e., find the longest
	 * literal string that must appear and make it the regmust.  Resolve
	 * ties in favor of later strings, since the regstart check works
	 * with the beginning of the r.e. and avoiding duplication
	 * strengthens checking.  Not a strong reason, but sufficient in the
	 * absence of others.
	 */
	/*
	 * When the r.e. starts with BOW, it is faster to look for a regmust
	 * first. Used a lot for "#" and "*" commands. (Added by mool).
	 */
	if ((flags & SPSTART || OP(scan) == BOW || OP(scan) == EOW)
							  && !(flags & HASNL))
	{
	    longest = NULL;
	    len = 0;
	    for (; scan != NULL; scan = regnext(scan))
		if (OP(scan) == EXACTLY && STRLEN(OPERAND(scan)) >= (size_t)len)
		{
		    longest = OPERAND(scan);
		    len = (int)STRLEN(OPERAND(scan));
		}
	    r->regmust = longest;
	    r->regmlen = len;
	}
    }
#ifdef BT_REGEXP_DUMP
    regdump(expr, r);
#endif
    r->engine = &bt_regengine;
    return (regprog_T *)r;
}

/*
 * Free a compiled regexp program, returned by bt_regcomp().
 */
    static void
bt_regfree(regprog_T *prog)
{
    vim_free(prog);
}

/*
 * Setup to parse the regexp.  Used once to get the length and once to do it.
 */
    static void
regcomp_start(
    char_u	*expr,
    int		re_flags)	    /* see vim_regcomp() */
{
    initchr(expr);
    if (re_flags & RE_MAGIC)
	reg_magic = MAGIC_ON;
    else
	reg_magic = MAGIC_OFF;
    reg_string = (re_flags & RE_STRING);
    reg_strict = (re_flags & RE_STRICT);
    get_cpo_flags();

    num_complex_braces = 0;
    regnpar = 1;
    vim_memset(had_endbrace, 0, sizeof(had_endbrace));
#ifdef FEAT_SYN_HL
    regnzpar = 1;
    re_has_z = 0;
#endif
    regsize = 0L;
    reg_toolong = FALSE;
    regflags = 0;
#if defined(FEAT_SYN_HL) || defined(PROTO)
    had_eol = FALSE;
#endif
}

#if defined(FEAT_SYN_HL) || defined(PROTO)
/*
 * Check if during the previous call to vim_regcomp the EOL item "$" has been
 * found.  This is messy, but it works fine.
 */
    int
vim_regcomp_had_eol(void)
{
    return had_eol;
}
#endif

// variables used for parsing
static int	at_start;	// True when on the first character
static int	prev_at_start;  // True when on the second character

/*
 * Parse regular expression, i.e. main body or parenthesized thing.
 *
 * Caller must absorb opening parenthesis.
 *
 * Combining parenthesis handling with the base level of regular expression
 * is a trifle forced, but the need to tie the tails of the branches to what
 * follows makes it hard to avoid.
 */
    static char_u *
reg(
    int		paren,	/* REG_NOPAREN, REG_PAREN, REG_NPAREN or REG_ZPAREN */
    int		*flagp)
{
    char_u	*ret;
    char_u	*br;
    char_u	*ender;
    int		parno = 0;
    int		flags;

    *flagp = HASWIDTH;		/* Tentatively. */

#ifdef FEAT_SYN_HL
    if (paren == REG_ZPAREN)
    {
	/* Make a ZOPEN node. */
	if (regnzpar >= NSUBEXP)
	    EMSG_RET_NULL(_("E50: Too many \\z("));
	parno = regnzpar;
	regnzpar++;
	ret = regnode(ZOPEN + parno);
    }
    else
#endif
	if (paren == REG_PAREN)
    {
	/* Make a MOPEN node. */
	if (regnpar >= NSUBEXP)
	    EMSG2_RET_NULL(_("E51: Too many %s("), reg_magic == MAGIC_ALL);
	parno = regnpar;
	++regnpar;
	ret = regnode(MOPEN + parno);
    }
    else if (paren == REG_NPAREN)
    {
	/* Make a NOPEN node. */
	ret = regnode(NOPEN);
    }
    else
	ret = NULL;

    /* Pick up the branches, linking them together. */
    br = regbranch(&flags);
    if (br == NULL)
	return NULL;
    if (ret != NULL)
	regtail(ret, br);	/* [MZ]OPEN -> first. */
    else
	ret = br;
    /* If one of the branches can be zero-width, the whole thing can.
     * If one of the branches has * at start or matches a line-break, the
     * whole thing can. */
    if (!(flags & HASWIDTH))
	*flagp &= ~HASWIDTH;
    *flagp |= flags & (SPSTART | HASNL | HASLOOKBH);
    while (peekchr() == Magic('|'))
    {
	skipchr();
	br = regbranch(&flags);
	if (br == NULL || reg_toolong)
	    return NULL;
	regtail(ret, br);	/* BRANCH -> BRANCH. */
	if (!(flags & HASWIDTH))
	    *flagp &= ~HASWIDTH;
	*flagp |= flags & (SPSTART | HASNL | HASLOOKBH);
    }

    /* Make a closing node, and hook it on the end. */
    ender = regnode(
#ifdef FEAT_SYN_HL
	    paren == REG_ZPAREN ? ZCLOSE + parno :
#endif
	    paren == REG_PAREN ? MCLOSE + parno :
	    paren == REG_NPAREN ? NCLOSE : END);
    regtail(ret, ender);

    /* Hook the tails of the branches to the closing node. */
    for (br = ret; br != NULL; br = regnext(br))
	regoptail(br, ender);

    /* Check for proper termination. */
    if (paren != REG_NOPAREN && getchr() != Magic(')'))
    {
#ifdef FEAT_SYN_HL
	if (paren == REG_ZPAREN)
	    EMSG_RET_NULL(_("E52: Unmatched \\z("));
	else
#endif
	    if (paren == REG_NPAREN)
	    EMSG2_RET_NULL(_(e_unmatchedpp), reg_magic == MAGIC_ALL);
	else
	    EMSG2_RET_NULL(_(e_unmatchedp), reg_magic == MAGIC_ALL);
    }
    else if (paren == REG_NOPAREN && peekchr() != NUL)
    {
	if (curchr == Magic(')'))
	    EMSG2_RET_NULL(_(e_unmatchedpar), reg_magic == MAGIC_ALL);
	else
	    EMSG_RET_NULL(_(e_trailing));	/* "Can't happen". */
	/* NOTREACHED */
    }
    /*
     * Here we set the flag allowing back references to this set of
     * parentheses.
     */
    if (paren == REG_PAREN)
	had_endbrace[parno] = TRUE;	/* have seen the close paren */
    return ret;
}

/*
 * Parse one alternative of an | operator.
 * Implements the & operator.
 */
    static char_u *
regbranch(int *flagp)
{
    char_u	*ret;
    char_u	*chain = NULL;
    char_u	*latest;
    int		flags;

    *flagp = WORST | HASNL;		/* Tentatively. */

    ret = regnode(BRANCH);
    for (;;)
    {
	latest = regconcat(&flags);
	if (latest == NULL)
	    return NULL;
	/* If one of the branches has width, the whole thing has.  If one of
	 * the branches anchors at start-of-line, the whole thing does.
	 * If one of the branches uses look-behind, the whole thing does. */
	*flagp |= flags & (HASWIDTH | SPSTART | HASLOOKBH);
	/* If one of the branches doesn't match a line-break, the whole thing
	 * doesn't. */
	*flagp &= ~HASNL | (flags & HASNL);
	if (chain != NULL)
	    regtail(chain, latest);
	if (peekchr() != Magic('&'))
	    break;
	skipchr();
	regtail(latest, regnode(END)); /* operand ends */
	if (reg_toolong)
	    break;
	reginsert(MATCH, latest);
	chain = latest;
    }

    return ret;
}

/*
 * Parse one alternative of an | or & operator.
 * Implements the concatenation operator.
 */
    static char_u *
regconcat(int *flagp)
{
    char_u	*first = NULL;
    char_u	*chain = NULL;
    char_u	*latest;
    int		flags;
    int		cont = TRUE;

    *flagp = WORST;		/* Tentatively. */

    while (cont)
    {
	switch (peekchr())
	{
	    case NUL:
	    case Magic('|'):
	    case Magic('&'):
	    case Magic(')'):
			    cont = FALSE;
			    break;
	    case Magic('Z'):
			    regflags |= RF_ICOMBINE;
			    skipchr_keepstart();
			    break;
	    case Magic('c'):
			    regflags |= RF_ICASE;
			    skipchr_keepstart();
			    break;
	    case Magic('C'):
			    regflags |= RF_NOICASE;
			    skipchr_keepstart();
			    break;
	    case Magic('v'):
			    reg_magic = MAGIC_ALL;
			    skipchr_keepstart();
			    curchr = -1;
			    break;
	    case Magic('m'):
			    reg_magic = MAGIC_ON;
			    skipchr_keepstart();
			    curchr = -1;
			    break;
	    case Magic('M'):
			    reg_magic = MAGIC_OFF;
			    skipchr_keepstart();
			    curchr = -1;
			    break;
	    case Magic('V'):
			    reg_magic = MAGIC_NONE;
			    skipchr_keepstart();
			    curchr = -1;
			    break;
	    default:
			    latest = regpiece(&flags);
			    if (latest == NULL || reg_toolong)
				return NULL;
			    *flagp |= flags & (HASWIDTH | HASNL | HASLOOKBH);
			    if (chain == NULL)	/* First piece. */
				*flagp |= flags & SPSTART;
			    else
				regtail(chain, latest);
			    chain = latest;
			    if (first == NULL)
				first = latest;
			    break;
	}
    }
    if (first == NULL)		/* Loop ran zero times. */
	first = regnode(NOTHING);
    return first;
}

/*
 * Parse something followed by possible [*+=].
 *
 * Note that the branching code sequences used for = and the general cases
 * of * and + are somewhat optimized:  they use the same NOTHING node as
 * both the endmarker for their branch list and the body of the last branch.
 * It might seem that this node could be dispensed with entirely, but the
 * endmarker role is not redundant.
 */
    static char_u *
regpiece(int *flagp)
{
    char_u	    *ret;
    int		    op;
    char_u	    *next;
    int		    flags;
    long	    minval;
    long	    maxval;

    ret = regatom(&flags);
    if (ret == NULL)
	return NULL;

    op = peekchr();
    if (re_multi_type(op) == NOT_MULTI)
    {
	*flagp = flags;
	return ret;
    }
    /* default flags */
    *flagp = (WORST | SPSTART | (flags & (HASNL | HASLOOKBH)));

    skipchr();
    switch (op)
    {
	case Magic('*'):
	    if (flags & SIMPLE)
		reginsert(STAR, ret);
	    else
	    {
		/* Emit x* as (x&|), where & means "self". */
		reginsert(BRANCH, ret); /* Either x */
		regoptail(ret, regnode(BACK));	/* and loop */
		regoptail(ret, ret);	/* back */
		regtail(ret, regnode(BRANCH));	/* or */
		regtail(ret, regnode(NOTHING)); /* null. */
	    }
	    break;

	case Magic('+'):
	    if (flags & SIMPLE)
		reginsert(PLUS, ret);
	    else
	    {
		/* Emit x+ as x(&|), where & means "self". */
		next = regnode(BRANCH); /* Either */
		regtail(ret, next);
		regtail(regnode(BACK), ret);	/* loop back */
		regtail(next, regnode(BRANCH)); /* or */
		regtail(ret, regnode(NOTHING)); /* null. */
	    }
	    *flagp = (WORST | HASWIDTH | (flags & (HASNL | HASLOOKBH)));
	    break;

	case Magic('@'):
	    {
		int	lop = END;
		long	nr;

		nr = getdecchrs();
		switch (no_Magic(getchr()))
		{
		    case '=': lop = MATCH; break;		  /* \@= */
		    case '!': lop = NOMATCH; break;		  /* \@! */
		    case '>': lop = SUBPAT; break;		  /* \@> */
		    case '<': switch (no_Magic(getchr()))
			      {
				  case '=': lop = BEHIND; break;   /* \@<= */
				  case '!': lop = NOBEHIND; break; /* \@<! */
			      }
		}
		if (lop == END)
		    EMSG2_RET_NULL(_("E59: invalid character after %s@"),
						      reg_magic == MAGIC_ALL);
		/* Look behind must match with behind_pos. */
		if (lop == BEHIND || lop == NOBEHIND)
		{
		    regtail(ret, regnode(BHPOS));
		    *flagp |= HASLOOKBH;
		}
		regtail(ret, regnode(END)); /* operand ends */
		if (lop == BEHIND || lop == NOBEHIND)
		{
		    if (nr < 0)
			nr = 0; /* no limit is same as zero limit */
		    reginsert_nr(lop, nr, ret);
		}
		else
		    reginsert(lop, ret);
		break;
	    }

	case Magic('?'):
	case Magic('='):
	    /* Emit x= as (x|) */
	    reginsert(BRANCH, ret);		/* Either x */
	    regtail(ret, regnode(BRANCH));	/* or */
	    next = regnode(NOTHING);		/* null. */
	    regtail(ret, next);
	    regoptail(ret, next);
	    break;

	case Magic('{'):
	    if (!read_limits(&minval, &maxval))
		return NULL;
	    if (flags & SIMPLE)
	    {
		reginsert(BRACE_SIMPLE, ret);
		reginsert_limits(BRACE_LIMITS, minval, maxval, ret);
	    }
	    else
	    {
		if (num_complex_braces >= 10)
		    EMSG2_RET_NULL(_("E60: Too many complex %s{...}s"),
						      reg_magic == MAGIC_ALL);
		reginsert(BRACE_COMPLEX + num_complex_braces, ret);
		regoptail(ret, regnode(BACK));
		regoptail(ret, ret);
		reginsert_limits(BRACE_LIMITS, minval, maxval, ret);
		++num_complex_braces;
	    }
	    if (minval > 0 && maxval > 0)
		*flagp = (HASWIDTH | (flags & (HASNL | HASLOOKBH)));
	    break;
    }
    if (re_multi_type(peekchr()) != NOT_MULTI)
    {
	// Can't have a multi follow a multi.
	if (peekchr() == Magic('*'))
	    EMSG2_RET_NULL(_("E61: Nested %s*"), reg_magic >= MAGIC_ON);
	EMSG3_RET_NULL(_("E62: Nested %s%c"), reg_magic == MAGIC_ALL,
							  no_Magic(peekchr()));
    }

    return ret;
}

/* When making changes to classchars also change nfa_classcodes. */
static char_u	*classchars = (char_u *)".iIkKfFpPsSdDxXoOwWhHaAlLuU";
static int	classcodes[] = {
    ANY, IDENT, SIDENT, KWORD, SKWORD,
    FNAME, SFNAME, PRINT, SPRINT,
    WHITE, NWHITE, DIGIT, NDIGIT,
    HEX, NHEX, OCTAL, NOCTAL,
    WORD, NWORD, HEAD, NHEAD,
    ALPHA, NALPHA, LOWER, NLOWER,
    UPPER, NUPPER
};

/*
 * Parse the lowest level.
 *
 * Optimization:  gobbles an entire sequence of ordinary characters so that
 * it can turn them into a single node, which is smaller to store and
 * faster to run.  Don't do this when one_exactly is set.
 */
    static char_u *
regatom(int *flagp)
{
    char_u	    *ret;
    int		    flags;
    int		    c;
    char_u	    *p;
    int		    extra = 0;
    int		    save_prev_at_start = prev_at_start;

    *flagp = WORST;		/* Tentatively. */

    c = getchr();
    switch (c)
    {
      case Magic('^'):
	ret = regnode(BOL);
	break;

      case Magic('$'):
	ret = regnode(EOL);
#if defined(FEAT_SYN_HL) || defined(PROTO)
	had_eol = TRUE;
#endif
	break;

      case Magic('<'):
	ret = regnode(BOW);
	break;

      case Magic('>'):
	ret = regnode(EOW);
	break;

      case Magic('_'):
	c = no_Magic(getchr());
	if (c == '^')		/* "\_^" is start-of-line */
	{
	    ret = regnode(BOL);
	    break;
	}
	if (c == '$')		/* "\_$" is end-of-line */
	{
	    ret = regnode(EOL);
#if defined(FEAT_SYN_HL) || defined(PROTO)
	    had_eol = TRUE;
#endif
	    break;
	}

	extra = ADD_NL;
	*flagp |= HASNL;

	/* "\_[" is character range plus newline */
	if (c == '[')
	    goto collection;

	/* "\_x" is character class plus newline */
	/* FALLTHROUGH */

	/*
	 * Character classes.
	 */
      case Magic('.'):
      case Magic('i'):
      case Magic('I'):
      case Magic('k'):
      case Magic('K'):
      case Magic('f'):
      case Magic('F'):
      case Magic('p'):
      case Magic('P'):
      case Magic('s'):
      case Magic('S'):
      case Magic('d'):
      case Magic('D'):
      case Magic('x'):
      case Magic('X'):
      case Magic('o'):
      case Magic('O'):
      case Magic('w'):
      case Magic('W'):
      case Magic('h'):
      case Magic('H'):
      case Magic('a'):
      case Magic('A'):
      case Magic('l'):
      case Magic('L'):
      case Magic('u'):
      case Magic('U'):
	p = vim_strchr(classchars, no_Magic(c));
	if (p == NULL)
	    EMSG_RET_NULL(_("E63: invalid use of \\_"));

	/* When '.' is followed by a composing char ignore the dot, so that
	 * the composing char is matched here. */
	if (enc_utf8 && c == Magic('.') && utf_iscomposing(peekchr()))
	{
	    c = getchr();
	    goto do_multibyte;
	}
	ret = regnode(classcodes[p - classchars] + extra);
	*flagp |= HASWIDTH | SIMPLE;
	break;

      case Magic('n'):
	if (reg_string)
	{
	    /* In a string "\n" matches a newline character. */
	    ret = regnode(EXACTLY);
	    regc(NL);
	    regc(NUL);
	    *flagp |= HASWIDTH | SIMPLE;
	}
	else
	{
	    /* In buffer text "\n" matches the end of a line. */
	    ret = regnode(NEWL);
	    *flagp |= HASWIDTH | HASNL;
	}
	break;

      case Magic('('):
	if (one_exactly)
	    EMSG_ONE_RET_NULL;
	ret = reg(REG_PAREN, &flags);
	if (ret == NULL)
	    return NULL;
	*flagp |= flags & (HASWIDTH | SPSTART | HASNL | HASLOOKBH);
	break;

      case NUL:
      case Magic('|'):
      case Magic('&'):
      case Magic(')'):
	if (one_exactly)
	    EMSG_ONE_RET_NULL;
	IEMSG_RET_NULL(_(e_internal));	/* Supposed to be caught earlier. */
	/* NOTREACHED */

      case Magic('='):
      case Magic('?'):
      case Magic('+'):
      case Magic('@'):
      case Magic('{'):
      case Magic('*'):
	c = no_Magic(c);
	EMSG3_RET_NULL(_("E64: %s%c follows nothing"),
		(c == '*' ? reg_magic >= MAGIC_ON : reg_magic == MAGIC_ALL), c);
	/* NOTREACHED */

      case Magic('~'):		/* previous substitute pattern */
	    if (reg_prev_sub != NULL)
	    {
		char_u	    *lp;

		ret = regnode(EXACTLY);
		lp = reg_prev_sub;
		while (*lp != NUL)
		    regc(*lp++);
		regc(NUL);
		if (*reg_prev_sub != NUL)
		{
		    *flagp |= HASWIDTH;
		    if ((lp - reg_prev_sub) == 1)
			*flagp |= SIMPLE;
		}
	    }
	    else
		EMSG_RET_NULL(_(e_nopresub));
	    break;

      case Magic('1'):
      case Magic('2'):
      case Magic('3'):
      case Magic('4'):
      case Magic('5'):
      case Magic('6'):
      case Magic('7'):
      case Magic('8'):
      case Magic('9'):
	    {
		int		    refnum;

		refnum = c - Magic('0');
		if (!seen_endbrace(refnum))
		    return NULL;
		ret = regnode(BACKREF + refnum);
	    }
	    break;

      case Magic('z'):
	{
	    c = no_Magic(getchr());
	    switch (c)
	    {
#ifdef FEAT_SYN_HL
		case '(': if ((reg_do_extmatch & REX_SET) == 0)
			      EMSG_RET_NULL(_(e_z_not_allowed));
			  if (one_exactly)
			      EMSG_ONE_RET_NULL;
			  ret = reg(REG_ZPAREN, &flags);
			  if (ret == NULL)
			      return NULL;
			  *flagp |= flags & (HASWIDTH|SPSTART|HASNL|HASLOOKBH);
			  re_has_z = REX_SET;
			  break;

		case '1':
		case '2':
		case '3':
		case '4':
		case '5':
		case '6':
		case '7':
		case '8':
		case '9': if ((reg_do_extmatch & REX_USE) == 0)
			      EMSG_RET_NULL(_(e_z1_not_allowed));
			  ret = regnode(ZREF + c - '0');
			  re_has_z = REX_USE;
			  break;
#endif

		case 's': ret = regnode(MOPEN + 0);
			  if (re_mult_next("\\zs") == FAIL)
			      return NULL;
			  break;

		case 'e': ret = regnode(MCLOSE + 0);
			  if (re_mult_next("\\ze") == FAIL)
			      return NULL;
			  break;

		default:  EMSG_RET_NULL(_("E68: Invalid character after \\z"));
	    }
	}
	break;

      case Magic('%'):
	{
	    c = no_Magic(getchr());
	    switch (c)
	    {
		/* () without a back reference */
		case '(':
		    if (one_exactly)
			EMSG_ONE_RET_NULL;
		    ret = reg(REG_NPAREN, &flags);
		    if (ret == NULL)
			return NULL;
		    *flagp |= flags & (HASWIDTH | SPSTART | HASNL | HASLOOKBH);
		    break;

		/* Catch \%^ and \%$ regardless of where they appear in the
		 * pattern -- regardless of whether or not it makes sense. */
		case '^':
		    ret = regnode(RE_BOF);
		    break;

		case '$':
		    ret = regnode(RE_EOF);
		    break;

		case '#':
		    ret = regnode(CURSOR);
		    break;

		case 'V':
		    ret = regnode(RE_VISUAL);
		    break;

		case 'C':
		    ret = regnode(RE_COMPOSING);
		    break;

		/* \%[abc]: Emit as a list of branches, all ending at the last
		 * branch which matches nothing. */
		case '[':
			  if (one_exactly)	/* doesn't nest */
			      EMSG_ONE_RET_NULL;
			  {
			      char_u	*lastbranch;
			      char_u	*lastnode = NULL;
			      char_u	*br;

			      ret = NULL;
			      while ((c = getchr()) != ']')
			      {
				  if (c == NUL)
				      EMSG2_RET_NULL(_(e_missing_sb),
						      reg_magic == MAGIC_ALL);
				  br = regnode(BRANCH);
				  if (ret == NULL)
				      ret = br;
				  else
				      regtail(lastnode, br);

				  ungetchr();
				  one_exactly = TRUE;
				  lastnode = regatom(flagp);
				  one_exactly = FALSE;
				  if (lastnode == NULL)
				      return NULL;
			      }
			      if (ret == NULL)
				  EMSG2_RET_NULL(_(e_empty_sb),
						      reg_magic == MAGIC_ALL);
			      lastbranch = regnode(BRANCH);
			      br = regnode(NOTHING);
			      if (ret != JUST_CALC_SIZE)
			      {
				  regtail(lastnode, br);
				  regtail(lastbranch, br);
				  /* connect all branches to the NOTHING
				   * branch at the end */
				  for (br = ret; br != lastnode; )
				  {
				      if (OP(br) == BRANCH)
				      {
					  regtail(br, lastbranch);
					  br = OPERAND(br);
				      }
				      else
					  br = regnext(br);
				  }
			      }
			      *flagp &= ~(HASWIDTH | SIMPLE);
			      break;
			  }

		case 'd':   /* %d123 decimal */
		case 'o':   /* %o123 octal */
		case 'x':   /* %xab hex 2 */
		case 'u':   /* %uabcd hex 4 */
		case 'U':   /* %U1234abcd hex 8 */
			  {
			      long i;

			      switch (c)
			      {
				  case 'd': i = getdecchrs(); break;
				  case 'o': i = getoctchrs(); break;
				  case 'x': i = gethexchrs(2); break;
				  case 'u': i = gethexchrs(4); break;
				  case 'U': i = gethexchrs(8); break;
				  default:  i = -1; break;
			      }

			      if (i < 0)
				  EMSG2_RET_NULL(
					_("E678: Invalid character after %s%%[dxouU]"),
					reg_magic == MAGIC_ALL);
			      if (use_multibytecode(i))
				  ret = regnode(MULTIBYTECODE);
			      else
				  ret = regnode(EXACTLY);
			      if (i == 0)
				  regc(0x0a);
			      else
				  regmbc(i);
			      regc(NUL);
			      *flagp |= HASWIDTH;
			      break;
			  }

		default:
			  if (VIM_ISDIGIT(c) || c == '<' || c == '>'
								 || c == '\'')
			  {
			      long_u	n = 0;
			      int	cmp;

			      cmp = c;
			      if (cmp == '<' || cmp == '>')
				  c = getchr();
			      while (VIM_ISDIGIT(c))
			      {
				  n = n * 10 + (c - '0');
				  c = getchr();
			      }
			      if (c == '\'' && n == 0)
			      {
				  /* "\%'m", "\%<'m" and "\%>'m": Mark */
				  c = getchr();
				  ret = regnode(RE_MARK);
				  if (ret == JUST_CALC_SIZE)
				      regsize += 2;
				  else
				  {
				      *regcode++ = c;
				      *regcode++ = cmp;
				  }
				  break;
			      }
			      else if (c == 'l' || c == 'c' || c == 'v')
			      {
				  if (c == 'l')
				  {
				      ret = regnode(RE_LNUM);
				      if (save_prev_at_start)
					  at_start = TRUE;
				  }
				  else if (c == 'c')
				      ret = regnode(RE_COL);
				  else
				      ret = regnode(RE_VCOL);
				  if (ret == JUST_CALC_SIZE)
				      regsize += 5;
				  else
				  {
				      /* put the number and the optional
				       * comparator after the opcode */
				      regcode = re_put_long(regcode, n);
				      *regcode++ = cmp;
				  }
				  break;
			      }
			  }

			  EMSG2_RET_NULL(_("E71: Invalid character after %s%%"),
						      reg_magic == MAGIC_ALL);
	    }
	}
	break;

      case Magic('['):
collection:
	{
	    char_u	*lp;

	    /*
	     * If there is no matching ']', we assume the '[' is a normal
	     * character.  This makes 'incsearch' and ":help [" work.
	     */
	    lp = skip_anyof(regparse);
	    if (*lp == ']')	/* there is a matching ']' */
	    {
		int	startc = -1;	/* > 0 when next '-' is a range */
		int	endc;

		/*
		 * In a character class, different parsing rules apply.
		 * Not even \ is special anymore, nothing is.
		 */
		if (*regparse == '^')	    /* Complement of range. */
		{
		    ret = regnode(ANYBUT + extra);
		    regparse++;
		}
		else
		    ret = regnode(ANYOF + extra);

		/* At the start ']' and '-' mean the literal character. */
		if (*regparse == ']' || *regparse == '-')
		{
		    startc = *regparse;
		    regc(*regparse++);
		}

		while (*regparse != NUL && *regparse != ']')
		{
		    if (*regparse == '-')
		    {
			++regparse;
			/* The '-' is not used for a range at the end and
			 * after or before a '\n'. */
			if (*regparse == ']' || *regparse == NUL
				|| startc == -1
				|| (regparse[0] == '\\' && regparse[1] == 'n'))
			{
			    regc('-');
			    startc = '-';	/* [--x] is a range */
			}
			else
			{
			    /* Also accept "a-[.z.]" */
			    endc = 0;
			    if (*regparse == '[')
				endc = get_coll_element(&regparse);
			    if (endc == 0)
			    {
				if (has_mbyte)
				    endc = mb_ptr2char_adv(&regparse);
				else
				    endc = *regparse++;
			    }

			    /* Handle \o40, \x20 and \u20AC style sequences */
			    if (endc == '\\' && !reg_cpo_lit && !reg_cpo_bsl)
				endc = coll_get_char();

			    if (startc > endc)
				EMSG_RET_NULL(_(e_reverse_range));
			    if (has_mbyte && ((*mb_char2len)(startc) > 1
						 || (*mb_char2len)(endc) > 1))
			    {
				/* Limit to a range of 256 chars. */
				if (endc > startc + 256)
				    EMSG_RET_NULL(_(e_large_class));
				while (++startc <= endc)
				    regmbc(startc);
			    }
			    else
			    {
#ifdef EBCDIC
				int	alpha_only = FALSE;

				/* for alphabetical range skip the gaps
				 * 'i'-'j', 'r'-'s', 'I'-'J' and 'R'-'S'.  */
				if (isalpha(startc) && isalpha(endc))
				    alpha_only = TRUE;
#endif
				while (++startc <= endc)
#ifdef EBCDIC
				    if (!alpha_only || isalpha(startc))
#endif
					regc(startc);
			    }
			    startc = -1;
			}
		    }
		    /*
		     * Only "\]", "\^", "\]" and "\\" are special in Vi.  Vim
		     * accepts "\t", "\e", etc., but only when the 'l' flag in
		     * 'cpoptions' is not included.
		     * Posix doesn't recognize backslash at all.
		     */
		    else if (*regparse == '\\'
			    && !reg_cpo_bsl
			    && (vim_strchr(REGEXP_INRANGE, regparse[1]) != NULL
				|| (!reg_cpo_lit
				    && vim_strchr(REGEXP_ABBR,
						       regparse[1]) != NULL)))
		    {
			regparse++;
			if (*regparse == 'n')
			{
			    /* '\n' in range: also match NL */
			    if (ret != JUST_CALC_SIZE)
			    {
				/* Using \n inside [^] does not change what
				 * matches. "[^\n]" is the same as ".". */
				if (*ret == ANYOF)
				{
				    *ret = ANYOF + ADD_NL;
				    *flagp |= HASNL;
				}
				/* else: must have had a \n already */
			    }
			    regparse++;
			    startc = -1;
			}
			else if (*regparse == 'd'
				|| *regparse == 'o'
				|| *regparse == 'x'
				|| *regparse == 'u'
				|| *regparse == 'U')
			{
			    startc = coll_get_char();
			    if (startc == 0)
				regc(0x0a);
			    else
				regmbc(startc);
			}
			else
			{
			    startc = backslash_trans(*regparse++);
			    regc(startc);
			}
		    }
		    else if (*regparse == '[')
		    {
			int c_class;
			int cu;

			c_class = get_char_class(&regparse);
			startc = -1;
			/* Characters assumed to be 8 bits! */
			switch (c_class)
			{
			    case CLASS_NONE:
				c_class = get_equi_class(&regparse);
				if (c_class != 0)
				{
				    /* produce equivalence class */
				    reg_equi_class(c_class);
				}
				else if ((c_class =
					    get_coll_element(&regparse)) != 0)
				{
				    /* produce a collating element */
				    regmbc(c_class);
				}
				else
				{
				    /* literal '[', allow [[-x] as a range */
				    startc = *regparse++;
				    regc(startc);
				}
				break;
			    case CLASS_ALNUM:
				for (cu = 1; cu < 128; cu++)
				    if (isalnum(cu))
					regmbc(cu);
				break;
			    case CLASS_ALPHA:
				for (cu = 1; cu < 128; cu++)
				    if (isalpha(cu))
					regmbc(cu);
				break;
			    case CLASS_BLANK:
				regc(' ');
				regc('\t');
				break;
			    case CLASS_CNTRL:
				for (cu = 1; cu <= 127; cu++)
				    if (iscntrl(cu))
					regmbc(cu);
				break;
			    case CLASS_DIGIT:
				for (cu = 1; cu <= 127; cu++)
				    if (VIM_ISDIGIT(cu))
					regmbc(cu);
				break;
			    case CLASS_GRAPH:
				for (cu = 1; cu <= 127; cu++)
				    if (isgraph(cu))
					regmbc(cu);
				break;
			    case CLASS_LOWER:
				for (cu = 1; cu <= 255; cu++)
				    if (MB_ISLOWER(cu) && cu != 170
								 && cu != 186)
					regmbc(cu);
				break;
			    case CLASS_PRINT:
				for (cu = 1; cu <= 255; cu++)
				    if (vim_isprintc(cu))
					regmbc(cu);
				break;
			    case CLASS_PUNCT:
				for (cu = 1; cu < 128; cu++)
				    if (ispunct(cu))
					regmbc(cu);
				break;
			    case CLASS_SPACE:
				for (cu = 9; cu <= 13; cu++)
				    regc(cu);
				regc(' ');
				break;
			    case CLASS_UPPER:
				for (cu = 1; cu <= 255; cu++)
				    if (MB_ISUPPER(cu))
					regmbc(cu);
				break;
			    case CLASS_XDIGIT:
				for (cu = 1; cu <= 255; cu++)
				    if (vim_isxdigit(cu))
					regmbc(cu);
				break;
			    case CLASS_TAB:
				regc('\t');
				break;
			    case CLASS_RETURN:
				regc('\r');
				break;
			    case CLASS_BACKSPACE:
				regc('\b');
				break;
			    case CLASS_ESCAPE:
				regc('\033');
				break;
			}
		    }
		    else
		    {
			if (has_mbyte)
			{
			    int	len;

			    /* produce a multibyte character, including any
			     * following composing characters */
			    startc = mb_ptr2char(regparse);
			    len = (*mb_ptr2len)(regparse);
			    if (enc_utf8 && utf_char2len(startc) != len)
				startc = -1;	/* composing chars */
			    while (--len >= 0)
				regc(*regparse++);
			}
			else
			{
			    startc = *regparse++;
			    regc(startc);
			}
		    }
		}
		regc(NUL);
		prevchr_len = 1;	/* last char was the ']' */
		if (*regparse != ']')
		    EMSG_RET_NULL(_(e_toomsbra));	/* Cannot happen? */
		skipchr();	    /* let's be friends with the lexer again */
		*flagp |= HASWIDTH | SIMPLE;
		break;
	    }
	    else if (reg_strict)
		EMSG2_RET_NULL(_(e_missingbracket), reg_magic > MAGIC_OFF);
	}
	/* FALLTHROUGH */

      default:
	{
	    int		len;

	    /* A multi-byte character is handled as a separate atom if it's
	     * before a multi and when it's a composing char. */
	    if (use_multibytecode(c))
	    {
do_multibyte:
		ret = regnode(MULTIBYTECODE);
		regmbc(c);
		*flagp |= HASWIDTH | SIMPLE;
		break;
	    }

	    ret = regnode(EXACTLY);

	    /*
	     * Append characters as long as:
	     * - there is no following multi, we then need the character in
	     *   front of it as a single character operand
	     * - not running into a Magic character
	     * - "one_exactly" is not set
	     * But always emit at least one character.  Might be a Multi,
	     * e.g., a "[" without matching "]".
	     */
	    for (len = 0; c != NUL && (len == 0
			|| (re_multi_type(peekchr()) == NOT_MULTI
			    && !one_exactly
			    && !is_Magic(c))); ++len)
	    {
		c = no_Magic(c);
		if (has_mbyte)
		{
		    regmbc(c);
		    if (enc_utf8)
		    {
			int	l;

			/* Need to get composing character too. */
			for (;;)
			{
			    l = utf_ptr2len(regparse);
			    if (!UTF_COMPOSINGLIKE(regparse, regparse + l))
				break;
			    regmbc(utf_ptr2char(regparse));
			    skipchr();
			}
		    }
		}
		else
		    regc(c);
		c = getchr();
	    }
	    ungetchr();

	    regc(NUL);
	    *flagp |= HASWIDTH;
	    if (len == 1)
		*flagp |= SIMPLE;
	}
	break;
    }

    return ret;
}

/*
 * Return TRUE if MULTIBYTECODE should be used instead of EXACTLY for
 * character "c".
 */
    static int
use_multibytecode(int c)
{
    return has_mbyte && (*mb_char2len)(c) > 1
		     && (re_multi_type(peekchr()) != NOT_MULTI
			     || (enc_utf8 && utf_iscomposing(c)));
}

/*
 * Emit a node.
 * Return pointer to generated code.
 */
    static char_u *
regnode(int op)
{
    char_u  *ret;

    ret = regcode;
    if (ret == JUST_CALC_SIZE)
	regsize += 3;
    else
    {
	*regcode++ = op;
	*regcode++ = NUL;		/* Null "next" pointer. */
	*regcode++ = NUL;
    }
    return ret;
}

/*
 * Emit (if appropriate) a byte of code
 */
    static void
regc(int b)
{
    if (regcode == JUST_CALC_SIZE)
	regsize++;
    else
	*regcode++ = b;
}

/*
 * Emit (if appropriate) a multi-byte character of code
 */
    static void
regmbc(int c)
{
    if (!has_mbyte && c > 0xff)
	return;
    if (regcode == JUST_CALC_SIZE)
	regsize += (*mb_char2len)(c);
    else
	regcode += (*mb_char2bytes)(c, regcode);
}

/*
 * Insert an operator in front of already-emitted operand
 *
 * Means relocating the operand.
 */
    static void
reginsert(int op, char_u *opnd)
{
    char_u	*src;
    char_u	*dst;
    char_u	*place;

    if (regcode == JUST_CALC_SIZE)
    {
	regsize += 3;
	return;
    }
    src = regcode;
    regcode += 3;
    dst = regcode;
    while (src > opnd)
	*--dst = *--src;

    place = opnd;		/* Op node, where operand used to be. */
    *place++ = op;
    *place++ = NUL;
    *place = NUL;
}

/*
 * Insert an operator in front of already-emitted operand.
 * Add a number to the operator.
 */
    static void
reginsert_nr(int op, long val, char_u *opnd)
{
    char_u	*src;
    char_u	*dst;
    char_u	*place;

    if (regcode == JUST_CALC_SIZE)
    {
	regsize += 7;
	return;
    }
    src = regcode;
    regcode += 7;
    dst = regcode;
    while (src > opnd)
	*--dst = *--src;

    place = opnd;		/* Op node, where operand used to be. */
    *place++ = op;
    *place++ = NUL;
    *place++ = NUL;
    place = re_put_long(place, (long_u)val);
}

/*
 * Insert an operator in front of already-emitted operand.
 * The operator has the given limit values as operands.  Also set next pointer.
 *
 * Means relocating the operand.
 */
    static void
reginsert_limits(
    int		op,
    long	minval,
    long	maxval,
    char_u	*opnd)
{
    char_u	*src;
    char_u	*dst;
    char_u	*place;

    if (regcode == JUST_CALC_SIZE)
    {
	regsize += 11;
	return;
    }
    src = regcode;
    regcode += 11;
    dst = regcode;
    while (src > opnd)
	*--dst = *--src;

    place = opnd;		/* Op node, where operand used to be. */
    *place++ = op;
    *place++ = NUL;
    *place++ = NUL;
    place = re_put_long(place, (long_u)minval);
    place = re_put_long(place, (long_u)maxval);
    regtail(opnd, place);
}

/*
 * Write a long as four bytes at "p" and return pointer to the next char.
 */
    static char_u *
re_put_long(char_u *p, long_u val)
{
    *p++ = (char_u) ((val >> 24) & 0377);
    *p++ = (char_u) ((val >> 16) & 0377);
    *p++ = (char_u) ((val >> 8) & 0377);
    *p++ = (char_u) (val & 0377);
    return p;
}

/*
 * Set the next-pointer at the end of a node chain.
 */
    static void
regtail(char_u *p, char_u *val)
{
    char_u	*scan;
    char_u	*temp;
    int		offset;

    if (p == JUST_CALC_SIZE)
	return;

    /* Find last node. */
    scan = p;
    for (;;)
    {
	temp = regnext(scan);
	if (temp == NULL)
	    break;
	scan = temp;
    }

    if (OP(scan) == BACK)
	offset = (int)(scan - val);
    else
	offset = (int)(val - scan);
    /* When the offset uses more than 16 bits it can no longer fit in the two
     * bytes available.  Use a global flag to avoid having to check return
     * values in too many places. */
    if (offset > 0xffff)
	reg_toolong = TRUE;
    else
    {
	*(scan + 1) = (char_u) (((unsigned)offset >> 8) & 0377);
	*(scan + 2) = (char_u) (offset & 0377);
    }
}

/*
 * Like regtail, on item after a BRANCH; nop if none.
 */
    static void
regoptail(char_u *p, char_u *val)
{
    /* When op is neither BRANCH nor BRACE_COMPLEX0-9, it is "operandless" */
    if (p == NULL || p == JUST_CALC_SIZE
	    || (OP(p) != BRANCH
		&& (OP(p) < BRACE_COMPLEX || OP(p) > BRACE_COMPLEX + 9)))
	return;
    regtail(OPERAND(p), val);
}

/*
 * Functions for getting characters from the regexp input.
 */
/*
 * Start parsing at "str".
 */
    static void
initchr(char_u *str)
{
    regparse = str;
    prevchr_len = 0;
    curchr = prevprevchr = prevchr = nextchr = -1;
    at_start = TRUE;
    prev_at_start = FALSE;
}

/*
 * Save the current parse state, so that it can be restored and parsing
 * starts in the same state again.
 */
    static void
save_parse_state(parse_state_T *ps)
{
    ps->regparse = regparse;
    ps->prevchr_len = prevchr_len;
    ps->curchr = curchr;
    ps->prevchr = prevchr;
    ps->prevprevchr = prevprevchr;
    ps->nextchr = nextchr;
    ps->at_start = at_start;
    ps->prev_at_start = prev_at_start;
    ps->regnpar = regnpar;
}

/*
 * Restore a previously saved parse state.
 */
    static void
restore_parse_state(parse_state_T *ps)
{
    regparse = ps->regparse;
    prevchr_len = ps->prevchr_len;
    curchr = ps->curchr;
    prevchr = ps->prevchr;
    prevprevchr = ps->prevprevchr;
    nextchr = ps->nextchr;
    at_start = ps->at_start;
    prev_at_start = ps->prev_at_start;
    regnpar = ps->regnpar;
}


/*
 * Get the next character without advancing.
 */
    static int
peekchr(void)
{
    static int	after_slash = FALSE;

    if (curchr == -1)
    {
	switch (curchr = regparse[0])
	{
	case '.':
	case '[':
	case '~':
	    /* magic when 'magic' is on */
	    if (reg_magic >= MAGIC_ON)
		curchr = Magic(curchr);
	    break;
	case '(':
	case ')':
	case '{':
	case '%':
	case '+':
	case '=':
	case '?':
	case '@':
	case '!':
	case '&':
	case '|':
	case '<':
	case '>':
	case '#':	/* future ext. */
	case '"':	/* future ext. */
	case '\'':	/* future ext. */
	case ',':	/* future ext. */
	case '-':	/* future ext. */
	case ':':	/* future ext. */
	case ';':	/* future ext. */
	case '`':	/* future ext. */
	case '/':	/* Can't be used in / command */
	    /* magic only after "\v" */
	    if (reg_magic == MAGIC_ALL)
		curchr = Magic(curchr);
	    break;
	case '*':
	    /* * is not magic as the very first character, eg "?*ptr", when
	     * after '^', eg "/^*ptr" and when after "\(", "\|", "\&".  But
	     * "\(\*" is not magic, thus must be magic if "after_slash" */
	    if (reg_magic >= MAGIC_ON
		    && !at_start
		    && !(prev_at_start && prevchr == Magic('^'))
		    && (after_slash
			|| (prevchr != Magic('(')
			    && prevchr != Magic('&')
			    && prevchr != Magic('|'))))
		curchr = Magic('*');
	    break;
	case '^':
	    /* '^' is only magic as the very first character and if it's after
	     * "\(", "\|", "\&' or "\n" */
	    if (reg_magic >= MAGIC_OFF
		    && (at_start
			|| reg_magic == MAGIC_ALL
			|| prevchr == Magic('(')
			|| prevchr == Magic('|')
			|| prevchr == Magic('&')
			|| prevchr == Magic('n')
			|| (no_Magic(prevchr) == '('
			    && prevprevchr == Magic('%'))))
	    {
		curchr = Magic('^');
		at_start = TRUE;
		prev_at_start = FALSE;
	    }
	    break;
	case '$':
	    /* '$' is only magic as the very last char and if it's in front of
	     * either "\|", "\)", "\&", or "\n" */
	    if (reg_magic >= MAGIC_OFF)
	    {
		char_u *p = regparse + 1;
		int is_magic_all = (reg_magic == MAGIC_ALL);

		/* ignore \c \C \m \M \v \V and \Z after '$' */
		while (p[0] == '\\' && (p[1] == 'c' || p[1] == 'C'
				|| p[1] == 'm' || p[1] == 'M'
				|| p[1] == 'v' || p[1] == 'V' || p[1] == 'Z'))
		{
		    if (p[1] == 'v')
			is_magic_all = TRUE;
		    else if (p[1] == 'm' || p[1] == 'M' || p[1] == 'V')
			is_magic_all = FALSE;
		    p += 2;
		}
		if (p[0] == NUL
			|| (p[0] == '\\'
			    && (p[1] == '|' || p[1] == '&' || p[1] == ')'
				|| p[1] == 'n'))
			|| (is_magic_all
			       && (p[0] == '|' || p[0] == '&' || p[0] == ')'))
			|| reg_magic == MAGIC_ALL)
		    curchr = Magic('$');
	    }
	    break;
	case '\\':
	    {
		int c = regparse[1];

		if (c == NUL)
		    curchr = '\\';	/* trailing '\' */
		else if (
#ifdef EBCDIC
			vim_strchr(META, c)
#else
			c <= '~' && META_flags[c]
#endif
			)
		{
		    /*
		     * META contains everything that may be magic sometimes,
		     * except ^ and $ ("\^" and "\$" are only magic after
		     * "\V").  We now fetch the next character and toggle its
		     * magicness.  Therefore, \ is so meta-magic that it is
		     * not in META.
		     */
		    curchr = -1;
		    prev_at_start = at_start;
		    at_start = FALSE;	/* be able to say "/\*ptr" */
		    ++regparse;
		    ++after_slash;
		    peekchr();
		    --regparse;
		    --after_slash;
		    curchr = toggle_Magic(curchr);
		}
		else if (vim_strchr(REGEXP_ABBR, c))
		{
		    /*
		     * Handle abbreviations, like "\t" for TAB -- webb
		     */
		    curchr = backslash_trans(c);
		}
		else if (reg_magic == MAGIC_NONE && (c == '$' || c == '^'))
		    curchr = toggle_Magic(c);
		else
		{
		    /*
		     * Next character can never be (made) magic?
		     * Then backslashing it won't do anything.
		     */
		    if (has_mbyte)
			curchr = (*mb_ptr2char)(regparse + 1);
		    else
			curchr = c;
		}
		break;
	    }

	default:
	    if (has_mbyte)
		curchr = (*mb_ptr2char)(regparse);
	}
    }

    return curchr;
}

/*
 * Eat one lexed character.  Do this in a way that we can undo it.
 */
    static void
skipchr(void)
{
    /* peekchr() eats a backslash, do the same here */
    if (*regparse == '\\')
	prevchr_len = 1;
    else
	prevchr_len = 0;
    if (regparse[prevchr_len] != NUL)
    {
	if (enc_utf8)
	    /* exclude composing chars that mb_ptr2len does include */
	    prevchr_len += utf_ptr2len(regparse + prevchr_len);
	else if (has_mbyte)
	    prevchr_len += (*mb_ptr2len)(regparse + prevchr_len);
	else
	    ++prevchr_len;
    }
    regparse += prevchr_len;
    prev_at_start = at_start;
    at_start = FALSE;
    prevprevchr = prevchr;
    prevchr = curchr;
    curchr = nextchr;	    /* use previously unget char, or -1 */
    nextchr = -1;
}

/*
 * Skip a character while keeping the value of prev_at_start for at_start.
 * prevchr and prevprevchr are also kept.
 */
    static void
skipchr_keepstart(void)
{
    int as = prev_at_start;
    int pr = prevchr;
    int prpr = prevprevchr;

    skipchr();
    at_start = as;
    prevchr = pr;
    prevprevchr = prpr;
}

/*
 * Get the next character from the pattern. We know about magic and such, so
 * therefore we need a lexical analyzer.
 */
    static int
getchr(void)
{
    int chr = peekchr();

    skipchr();
    return chr;
}

/*
 * put character back.  Works only once!
 */
    static void
ungetchr(void)
{
    nextchr = curchr;
    curchr = prevchr;
    prevchr = prevprevchr;
    at_start = prev_at_start;
    prev_at_start = FALSE;

    /* Backup regparse, so that it's at the same position as before the
     * getchr(). */
    regparse -= prevchr_len;
}

/*
 * Get and return the value of the hex string at the current position.
 * Return -1 if there is no valid hex number.
 * The position is updated:
 *     blahblah\%x20asdf
 *	   before-^ ^-after
 * The parameter controls the maximum number of input characters. This will be
 * 2 when reading a \%x20 sequence and 4 when reading a \%u20AC sequence.
 */
    static long
gethexchrs(int maxinputlen)
{
    long_u	nr = 0;
    int		c;
    int		i;

    for (i = 0; i < maxinputlen; ++i)
    {
	c = regparse[0];
	if (!vim_isxdigit(c))
	    break;
	nr <<= 4;
	nr |= hex2nr(c);
	++regparse;
    }

    if (i == 0)
	return -1;
    return (long)nr;
}

/*
 * Get and return the value of the decimal string immediately after the
 * current position. Return -1 for invalid.  Consumes all digits.
 */
    static long
getdecchrs(void)
{
    long_u	nr = 0;
    int		c;
    int		i;

    for (i = 0; ; ++i)
    {
	c = regparse[0];
	if (c < '0' || c > '9')
	    break;
	nr *= 10;
	nr += c - '0';
	++regparse;
	curchr = -1; /* no longer valid */
    }

    if (i == 0)
	return -1;
    return (long)nr;
}

/*
 * get and return the value of the octal string immediately after the current
 * position. Return -1 for invalid, or 0-255 for valid. Smart enough to handle
 * numbers > 377 correctly (for example, 400 is treated as 40) and doesn't
 * treat 8 or 9 as recognised characters. Position is updated:
 *     blahblah\%o210asdf
 *	   before-^  ^-after
 */
    static long
getoctchrs(void)
{
    long_u	nr = 0;
    int		c;
    int		i;

    for (i = 0; i < 3 && nr < 040; ++i)
    {
	c = regparse[0];
	if (c < '0' || c > '7')
	    break;
	nr <<= 3;
	nr |= hex2nr(c);
	++regparse;
    }

    if (i == 0)
	return -1;
    return (long)nr;
}

/*
 * Get a number after a backslash that is inside [].
 * When nothing is recognized return a backslash.
 */
    static int
coll_get_char(void)
{
    long	nr = -1;

    switch (*regparse++)
    {
	case 'd': nr = getdecchrs(); break;
	case 'o': nr = getoctchrs(); break;
	case 'x': nr = gethexchrs(2); break;
	case 'u': nr = gethexchrs(4); break;
	case 'U': nr = gethexchrs(8); break;
    }
    if (nr < 0)
    {
	/* If getting the number fails be backwards compatible: the character
	 * is a backslash. */
	--regparse;
	nr = '\\';
    }
    return nr;
}

/*
 * read_limits - Read two integers to be taken as a minimum and maximum.
 * If the first character is '-', then the range is reversed.
 * Should end with 'end'.  If minval is missing, zero is default, if maxval is
 * missing, a very big number is the default.
 */
    static int
read_limits(long *minval, long *maxval)
{
    int		reverse = FALSE;
    char_u	*first_char;
    long	tmp;

    if (*regparse == '-')
    {
	/* Starts with '-', so reverse the range later */
	regparse++;
	reverse = TRUE;
    }
    first_char = regparse;
    *minval = getdigits(&regparse);
    if (*regparse == ',')	    /* There is a comma */
    {
	if (vim_isdigit(*++regparse))
	    *maxval = getdigits(&regparse);
	else
	    *maxval = MAX_LIMIT;
    }
    else if (VIM_ISDIGIT(*first_char))
	*maxval = *minval;	    /* It was \{n} or \{-n} */
    else
	*maxval = MAX_LIMIT;	    /* It was \{} or \{-} */
    if (*regparse == '\\')
	regparse++;	/* Allow either \{...} or \{...\} */
    if (*regparse != '}')
	EMSG2_RET_FAIL(_("E554: Syntax error in %s{...}"),
						       reg_magic == MAGIC_ALL);

    /*
     * Reverse the range if there was a '-', or make sure it is in the right
     * order otherwise.
     */
    if ((!reverse && *minval > *maxval) || (reverse && *minval < *maxval))
    {
	tmp = *minval;
	*minval = *maxval;
	*maxval = tmp;
    }
    skipchr();		/* let's be friends with the lexer again */
    return OK;
}

/*
 * vim_regexec and friends
 */

/*
 * Global work variables for vim_regexec().
 */

/*
 * Structure used to save the current input state, when it needs to be
 * restored after trying a match.  Used by reg_save() and reg_restore().
 * Also stores the length of "backpos".
 */
typedef struct
{
    union
    {
	char_u	*ptr;	/* rex.input pointer, for single-line regexp */
	lpos_T	pos;	/* rex.input pos, for multi-line regexp */
    } rs_u;
    int		rs_len;
} regsave_T;

/* struct to save start/end pointer/position in for \(\) */
typedef struct
{
    union
    {
	char_u	*ptr;
	lpos_T	pos;
    } se_u;
} save_se_T;

/* used for BEHIND and NOBEHIND matching */
typedef struct regbehind_S
{
    regsave_T	save_after;
    regsave_T	save_behind;
    int		save_need_clear_subexpr;
    save_se_T   save_start[NSUBEXP];
    save_se_T   save_end[NSUBEXP];
} regbehind_T;

static long	bt_regexec_both(char_u *line, colnr_T col, proftime_T *tm, int *timed_out);
static long	regtry(bt_regprog_T *prog, colnr_T col, proftime_T *tm, int *timed_out);
static void	cleanup_subexpr(void);
#ifdef FEAT_SYN_HL
static void	cleanup_zsubexpr(void);
#endif
static void	save_subexpr(regbehind_T *bp);
static void	restore_subexpr(regbehind_T *bp);
static void	reg_nextline(void);
static void	reg_save(regsave_T *save, garray_T *gap);
static void	reg_restore(regsave_T *save, garray_T *gap);
static int	reg_save_equal(regsave_T *save);
static void	save_se_multi(save_se_T *savep, lpos_T *posp);
static void	save_se_one(save_se_T *savep, char_u **pp);

/* Save the sub-expressions before attempting a match. */
#define save_se(savep, posp, pp) \
    REG_MULTI ? save_se_multi((savep), (posp)) : save_se_one((savep), (pp))

/* After a failed match restore the sub-expressions. */
#define restore_se(savep, posp, pp) { \
    if (REG_MULTI) \
	*(posp) = (savep)->se_u.pos; \
    else \
	*(pp) = (savep)->se_u.ptr; }

static int	re_num_cmp(long_u val, char_u *scan);
static int	match_with_backref(linenr_T start_lnum, colnr_T start_col, linenr_T end_lnum, colnr_T end_col, int *bytelen);
static int	regmatch(char_u *prog, proftime_T *tm, int *timed_out);
static int	regrepeat(char_u *p, long maxcount);

#ifdef DEBUG
int		regnarrate = 0;
#endif

/*
 * Sometimes need to save a copy of a line.  Since alloc()/free() is very
 * slow, we keep one allocated piece of memory and only re-allocate it when
 * it's too small.  It's freed in bt_regexec_both() when finished.
 */
static char_u	*reg_tofree = NULL;
static unsigned	reg_tofreelen;

/*
 * Structure used to store the execution state of the regex engine.
 * Which ones are set depends on whether a single-line or multi-line match is
 * done:
 *			single-line		multi-line
 * reg_match		&regmatch_T		NULL
 * reg_mmatch		NULL			&regmmatch_T
 * reg_startp		reg_match->startp	<invalid>
 * reg_endp		reg_match->endp		<invalid>
 * reg_startpos		<invalid>		reg_mmatch->startpos
 * reg_endpos		<invalid>		reg_mmatch->endpos
 * reg_win		NULL			window in which to search
 * reg_buf		curbuf			buffer in which to search
 * reg_firstlnum	<invalid>		first line in which to search
 * reg_maxline		0			last line nr
 * reg_line_lbr		FALSE or TRUE		FALSE
 */
typedef struct {
    regmatch_T		*reg_match;
    regmmatch_T		*reg_mmatch;
    char_u		**reg_startp;
    char_u		**reg_endp;
    lpos_T		*reg_startpos;
    lpos_T		*reg_endpos;
    win_T		*reg_win;
    buf_T		*reg_buf;
    linenr_T		reg_firstlnum;
    linenr_T		reg_maxline;
    int			reg_line_lbr;	/* "\n" in string is line break */

    // The current match-position is stord in these variables:
    linenr_T	lnum;		// line number, relative to first line
    char_u	*line;		// start of current line
    char_u	*input;		// current input, points into "regline"

    int	need_clear_subexpr;	// subexpressions still need to be cleared
#ifdef FEAT_SYN_HL
    int	need_clear_zsubexpr;	// extmatch subexpressions still need to be
				// cleared
#endif

    /* Internal copy of 'ignorecase'.  It is set at each call to vim_regexec().
     * Normally it gets the value of "rm_ic" or "rmm_ic", but when the pattern
     * contains '\c' or '\C' the value is overruled. */
    int			reg_ic;

    /* Similar to "reg_ic", but only for 'combining' characters.  Set with \Z
     * flag in the regexp.  Defaults to false, always. */
    int			reg_icombine;

    /* Copy of "rmm_maxcol": maximum column to search for a match.  Zero when
     * there is no maximum. */
    colnr_T		reg_maxcol;

    // State for the NFA engine regexec.
    int nfa_has_zend;	    // NFA regexp \ze operator encountered.
    int nfa_has_backref;    // NFA regexp \1 .. \9 encountered.
    int nfa_nsubexpr;	    // Number of sub expressions actually being used
			    // during execution. 1 if only the whole match
			    // (subexpr 0) is used.
    // listid is global, so that it increases on recursive calls to
    // nfa_regmatch(), which means we don't have to clear the lastlist field of
    // all the states.
    int nfa_listid;
    int nfa_alt_listid;

#ifdef FEAT_SYN_HL
    int nfa_has_zsubexpr;   // NFA regexp has \z( ), set zsubexpr.
#endif
} regexec_T;

static regexec_T	rex;
static int		rex_in_use = FALSE;


/* Values for rs_state in regitem_T. */
typedef enum regstate_E
{
    RS_NOPEN = 0	/* NOPEN and NCLOSE */
    , RS_MOPEN		/* MOPEN + [0-9] */
    , RS_MCLOSE		/* MCLOSE + [0-9] */
#ifdef FEAT_SYN_HL
    , RS_ZOPEN		/* ZOPEN + [0-9] */
    , RS_ZCLOSE		/* ZCLOSE + [0-9] */
#endif
    , RS_BRANCH		/* BRANCH */
    , RS_BRCPLX_MORE	/* BRACE_COMPLEX and trying one more match */
    , RS_BRCPLX_LONG	/* BRACE_COMPLEX and trying longest match */
    , RS_BRCPLX_SHORT	/* BRACE_COMPLEX and trying shortest match */
    , RS_NOMATCH	/* NOMATCH */
    , RS_BEHIND1	/* BEHIND / NOBEHIND matching rest */
    , RS_BEHIND2	/* BEHIND / NOBEHIND matching behind part */
    , RS_STAR_LONG	/* STAR/PLUS/BRACE_SIMPLE longest match */
    , RS_STAR_SHORT	/* STAR/PLUS/BRACE_SIMPLE shortest match */
} regstate_T;

/*
 * When there are alternatives a regstate_T is put on the regstack to remember
 * what we are doing.
 * Before it may be another type of item, depending on rs_state, to remember
 * more things.
 */
typedef struct regitem_S
{
    regstate_T	rs_state;	/* what we are doing, one of RS_ above */
    char_u	*rs_scan;	/* current node in program */
    union
    {
	save_se_T  sesave;
	regsave_T  regsave;
    } rs_un;			/* room for saving rex.input */
    short	rs_no;		/* submatch nr or BEHIND/NOBEHIND */
} regitem_T;

static regitem_T *regstack_push(regstate_T state, char_u *scan);
static void regstack_pop(char_u **scan);

/* used for STAR, PLUS and BRACE_SIMPLE matching */
typedef struct regstar_S
{
    int		nextb;		/* next byte */
    int		nextb_ic;	/* next byte reverse case */
    long	count;
    long	minval;
    long	maxval;
} regstar_T;

/* used to store input position when a BACK was encountered, so that we now if
 * we made any progress since the last time. */
typedef struct backpos_S
{
    char_u	*bp_scan;	/* "scan" where BACK was encountered */
    regsave_T	bp_pos;		/* last input position */
} backpos_T;

/*
 * "regstack" and "backpos" are used by regmatch().  They are kept over calls
 * to avoid invoking malloc() and free() often.
 * "regstack" is a stack with regitem_T items, sometimes preceded by regstar_T
 * or regbehind_T.
 * "backpos_T" is a table with backpos_T for BACK
 */
static garray_T	regstack = {0, 0, 0, 0, NULL};
static garray_T	backpos = {0, 0, 0, 0, NULL};

/*
 * Both for regstack and backpos tables we use the following strategy of
 * allocation (to reduce malloc/free calls):
 * - Initial size is fairly small.
 * - When needed, the tables are grown bigger (8 times at first, double after
 *   that).
 * - After executing the match we free the memory only if the array has grown.
 *   Thus the memory is kept allocated when it's at the initial size.
 * This makes it fast while not keeping a lot of memory allocated.
 * A three times speed increase was observed when using many simple patterns.
 */
#define REGSTACK_INITIAL	2048
#define BACKPOS_INITIAL		64

#if defined(EXITFREE) || defined(PROTO)
    void
free_regexp_stuff(void)
{
    ga_clear(&regstack);
    ga_clear(&backpos);
    vim_free(reg_tofree);
    vim_free(reg_prev_sub);
}
#endif

/*
 * Get pointer to the line "lnum", which is relative to "reg_firstlnum".
 */
    static char_u *
reg_getline(linenr_T lnum)
{
    /* when looking behind for a match/no-match lnum is negative.  But we
     * can't go before line 1 */
    if (rex.reg_firstlnum + lnum < 1)
	return NULL;
    if (lnum > rex.reg_maxline)
	/* Must have matched the "\n" in the last line. */
	return (char_u *)"";
    return ml_get_buf(rex.reg_buf, rex.reg_firstlnum + lnum, FALSE);
}

static regsave_T behind_pos;

#ifdef FEAT_SYN_HL
static char_u	*reg_startzp[NSUBEXP];	/* Workspace to mark beginning */
static char_u	*reg_endzp[NSUBEXP];	/*   and end of \z(...\) matches */
static lpos_T	reg_startzpos[NSUBEXP];	/* idem, beginning pos */
static lpos_T	reg_endzpos[NSUBEXP];	/* idem, end pos */
#endif

/* TRUE if using multi-line regexp. */
#define REG_MULTI	(rex.reg_match == NULL)

/*
 * Match a regexp against a string.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Uses curbuf for line count and 'iskeyword'.
 * if "line_lbr" is TRUE  consider a "\n" in "line" to be a line break.
 *
 * Returns 0 for failure, number of lines contained in the match otherwise.
 */
    static int
bt_regexec_nl(
    regmatch_T	*rmp,
    char_u	*line,	/* string to match against */
    colnr_T	col,	/* column to start looking for match */
    int		line_lbr)
{
    rex.reg_match = rmp;
    rex.reg_mmatch = NULL;
    rex.reg_maxline = 0;
    rex.reg_line_lbr = line_lbr;
    rex.reg_buf = curbuf;
    rex.reg_win = NULL;
    rex.reg_ic = rmp->rm_ic;
    rex.reg_icombine = FALSE;
    rex.reg_maxcol = 0;

    return bt_regexec_both(line, col, NULL, NULL);
}

/*
 * Match a regexp against multiple lines.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Uses curbuf for line count and 'iskeyword'.
 *
 * Return zero if there is no match.  Return number of lines contained in the
 * match otherwise.
 */
    static long
bt_regexec_multi(
    regmmatch_T	*rmp,
    win_T	*win,		/* window in which to search or NULL */
    buf_T	*buf,		/* buffer in which to search */
    linenr_T	lnum,		/* nr of line to start looking for match */
    colnr_T	col,		/* column to start looking for match */
    proftime_T	*tm,		/* timeout limit or NULL */
    int		*timed_out)	/* flag set on timeout or NULL */
{
    rex.reg_match = NULL;
    rex.reg_mmatch = rmp;
    rex.reg_buf = buf;
    rex.reg_win = win;
    rex.reg_firstlnum = lnum;
    rex.reg_maxline = rex.reg_buf->b_ml.ml_line_count - lnum;
    rex.reg_line_lbr = FALSE;
    rex.reg_ic = rmp->rmm_ic;
    rex.reg_icombine = FALSE;
    rex.reg_maxcol = rmp->rmm_maxcol;

    return bt_regexec_both(NULL, col, tm, timed_out);
}

/*
 * Match a regexp against a string ("line" points to the string) or multiple
 * lines ("line" is NULL, use reg_getline()).
 * Returns 0 for failure, number of lines contained in the match otherwise.
 */
    static long
bt_regexec_both(
    char_u	*line,
    colnr_T	col,		/* column to start looking for match */
    proftime_T	*tm,		/* timeout limit or NULL */
    int		*timed_out)	/* flag set on timeout or NULL */
{
    bt_regprog_T    *prog;
    char_u	    *s;
    long	    retval = 0L;

    /* Create "regstack" and "backpos" if they are not allocated yet.
     * We allocate *_INITIAL amount of bytes first and then set the grow size
     * to much bigger value to avoid many malloc calls in case of deep regular
     * expressions.  */
    if (regstack.ga_data == NULL)
    {
	/* Use an item size of 1 byte, since we push different things
	 * onto the regstack. */
	ga_init2(&regstack, 1, REGSTACK_INITIAL);
	(void)ga_grow(&regstack, REGSTACK_INITIAL);
	regstack.ga_growsize = REGSTACK_INITIAL * 8;
    }

    if (backpos.ga_data == NULL)
    {
	ga_init2(&backpos, sizeof(backpos_T), BACKPOS_INITIAL);
	(void)ga_grow(&backpos, BACKPOS_INITIAL);
	backpos.ga_growsize = BACKPOS_INITIAL * 8;
    }

    if (REG_MULTI)
    {
	prog = (bt_regprog_T *)rex.reg_mmatch->regprog;
	line = reg_getline((linenr_T)0);
	rex.reg_startpos = rex.reg_mmatch->startpos;
	rex.reg_endpos = rex.reg_mmatch->endpos;
    }
    else
    {
	prog = (bt_regprog_T *)rex.reg_match->regprog;
	rex.reg_startp = rex.reg_match->startp;
	rex.reg_endp = rex.reg_match->endp;
    }

    /* Be paranoid... */
    if (prog == NULL || line == NULL)
    {
	emsg(_(e_null));
	goto theend;
    }

    /* Check validity of program. */
    if (prog_magic_wrong())
	goto theend;

    /* If the start column is past the maximum column: no need to try. */
    if (rex.reg_maxcol > 0 && col >= rex.reg_maxcol)
	goto theend;

    /* If pattern contains "\c" or "\C": overrule value of rex.reg_ic */
    if (prog->regflags & RF_ICASE)
	rex.reg_ic = TRUE;
    else if (prog->regflags & RF_NOICASE)
	rex.reg_ic = FALSE;

    /* If pattern contains "\Z" overrule value of rex.reg_icombine */
    if (prog->regflags & RF_ICOMBINE)
	rex.reg_icombine = TRUE;

    /* If there is a "must appear" string, look for it. */
    if (prog->regmust != NULL)
    {
	int c;

	if (has_mbyte)
	    c = (*mb_ptr2char)(prog->regmust);
	else
	    c = *prog->regmust;
	s = line + col;

	/*
	 * This is used very often, esp. for ":global".  Use three versions of
	 * the loop to avoid overhead of conditions.
	 */
	if (!rex.reg_ic && !has_mbyte)
	    while ((s = vim_strbyte(s, c)) != NULL)
	    {
		if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
		    break;		/* Found it. */
		++s;
	    }
	else if (!rex.reg_ic || (!enc_utf8 && mb_char2len(c) > 1))
	    while ((s = vim_strchr(s, c)) != NULL)
	    {
		if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
		    break;		/* Found it. */
		MB_PTR_ADV(s);
	    }
	else
	    while ((s = cstrchr(s, c)) != NULL)
	    {
		if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
		    break;		/* Found it. */
		MB_PTR_ADV(s);
	    }
	if (s == NULL)		/* Not present. */
	    goto theend;
    }

    rex.line = line;
    rex.lnum = 0;
    reg_toolong = FALSE;

    /* Simplest case: Anchored match need be tried only once. */
    if (prog->reganch)
    {
	int	c;

	if (has_mbyte)
	    c = (*mb_ptr2char)(rex.line + col);
	else
	    c = rex.line[col];
	if (prog->regstart == NUL
		|| prog->regstart == c
		|| (rex.reg_ic
		    && (((enc_utf8 && utf_fold(prog->regstart) == utf_fold(c)))
			|| (c < 255 && prog->regstart < 255 &&
			    MB_TOLOWER(prog->regstart) == MB_TOLOWER(c)))))
	    retval = regtry(prog, col, tm, timed_out);
	else
	    retval = 0;
    }
    else
    {
#ifdef FEAT_RELTIME
	int tm_count = 0;
#endif
	/* Messy cases:  unanchored match. */
	while (!got_int)
	{
	    if (prog->regstart != NUL)
	    {
		/* Skip until the char we know it must start with.
		 * Used often, do some work to avoid call overhead. */
		if (!rex.reg_ic && !has_mbyte)
		    s = vim_strbyte(rex.line + col, prog->regstart);
		else
		    s = cstrchr(rex.line + col, prog->regstart);
		if (s == NULL)
		{
		    retval = 0;
		    break;
		}
		col = (int)(s - rex.line);
	    }

	    /* Check for maximum column to try. */
	    if (rex.reg_maxcol > 0 && col >= rex.reg_maxcol)
	    {
		retval = 0;
		break;
	    }

	    retval = regtry(prog, col, tm, timed_out);
	    if (retval > 0)
		break;

	    /* if not currently on the first line, get it again */
	    if (rex.lnum != 0)
	    {
		rex.lnum = 0;
		rex.line = reg_getline((linenr_T)0);
	    }
	    if (rex.line[col] == NUL)
		break;
	    if (has_mbyte)
		col += (*mb_ptr2len)(rex.line + col);
	    else
		++col;
#ifdef FEAT_RELTIME
	    /* Check for timeout once in a twenty times to avoid overhead. */
	    if (tm != NULL && ++tm_count == 20)
	    {
		tm_count = 0;
		if (profile_passed_limit(tm))
		{
		    if (timed_out != NULL)
			*timed_out = TRUE;
		    break;
		}
	    }
#endif
	}
    }

theend:
    /* Free "reg_tofree" when it's a bit big.
     * Free regstack and backpos if they are bigger than their initial size. */
    if (reg_tofreelen > 400)
	VIM_CLEAR(reg_tofree);
    if (regstack.ga_maxlen > REGSTACK_INITIAL)
	ga_clear(&regstack);
    if (backpos.ga_maxlen > BACKPOS_INITIAL)
	ga_clear(&backpos);

    return retval;
}

#ifdef FEAT_SYN_HL
/*
 * Create a new extmatch and mark it as referenced once.
 */
    static reg_extmatch_T *
make_extmatch(void)
{
    reg_extmatch_T	*em;

    em = (reg_extmatch_T *)alloc_clear((unsigned)sizeof(reg_extmatch_T));
    if (em != NULL)
	em->refcnt = 1;
    return em;
}

/*
 * Add a reference to an extmatch.
 */
    reg_extmatch_T *
ref_extmatch(reg_extmatch_T *em)
{
    if (em != NULL)
	em->refcnt++;
    return em;
}

/*
 * Remove a reference to an extmatch.  If there are no references left, free
 * the info.
 */
    void
unref_extmatch(reg_extmatch_T *em)
{
    int i;

    if (em != NULL && --em->refcnt <= 0)
    {
	for (i = 0; i < NSUBEXP; ++i)
	    vim_free(em->matches[i]);
	vim_free(em);
    }
}
#endif

/*
 * regtry - try match of "prog" with at rex.line["col"].
 * Returns 0 for failure, number of lines contained in the match otherwise.
 */
    static long
regtry(
    bt_regprog_T	*prog,
    colnr_T		col,
    proftime_T		*tm,		/* timeout limit or NULL */
    int			*timed_out)	/* flag set on timeout or NULL */
{
    rex.input = rex.line + col;
    rex.need_clear_subexpr = TRUE;
#ifdef FEAT_SYN_HL
    // Clear the external match subpointers if necessary.
    rex.need_clear_zsubexpr = (prog->reghasz == REX_SET);
#endif

    if (regmatch(prog->program + 1, tm, timed_out) == 0)
	return 0;

    cleanup_subexpr();
    if (REG_MULTI)
    {
	if (rex.reg_startpos[0].lnum < 0)
	{
	    rex.reg_startpos[0].lnum = 0;
	    rex.reg_startpos[0].col = col;
	}
	if (rex.reg_endpos[0].lnum < 0)
	{
	    rex.reg_endpos[0].lnum = rex.lnum;
	    rex.reg_endpos[0].col = (int)(rex.input - rex.line);
	}
	else
	    /* Use line number of "\ze". */
	    rex.lnum = rex.reg_endpos[0].lnum;
    }
    else
    {
	if (rex.reg_startp[0] == NULL)
	    rex.reg_startp[0] = rex.line + col;
	if (rex.reg_endp[0] == NULL)
	    rex.reg_endp[0] = rex.input;
    }
#ifdef FEAT_SYN_HL
    /* Package any found \z(...\) matches for export. Default is none. */
    unref_extmatch(re_extmatch_out);
    re_extmatch_out = NULL;

    if (prog->reghasz == REX_SET)
    {
	int		i;

	cleanup_zsubexpr();
	re_extmatch_out = make_extmatch();
	for (i = 0; i < NSUBEXP; i++)
	{
	    if (REG_MULTI)
	    {
		/* Only accept single line matches. */
		if (reg_startzpos[i].lnum >= 0
			&& reg_endzpos[i].lnum == reg_startzpos[i].lnum
			&& reg_endzpos[i].col >= reg_startzpos[i].col)
		    re_extmatch_out->matches[i] =
			vim_strnsave(reg_getline(reg_startzpos[i].lnum)
						       + reg_startzpos[i].col,
				   reg_endzpos[i].col - reg_startzpos[i].col);
	    }
	    else
	    {
		if (reg_startzp[i] != NULL && reg_endzp[i] != NULL)
		    re_extmatch_out->matches[i] =
			    vim_strnsave(reg_startzp[i],
					(int)(reg_endzp[i] - reg_startzp[i]));
	    }
	}
    }
#endif
    return 1 + rex.lnum;
}

/*
 * Get class of previous character.
 */
    static int
reg_prev_class(void)
{
    if (rex.input > rex.line)
	return mb_get_class_buf(rex.input - 1
		       - (*mb_head_off)(rex.line, rex.input - 1), rex.reg_buf);
    return -1;
}

/*
 * Return TRUE if the current rex.input position matches the Visual area.
 */
    static int
reg_match_visual(void)
{
    pos_T	top, bot;
    linenr_T    lnum;
    colnr_T	col;
    win_T	*wp = rex.reg_win == NULL ? curwin : rex.reg_win;
    int		mode;
    colnr_T	start, end;
    colnr_T	start2, end2;
    colnr_T	cols;

    /* Check if the buffer is the current buffer. */
    if (rex.reg_buf != curbuf || VIsual.lnum == 0)
	return FALSE;

    if (VIsual_active)
    {
	if (LT_POS(VIsual, wp->w_cursor))
	{
	    top = VIsual;
	    bot = wp->w_cursor;
	}
	else
	{
	    top = wp->w_cursor;
	    bot = VIsual;
	}
	mode = VIsual_mode;
    }
    else
    {
	if (LT_POS(curbuf->b_visual.vi_start, curbuf->b_visual.vi_end))
	{
	    top = curbuf->b_visual.vi_start;
	    bot = curbuf->b_visual.vi_end;
	}
	else
	{
	    top = curbuf->b_visual.vi_end;
	    bot = curbuf->b_visual.vi_start;
	}
	mode = curbuf->b_visual.vi_mode;
    }
    lnum = rex.lnum + rex.reg_firstlnum;
    if (lnum < top.lnum || lnum > bot.lnum)
	return FALSE;

    if (mode == 'v')
    {
	col = (colnr_T)(rex.input - rex.line);
	if ((lnum == top.lnum && col < top.col)
		|| (lnum == bot.lnum && col >= bot.col + (*p_sel != 'e')))
	    return FALSE;
    }
    else if (mode == Ctrl_V)
    {
	getvvcol(wp, &top, &start, NULL, &end);
	getvvcol(wp, &bot, &start2, NULL, &end2);
	if (start2 < start)
	    start = start2;
	if (end2 > end)
	    end = end2;
	if (top.col == MAXCOL || bot.col == MAXCOL)
	    end = MAXCOL;
	cols = win_linetabsize(wp, rex.line, (colnr_T)(rex.input - rex.line));
	if (cols < start || cols > end - (*p_sel == 'e'))
	    return FALSE;
    }
    return TRUE;
}

#define ADVANCE_REGINPUT() MB_PTR_ADV(rex.input)

/*
 * The arguments from BRACE_LIMITS are stored here.  They are actually local
 * to regmatch(), but they are here to reduce the amount of stack space used
 * (it can be called recursively many times).
 */
static long	bl_minval;
static long	bl_maxval;

/*
 * regmatch - main matching routine
 *
 * Conceptually the strategy is simple: Check to see whether the current node
 * matches, push an item onto the regstack and loop to see whether the rest
 * matches, and then act accordingly.  In practice we make some effort to
 * avoid using the regstack, in particular by going through "ordinary" nodes
 * (that don't need to know whether the rest of the match failed) by a nested
 * loop.
 *
 * Returns TRUE when there is a match.  Leaves rex.input and rex.lnum just after
 * the last matched character.
 * Returns FALSE when there is no match.  Leaves rex.input and rex.lnum in an
 * undefined state!
 */
    static int
regmatch(
    char_u	*scan,		    /* Current node. */
    proftime_T	*tm UNUSED,	    /* timeout limit or NULL */
    int		*timed_out UNUSED)  /* flag set on timeout or NULL */
{
  char_u	*next;		/* Next node. */
  int		op;
  int		c;
  regitem_T	*rp;
  int		no;
  int		status;		/* one of the RA_ values: */
#define RA_FAIL		1	/* something failed, abort */
#define RA_CONT		2	/* continue in inner loop */
#define RA_BREAK	3	/* break inner loop */
#define RA_MATCH	4	/* successful match */
#define RA_NOMATCH	5	/* didn't match */
#ifdef FEAT_RELTIME
  int		tm_count = 0;
#endif

  /* Make "regstack" and "backpos" empty.  They are allocated and freed in
   * bt_regexec_both() to reduce malloc()/free() calls. */
  regstack.ga_len = 0;
  backpos.ga_len = 0;

  /*
   * Repeat until "regstack" is empty.
   */
  for (;;)
  {
    /* Some patterns may take a long time to match, e.g., "\([a-z]\+\)\+Q".
     * Allow interrupting them with CTRL-C. */
    fast_breakcheck();

#ifdef DEBUG
    if (scan != NULL && regnarrate)
    {
	mch_errmsg((char *)regprop(scan));
	mch_errmsg("(\n");
    }
#endif

    /*
     * Repeat for items that can be matched sequentially, without using the
     * regstack.
     */
    for (;;)
    {
	if (got_int || scan == NULL)
	{
	    status = RA_FAIL;
	    break;
	}
#ifdef FEAT_RELTIME
	/* Check for timeout once in a 100 times to avoid overhead. */
	if (tm != NULL && ++tm_count == 100)
	{
	    tm_count = 0;
	    if (profile_passed_limit(tm))
	    {
		if (timed_out != NULL)
		    *timed_out = TRUE;
		status = RA_FAIL;
		break;
	    }
	}
#endif
	status = RA_CONT;

#ifdef DEBUG
	if (regnarrate)
	{
	    mch_errmsg((char *)regprop(scan));
	    mch_errmsg("...\n");
# ifdef FEAT_SYN_HL
	    if (re_extmatch_in != NULL)
	    {
		int i;

		mch_errmsg(_("External submatches:\n"));
		for (i = 0; i < NSUBEXP; i++)
		{
		    mch_errmsg("    \"");
		    if (re_extmatch_in->matches[i] != NULL)
			mch_errmsg((char *)re_extmatch_in->matches[i]);
		    mch_errmsg("\"\n");
		}
	    }
# endif
	}
#endif
	next = regnext(scan);

	op = OP(scan);
	/* Check for character class with NL added. */
	if (!rex.reg_line_lbr && WITH_NL(op) && REG_MULTI
			     && *rex.input == NUL && rex.lnum <= rex.reg_maxline)
	{
	    reg_nextline();
	}
	else if (rex.reg_line_lbr && WITH_NL(op) && *rex.input == '\n')
	{
	    ADVANCE_REGINPUT();
	}
	else
	{
	  if (WITH_NL(op))
	      op -= ADD_NL;
	  if (has_mbyte)
	      c = (*mb_ptr2char)(rex.input);
	  else
	      c = *rex.input;
	  switch (op)
	  {
	  case BOL:
	    if (rex.input != rex.line)
		status = RA_NOMATCH;
	    break;

	  case EOL:
	    if (c != NUL)
		status = RA_NOMATCH;
	    break;

	  case RE_BOF:
	    /* We're not at the beginning of the file when below the first
	     * line where we started, not at the start of the line or we
	     * didn't start at the first line of the buffer. */
	    if (rex.lnum != 0 || rex.input != rex.line
				       || (REG_MULTI && rex.reg_firstlnum > 1))
		status = RA_NOMATCH;
	    break;

	  case RE_EOF:
	    if (rex.lnum != rex.reg_maxline || c != NUL)
		status = RA_NOMATCH;
	    break;

	  case CURSOR:
	    /* Check if the buffer is in a window and compare the
	     * rex.reg_win->w_cursor position to the match position. */
	    if (rex.reg_win == NULL
		    || (rex.lnum + rex.reg_firstlnum
						 != rex.reg_win->w_cursor.lnum)
		    || ((colnr_T)(rex.input - rex.line)
						 != rex.reg_win->w_cursor.col))
		status = RA_NOMATCH;
	    break;

	  case RE_MARK:
	    /* Compare the mark position to the match position. */
	    {
		int	mark = OPERAND(scan)[0];
		int	cmp = OPERAND(scan)[1];
		pos_T	*pos;

		pos = getmark_buf(rex.reg_buf, mark, FALSE);
		if (pos == NULL		     /* mark doesn't exist */
			|| pos->lnum <= 0    /* mark isn't set in reg_buf */
			|| (pos->lnum == rex.lnum + rex.reg_firstlnum
				? (pos->col == (colnr_T)(rex.input - rex.line)
				    ? (cmp == '<' || cmp == '>')
				    : (pos->col < (colnr_T)(rex.input - rex.line)
					? cmp != '>'
					: cmp != '<'))
				: (pos->lnum < rex.lnum + rex.reg_firstlnum
				    ? cmp != '>'
				    : cmp != '<')))
		    status = RA_NOMATCH;
	    }
	    break;

	  case RE_VISUAL:
	    if (!reg_match_visual())
		status = RA_NOMATCH;
	    break;

	  case RE_LNUM:
	    if (!REG_MULTI || !re_num_cmp((long_u)(rex.lnum + rex.reg_firstlnum),
									scan))
		status = RA_NOMATCH;
	    break;

	  case RE_COL:
	    if (!re_num_cmp((long_u)(rex.input - rex.line) + 1, scan))
		status = RA_NOMATCH;
	    break;

	  case RE_VCOL:
	    if (!re_num_cmp((long_u)win_linetabsize(
			    rex.reg_win == NULL ? curwin : rex.reg_win,
			    rex.line, (colnr_T)(rex.input - rex.line)) + 1, scan))
		status = RA_NOMATCH;
	    break;

	  case BOW:	/* \<word; rex.input points to w */
	    if (c == NUL)	/* Can't match at end of line */
		status = RA_NOMATCH;
	    else if (has_mbyte)
	    {
		int this_class;

		/* Get class of current and previous char (if it exists). */
		this_class = mb_get_class_buf(rex.input, rex.reg_buf);
		if (this_class <= 1)
		    status = RA_NOMATCH;  /* not on a word at all */
		else if (reg_prev_class() == this_class)
		    status = RA_NOMATCH;  /* previous char is in same word */
	    }
	    else
	    {
		if (!vim_iswordc_buf(c, rex.reg_buf) || (rex.input > rex.line
				&& vim_iswordc_buf(rex.input[-1], rex.reg_buf)))
		    status = RA_NOMATCH;
	    }
	    break;

	  case EOW:	/* word\>; rex.input points after d */
	    if (rex.input == rex.line)    /* Can't match at start of line */
		status = RA_NOMATCH;
	    else if (has_mbyte)
	    {
		int this_class, prev_class;

		/* Get class of current and previous char (if it exists). */
		this_class = mb_get_class_buf(rex.input, rex.reg_buf);
		prev_class = reg_prev_class();
		if (this_class == prev_class
			|| prev_class == 0 || prev_class == 1)
		    status = RA_NOMATCH;
	    }
	    else
	    {
		if (!vim_iswordc_buf(rex.input[-1], rex.reg_buf)
			|| (rex.input[0] != NUL
					   && vim_iswordc_buf(c, rex.reg_buf)))
		    status = RA_NOMATCH;
	    }
	    break; /* Matched with EOW */

	  case ANY:
	    /* ANY does not match new lines. */
	    if (c == NUL)
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case IDENT:
	    if (!vim_isIDc(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case SIDENT:
	    if (VIM_ISDIGIT(*rex.input) || !vim_isIDc(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case KWORD:
	    if (!vim_iswordp_buf(rex.input, rex.reg_buf))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case SKWORD:
	    if (VIM_ISDIGIT(*rex.input)
				    || !vim_iswordp_buf(rex.input, rex.reg_buf))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case FNAME:
	    if (!vim_isfilec(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case SFNAME:
	    if (VIM_ISDIGIT(*rex.input) || !vim_isfilec(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case PRINT:
	    if (!vim_isprintc(PTR2CHAR(rex.input)))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case SPRINT:
	    if (VIM_ISDIGIT(*rex.input) || !vim_isprintc(PTR2CHAR(rex.input)))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case WHITE:
	    if (!VIM_ISWHITE(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NWHITE:
	    if (c == NUL || VIM_ISWHITE(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case DIGIT:
	    if (!ri_digit(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NDIGIT:
	    if (c == NUL || ri_digit(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case HEX:
	    if (!ri_hex(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NHEX:
	    if (c == NUL || ri_hex(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case OCTAL:
	    if (!ri_octal(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NOCTAL:
	    if (c == NUL || ri_octal(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case WORD:
	    if (!ri_word(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NWORD:
	    if (c == NUL || ri_word(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case HEAD:
	    if (!ri_head(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NHEAD:
	    if (c == NUL || ri_head(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case ALPHA:
	    if (!ri_alpha(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NALPHA:
	    if (c == NUL || ri_alpha(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case LOWER:
	    if (!ri_lower(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NLOWER:
	    if (c == NUL || ri_lower(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case UPPER:
	    if (!ri_upper(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case NUPPER:
	    if (c == NUL || ri_upper(c))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case EXACTLY:
	    {
		int	len;
		char_u	*opnd;

		opnd = OPERAND(scan);
		/* Inline the first byte, for speed. */
		if (*opnd != *rex.input
			&& (!rex.reg_ic
			    || (!enc_utf8
			      && MB_TOLOWER(*opnd) != MB_TOLOWER(*rex.input))))
		    status = RA_NOMATCH;
		else if (*opnd == NUL)
		{
		    /* match empty string always works; happens when "~" is
		     * empty. */
		}
		else
		{
		    if (opnd[1] == NUL && !(enc_utf8 && rex.reg_ic))
		    {
			len = 1;	/* matched a single byte above */
		    }
		    else
		    {
			/* Need to match first byte again for multi-byte. */
			len = (int)STRLEN(opnd);
			if (cstrncmp(opnd, rex.input, &len) != 0)
			    status = RA_NOMATCH;
		    }
		    /* Check for following composing character, unless %C
		     * follows (skips over all composing chars). */
		    if (status != RA_NOMATCH
			    && enc_utf8
			    && UTF_COMPOSINGLIKE(rex.input, rex.input + len)
			    && !rex.reg_icombine
			    && OP(next) != RE_COMPOSING)
		    {
			/* raaron: This code makes a composing character get
			 * ignored, which is the correct behavior (sometimes)
			 * for voweled Hebrew texts. */
			status = RA_NOMATCH;
		    }
		    if (status != RA_NOMATCH)
			rex.input += len;
		}
	    }
	    break;

	  case ANYOF:
	  case ANYBUT:
	    if (c == NUL)
		status = RA_NOMATCH;
	    else if ((cstrchr(OPERAND(scan), c) == NULL) == (op == ANYOF))
		status = RA_NOMATCH;
	    else
		ADVANCE_REGINPUT();
	    break;

	  case MULTIBYTECODE:
	    if (has_mbyte)
	    {
		int	i, len;
		char_u	*opnd;
		int	opndc = 0, inpc;

		opnd = OPERAND(scan);
		/* Safety check (just in case 'encoding' was changed since
		 * compiling the program). */
		if ((len = (*mb_ptr2len)(opnd)) < 2)
		{
		    status = RA_NOMATCH;
		    break;
		}
		if (enc_utf8)
		    opndc = utf_ptr2char(opnd);
		if (enc_utf8 && utf_iscomposing(opndc))
		{
		    /* When only a composing char is given match at any
		     * position where that composing char appears. */
		    status = RA_NOMATCH;
		    for (i = 0; rex.input[i] != NUL;
						i += utf_ptr2len(rex.input + i))
		    {
			inpc = utf_ptr2char(rex.input + i);
			if (!utf_iscomposing(inpc))
			{
			    if (i > 0)
				break;
			}
			else if (opndc == inpc)
			{
			    /* Include all following composing chars. */
			    len = i + utfc_ptr2len(rex.input + i);
			    status = RA_MATCH;
			    break;
			}
		    }
		}
		else
		    for (i = 0; i < len; ++i)
			if (opnd[i] != rex.input[i])
			{
			    status = RA_NOMATCH;
			    break;
			}
		rex.input += len;
	    }
	    else
		status = RA_NOMATCH;
	    break;
	  case RE_COMPOSING:
	    if (enc_utf8)
	    {
		/* Skip composing characters. */
		while (utf_iscomposing(utf_ptr2char(rex.input)))
		    MB_CPTR_ADV(rex.input);
	    }
	    break;

	  case NOTHING:
	    break;

	  case BACK:
	    {
		int		i;
		backpos_T	*bp;

		/*
		 * When we run into BACK we need to check if we don't keep
		 * looping without matching any input.  The second and later
		 * times a BACK is encountered it fails if the input is still
		 * at the same position as the previous time.
		 * The positions are stored in "backpos" and found by the
		 * current value of "scan", the position in the RE program.
		 */
		bp = (backpos_T *)backpos.ga_data;
		for (i = 0; i < backpos.ga_len; ++i)
		    if (bp[i].bp_scan == scan)
			break;
		if (i == backpos.ga_len)
		{
		    /* First time at this BACK, make room to store the pos. */
		    if (ga_grow(&backpos, 1) == FAIL)
			status = RA_FAIL;
		    else
		    {
			/* get "ga_data" again, it may have changed */
			bp = (backpos_T *)backpos.ga_data;
			bp[i].bp_scan = scan;
			++backpos.ga_len;
		    }
		}
		else if (reg_save_equal(&bp[i].bp_pos))
		    /* Still at same position as last time, fail. */
		    status = RA_NOMATCH;

		if (status != RA_FAIL && status != RA_NOMATCH)
		    reg_save(&bp[i].bp_pos, &backpos);
	    }
	    break;

	  case MOPEN + 0:   /* Match start: \zs */
	  case MOPEN + 1:   /* \( */
	  case MOPEN + 2:
	  case MOPEN + 3:
	  case MOPEN + 4:
	  case MOPEN + 5:
	  case MOPEN + 6:
	  case MOPEN + 7:
	  case MOPEN + 8:
	  case MOPEN + 9:
	    {
		no = op - MOPEN;
		cleanup_subexpr();
		rp = regstack_push(RS_MOPEN, scan);
		if (rp == NULL)
		    status = RA_FAIL;
		else
		{
		    rp->rs_no = no;
		    save_se(&rp->rs_un.sesave, &rex.reg_startpos[no],
							  &rex.reg_startp[no]);
		    /* We simply continue and handle the result when done. */
		}
	    }
	    break;

	  case NOPEN:	    /* \%( */
	  case NCLOSE:	    /* \) after \%( */
		if (regstack_push(RS_NOPEN, scan) == NULL)
		    status = RA_FAIL;
		/* We simply continue and handle the result when done. */
		break;

#ifdef FEAT_SYN_HL
	  case ZOPEN + 1:
	  case ZOPEN + 2:
	  case ZOPEN + 3:
	  case ZOPEN + 4:
	  case ZOPEN + 5:
	  case ZOPEN + 6:
	  case ZOPEN + 7:
	  case ZOPEN + 8:
	  case ZOPEN + 9:
	    {
		no = op - ZOPEN;
		cleanup_zsubexpr();
		rp = regstack_push(RS_ZOPEN, scan);
		if (rp == NULL)
		    status = RA_FAIL;
		else
		{
		    rp->rs_no = no;
		    save_se(&rp->rs_un.sesave, &reg_startzpos[no],
							     &reg_startzp[no]);
		    /* We simply continue and handle the result when done. */
		}
	    }
	    break;
#endif

	  case MCLOSE + 0:  /* Match end: \ze */
	  case MCLOSE + 1:  /* \) */
	  case MCLOSE + 2:
	  case MCLOSE + 3:
	  case MCLOSE + 4:
	  case MCLOSE + 5:
	  case MCLOSE + 6:
	  case MCLOSE + 7:
	  case MCLOSE + 8:
	  case MCLOSE + 9:
	    {
		no = op - MCLOSE;
		cleanup_subexpr();
		rp = regstack_push(RS_MCLOSE, scan);
		if (rp == NULL)
		    status = RA_FAIL;
		else
		{
		    rp->rs_no = no;
		    save_se(&rp->rs_un.sesave, &rex.reg_endpos[no],
							    &rex.reg_endp[no]);
		    /* We simply continue and handle the result when done. */
		}
	    }
	    break;

#ifdef FEAT_SYN_HL
	  case ZCLOSE + 1:  /* \) after \z( */
	  case ZCLOSE + 2:
	  case ZCLOSE + 3:
	  case ZCLOSE + 4:
	  case ZCLOSE + 5:
	  case ZCLOSE + 6:
	  case ZCLOSE + 7:
	  case ZCLOSE + 8:
	  case ZCLOSE + 9:
	    {
		no = op - ZCLOSE;
		cleanup_zsubexpr();
		rp = regstack_push(RS_ZCLOSE, scan);
		if (rp == NULL)
		    status = RA_FAIL;
		else
		{
		    rp->rs_no = no;
		    save_se(&rp->rs_un.sesave, &reg_endzpos[no],
							      &reg_endzp[no]);
		    /* We simply continue and handle the result when done. */
		}
	    }
	    break;
#endif

	  case BACKREF + 1:
	  case BACKREF + 2:
	  case BACKREF + 3:
	  case BACKREF + 4:
	  case BACKREF + 5:
	  case BACKREF + 6:
	  case BACKREF + 7:
	  case BACKREF + 8:
	  case BACKREF + 9:
	    {
		int		len;

		no = op - BACKREF;
		cleanup_subexpr();
		if (!REG_MULTI)		/* Single-line regexp */
		{
		    if (rex.reg_startp[no] == NULL || rex.reg_endp[no] == NULL)
		    {
			/* Backref was not set: Match an empty string. */
			len = 0;
		    }
		    else
		    {
			/* Compare current input with back-ref in the same
			 * line. */
			len = (int)(rex.reg_endp[no] - rex.reg_startp[no]);
			if (cstrncmp(rex.reg_startp[no], rex.input, &len) != 0)
			    status = RA_NOMATCH;
		    }
		}
		else				/* Multi-line regexp */
		{
		    if (rex.reg_startpos[no].lnum < 0
						|| rex.reg_endpos[no].lnum < 0)
		    {
			/* Backref was not set: Match an empty string. */
			len = 0;
		    }
		    else
		    {
			if (rex.reg_startpos[no].lnum == rex.lnum
				&& rex.reg_endpos[no].lnum == rex.lnum)
			{
			    /* Compare back-ref within the current line. */
			    len = rex.reg_endpos[no].col
						    - rex.reg_startpos[no].col;
			    if (cstrncmp(rex.line + rex.reg_startpos[no].col,
							  rex.input, &len) != 0)
				status = RA_NOMATCH;
			}
			else
			{
			    /* Messy situation: Need to compare between two
			     * lines. */
			    int r = match_with_backref(
					    rex.reg_startpos[no].lnum,
					    rex.reg_startpos[no].col,
					    rex.reg_endpos[no].lnum,
					    rex.reg_endpos[no].col,
					    &len);

			    if (r != RA_MATCH)
				status = r;
			}
		    }
		}

		/* Matched the backref, skip over it. */
		rex.input += len;
	    }
	    break;

#ifdef FEAT_SYN_HL
	  case ZREF + 1:
	  case ZREF + 2:
	  case ZREF + 3:
	  case ZREF + 4:
	  case ZREF + 5:
	  case ZREF + 6:
	  case ZREF + 7:
	  case ZREF + 8:
	  case ZREF + 9:
	    {
		int	len;

		cleanup_zsubexpr();
		no = op - ZREF;
		if (re_extmatch_in != NULL
			&& re_extmatch_in->matches[no] != NULL)
		{
		    len = (int)STRLEN(re_extmatch_in->matches[no]);
		    if (cstrncmp(re_extmatch_in->matches[no],
							  rex.input, &len) != 0)
			status = RA_NOMATCH;
		    else
			rex.input += len;
		}
		else
		{
		    /* Backref was not set: Match an empty string. */
		}
	    }
	    break;
#endif

	  case BRANCH:
	    {
		if (OP(next) != BRANCH) /* No choice. */
		    next = OPERAND(scan);	/* Avoid recursion. */
		else
		{
		    rp = regstack_push(RS_BRANCH, scan);
		    if (rp == NULL)
			status = RA_FAIL;
		    else
			status = RA_BREAK;	/* rest is below */
		}
	    }
	    break;

	  case BRACE_LIMITS:
	    {
		if (OP(next) == BRACE_SIMPLE)
		{
		    bl_minval = OPERAND_MIN(scan);
		    bl_maxval = OPERAND_MAX(scan);
		}
		else if (OP(next) >= BRACE_COMPLEX
			&& OP(next) < BRACE_COMPLEX + 10)
		{
		    no = OP(next) - BRACE_COMPLEX;
		    brace_min[no] = OPERAND_MIN(scan);
		    brace_max[no] = OPERAND_MAX(scan);
		    brace_count[no] = 0;
		}
		else
		{
		    internal_error("BRACE_LIMITS");
		    status = RA_FAIL;
		}
	    }
	    break;

	  case BRACE_COMPLEX + 0:
	  case BRACE_COMPLEX + 1:
	  case BRACE_COMPLEX + 2:
	  case BRACE_COMPLEX + 3:
	  case BRACE_COMPLEX + 4:
	  case BRACE_COMPLEX + 5:
	  case BRACE_COMPLEX + 6:
	  case BRACE_COMPLEX + 7:
	  case BRACE_COMPLEX + 8:
	  case BRACE_COMPLEX + 9:
	    {
		no = op - BRACE_COMPLEX;
		++brace_count[no];

		/* If not matched enough times yet, try one more */
		if (brace_count[no] <= (brace_min[no] <= brace_max[no]
					     ? brace_min[no] : brace_max[no]))
		{
		    rp = regstack_push(RS_BRCPLX_MORE, scan);
		    if (rp == NULL)
			status = RA_FAIL;
		    else
		    {
			rp->rs_no = no;
			reg_save(&rp->rs_un.regsave, &backpos);
			next = OPERAND(scan);
			/* We continue and handle the result when done. */
		    }
		    break;
		}

		/* If matched enough times, may try matching some more */
		if (brace_min[no] <= brace_max[no])
		{
		    /* Range is the normal way around, use longest match */
		    if (brace_count[no] <= brace_max[no])
		    {
			rp = regstack_push(RS_BRCPLX_LONG, scan);
			if (rp == NULL)
			    status = RA_FAIL;
			else
			{
			    rp->rs_no = no;
			    reg_save(&rp->rs_un.regsave, &backpos);
			    next = OPERAND(scan);
			    /* We continue and handle the result when done. */
			}
		    }
		}
		else
		{
		    /* Range is backwards, use shortest match first */
		    if (brace_count[no] <= brace_min[no])
		    {
			rp = regstack_push(RS_BRCPLX_SHORT, scan);
			if (rp == NULL)
			    status = RA_FAIL;
			else
			{
			    reg_save(&rp->rs_un.regsave, &backpos);
			    /* We continue and handle the result when done. */
			}
		    }
		}
	    }
	    break;

	  case BRACE_SIMPLE:
	  case STAR:
	  case PLUS:
	    {
		regstar_T	rst;

		/*
		 * Lookahead to avoid useless match attempts when we know
		 * what character comes next.
		 */
		if (OP(next) == EXACTLY)
		{
		    rst.nextb = *OPERAND(next);
		    if (rex.reg_ic)
		    {
			if (MB_ISUPPER(rst.nextb))
			    rst.nextb_ic = MB_TOLOWER(rst.nextb);
			else
			    rst.nextb_ic = MB_TOUPPER(rst.nextb);
		    }
		    else
			rst.nextb_ic = rst.nextb;
		}
		else
		{
		    rst.nextb = NUL;
		    rst.nextb_ic = NUL;
		}
		if (op != BRACE_SIMPLE)
		{
		    rst.minval = (op == STAR) ? 0 : 1;
		    rst.maxval = MAX_LIMIT;
		}
		else
		{
		    rst.minval = bl_minval;
		    rst.maxval = bl_maxval;
		}

		/*
		 * When maxval > minval, try matching as much as possible, up
		 * to maxval.  When maxval < minval, try matching at least the
		 * minimal number (since the range is backwards, that's also
		 * maxval!).
		 */
		rst.count = regrepeat(OPERAND(scan), rst.maxval);
		if (got_int)
		{
		    status = RA_FAIL;
		    break;
		}
		if (rst.minval <= rst.maxval
			  ? rst.count >= rst.minval : rst.count >= rst.maxval)
		{
		    /* It could match.  Prepare for trying to match what
		     * follows.  The code is below.  Parameters are stored in
		     * a regstar_T on the regstack. */
		    if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
		    {
			emsg(_(e_maxmempat));
			status = RA_FAIL;
		    }
		    else if (ga_grow(&regstack, sizeof(regstar_T)) == FAIL)
			status = RA_FAIL;
		    else
		    {
			regstack.ga_len += sizeof(regstar_T);
			rp = regstack_push(rst.minval <= rst.maxval
					? RS_STAR_LONG : RS_STAR_SHORT, scan);
			if (rp == NULL)
			    status = RA_FAIL;
			else
			{
			    *(((regstar_T *)rp) - 1) = rst;
			    status = RA_BREAK;	    /* skip the restore bits */
			}
		    }
		}
		else
		    status = RA_NOMATCH;

	    }
	    break;

	  case NOMATCH:
	  case MATCH:
	  case SUBPAT:
	    rp = regstack_push(RS_NOMATCH, scan);
	    if (rp == NULL)
		status = RA_FAIL;
	    else
	    {
		rp->rs_no = op;
		reg_save(&rp->rs_un.regsave, &backpos);
		next = OPERAND(scan);
		/* We continue and handle the result when done. */
	    }
	    break;

	  case BEHIND:
	  case NOBEHIND:
	    /* Need a bit of room to store extra positions. */
	    if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
	    {
		emsg(_(e_maxmempat));
		status = RA_FAIL;
	    }
	    else if (ga_grow(&regstack, sizeof(regbehind_T)) == FAIL)
		status = RA_FAIL;
	    else
	    {
		regstack.ga_len += sizeof(regbehind_T);
		rp = regstack_push(RS_BEHIND1, scan);
		if (rp == NULL)
		    status = RA_FAIL;
		else
		{
		    /* Need to save the subexpr to be able to restore them
		     * when there is a match but we don't use it. */
		    save_subexpr(((regbehind_T *)rp) - 1);

		    rp->rs_no = op;
		    reg_save(&rp->rs_un.regsave, &backpos);
		    /* First try if what follows matches.  If it does then we
		     * check the behind match by looping. */
		}
	    }
	    break;

	  case BHPOS:
	    if (REG_MULTI)
	    {
		if (behind_pos.rs_u.pos.col != (colnr_T)(rex.input - rex.line)
			|| behind_pos.rs_u.pos.lnum != rex.lnum)
		    status = RA_NOMATCH;
	    }
	    else if (behind_pos.rs_u.ptr != rex.input)
		status = RA_NOMATCH;
	    break;

	  case NEWL:
	    if ((c != NUL || !REG_MULTI || rex.lnum > rex.reg_maxline
			     || rex.reg_line_lbr)
					   && (c != '\n' || !rex.reg_line_lbr))
		status = RA_NOMATCH;
	    else if (rex.reg_line_lbr)
		ADVANCE_REGINPUT();
	    else
		reg_nextline();
	    break;

	  case END:
	    status = RA_MATCH;	/* Success! */
	    break;

	  default:
	    emsg(_(e_re_corr));
#ifdef DEBUG
	    printf("Illegal op code %d\n", op);
#endif
	    status = RA_FAIL;
	    break;
	  }
	}

	/* If we can't continue sequentially, break the inner loop. */
	if (status != RA_CONT)
	    break;

	/* Continue in inner loop, advance to next item. */
	scan = next;

    } /* end of inner loop */

    /*
     * If there is something on the regstack execute the code for the state.
     * If the state is popped then loop and use the older state.
     */
    while (regstack.ga_len > 0 && status != RA_FAIL)
    {
	rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len) - 1;
	switch (rp->rs_state)
	{
	  case RS_NOPEN:
	    /* Result is passed on as-is, simply pop the state. */
	    regstack_pop(&scan);
	    break;

	  case RS_MOPEN:
	    /* Pop the state.  Restore pointers when there is no match. */
	    if (status == RA_NOMATCH)
		restore_se(&rp->rs_un.sesave, &rex.reg_startpos[rp->rs_no],
						  &rex.reg_startp[rp->rs_no]);
	    regstack_pop(&scan);
	    break;

#ifdef FEAT_SYN_HL
	  case RS_ZOPEN:
	    /* Pop the state.  Restore pointers when there is no match. */
	    if (status == RA_NOMATCH)
		restore_se(&rp->rs_un.sesave, &reg_startzpos[rp->rs_no],
						 &reg_startzp[rp->rs_no]);
	    regstack_pop(&scan);
	    break;
#endif

	  case RS_MCLOSE:
	    /* Pop the state.  Restore pointers when there is no match. */
	    if (status == RA_NOMATCH)
		restore_se(&rp->rs_un.sesave, &rex.reg_endpos[rp->rs_no],
						    &rex.reg_endp[rp->rs_no]);
	    regstack_pop(&scan);
	    break;

#ifdef FEAT_SYN_HL
	  case RS_ZCLOSE:
	    /* Pop the state.  Restore pointers when there is no match. */
	    if (status == RA_NOMATCH)
		restore_se(&rp->rs_un.sesave, &reg_endzpos[rp->rs_no],
						   &reg_endzp[rp->rs_no]);
	    regstack_pop(&scan);
	    break;
#endif

	  case RS_BRANCH:
	    if (status == RA_MATCH)
		/* this branch matched, use it */
		regstack_pop(&scan);
	    else
	    {
		if (status != RA_BREAK)
		{
		    /* After a non-matching branch: try next one. */
		    reg_restore(&rp->rs_un.regsave, &backpos);
		    scan = rp->rs_scan;
		}
		if (scan == NULL || OP(scan) != BRANCH)
		{
		    /* no more branches, didn't find a match */
		    status = RA_NOMATCH;
		    regstack_pop(&scan);
		}
		else
		{
		    /* Prepare to try a branch. */
		    rp->rs_scan = regnext(scan);
		    reg_save(&rp->rs_un.regsave, &backpos);
		    scan = OPERAND(scan);
		}
	    }
	    break;

	  case RS_BRCPLX_MORE:
	    /* Pop the state.  Restore pointers when there is no match. */
	    if (status == RA_NOMATCH)
	    {
		reg_restore(&rp->rs_un.regsave, &backpos);
		--brace_count[rp->rs_no];	/* decrement match count */
	    }
	    regstack_pop(&scan);
	    break;

	  case RS_BRCPLX_LONG:
	    /* Pop the state.  Restore pointers when there is no match. */
	    if (status == RA_NOMATCH)
	    {
		/* There was no match, but we did find enough matches. */
		reg_restore(&rp->rs_un.regsave, &backpos);
		--brace_count[rp->rs_no];
		/* continue with the items after "\{}" */
		status = RA_CONT;
	    }
	    regstack_pop(&scan);
	    if (status == RA_CONT)
		scan = regnext(scan);
	    break;

	  case RS_BRCPLX_SHORT:
	    /* Pop the state.  Restore pointers when there is no match. */
	    if (status == RA_NOMATCH)
		/* There was no match, try to match one more item. */
		reg_restore(&rp->rs_un.regsave, &backpos);
	    regstack_pop(&scan);
	    if (status == RA_NOMATCH)
	    {
		scan = OPERAND(scan);
		status = RA_CONT;
	    }
	    break;

	  case RS_NOMATCH:
	    /* Pop the state.  If the operand matches for NOMATCH or
	     * doesn't match for MATCH/SUBPAT, we fail.  Otherwise backup,
	     * except for SUBPAT, and continue with the next item. */
	    if (status == (rp->rs_no == NOMATCH ? RA_MATCH : RA_NOMATCH))
		status = RA_NOMATCH;
	    else
	    {
		status = RA_CONT;
		if (rp->rs_no != SUBPAT)	/* zero-width */
		    reg_restore(&rp->rs_un.regsave, &backpos);
	    }
	    regstack_pop(&scan);
	    if (status == RA_CONT)
		scan = regnext(scan);
	    break;

	  case RS_BEHIND1:
	    if (status == RA_NOMATCH)
	    {
		regstack_pop(&scan);
		regstack.ga_len -= sizeof(regbehind_T);
	    }
	    else
	    {
		/* The stuff after BEHIND/NOBEHIND matches.  Now try if
		 * the behind part does (not) match before the current
		 * position in the input.  This must be done at every
		 * position in the input and checking if the match ends at
		 * the current position. */

		/* save the position after the found match for next */
		reg_save(&(((regbehind_T *)rp) - 1)->save_after, &backpos);

		/* Start looking for a match with operand at the current
		 * position.  Go back one character until we find the
		 * result, hitting the start of the line or the previous
		 * line (for multi-line matching).
		 * Set behind_pos to where the match should end, BHPOS
		 * will match it.  Save the current value. */
		(((regbehind_T *)rp) - 1)->save_behind = behind_pos;
		behind_pos = rp->rs_un.regsave;

		rp->rs_state = RS_BEHIND2;

		reg_restore(&rp->rs_un.regsave, &backpos);
		scan = OPERAND(rp->rs_scan) + 4;
	    }
	    break;

	  case RS_BEHIND2:
	    /*
	     * Looping for BEHIND / NOBEHIND match.
	     */
	    if (status == RA_MATCH && reg_save_equal(&behind_pos))
	    {
		/* found a match that ends where "next" started */
		behind_pos = (((regbehind_T *)rp) - 1)->save_behind;
		if (rp->rs_no == BEHIND)
		    reg_restore(&(((regbehind_T *)rp) - 1)->save_after,
								    &backpos);
		else
		{
		    /* But we didn't want a match.  Need to restore the
		     * subexpr, because what follows matched, so they have
		     * been set. */
		    status = RA_NOMATCH;
		    restore_subexpr(((regbehind_T *)rp) - 1);
		}
		regstack_pop(&scan);
		regstack.ga_len -= sizeof(regbehind_T);
	    }
	    else
	    {
		long limit;

		/* No match or a match that doesn't end where we want it: Go
		 * back one character.  May go to previous line once. */
		no = OK;
		limit = OPERAND_MIN(rp->rs_scan);
		if (REG_MULTI)
		{
		    if (limit > 0
			    && ((rp->rs_un.regsave.rs_u.pos.lnum
						    < behind_pos.rs_u.pos.lnum
				    ? (colnr_T)STRLEN(rex.line)
				    : behind_pos.rs_u.pos.col)
				- rp->rs_un.regsave.rs_u.pos.col >= limit))
			no = FAIL;
		    else if (rp->rs_un.regsave.rs_u.pos.col == 0)
		    {
			if (rp->rs_un.regsave.rs_u.pos.lnum
					< behind_pos.rs_u.pos.lnum
				|| reg_getline(
					--rp->rs_un.regsave.rs_u.pos.lnum)
								  == NULL)
			    no = FAIL;
			else
			{
			    reg_restore(&rp->rs_un.regsave, &backpos);
			    rp->rs_un.regsave.rs_u.pos.col =
						 (colnr_T)STRLEN(rex.line);
			}
		    }
		    else
		    {
			if (has_mbyte)
			{
			    char_u *line =
				  reg_getline(rp->rs_un.regsave.rs_u.pos.lnum);

			    rp->rs_un.regsave.rs_u.pos.col -=
				(*mb_head_off)(line, line
				    + rp->rs_un.regsave.rs_u.pos.col - 1) + 1;
			}
			else
			    --rp->rs_un.regsave.rs_u.pos.col;
		    }
		}
		else
		{
		    if (rp->rs_un.regsave.rs_u.ptr == rex.line)
			no = FAIL;
		    else
		    {
			MB_PTR_BACK(rex.line, rp->rs_un.regsave.rs_u.ptr);
			if (limit > 0 && (long)(behind_pos.rs_u.ptr
				     - rp->rs_un.regsave.rs_u.ptr) > limit)
			    no = FAIL;
		    }
		}
		if (no == OK)
		{
		    /* Advanced, prepare for finding match again. */
		    reg_restore(&rp->rs_un.regsave, &backpos);
		    scan = OPERAND(rp->rs_scan) + 4;
		    if (status == RA_MATCH)
		    {
			/* We did match, so subexpr may have been changed,
			 * need to restore them for the next try. */
			status = RA_NOMATCH;
			restore_subexpr(((regbehind_T *)rp) - 1);
		    }
		}
		else
		{
		    /* Can't advance.  For NOBEHIND that's a match. */
		    behind_pos = (((regbehind_T *)rp) - 1)->save_behind;
		    if (rp->rs_no == NOBEHIND)
		    {
			reg_restore(&(((regbehind_T *)rp) - 1)->save_after,
								    &backpos);
			status = RA_MATCH;
		    }
		    else
		    {
			/* We do want a proper match.  Need to restore the
			 * subexpr if we had a match, because they may have
			 * been set. */
			if (status == RA_MATCH)
			{
			    status = RA_NOMATCH;
			    restore_subexpr(((regbehind_T *)rp) - 1);
			}
		    }
		    regstack_pop(&scan);
		    regstack.ga_len -= sizeof(regbehind_T);
		}
	    }
	    break;

	  case RS_STAR_LONG:
	  case RS_STAR_SHORT:
	    {
		regstar_T	    *rst = ((regstar_T *)rp) - 1;

		if (status == RA_MATCH)
		{
		    regstack_pop(&scan);
		    regstack.ga_len -= sizeof(regstar_T);
		    break;
		}

		/* Tried once already, restore input pointers. */
		if (status != RA_BREAK)
		    reg_restore(&rp->rs_un.regsave, &backpos);

		/* Repeat until we found a position where it could match. */
		for (;;)
		{
		    if (status != RA_BREAK)
		    {
			/* Tried first position already, advance. */
			if (rp->rs_state == RS_STAR_LONG)
			{
			    /* Trying for longest match, but couldn't or
			     * didn't match -- back up one char. */
			    if (--rst->count < rst->minval)
				break;
			    if (rex.input == rex.line)
			    {
				/* backup to last char of previous line */
				--rex.lnum;
				rex.line = reg_getline(rex.lnum);
				/* Just in case regrepeat() didn't count
				 * right. */
				if (rex.line == NULL)
				    break;
				rex.input = rex.line + STRLEN(rex.line);
				fast_breakcheck();
			    }
			    else
				MB_PTR_BACK(rex.line, rex.input);
			}
			else
			{
			    /* Range is backwards, use shortest match first.
			     * Careful: maxval and minval are exchanged!
			     * Couldn't or didn't match: try advancing one
			     * char. */
			    if (rst->count == rst->minval
				  || regrepeat(OPERAND(rp->rs_scan), 1L) == 0)
				break;
			    ++rst->count;
			}
			if (got_int)
			    break;
		    }
		    else
			status = RA_NOMATCH;

		    /* If it could match, try it. */
		    if (rst->nextb == NUL || *rex.input == rst->nextb
					     || *rex.input == rst->nextb_ic)
		    {
			reg_save(&rp->rs_un.regsave, &backpos);
			scan = regnext(rp->rs_scan);
			status = RA_CONT;
			break;
		    }
		}
		if (status != RA_CONT)
		{
		    /* Failed. */
		    regstack_pop(&scan);
		    regstack.ga_len -= sizeof(regstar_T);
		    status = RA_NOMATCH;
		}
	    }
	    break;
	}

	/* If we want to continue the inner loop or didn't pop a state
	 * continue matching loop */
	if (status == RA_CONT || rp == (regitem_T *)
			     ((char *)regstack.ga_data + regstack.ga_len) - 1)
	    break;
    }

    /* May need to continue with the inner loop, starting at "scan". */
    if (status == RA_CONT)
	continue;

    /*
     * If the regstack is empty or something failed we are done.
     */
    if (regstack.ga_len == 0 || status == RA_FAIL)
    {
	if (scan == NULL)
	{
	    /*
	     * We get here only if there's trouble -- normally "case END" is
	     * the terminating point.
	     */
	    emsg(_(e_re_corr));
#ifdef DEBUG
	    printf("Premature EOL\n");
#endif
	}
	return (status == RA_MATCH);
    }

  } /* End of loop until the regstack is empty. */

  /* NOTREACHED */
}

/*
 * Push an item onto the regstack.
 * Returns pointer to new item.  Returns NULL when out of memory.
 */
    static regitem_T *
regstack_push(regstate_T state, char_u *scan)
{
    regitem_T	*rp;

    if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
    {
	emsg(_(e_maxmempat));
	return NULL;
    }
    if (ga_grow(&regstack, sizeof(regitem_T)) == FAIL)
	return NULL;

    rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len);
    rp->rs_state = state;
    rp->rs_scan = scan;

    regstack.ga_len += sizeof(regitem_T);
    return rp;
}

/*
 * Pop an item from the regstack.
 */
    static void
regstack_pop(char_u **scan)
{
    regitem_T	*rp;

    rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len) - 1;
    *scan = rp->rs_scan;

    regstack.ga_len -= sizeof(regitem_T);
}

/*
 * regrepeat - repeatedly match something simple, return how many.
 * Advances rex.input (and rex.lnum) to just after the matched chars.
 */
    static int
regrepeat(
    char_u	*p,
    long	maxcount)   /* maximum number of matches allowed */
{
    long	count = 0;
    char_u	*scan;
    char_u	*opnd;
    int		mask;
    int		testval = 0;

    scan = rex.input;	    /* Make local copy of rex.input for speed. */
    opnd = OPERAND(p);
    switch (OP(p))
    {
      case ANY:
      case ANY + ADD_NL:
	while (count < maxcount)
	{
	    /* Matching anything means we continue until end-of-line (or
	     * end-of-file for ANY + ADD_NL), only limited by maxcount. */
	    while (*scan != NUL && count < maxcount)
	    {
		++count;
		MB_PTR_ADV(scan);
	    }
	    if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline
				      || rex.reg_line_lbr || count == maxcount)
		break;
	    ++count;		/* count the line-break */
	    reg_nextline();
	    scan = rex.input;
	    if (got_int)
		break;
	}
	break;

      case IDENT:
      case IDENT + ADD_NL:
	testval = TRUE;
	/* FALLTHROUGH */
      case SIDENT:
      case SIDENT + ADD_NL:
	while (count < maxcount)
	{
	    if (vim_isIDc(PTR2CHAR(scan)) && (testval || !VIM_ISDIGIT(*scan)))
	    {
		MB_PTR_ADV(scan);
	    }
	    else if (*scan == NUL)
	    {
		if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline
							   || rex.reg_line_lbr)
		    break;
		reg_nextline();
		scan = rex.input;
		if (got_int)
		    break;
	    }
	    else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
		++scan;
	    else
		break;
	    ++count;
	}
	break;

      case KWORD:
      case KWORD + ADD_NL:
	testval = TRUE;
	/* FALLTHROUGH */
      case SKWORD:
      case SKWORD + ADD_NL:
	while (count < maxcount)
	{
	    if (vim_iswordp_buf(scan, rex.reg_buf)
					  && (testval || !VIM_ISDIGIT(*scan)))
	    {
		MB_PTR_ADV(scan);
	    }
	    else if (*scan == NUL)
	    {
		if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline
							   || rex.reg_line_lbr)
		    break;
		reg_nextline();
		scan = rex.input;
		if (got_int)
		    break;
	    }
	    else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
		++scan;
	    else
		break;
	    ++count;
	}
	break;

      case FNAME:
      case FNAME + ADD_NL:
	testval = TRUE;
	/* FALLTHROUGH */
      case SFNAME:
      case SFNAME + ADD_NL:
	while (count < maxcount)
	{
	    if (vim_isfilec(PTR2CHAR(scan)) && (testval || !VIM_ISDIGIT(*scan)))
	    {
		MB_PTR_ADV(scan);
	    }
	    else if (*scan == NUL)
	    {
		if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline
							   || rex.reg_line_lbr)
		    break;
		reg_nextline();
		scan = rex.input;
		if (got_int)
		    break;
	    }
	    else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
		++scan;
	    else
		break;
	    ++count;
	}
	break;

      case PRINT:
      case PRINT + ADD_NL:
	testval = TRUE;
	/* FALLTHROUGH */
      case SPRINT:
      case SPRINT + ADD_NL:
	while (count < maxcount)
	{
	    if (*scan == NUL)
	    {
		if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline
							   || rex.reg_line_lbr)
		    break;
		reg_nextline();
		scan = rex.input;
		if (got_int)
		    break;
	    }
	    else if (vim_isprintc(PTR2CHAR(scan)) == 1
					  && (testval || !VIM_ISDIGIT(*scan)))
	    {
		MB_PTR_ADV(scan);
	    }
	    else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
		++scan;
	    else
		break;
	    ++count;
	}
	break;

      case WHITE:
      case WHITE + ADD_NL:
	testval = mask = RI_WHITE;
do_class:
	while (count < maxcount)
	{
	    int		l;

	    if (*scan == NUL)
	    {
		if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline
							   || rex.reg_line_lbr)
		    break;
		reg_nextline();
		scan = rex.input;
		if (got_int)
		    break;
	    }
	    else if (has_mbyte && (l = (*mb_ptr2len)(scan)) > 1)
	    {
		if (testval != 0)
		    break;
		scan += l;
	    }
	    else if ((class_tab[*scan] & mask) == testval)
		++scan;
	    else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
		++scan;
	    else
		break;
	    ++count;
	}
	break;

      case NWHITE:
      case NWHITE + ADD_NL:
	mask = RI_WHITE;
	goto do_class;
      case DIGIT:
      case DIGIT + ADD_NL:
	testval = mask = RI_DIGIT;
	goto do_class;
      case NDIGIT:
      case NDIGIT + ADD_NL:
	mask = RI_DIGIT;
	goto do_class;
      case HEX:
      case HEX + ADD_NL:
	testval = mask = RI_HEX;
	goto do_class;
      case NHEX:
      case NHEX + ADD_NL:
	mask = RI_HEX;
	goto do_class;
      case OCTAL:
      case OCTAL + ADD_NL:
	testval = mask = RI_OCTAL;
	goto do_class;
      case NOCTAL:
      case NOCTAL + ADD_NL:
	mask = RI_OCTAL;
	goto do_class;
      case WORD:
      case WORD + ADD_NL:
	testval = mask = RI_WORD;
	goto do_class;
      case NWORD:
      case NWORD + ADD_NL:
	mask = RI_WORD;
	goto do_class;
      case HEAD:
      case HEAD + ADD_NL:
	testval = mask = RI_HEAD;
	goto do_class;
      case NHEAD:
      case NHEAD + ADD_NL:
	mask = RI_HEAD;
	goto do_class;
      case ALPHA:
      case ALPHA + ADD_NL:
	testval = mask = RI_ALPHA;
	goto do_class;
      case NALPHA:
      case NALPHA + ADD_NL:
	mask = RI_ALPHA;
	goto do_class;
      case LOWER:
      case LOWER + ADD_NL:
	testval = mask = RI_LOWER;
	goto do_class;
      case NLOWER:
      case NLOWER + ADD_NL:
	mask = RI_LOWER;
	goto do_class;
      case UPPER:
      case UPPER + ADD_NL:
	testval = mask = RI_UPPER;
	goto do_class;
      case NUPPER:
      case NUPPER + ADD_NL:
	mask = RI_UPPER;
	goto do_class;

      case EXACTLY:
	{
	    int	    cu, cl;

	    /* This doesn't do a multi-byte character, because a MULTIBYTECODE
	     * would have been used for it.  It does handle single-byte
	     * characters, such as latin1. */
	    if (rex.reg_ic)
	    {
		cu = MB_TOUPPER(*opnd);
		cl = MB_TOLOWER(*opnd);
		while (count < maxcount && (*scan == cu || *scan == cl))
		{
		    count++;
		    scan++;
		}
	    }
	    else
	    {
		cu = *opnd;
		while (count < maxcount && *scan == cu)
		{
		    count++;
		    scan++;
		}
	    }
	    break;
	}

      case MULTIBYTECODE:
	{
	    int		i, len, cf = 0;

	    /* Safety check (just in case 'encoding' was changed since
	     * compiling the program). */
	    if ((len = (*mb_ptr2len)(opnd)) > 1)
	    {
		if (rex.reg_ic && enc_utf8)
		    cf = utf_fold(utf_ptr2char(opnd));
		while (count < maxcount && (*mb_ptr2len)(scan) >= len)
		{
		    for (i = 0; i < len; ++i)
			if (opnd[i] != scan[i])
			    break;
		    if (i < len && (!rex.reg_ic || !enc_utf8
					|| utf_fold(utf_ptr2char(scan)) != cf))
			break;
		    scan += len;
		    ++count;
		}
	    }
	}
	break;

      case ANYOF:
      case ANYOF + ADD_NL:
	testval = TRUE;
	/* FALLTHROUGH */

      case ANYBUT:
      case ANYBUT + ADD_NL:
	while (count < maxcount)
	{
	    int len;

	    if (*scan == NUL)
	    {
		if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline
							   || rex.reg_line_lbr)
		    break;
		reg_nextline();
		scan = rex.input;
		if (got_int)
		    break;
	    }
	    else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
		++scan;
	    else if (has_mbyte && (len = (*mb_ptr2len)(scan)) > 1)
	    {
		if ((cstrchr(opnd, (*mb_ptr2char)(scan)) == NULL) == testval)
		    break;
		scan += len;
	    }
	    else
	    {
		if ((cstrchr(opnd, *scan) == NULL) == testval)
		    break;
		++scan;
	    }
	    ++count;
	}
	break;

      case NEWL:
	while (count < maxcount
		&& ((*scan == NUL && rex.lnum <= rex.reg_maxline
				       && !rex.reg_line_lbr && REG_MULTI)
		    || (*scan == '\n' && rex.reg_line_lbr)))
	{
	    count++;
	    if (rex.reg_line_lbr)
		ADVANCE_REGINPUT();
	    else
		reg_nextline();
	    scan = rex.input;
	    if (got_int)
		break;
	}
	break;

      default:			/* Oh dear.  Called inappropriately. */
	emsg(_(e_re_corr));
#ifdef DEBUG
	printf("Called regrepeat with op code %d\n", OP(p));
#endif
	break;
    }

    rex.input = scan;

    return (int)count;
}

/*
 * regnext - dig the "next" pointer out of a node
 * Returns NULL when calculating size, when there is no next item and when
 * there is an error.
 */
    static char_u *
regnext(char_u *p)
{
    int	    offset;

    if (p == JUST_CALC_SIZE || reg_toolong)
	return NULL;

    offset = NEXT(p);
    if (offset == 0)
	return NULL;

    if (OP(p) == BACK)
	return p - offset;
    else
	return p + offset;
}

/*
 * Check the regexp program for its magic number.
 * Return TRUE if it's wrong.
 */
    static int
prog_magic_wrong(void)
{
    regprog_T	*prog;

    prog = REG_MULTI ? rex.reg_mmatch->regprog : rex.reg_match->regprog;
    if (prog->engine == &nfa_regengine)
	/* For NFA matcher we don't check the magic */
	return FALSE;

    if (UCHARAT(((bt_regprog_T *)prog)->program) != REGMAGIC)
    {
	emsg(_(e_re_corr));
	return TRUE;
    }
    return FALSE;
}

/*
 * Cleanup the subexpressions, if this wasn't done yet.
 * This construction is used to clear the subexpressions only when they are
 * used (to increase speed).
 */
    static void
cleanup_subexpr(void)
{
    if (rex.need_clear_subexpr)
    {
	if (REG_MULTI)
	{
	    /* Use 0xff to set lnum to -1 */
	    vim_memset(rex.reg_startpos, 0xff, sizeof(lpos_T) * NSUBEXP);
	    vim_memset(rex.reg_endpos, 0xff, sizeof(lpos_T) * NSUBEXP);
	}
	else
	{
	    vim_memset(rex.reg_startp, 0, sizeof(char_u *) * NSUBEXP);
	    vim_memset(rex.reg_endp, 0, sizeof(char_u *) * NSUBEXP);
	}
	rex.need_clear_subexpr = FALSE;
    }
}

#ifdef FEAT_SYN_HL
    static void
cleanup_zsubexpr(void)
{
    if (rex.need_clear_zsubexpr)
    {
	if (REG_MULTI)
	{
	    /* Use 0xff to set lnum to -1 */
	    vim_memset(reg_startzpos, 0xff, sizeof(lpos_T) * NSUBEXP);
	    vim_memset(reg_endzpos, 0xff, sizeof(lpos_T) * NSUBEXP);
	}
	else
	{
	    vim_memset(reg_startzp, 0, sizeof(char_u *) * NSUBEXP);
	    vim_memset(reg_endzp, 0, sizeof(char_u *) * NSUBEXP);
	}
	rex.need_clear_zsubexpr = FALSE;
    }
}
#endif

/*
 * Save the current subexpr to "bp", so that they can be restored
 * later by restore_subexpr().
 */
    static void
save_subexpr(regbehind_T *bp)
{
    int i;

    /* When "rex.need_clear_subexpr" is set we don't need to save the values, only
     * remember that this flag needs to be set again when restoring. */
    bp->save_need_clear_subexpr = rex.need_clear_subexpr;
    if (!rex.need_clear_subexpr)
    {
	for (i = 0; i < NSUBEXP; ++i)
	{
	    if (REG_MULTI)
	    {
		bp->save_start[i].se_u.pos = rex.reg_startpos[i];
		bp->save_end[i].se_u.pos = rex.reg_endpos[i];
	    }
	    else
	    {
		bp->save_start[i].se_u.ptr = rex.reg_startp[i];
		bp->save_end[i].se_u.ptr = rex.reg_endp[i];
	    }
	}
    }
}

/*
 * Restore the subexpr from "bp".
 */
    static void
restore_subexpr(regbehind_T *bp)
{
    int i;

    /* Only need to restore saved values when they are not to be cleared. */
    rex.need_clear_subexpr = bp->save_need_clear_subexpr;
    if (!rex.need_clear_subexpr)
    {
	for (i = 0; i < NSUBEXP; ++i)
	{
	    if (REG_MULTI)
	    {
		rex.reg_startpos[i] = bp->save_start[i].se_u.pos;
		rex.reg_endpos[i] = bp->save_end[i].se_u.pos;
	    }
	    else
	    {
		rex.reg_startp[i] = bp->save_start[i].se_u.ptr;
		rex.reg_endp[i] = bp->save_end[i].se_u.ptr;
	    }
	}
    }
}

/*
 * Advance rex.lnum, rex.line and rex.input to the next line.
 */
    static void
reg_nextline(void)
{
    rex.line = reg_getline(++rex.lnum);
    rex.input = rex.line;
    fast_breakcheck();
}

/*
 * Save the input line and position in a regsave_T.
 */
    static void
reg_save(regsave_T *save, garray_T *gap)
{
    if (REG_MULTI)
    {
	save->rs_u.pos.col = (colnr_T)(rex.input - rex.line);
	save->rs_u.pos.lnum = rex.lnum;
    }
    else
	save->rs_u.ptr = rex.input;
    save->rs_len = gap->ga_len;
}

/*
 * Restore the input line and position from a regsave_T.
 */
    static void
reg_restore(regsave_T *save, garray_T *gap)
{
    if (REG_MULTI)
    {
	if (rex.lnum != save->rs_u.pos.lnum)
	{
	    /* only call reg_getline() when the line number changed to save
	     * a bit of time */
	    rex.lnum = save->rs_u.pos.lnum;
	    rex.line = reg_getline(rex.lnum);
	}
	rex.input = rex.line + save->rs_u.pos.col;
    }
    else
	rex.input = save->rs_u.ptr;
    gap->ga_len = save->rs_len;
}

/*
 * Return TRUE if current position is equal to saved position.
 */
    static int
reg_save_equal(regsave_T *save)
{
    if (REG_MULTI)
	return rex.lnum == save->rs_u.pos.lnum
				  && rex.input == rex.line + save->rs_u.pos.col;
    return rex.input == save->rs_u.ptr;
}

/*
 * Tentatively set the sub-expression start to the current position (after
 * calling regmatch() they will have changed).  Need to save the existing
 * values for when there is no match.
 * Use se_save() to use pointer (save_se_multi()) or position (save_se_one()),
 * depending on REG_MULTI.
 */
    static void
save_se_multi(save_se_T *savep, lpos_T *posp)
{
    savep->se_u.pos = *posp;
    posp->lnum = rex.lnum;
    posp->col = (colnr_T)(rex.input - rex.line);
}

    static void
save_se_one(save_se_T *savep, char_u **pp)
{
    savep->se_u.ptr = *pp;
    *pp = rex.input;
}

/*
 * Compare a number with the operand of RE_LNUM, RE_COL or RE_VCOL.
 */
    static int
re_num_cmp(long_u val, char_u *scan)
{
    long_u  n = OPERAND_MIN(scan);

    if (OPERAND_CMP(scan) == '>')
	return val > n;
    if (OPERAND_CMP(scan) == '<')
	return val < n;
    return val == n;
}

/*
 * Check whether a backreference matches.
 * Returns RA_FAIL, RA_NOMATCH or RA_MATCH.
 * If "bytelen" is not NULL, it is set to the byte length of the match in the
 * last line.
 */
    static int
match_with_backref(
    linenr_T start_lnum,
    colnr_T  start_col,
    linenr_T end_lnum,
    colnr_T  end_col,
    int	     *bytelen)
{
    linenr_T	clnum = start_lnum;
    colnr_T	ccol = start_col;
    int		len;
    char_u	*p;

    if (bytelen != NULL)
	*bytelen = 0;
    for (;;)
    {
	/* Since getting one line may invalidate the other, need to make copy.
	 * Slow! */
	if (rex.line != reg_tofree)
	{
	    len = (int)STRLEN(rex.line);
	    if (reg_tofree == NULL || len >= (int)reg_tofreelen)
	    {
		len += 50;	/* get some extra */
		vim_free(reg_tofree);
		reg_tofree = alloc(len);
		if (reg_tofree == NULL)
		    return RA_FAIL; /* out of memory!*/
		reg_tofreelen = len;
	    }
	    STRCPY(reg_tofree, rex.line);
	    rex.input = reg_tofree + (rex.input - rex.line);
	    rex.line = reg_tofree;
	}

	/* Get the line to compare with. */
	p = reg_getline(clnum);
	if (clnum == end_lnum)
	    len = end_col - ccol;
	else
	    len = (int)STRLEN(p + ccol);

	if (cstrncmp(p + ccol, rex.input, &len) != 0)
	    return RA_NOMATCH;  /* doesn't match */
	if (bytelen != NULL)
	    *bytelen += len;
	if (clnum == end_lnum)
	    break;		/* match and at end! */
	if (rex.lnum >= rex.reg_maxline)
	    return RA_NOMATCH;  /* text too short */

	/* Advance to next line. */
	reg_nextline();
	if (bytelen != NULL)
	    *bytelen = 0;
	++clnum;
	ccol = 0;
	if (got_int)
	    return RA_FAIL;
    }

    /* found a match!  Note that rex.line may now point to a copy of the line,
     * that should not matter. */
    return RA_MATCH;
}

#ifdef BT_REGEXP_DUMP

/*
 * regdump - dump a regexp onto stdout in vaguely comprehensible form
 */
    static void
regdump(char_u *pattern, bt_regprog_T *r)
{
    char_u  *s;
    int	    op = EXACTLY;	/* Arbitrary non-END op. */
    char_u  *next;
    char_u  *end = NULL;
    FILE    *f;

#ifdef BT_REGEXP_LOG
    f = fopen("bt_regexp_log.log", "a");
#else
    f = stdout;
#endif
    if (f == NULL)
	return;
    fprintf(f, "-------------------------------------\n\r\nregcomp(%s):\r\n", pattern);

    s = r->program + 1;
    /*
     * Loop until we find the END that isn't before a referred next (an END
     * can also appear in a NOMATCH operand).
     */
    while (op != END || s <= end)
    {
	op = OP(s);
	fprintf(f, "%2d%s", (int)(s - r->program), regprop(s)); /* Where, what. */
	next = regnext(s);
	if (next == NULL)	/* Next ptr. */
	    fprintf(f, "(0)");
	else
	    fprintf(f, "(%d)", (int)((s - r->program) + (next - s)));
	if (end < next)
	    end = next;
	if (op == BRACE_LIMITS)
	{
	    /* Two ints */
	    fprintf(f, " minval %ld, maxval %ld", OPERAND_MIN(s), OPERAND_MAX(s));
	    s += 8;
	}
	else if (op == BEHIND || op == NOBEHIND)
	{
	    /* one int */
	    fprintf(f, " count %ld", OPERAND_MIN(s));
	    s += 4;
	}
	else if (op == RE_LNUM || op == RE_COL || op == RE_VCOL)
	{
	    /* one int plus comperator */
	    fprintf(f, " count %ld", OPERAND_MIN(s));
	    s += 5;
	}
	s += 3;
	if (op == ANYOF || op == ANYOF + ADD_NL
		|| op == ANYBUT || op == ANYBUT + ADD_NL
		|| op == EXACTLY)
	{
	    /* Literal string, where present. */
	    fprintf(f, "\nxxxxxxxxx\n");
	    while (*s != NUL)
		fprintf(f, "%c", *s++);
	    fprintf(f, "\nxxxxxxxxx\n");
	    s++;
	}
	fprintf(f, "\r\n");
    }

    /* Header fields of interest. */
    if (r->regstart != NUL)
	fprintf(f, "start `%s' 0x%x; ", r->regstart < 256
		? (char *)transchar(r->regstart)
		: "multibyte", r->regstart);
    if (r->reganch)
	fprintf(f, "anchored; ");
    if (r->regmust != NULL)
	fprintf(f, "must have \"%s\"", r->regmust);
    fprintf(f, "\r\n");

#ifdef BT_REGEXP_LOG
    fclose(f);
#endif
}
#endif	    /* BT_REGEXP_DUMP */

#ifdef DEBUG
/*
 * regprop - printable representation of opcode
 */
    static char_u *
regprop(char_u *op)
{
    char	    *p;
    static char	    buf[50];

    STRCPY(buf, ":");

    switch ((int) OP(op))
    {
      case BOL:
	p = "BOL";
	break;
      case EOL:
	p = "EOL";
	break;
      case RE_BOF:
	p = "BOF";
	break;
      case RE_EOF:
	p = "EOF";
	break;
      case CURSOR:
	p = "CURSOR";
	break;
      case RE_VISUAL:
	p = "RE_VISUAL";
	break;
      case RE_LNUM:
	p = "RE_LNUM";
	break;
      case RE_MARK:
	p = "RE_MARK";
	break;
      case RE_COL:
	p = "RE_COL";
	break;
      case RE_VCOL:
	p = "RE_VCOL";
	break;
      case BOW:
	p = "BOW";
	break;
      case EOW:
	p = "EOW";
	break;
      case ANY:
	p = "ANY";
	break;
      case ANY + ADD_NL:
	p = "ANY+NL";
	break;
      case ANYOF:
	p = "ANYOF";
	break;
      case ANYOF + ADD_NL:
	p = "ANYOF+NL";
	break;
      case ANYBUT:
	p = "ANYBUT";
	break;
      case ANYBUT + ADD_NL:
	p = "ANYBUT+NL";
	break;
      case IDENT:
	p = "IDENT";
	break;
      case IDENT + ADD_NL:
	p = "IDENT+NL";
	break;
      case SIDENT:
	p = "SIDENT";
	break;
      case SIDENT + ADD_NL:
	p = "SIDENT+NL";
	break;
      case KWORD:
	p = "KWORD";
	break;
      case KWORD + ADD_NL:
	p = "KWORD+NL";
	break;
      case SKWORD:
	p = "SKWORD";
	break;
      case SKWORD + ADD_NL:
	p = "SKWORD+NL";
	break;
      case FNAME:
	p = "FNAME";
	break;
      case FNAME + ADD_NL:
	p = "FNAME+NL";
	break;
      case SFNAME:
	p = "SFNAME";
	break;
      case SFNAME + ADD_NL:
	p = "SFNAME+NL";
	break;
      case PRINT:
	p = "PRINT";
	break;
      case PRINT + ADD_NL:
	p = "PRINT+NL";
	break;
      case SPRINT:
	p = "SPRINT";
	break;
      case SPRINT + ADD_NL:
	p = "SPRINT+NL";
	break;
      case WHITE:
	p = "WHITE";
	break;
      case WHITE + ADD_NL:
	p = "WHITE+NL";
	break;
      case NWHITE:
	p = "NWHITE";
	break;
      case NWHITE + ADD_NL:
	p = "NWHITE+NL";
	break;
      case DIGIT:
	p = "DIGIT";
	break;
      case DIGIT + ADD_NL:
	p = "DIGIT+NL";
	break;
      case NDIGIT:
	p = "NDIGIT";
	break;
      case NDIGIT + ADD_NL:
	p = "NDIGIT+NL";
	break;
      case HEX:
	p = "HEX";
	break;
      case HEX + ADD_NL:
	p = "HEX+NL";
	break;
      case NHEX:
	p = "NHEX";
	break;
      case NHEX + ADD_NL:
	p = "NHEX+NL";
	break;
      case OCTAL:
	p = "OCTAL";
	break;
      case OCTAL + ADD_NL:
	p = "OCTAL+NL";
	break;
      case NOCTAL:
	p = "NOCTAL";
	break;
      case NOCTAL + ADD_NL:
	p = "NOCTAL+NL";
	break;
      case WORD:
	p = "WORD";
	break;
      case WORD + ADD_NL:
	p = "WORD+NL";
	break;
      case NWORD:
	p = "NWORD";
	break;
      case NWORD + ADD_NL:
	p = "NWORD+NL";
	break;
      case HEAD:
	p = "HEAD";
	break;
      case HEAD + ADD_NL:
	p = "HEAD+NL";
	break;
      case NHEAD:
	p = "NHEAD";
	break;
      case NHEAD + ADD_NL:
	p = "NHEAD+NL";
	break;
      case ALPHA:
	p = "ALPHA";
	break;
      case ALPHA + ADD_NL:
	p = "ALPHA+NL";
	break;
      case NALPHA:
	p = "NALPHA";
	break;
      case NALPHA + ADD_NL:
	p = "NALPHA+NL";
	break;
      case LOWER:
	p = "LOWER";
	break;
      case LOWER + ADD_NL:
	p = "LOWER+NL";
	break;
      case NLOWER:
	p = "NLOWER";
	break;
      case NLOWER + ADD_NL:
	p = "NLOWER+NL";
	break;
      case UPPER:
	p = "UPPER";
	break;
      case UPPER + ADD_NL:
	p = "UPPER+NL";
	break;
      case NUPPER:
	p = "NUPPER";
	break;
      case NUPPER + ADD_NL:
	p = "NUPPER+NL";
	break;
      case BRANCH:
	p = "BRANCH";
	break;
      case EXACTLY:
	p = "EXACTLY";
	break;
      case NOTHING:
	p = "NOTHING";
	break;
      case BACK:
	p = "BACK";
	break;
      case END:
	p = "END";
	break;
      case MOPEN + 0:
	p = "MATCH START";
	break;
      case MOPEN + 1:
      case MOPEN + 2:
      case MOPEN + 3:
      case MOPEN + 4:
      case MOPEN + 5:
      case MOPEN + 6:
      case MOPEN + 7:
      case MOPEN + 8:
      case MOPEN + 9:
	sprintf(buf + STRLEN(buf), "MOPEN%d", OP(op) - MOPEN);
	p = NULL;
	break;
      case MCLOSE + 0:
	p = "MATCH END";
	break;
      case MCLOSE + 1:
      case MCLOSE + 2:
      case MCLOSE + 3:
      case MCLOSE + 4:
      case MCLOSE + 5:
      case MCLOSE + 6:
      case MCLOSE + 7:
      case MCLOSE + 8:
      case MCLOSE + 9:
	sprintf(buf + STRLEN(buf), "MCLOSE%d", OP(op) - MCLOSE);
	p = NULL;
	break;
      case BACKREF + 1:
      case BACKREF + 2:
      case BACKREF + 3:
      case BACKREF + 4:
      case BACKREF + 5:
      case BACKREF + 6:
      case BACKREF + 7:
      case BACKREF + 8:
      case BACKREF + 9:
	sprintf(buf + STRLEN(buf), "BACKREF%d", OP(op) - BACKREF);
	p = NULL;
	break;
      case NOPEN:
	p = "NOPEN";
	break;
      case NCLOSE:
	p = "NCLOSE";
	break;
#ifdef FEAT_SYN_HL
      case ZOPEN + 1:
      case ZOPEN + 2:
      case ZOPEN + 3:
      case ZOPEN + 4:
      case ZOPEN + 5:
      case ZOPEN + 6:
      case ZOPEN + 7:
      case ZOPEN + 8:
      case ZOPEN + 9:
	sprintf(buf + STRLEN(buf), "ZOPEN%d", OP(op) - ZOPEN);
	p = NULL;
	break;
      case ZCLOSE + 1:
      case ZCLOSE + 2:
      case ZCLOSE + 3:
      case ZCLOSE + 4:
      case ZCLOSE + 5:
      case ZCLOSE + 6:
      case ZCLOSE + 7:
      case ZCLOSE + 8:
      case ZCLOSE + 9:
	sprintf(buf + STRLEN(buf), "ZCLOSE%d", OP(op) - ZCLOSE);
	p = NULL;
	break;
      case ZREF + 1:
      case ZREF + 2:
      case ZREF + 3:
      case ZREF + 4:
      case ZREF + 5:
      case ZREF + 6:
      case ZREF + 7:
      case ZREF + 8:
      case ZREF + 9:
	sprintf(buf + STRLEN(buf), "ZREF%d", OP(op) - ZREF);
	p = NULL;
	break;
#endif
      case STAR:
	p = "STAR";
	break;
      case PLUS:
	p = "PLUS";
	break;
      case NOMATCH:
	p = "NOMATCH";
	break;
      case MATCH:
	p = "MATCH";
	break;
      case BEHIND:
	p = "BEHIND";
	break;
      case NOBEHIND:
	p = "NOBEHIND";
	break;
      case SUBPAT:
	p = "SUBPAT";
	break;
      case BRACE_LIMITS:
	p = "BRACE_LIMITS";
	break;
      case BRACE_SIMPLE:
	p = "BRACE_SIMPLE";
	break;
      case BRACE_COMPLEX + 0:
      case BRACE_COMPLEX + 1:
      case BRACE_COMPLEX + 2:
      case BRACE_COMPLEX + 3:
      case BRACE_COMPLEX + 4:
      case BRACE_COMPLEX + 5:
      case BRACE_COMPLEX + 6:
      case BRACE_COMPLEX + 7:
      case BRACE_COMPLEX + 8:
      case BRACE_COMPLEX + 9:
	sprintf(buf + STRLEN(buf), "BRACE_COMPLEX%d", OP(op) - BRACE_COMPLEX);
	p = NULL;
	break;
      case MULTIBYTECODE:
	p = "MULTIBYTECODE";
	break;
      case NEWL:
	p = "NEWL";
	break;
      default:
	sprintf(buf + STRLEN(buf), "corrupt %d", OP(op));
	p = NULL;
	break;
    }
    if (p != NULL)
	STRCAT(buf, p);
    return (char_u *)buf;
}
#endif	    /* DEBUG */

/*
 * Used in a place where no * or \+ can follow.
 */
    static int
re_mult_next(char *what)
{
    if (re_multi_type(peekchr()) == MULTI_MULT)
    {
       semsg(_("E888: (NFA regexp) cannot repeat %s"), what);
       rc_did_emsg = TRUE;
       return FAIL;
    }
    return OK;
}

typedef struct
{
    int a, b, c;
} decomp_T;


/* 0xfb20 - 0xfb4f */
static decomp_T decomp_table[0xfb4f-0xfb20+1] =
{
    {0x5e2,0,0},		/* 0xfb20	alt ayin */
    {0x5d0,0,0},		/* 0xfb21	alt alef */
    {0x5d3,0,0},		/* 0xfb22	alt dalet */
    {0x5d4,0,0},		/* 0xfb23	alt he */
    {0x5db,0,0},		/* 0xfb24	alt kaf */
    {0x5dc,0,0},		/* 0xfb25	alt lamed */
    {0x5dd,0,0},		/* 0xfb26	alt mem-sofit */
    {0x5e8,0,0},		/* 0xfb27	alt resh */
    {0x5ea,0,0},		/* 0xfb28	alt tav */
    {'+', 0, 0},		/* 0xfb29	alt plus */
    {0x5e9, 0x5c1, 0},		/* 0xfb2a	shin+shin-dot */
    {0x5e9, 0x5c2, 0},		/* 0xfb2b	shin+sin-dot */
    {0x5e9, 0x5c1, 0x5bc},	/* 0xfb2c	shin+shin-dot+dagesh */
    {0x5e9, 0x5c2, 0x5bc},	/* 0xfb2d	shin+sin-dot+dagesh */
    {0x5d0, 0x5b7, 0},		/* 0xfb2e	alef+patah */
    {0x5d0, 0x5b8, 0},		/* 0xfb2f	alef+qamats */
    {0x5d0, 0x5b4, 0},		/* 0xfb30	alef+hiriq */
    {0x5d1, 0x5bc, 0},		/* 0xfb31	bet+dagesh */
    {0x5d2, 0x5bc, 0},		/* 0xfb32	gimel+dagesh */
    {0x5d3, 0x5bc, 0},		/* 0xfb33	dalet+dagesh */
    {0x5d4, 0x5bc, 0},		/* 0xfb34	he+dagesh */
    {0x5d5, 0x5bc, 0},		/* 0xfb35	vav+dagesh */
    {0x5d6, 0x5bc, 0},		/* 0xfb36	zayin+dagesh */
    {0xfb37, 0, 0},		/* 0xfb37 -- UNUSED */
    {0x5d8, 0x5bc, 0},		/* 0xfb38	tet+dagesh */
    {0x5d9, 0x5bc, 0},		/* 0xfb39	yud+dagesh */
    {0x5da, 0x5bc, 0},		/* 0xfb3a	kaf sofit+dagesh */
    {0x5db, 0x5bc, 0},		/* 0xfb3b	kaf+dagesh */
    {0x5dc, 0x5bc, 0},		/* 0xfb3c	lamed+dagesh */
    {0xfb3d, 0, 0},		/* 0xfb3d -- UNUSED */
    {0x5de, 0x5bc, 0},		/* 0xfb3e	mem+dagesh */
    {0xfb3f, 0, 0},		/* 0xfb3f -- UNUSED */
    {0x5e0, 0x5bc, 0},		/* 0xfb40	nun+dagesh */
    {0x5e1, 0x5bc, 0},		/* 0xfb41	samech+dagesh */
    {0xfb42, 0, 0},		/* 0xfb42 -- UNUSED */
    {0x5e3, 0x5bc, 0},		/* 0xfb43	pe sofit+dagesh */
    {0x5e4, 0x5bc,0},		/* 0xfb44	pe+dagesh */
    {0xfb45, 0, 0},		/* 0xfb45 -- UNUSED */
    {0x5e6, 0x5bc, 0},		/* 0xfb46	tsadi+dagesh */
    {0x5e7, 0x5bc, 0},		/* 0xfb47	qof+dagesh */
    {0x5e8, 0x5bc, 0},		/* 0xfb48	resh+dagesh */
    {0x5e9, 0x5bc, 0},		/* 0xfb49	shin+dagesh */
    {0x5ea, 0x5bc, 0},		/* 0xfb4a	tav+dagesh */
    {0x5d5, 0x5b9, 0},		/* 0xfb4b	vav+holam */
    {0x5d1, 0x5bf, 0},		/* 0xfb4c	bet+rafe */
    {0x5db, 0x5bf, 0},		/* 0xfb4d	kaf+rafe */
    {0x5e4, 0x5bf, 0},		/* 0xfb4e	pe+rafe */
    {0x5d0, 0x5dc, 0}		/* 0xfb4f	alef-lamed */
};

    static void
mb_decompose(int c, int *c1, int *c2, int *c3)
{
    decomp_T d;

    if (c >= 0xfb20 && c <= 0xfb4f)
    {
	d = decomp_table[c - 0xfb20];
	*c1 = d.a;
	*c2 = d.b;
	*c3 = d.c;
    }
    else
    {
	*c1 = c;
	*c2 = *c3 = 0;
    }
}

/*
 * Compare two strings, ignore case if rex.reg_ic set.
 * Return 0 if strings match, non-zero otherwise.
 * Correct the length "*n" when composing characters are ignored.
 */
    static int
cstrncmp(char_u *s1, char_u *s2, int *n)
{
    int		result;

    if (!rex.reg_ic)
	result = STRNCMP(s1, s2, *n);
    else
	result = MB_STRNICMP(s1, s2, *n);

    /* if it failed and it's utf8 and we want to combineignore: */
    if (result != 0 && enc_utf8 && rex.reg_icombine)
    {
	char_u	*str1, *str2;
	int	c1, c2, c11, c12;
	int	junk;

	/* we have to handle the strcmp ourselves, since it is necessary to
	 * deal with the composing characters by ignoring them: */
	str1 = s1;
	str2 = s2;
	c1 = c2 = 0;
	while ((int)(str1 - s1) < *n)
	{
	    c1 = mb_ptr2char_adv(&str1);
	    c2 = mb_ptr2char_adv(&str2);

	    /* decompose the character if necessary, into 'base' characters
	     * because I don't care about Arabic, I will hard-code the Hebrew
	     * which I *do* care about!  So sue me... */
	    if (c1 != c2 && (!rex.reg_ic || utf_fold(c1) != utf_fold(c2)))
	    {
		/* decomposition necessary? */
		mb_decompose(c1, &c11, &junk, &junk);
		mb_decompose(c2, &c12, &junk, &junk);
		c1 = c11;
		c2 = c12;
		if (c11 != c12
			    && (!rex.reg_ic || utf_fold(c11) != utf_fold(c12)))
		    break;
	    }
	}
	result = c2 - c1;
	if (result == 0)
	    *n = (int)(str2 - s2);
    }

    return result;
}

/*
 * cstrchr: This function is used a lot for simple searches, keep it fast!
 */
    static char_u *
cstrchr(char_u *s, int c)
{
    char_u	*p;
    int		cc;

    if (!rex.reg_ic || (!enc_utf8 && mb_char2len(c) > 1))
	return vim_strchr(s, c);

    /* tolower() and toupper() can be slow, comparing twice should be a lot
     * faster (esp. when using MS Visual C++!).
     * For UTF-8 need to use folded case. */
    if (enc_utf8 && c > 0x80)
	cc = utf_fold(c);
    else
	 if (MB_ISUPPER(c))
	cc = MB_TOLOWER(c);
    else if (MB_ISLOWER(c))
	cc = MB_TOUPPER(c);
    else
	return vim_strchr(s, c);

    if (has_mbyte)
    {
	for (p = s; *p != NUL; p += (*mb_ptr2len)(p))
	{
	    if (enc_utf8 && c > 0x80)
	    {
		if (utf_fold(utf_ptr2char(p)) == cc)
		    return p;
	    }
	    else if (*p == c || *p == cc)
		return p;
	}
    }
    else
	/* Faster version for when there are no multi-byte characters. */
	for (p = s; *p != NUL; ++p)
	    if (*p == c || *p == cc)
		return p;

    return NULL;
}

/***************************************************************
 *		      regsub stuff			       *
 ***************************************************************/

/*
 * We should define ftpr as a pointer to a function returning a pointer to
 * a function returning a pointer to a function ...
 * This is impossible, so we declare a pointer to a function returning a
 * pointer to a function returning void. This should work for all compilers.
 */
typedef void (*(*fptr_T)(int *, int))();

static int vim_regsub_both(char_u *source, typval_T *expr, char_u *dest, int copy, int magic, int backslash);

    static fptr_T
do_upper(int *d, int c)
{
    *d = MB_TOUPPER(c);

    return (fptr_T)NULL;
}

    static fptr_T
do_Upper(int *d, int c)
{
    *d = MB_TOUPPER(c);

    return (fptr_T)do_Upper;
}

    static fptr_T
do_lower(int *d, int c)
{
    *d = MB_TOLOWER(c);

    return (fptr_T)NULL;
}

    static fptr_T
do_Lower(int *d, int c)
{
    *d = MB_TOLOWER(c);

    return (fptr_T)do_Lower;
}

/*
 * regtilde(): Replace tildes in the pattern by the old pattern.
 *
 * Short explanation of the tilde: It stands for the previous replacement
 * pattern.  If that previous pattern also contains a ~ we should go back a
 * step further...  But we insert the previous pattern into the current one
 * and remember that.
 * This still does not handle the case where "magic" changes.  So require the
 * user to keep his hands off of "magic".
 *
 * The tildes are parsed once before the first call to vim_regsub().
 */
    char_u *
regtilde(char_u *source, int magic)
{
    char_u	*newsub = source;
    char_u	*tmpsub;
    char_u	*p;
    int		len;
    int		prevlen;

    for (p = newsub; *p; ++p)
    {
	if ((*p == '~' && magic) || (*p == '\\' && *(p + 1) == '~' && !magic))
	{
	    if (reg_prev_sub != NULL)
	    {
		/* length = len(newsub) - 1 + len(prev_sub) + 1 */
		prevlen = (int)STRLEN(reg_prev_sub);
		tmpsub = alloc((unsigned)(STRLEN(newsub) + prevlen));
		if (tmpsub != NULL)
		{
		    /* copy prefix */
		    len = (int)(p - newsub);	/* not including ~ */
		    mch_memmove(tmpsub, newsub, (size_t)len);
		    /* interpret tilde */
		    mch_memmove(tmpsub + len, reg_prev_sub, (size_t)prevlen);
		    /* copy postfix */
		    if (!magic)
			++p;			/* back off \ */
		    STRCPY(tmpsub + len + prevlen, p + 1);

		    if (newsub != source)	/* already allocated newsub */
			vim_free(newsub);
		    newsub = tmpsub;
		    p = newsub + len + prevlen;
		}
	    }
	    else if (magic)
		STRMOVE(p, p + 1);	/* remove '~' */
	    else
		STRMOVE(p, p + 2);	/* remove '\~' */
	    --p;
	}
	else
	{
	    if (*p == '\\' && p[1])		/* skip escaped characters */
		++p;
	    if (has_mbyte)
		p += (*mb_ptr2len)(p) - 1;
	}
    }

    vim_free(reg_prev_sub);
    if (newsub != source)	/* newsub was allocated, just keep it */
	reg_prev_sub = newsub;
    else			/* no ~ found, need to save newsub  */
	reg_prev_sub = vim_strsave(newsub);
    return newsub;
}

#ifdef FEAT_EVAL
static int can_f_submatch = FALSE;	/* TRUE when submatch() can be used */

/* These pointers are used for reg_submatch().  Needed for when the
 * substitution string is an expression that contains a call to substitute()
 * and submatch(). */
typedef struct {
    regmatch_T	*sm_match;
    regmmatch_T	*sm_mmatch;
    linenr_T	sm_firstlnum;
    linenr_T	sm_maxline;
    int		sm_line_lbr;
} regsubmatch_T;

static regsubmatch_T rsm;  /* can only be used when can_f_submatch is TRUE */
#endif

#if defined(FEAT_MODIFY_FNAME) || defined(FEAT_EVAL) || defined(PROTO)

/*
 * Put the submatches in "argv[0]" which is a list passed into call_func() by
 * vim_regsub_both().
 */
    static int
fill_submatch_list(int argc UNUSED, typval_T *argv, int argcount)
{
    listitem_T	*li;
    int		i;
    char_u	*s;

    if (argcount == 0)
	/* called function doesn't take an argument */
	return 0;

    /* Relies on sl_list to be the first item in staticList10_T. */
    init_static_list((staticList10_T *)(argv->vval.v_list));

    /* There are always 10 list items in staticList10_T. */
    li = argv->vval.v_list->lv_first;
    for (i = 0; i < 10; ++i)
    {
	s = rsm.sm_match->startp[i];
	if (s == NULL || rsm.sm_match->endp[i] == NULL)
	    s = NULL;
	else
	    s = vim_strnsave(s, (int)(rsm.sm_match->endp[i] - s));
	li->li_tv.v_type = VAR_STRING;
	li->li_tv.vval.v_string = s;
	li = li->li_next;
    }
    return 1;
}

    static void
clear_submatch_list(staticList10_T *sl)
{
    int i;

    for (i = 0; i < 10; ++i)
	vim_free(sl->sl_items[i].li_tv.vval.v_string);
}

/*
 * vim_regsub() - perform substitutions after a vim_regexec() or
 * vim_regexec_multi() match.
 *
 * If "copy" is TRUE really copy into "dest".
 * If "copy" is FALSE nothing is copied, this is just to find out the length
 * of the result.
 *
 * If "backslash" is TRUE, a backslash will be removed later, need to double
 * them to keep them, and insert a backslash before a CR to avoid it being
 * replaced with a line break later.
 *
 * Note: The matched text must not change between the call of
 * vim_regexec()/vim_regexec_multi() and vim_regsub()!  It would make the back
 * references invalid!
 *
 * Returns the size of the replacement, including terminating NUL.
 */
    int
vim_regsub(
    regmatch_T	*rmp,
    char_u	*source,
    typval_T	*expr,
    char_u	*dest,
    int		copy,
    int		magic,
    int		backslash)
{
    int		result;
    regexec_T	rex_save;
    int		rex_in_use_save = rex_in_use;

    if (rex_in_use)
	/* Being called recursively, save the state. */
	rex_save = rex;
    rex_in_use = TRUE;

    rex.reg_match = rmp;
    rex.reg_mmatch = NULL;
    rex.reg_maxline = 0;
    rex.reg_buf = curbuf;
    rex.reg_line_lbr = TRUE;
    result = vim_regsub_both(source, expr, dest, copy, magic, backslash);

    rex_in_use = rex_in_use_save;
    if (rex_in_use)
	rex = rex_save;

    return result;
}
#endif

    int
vim_regsub_multi(
    regmmatch_T	*rmp,
    linenr_T	lnum,
    char_u	*source,
    char_u	*dest,
    int		copy,
    int		magic,
    int		backslash)
{
    int		result;
    regexec_T	rex_save;
    int		rex_in_use_save = rex_in_use;

    if (rex_in_use)
	/* Being called recursively, save the state. */
	rex_save = rex;
    rex_in_use = TRUE;

    rex.reg_match = NULL;
    rex.reg_mmatch = rmp;
    rex.reg_buf = curbuf;	/* always works on the current buffer! */
    rex.reg_firstlnum = lnum;
    rex.reg_maxline = curbuf->b_ml.ml_line_count - lnum;
    rex.reg_line_lbr = FALSE;
    result = vim_regsub_both(source, NULL, dest, copy, magic, backslash);

    rex_in_use = rex_in_use_save;
    if (rex_in_use)
	rex = rex_save;

    return result;
}

    static int
vim_regsub_both(
    char_u	*source,
    typval_T	*expr,
    char_u	*dest,
    int		copy,
    int		magic,
    int		backslash)
{
    char_u	*src;
    char_u	*dst;
    char_u	*s;
    int		c;
    int		cc;
    int		no = -1;
    fptr_T	func_all = (fptr_T)NULL;
    fptr_T	func_one = (fptr_T)NULL;
    linenr_T	clnum = 0;	/* init for GCC */
    int		len = 0;	/* init for GCC */
#ifdef FEAT_EVAL
    static char_u   *eval_result = NULL;
#endif

    /* Be paranoid... */
    if ((source == NULL && expr == NULL) || dest == NULL)
    {
	emsg(_(e_null));
	return 0;
    }
    if (prog_magic_wrong())
	return 0;
    src = source;
    dst = dest;

    /*
     * When the substitute part starts with "\=" evaluate it as an expression.
     */
    if (expr != NULL || (source[0] == '\\' && source[1] == '='))
    {
#ifdef FEAT_EVAL
	/* To make sure that the length doesn't change between checking the
	 * length and copying the string, and to speed up things, the
	 * resulting string is saved from the call with "copy" == FALSE to the
	 * call with "copy" == TRUE. */
	if (copy)
	{
	    if (eval_result != NULL)
	    {
		STRCPY(dest, eval_result);
		dst += STRLEN(eval_result);
		VIM_CLEAR(eval_result);
	    }
	}
	else
	{
	    int		    prev_can_f_submatch = can_f_submatch;
	    regsubmatch_T   rsm_save;

	    vim_free(eval_result);

	    /* The expression may contain substitute(), which calls us
	     * recursively.  Make sure submatch() gets the text from the first
	     * level. */
	    if (can_f_submatch)
		rsm_save = rsm;
	    can_f_submatch = TRUE;
	    rsm.sm_match = rex.reg_match;
	    rsm.sm_mmatch = rex.reg_mmatch;
	    rsm.sm_firstlnum = rex.reg_firstlnum;
	    rsm.sm_maxline = rex.reg_maxline;
	    rsm.sm_line_lbr = rex.reg_line_lbr;

	    if (expr != NULL)
	    {
		typval_T	argv[2];
		int		dummy;
		char_u		buf[NUMBUFLEN];
		typval_T	rettv;
		staticList10_T	matchList;

		rettv.v_type = VAR_STRING;
		rettv.vval.v_string = NULL;
		argv[0].v_type = VAR_LIST;
		argv[0].vval.v_list = &matchList.sl_list;
		matchList.sl_list.lv_len = 0;
		if (expr->v_type == VAR_FUNC)
		{
		    s = expr->vval.v_string;
		    call_func(s, (int)STRLEN(s), &rettv,
				    1, argv, fill_submatch_list,
					 0L, 0L, &dummy, TRUE, NULL, NULL);
		}
		else if (expr->v_type == VAR_PARTIAL)
		{
		    partial_T   *partial = expr->vval.v_partial;

		    s = partial_name(partial);
		    call_func(s, (int)STRLEN(s), &rettv,
				    1, argv, fill_submatch_list,
				      0L, 0L, &dummy, TRUE, partial, NULL);
		}
		if (matchList.sl_list.lv_len > 0)
		    /* fill_submatch_list() was called */
		    clear_submatch_list(&matchList);

		eval_result = tv_get_string_buf_chk(&rettv, buf);
		if (eval_result != NULL)
		    eval_result = vim_strsave(eval_result);
		clear_tv(&rettv);
	    }
	    else
		eval_result = eval_to_string(source + 2, NULL, TRUE);

	    if (eval_result != NULL)
	    {
		int had_backslash = FALSE;

		for (s = eval_result; *s != NUL; MB_PTR_ADV(s))
		{
		    /* Change NL to CR, so that it becomes a line break,
		     * unless called from vim_regexec_nl().
		     * Skip over a backslashed character. */
		    if (*s == NL && !rsm.sm_line_lbr)
			*s = CAR;
		    else if (*s == '\\' && s[1] != NUL)
		    {
			++s;
			/* Change NL to CR here too, so that this works:
			 * :s/abc\\\ndef/\="aaa\\\nbbb"/  on text:
			 *   abc\
			 *   def
			 * Not when called from vim_regexec_nl().
			 */
			if (*s == NL && !rsm.sm_line_lbr)
			    *s = CAR;
			had_backslash = TRUE;
		    }
		}
		if (had_backslash && backslash)
		{
		    /* Backslashes will be consumed, need to double them. */
		    s = vim_strsave_escaped(eval_result, (char_u *)"\\");
		    if (s != NULL)
		    {
			vim_free(eval_result);
			eval_result = s;
		    }
		}

		dst += STRLEN(eval_result);
	    }

	    can_f_submatch = prev_can_f_submatch;
	    if (can_f_submatch)
		rsm = rsm_save;
	}
#endif
    }
    else
      while ((c = *src++) != NUL)
      {
	if (c == '&' && magic)
	    no = 0;
	else if (c == '\\' && *src != NUL)
	{
	    if (*src == '&' && !magic)
	    {
		++src;
		no = 0;
	    }
	    else if ('0' <= *src && *src <= '9')
	    {
		no = *src++ - '0';
	    }
	    else if (vim_strchr((char_u *)"uUlLeE", *src))
	    {
		switch (*src++)
		{
		case 'u':   func_one = (fptr_T)do_upper;
			    continue;
		case 'U':   func_all = (fptr_T)do_Upper;
			    continue;
		case 'l':   func_one = (fptr_T)do_lower;
			    continue;
		case 'L':   func_all = (fptr_T)do_Lower;
			    continue;
		case 'e':
		case 'E':   func_one = func_all = (fptr_T)NULL;
			    continue;
		}
	    }
	}
	if (no < 0)	      /* Ordinary character. */
	{
	    if (c == K_SPECIAL && src[0] != NUL && src[1] != NUL)
	    {
		/* Copy a special key as-is. */
		if (copy)
		{
		    *dst++ = c;
		    *dst++ = *src++;
		    *dst++ = *src++;
		}
		else
		{
		    dst += 3;
		    src += 2;
		}
		continue;
	    }

	    if (c == '\\' && *src != NUL)
	    {
		/* Check for abbreviations -- webb */
		switch (*src)
		{
		    case 'r':	c = CAR;	++src;	break;
		    case 'n':	c = NL;		++src;	break;
		    case 't':	c = TAB;	++src;	break;
		 /* Oh no!  \e already has meaning in subst pat :-( */
		 /* case 'e':   c = ESC;	++src;	break; */
		    case 'b':	c = Ctrl_H;	++src;	break;

		    /* If "backslash" is TRUE the backslash will be removed
		     * later.  Used to insert a literal CR. */
		    default:	if (backslash)
				{
				    if (copy)
					*dst = '\\';
				    ++dst;
				}
				c = *src++;
		}
	    }
	    else if (has_mbyte)
		c = mb_ptr2char(src - 1);

	    /* Write to buffer, if copy is set. */
	    if (func_one != (fptr_T)NULL)
		/* Turbo C complains without the typecast */
		func_one = (fptr_T)(func_one(&cc, c));
	    else if (func_all != (fptr_T)NULL)
		/* Turbo C complains without the typecast */
		func_all = (fptr_T)(func_all(&cc, c));
	    else /* just copy */
		cc = c;

	    if (has_mbyte)
	    {
		int totlen = mb_ptr2len(src - 1);

		if (copy)
		    mb_char2bytes(cc, dst);
		dst += mb_char2len(cc) - 1;
		if (enc_utf8)
		{
		    int clen = utf_ptr2len(src - 1);

		    /* If the character length is shorter than "totlen", there
		     * are composing characters; copy them as-is. */
		    if (clen < totlen)
		    {
			if (copy)
			    mch_memmove(dst + 1, src - 1 + clen,
						     (size_t)(totlen - clen));
			dst += totlen - clen;
		    }
		}
		src += totlen - 1;
	    }
	    else if (copy)
		    *dst = cc;
	    dst++;
	}
	else
	{
	    if (REG_MULTI)
	    {
		clnum = rex.reg_mmatch->startpos[no].lnum;
		if (clnum < 0 || rex.reg_mmatch->endpos[no].lnum < 0)
		    s = NULL;
		else
		{
		    s = reg_getline(clnum) + rex.reg_mmatch->startpos[no].col;
		    if (rex.reg_mmatch->endpos[no].lnum == clnum)
			len = rex.reg_mmatch->endpos[no].col
					    - rex.reg_mmatch->startpos[no].col;
		    else
			len = (int)STRLEN(s);
		}
	    }
	    else
	    {
		s = rex.reg_match->startp[no];
		if (rex.reg_match->endp[no] == NULL)
		    s = NULL;
		else
		    len = (int)(rex.reg_match->endp[no] - s);
	    }
	    if (s != NULL)
	    {
		for (;;)
		{
		    if (len == 0)
		    {
			if (REG_MULTI)
			{
			    if (rex.reg_mmatch->endpos[no].lnum == clnum)
				break;
			    if (copy)
				*dst = CAR;
			    ++dst;
			    s = reg_getline(++clnum);
			    if (rex.reg_mmatch->endpos[no].lnum == clnum)
				len = rex.reg_mmatch->endpos[no].col;
			    else
				len = (int)STRLEN(s);
			}
			else
			    break;
		    }
		    else if (*s == NUL) /* we hit NUL. */
		    {
			if (copy)
			    emsg(_(e_re_damg));
			goto exit;
		    }
		    else
		    {
			if (backslash && (*s == CAR || *s == '\\'))
			{
			    /*
			     * Insert a backslash in front of a CR, otherwise
			     * it will be replaced by a line break.
			     * Number of backslashes will be halved later,
			     * double them here.
			     */
			    if (copy)
			    {
				dst[0] = '\\';
				dst[1] = *s;
			    }
			    dst += 2;
			}
			else
			{
			    if (has_mbyte)
				c = mb_ptr2char(s);
			    else
				c = *s;

			    if (func_one != (fptr_T)NULL)
				/* Turbo C complains without the typecast */
				func_one = (fptr_T)(func_one(&cc, c));
			    else if (func_all != (fptr_T)NULL)
				/* Turbo C complains without the typecast */
				func_all = (fptr_T)(func_all(&cc, c));
			    else /* just copy */
				cc = c;

			    if (has_mbyte)
			    {
				int l;

				/* Copy composing characters separately, one
				 * at a time. */
				if (enc_utf8)
				    l = utf_ptr2len(s) - 1;
				else
				    l = mb_ptr2len(s) - 1;

				s += l;
				len -= l;
				if (copy)
				    mb_char2bytes(cc, dst);
				dst += mb_char2len(cc) - 1;
			    }
			    else if (copy)
				    *dst = cc;
			    dst++;
			}

			++s;
			--len;
		    }
		}
	    }
	    no = -1;
	}
      }
    if (copy)
	*dst = NUL;

exit:
    return (int)((dst - dest) + 1);
}

#ifdef FEAT_EVAL
/*
 * Call reg_getline() with the line numbers from the submatch.  If a
 * substitute() was used the reg_maxline and other values have been
 * overwritten.
 */
    static char_u *
reg_getline_submatch(linenr_T lnum)
{
    char_u *s;
    linenr_T save_first = rex.reg_firstlnum;
    linenr_T save_max = rex.reg_maxline;

    rex.reg_firstlnum = rsm.sm_firstlnum;
    rex.reg_maxline = rsm.sm_maxline;

    s = reg_getline(lnum);

    rex.reg_firstlnum = save_first;
    rex.reg_maxline = save_max;
    return s;
}

/*
 * Used for the submatch() function: get the string from the n'th submatch in
 * allocated memory.
 * Returns NULL when not in a ":s" command and for a non-existing submatch.
 */
    char_u *
reg_submatch(int no)
{
    char_u	*retval = NULL;
    char_u	*s;
    int		len;
    int		round;
    linenr_T	lnum;

    if (!can_f_submatch || no < 0)
	return NULL;

    if (rsm.sm_match == NULL)
    {
	/*
	 * First round: compute the length and allocate memory.
	 * Second round: copy the text.
	 */
	for (round = 1; round <= 2; ++round)
	{
	    lnum = rsm.sm_mmatch->startpos[no].lnum;
	    if (lnum < 0 || rsm.sm_mmatch->endpos[no].lnum < 0)
		return NULL;

	    s = reg_getline_submatch(lnum) + rsm.sm_mmatch->startpos[no].col;
	    if (s == NULL)  /* anti-crash check, cannot happen? */
		break;
	    if (rsm.sm_mmatch->endpos[no].lnum == lnum)
	    {
		/* Within one line: take form start to end col. */
		len = rsm.sm_mmatch->endpos[no].col
					  - rsm.sm_mmatch->startpos[no].col;
		if (round == 2)
		    vim_strncpy(retval, s, len);
		++len;
	    }
	    else
	    {
		/* Multiple lines: take start line from start col, middle
		 * lines completely and end line up to end col. */
		len = (int)STRLEN(s);
		if (round == 2)
		{
		    STRCPY(retval, s);
		    retval[len] = '\n';
		}
		++len;
		++lnum;
		while (lnum < rsm.sm_mmatch->endpos[no].lnum)
		{
		    s = reg_getline_submatch(lnum++);
		    if (round == 2)
			STRCPY(retval + len, s);
		    len += (int)STRLEN(s);
		    if (round == 2)
			retval[len] = '\n';
		    ++len;
		}
		if (round == 2)
		    STRNCPY(retval + len, reg_getline_submatch(lnum),
					     rsm.sm_mmatch->endpos[no].col);
		len += rsm.sm_mmatch->endpos[no].col;
		if (round == 2)
		    retval[len] = NUL;
		++len;
	    }

	    if (retval == NULL)
	    {
		retval = lalloc((long_u)len, TRUE);
		if (retval == NULL)
		    return NULL;
	    }
	}
    }
    else
    {
	s = rsm.sm_match->startp[no];
	if (s == NULL || rsm.sm_match->endp[no] == NULL)
	    retval = NULL;
	else
	    retval = vim_strnsave(s, (int)(rsm.sm_match->endp[no] - s));
    }

    return retval;
}

/*
 * Used for the submatch() function with the optional non-zero argument: get
 * the list of strings from the n'th submatch in allocated memory with NULs
 * represented in NLs.
 * Returns a list of allocated strings.  Returns NULL when not in a ":s"
 * command, for a non-existing submatch and for any error.
 */
    list_T *
reg_submatch_list(int no)
{
    char_u	*s;
    linenr_T	slnum;
    linenr_T	elnum;
    colnr_T	scol;
    colnr_T	ecol;
    int		i;
    list_T	*list;
    int		error = FALSE;

    if (!can_f_submatch || no < 0)
	return NULL;

    if (rsm.sm_match == NULL)
    {
	slnum = rsm.sm_mmatch->startpos[no].lnum;
	elnum = rsm.sm_mmatch->endpos[no].lnum;
	if (slnum < 0 || elnum < 0)
	    return NULL;

	scol = rsm.sm_mmatch->startpos[no].col;
	ecol = rsm.sm_mmatch->endpos[no].col;

	list = list_alloc();
	if (list == NULL)
	    return NULL;

	s = reg_getline_submatch(slnum) + scol;
	if (slnum == elnum)
	{
	    if (list_append_string(list, s, ecol - scol) == FAIL)
		error = TRUE;
	}
	else
	{
	    if (list_append_string(list, s, -1) == FAIL)
		error = TRUE;
	    for (i = 1; i < elnum - slnum; i++)
	    {
		s = reg_getline_submatch(slnum + i);
		if (list_append_string(list, s, -1) == FAIL)
		    error = TRUE;
	    }
	    s = reg_getline_submatch(elnum);
	    if (list_append_string(list, s, ecol) == FAIL)
		error = TRUE;
	}
    }
    else
    {
	s = rsm.sm_match->startp[no];
	if (s == NULL || rsm.sm_match->endp[no] == NULL)
	    return NULL;
	list = list_alloc();
	if (list == NULL)
	    return NULL;
	if (list_append_string(list, s,
				 (int)(rsm.sm_match->endp[no] - s)) == FAIL)
	    error = TRUE;
    }

    if (error)
    {
	list_free(list);
	return NULL;
    }
    return list;
}
#endif

static regengine_T bt_regengine =
{
    bt_regcomp,
    bt_regfree,
    bt_regexec_nl,
    bt_regexec_multi,
    (char_u *)""
};

#include "regexp_nfa.c"

static regengine_T nfa_regengine =
{
    nfa_regcomp,
    nfa_regfree,
    nfa_regexec_nl,
    nfa_regexec_multi,
    (char_u *)""
};

/* Which regexp engine to use? Needed for vim_regcomp().
 * Must match with 'regexpengine'. */
static int regexp_engine = 0;

#ifdef DEBUG
static char_u regname[][30] = {
		    "AUTOMATIC Regexp Engine",
		    "BACKTRACKING Regexp Engine",
		    "NFA Regexp Engine"
			    };
#endif

/*
 * Compile a regular expression into internal code.
 * Returns the program in allocated memory.
 * Use vim_regfree() to free the memory.
 * Returns NULL for an error.
 */
    regprog_T *
vim_regcomp(char_u *expr_arg, int re_flags)
{
    regprog_T   *prog = NULL;
    char_u	*expr = expr_arg;

    regexp_engine = p_re;

    /* Check for prefix "\%#=", that sets the regexp engine */
    if (STRNCMP(expr, "\\%#=", 4) == 0)
    {
	int newengine = expr[4] - '0';

	if (newengine == AUTOMATIC_ENGINE
	    || newengine == BACKTRACKING_ENGINE
	    || newengine == NFA_ENGINE)
	{
	    regexp_engine = expr[4] - '0';
	    expr += 5;
#ifdef DEBUG
	    smsg("New regexp mode selected (%d): %s",
					   regexp_engine, regname[newengine]);
#endif
	}
	else
	{
	    emsg(_("E864: \\%#= can only be followed by 0, 1, or 2. The automatic engine will be used "));
	    regexp_engine = AUTOMATIC_ENGINE;
	}
    }
#ifdef DEBUG
    bt_regengine.expr = expr;
    nfa_regengine.expr = expr;
#endif

    /*
     * First try the NFA engine, unless backtracking was requested.
     */
    if (regexp_engine != BACKTRACKING_ENGINE)
	prog = nfa_regengine.regcomp(expr,
		re_flags + (regexp_engine == AUTOMATIC_ENGINE ? RE_AUTO : 0));
    else
	prog = bt_regengine.regcomp(expr, re_flags);

    /* Check for error compiling regexp with initial engine. */
    if (prog == NULL)
    {
#ifdef BT_REGEXP_DEBUG_LOG
	if (regexp_engine != BACKTRACKING_ENGINE)   /* debugging log for NFA */
	{
	    FILE *f;
	    f = fopen(BT_REGEXP_DEBUG_LOG_NAME, "a");
	    if (f)
	    {
		fprintf(f, "Syntax error in \"%s\"\n", expr);
		fclose(f);
	    }
	    else
		semsg("(NFA) Could not open \"%s\" to write !!!",
			BT_REGEXP_DEBUG_LOG_NAME);
	}
#endif
	/*
	 * If the NFA engine failed, try the backtracking engine.
	 * The NFA engine also fails for patterns that it can't handle well
	 * but are still valid patterns, thus a retry should work.
	 */
	if (regexp_engine == AUTOMATIC_ENGINE)
	{
	    regexp_engine = BACKTRACKING_ENGINE;
	    prog = bt_regengine.regcomp(expr, re_flags);
	}
    }

    if (prog != NULL)
    {
	/* Store the info needed to call regcomp() again when the engine turns
	 * out to be very slow when executing it. */
	prog->re_engine = regexp_engine;
	prog->re_flags  = re_flags;
    }

    return prog;
}

/*
 * Free a compiled regexp program, returned by vim_regcomp().
 */
    void
vim_regfree(regprog_T *prog)
{
    if (prog != NULL)
	prog->engine->regfree(prog);
}

#ifdef FEAT_EVAL
    static void
report_re_switch(char_u *pat)
{
    if (p_verbose > 0)
    {
	verbose_enter();
	msg_puts(_("Switching to backtracking RE engine for pattern: "));
	msg_puts((char *)pat);
	verbose_leave();
    }
}
#endif

#if (defined(FEAT_X11) && (defined(FEAT_TITLE) || defined(FEAT_XCLIPBOARD))) \
	|| defined(PROTO)
/*
 * Return whether "prog" is currently being executed.
 */
    int
regprog_in_use(regprog_T *prog)
{
    return prog->re_in_use;
}
#endif

/*
 * Match a regexp against a string.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Note: "rmp->regprog" may be freed and changed.
 * Uses curbuf for line count and 'iskeyword'.
 * When "nl" is TRUE consider a "\n" in "line" to be a line break.
 *
 * Return TRUE if there is a match, FALSE if not.
 */
    static int
vim_regexec_string(
    regmatch_T	*rmp,
    char_u	*line,  /* string to match against */
    colnr_T	col,    /* column to start looking for match */
    int		nl)
{
    int		result;
    regexec_T	rex_save;
    int		rex_in_use_save = rex_in_use;

    // Cannot use the same prog recursively, it contains state.
    if (rmp->regprog->re_in_use)
    {
	emsg(_(e_recursive));
	return FALSE;
    }
    rmp->regprog->re_in_use = TRUE;

    if (rex_in_use)
	// Being called recursively, save the state.
	rex_save = rex;
    rex_in_use = TRUE;

    rex.reg_startp = NULL;
    rex.reg_endp = NULL;
    rex.reg_startpos = NULL;
    rex.reg_endpos = NULL;

    result = rmp->regprog->engine->regexec_nl(rmp, line, col, nl);
    rmp->regprog->re_in_use = FALSE;

    /* NFA engine aborted because it's very slow. */
    if (rmp->regprog->re_engine == AUTOMATIC_ENGINE
					       && result == NFA_TOO_EXPENSIVE)
    {
	int    save_p_re = p_re;
	int    re_flags = rmp->regprog->re_flags;
	char_u *pat = vim_strsave(((nfa_regprog_T *)rmp->regprog)->pattern);

	p_re = BACKTRACKING_ENGINE;
	vim_regfree(rmp->regprog);
	if (pat != NULL)
	{
#ifdef FEAT_EVAL
	    report_re_switch(pat);
#endif
	    rmp->regprog = vim_regcomp(pat, re_flags);
	    if (rmp->regprog != NULL)
	    {
		rmp->regprog->re_in_use = TRUE;
		result = rmp->regprog->engine->regexec_nl(rmp, line, col, nl);
		rmp->regprog->re_in_use = FALSE;
	    }
	    vim_free(pat);
	}

	p_re = save_p_re;
    }

    rex_in_use = rex_in_use_save;
    if (rex_in_use)
	rex = rex_save;

    return result > 0;
}

/*
 * Note: "*prog" may be freed and changed.
 * Return TRUE if there is a match, FALSE if not.
 */
    int
vim_regexec_prog(
    regprog_T	**prog,
    int		ignore_case,
    char_u	*line,
    colnr_T	col)
{
    int		r;
    regmatch_T	regmatch;

    regmatch.regprog = *prog;
    regmatch.rm_ic = ignore_case;
    r = vim_regexec_string(&regmatch, line, col, FALSE);
    *prog = regmatch.regprog;
    return r;
}

/*
 * Note: "rmp->regprog" may be freed and changed.
 * Return TRUE if there is a match, FALSE if not.
 */
    int
vim_regexec(regmatch_T *rmp, char_u *line, colnr_T col)
{
    return vim_regexec_string(rmp, line, col, FALSE);
}

#if defined(FEAT_MODIFY_FNAME) || defined(FEAT_EVAL) \
	|| defined(FIND_REPLACE_DIALOG) || defined(PROTO)
/*
 * Like vim_regexec(), but consider a "\n" in "line" to be a line break.
 * Note: "rmp->regprog" may be freed and changed.
 * Return TRUE if there is a match, FALSE if not.
 */
    int
vim_regexec_nl(regmatch_T *rmp, char_u *line, colnr_T col)
{
    return vim_regexec_string(rmp, line, col, TRUE);
}
#endif

/*
 * Match a regexp against multiple lines.
 * "rmp->regprog" must be a compiled regexp as returned by vim_regcomp().
 * Note: "rmp->regprog" may be freed and changed, even set to NULL.
 * Uses curbuf for line count and 'iskeyword'.
 *
 * Return zero if there is no match.  Return number of lines contained in the
 * match otherwise.
 */
    long
vim_regexec_multi(
    regmmatch_T *rmp,
    win_T       *win,		/* window in which to search or NULL */
    buf_T       *buf,		/* buffer in which to search */
    linenr_T	lnum,		/* nr of line to start looking for match */
    colnr_T	col,		/* column to start looking for match */
    proftime_T	*tm,		/* timeout limit or NULL */
    int		*timed_out)	/* flag is set when timeout limit reached */
{
    int		result;
    regexec_T	rex_save;
    int		rex_in_use_save = rex_in_use;

    // Cannot use the same prog recursively, it contains state.
    if (rmp->regprog->re_in_use)
    {
	emsg(_(e_recursive));
	return FALSE;
    }
    rmp->regprog->re_in_use = TRUE;

    if (rex_in_use)
	/* Being called recursively, save the state. */
	rex_save = rex;
    rex_in_use = TRUE;

    result = rmp->regprog->engine->regexec_multi(
				      rmp, win, buf, lnum, col, tm, timed_out);
    rmp->regprog->re_in_use = FALSE;

    /* NFA engine aborted because it's very slow. */
    if (rmp->regprog->re_engine == AUTOMATIC_ENGINE
					       && result == NFA_TOO_EXPENSIVE)
    {
	int    save_p_re = p_re;
	int    re_flags = rmp->regprog->re_flags;
	char_u *pat = vim_strsave(((nfa_regprog_T *)rmp->regprog)->pattern);

	p_re = BACKTRACKING_ENGINE;
	vim_regfree(rmp->regprog);
	if (pat != NULL)
	{
#ifdef FEAT_EVAL
	    report_re_switch(pat);
#endif
#ifdef FEAT_SYN_HL
	    // checking for \z misuse was already done when compiling for NFA,
	    // allow all here
	    reg_do_extmatch = REX_ALL;
#endif
	    rmp->regprog = vim_regcomp(pat, re_flags);
#ifdef FEAT_SYN_HL
	    reg_do_extmatch = 0;
#endif

	    if (rmp->regprog != NULL)
	    {
		rmp->regprog->re_in_use = TRUE;
		result = rmp->regprog->engine->regexec_multi(
				      rmp, win, buf, lnum, col, tm, timed_out);
		rmp->regprog->re_in_use = FALSE;
	    }
	    vim_free(pat);
	}
	p_re = save_p_re;
    }

    rex_in_use = rex_in_use_save;
    if (rex_in_use)
	rex = rex_save;

    return result <= 0 ? 0 : result;
}