diff --git a/src/fold.c b/src/fold.c
new file mode 100644
index 0000000..ceac00b
--- /dev/null
+++ b/src/fold.c
@@ -0,0 +1,3250 @@
+/* vim:set ts=8 sts=4 sw=4:
+ * vim600:fdm=marker fdl=1 fdc=3:
+ *
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ * See README.txt for an overview of the Vim source code.
+ */
+
+/*
+ * fold.c: code for folding
+ */
+
+#include "vim.h"
+
+#if defined(FEAT_FOLDING) || defined(PROTO)
+
+/* local declarations. {{{1 */
+/* typedef fold_T {{{2 */
+/*
+ * The toplevel folds for each window are stored in the w_folds growarray.
+ * Each toplevel fold can contain an array of second level folds in the
+ * fd_nested growarray.
+ * The info stored in both growarrays is the same: An array of fold_T.
+ */
+typedef struct
+{
+    linenr_T	fd_top;		/* first line of fold; for nested fold
+				 * relative to parent */
+    linenr_T	fd_len;		/* number of lines in the fold */
+    garray_T	fd_nested;	/* array of nested folds */
+    char	fd_flags;	/* see below */
+    char	fd_small;	/* TRUE, FALSE or MAYBE: fold smaller than
+				   'foldminlines'; MAYBE applies to nested
+				   folds too */
+} fold_T;
+
+#define FD_OPEN		0	/* fold is open (nested ones can be closed) */
+#define FD_CLOSED	1	/* fold is closed */
+#define FD_LEVEL	2	/* depends on 'foldlevel' (nested folds too) */
+
+#define MAX_LEVEL	20	/* maximum fold depth */
+
+/* static functions {{{2 */
+static void newFoldLevelWin __ARGS((win_T *wp));
+static int checkCloseRec __ARGS((garray_T *gap, linenr_T lnum, int level));
+static int foldFind __ARGS((garray_T *gap, linenr_T lnum, fold_T **fpp));
+static int foldLevelWin __ARGS((win_T *wp, linenr_T lnum));
+static void checkupdate __ARGS((win_T *wp));
+static void setFoldRepeat __ARGS((linenr_T lnum, long count, int open));
+static linenr_T setManualFold __ARGS((linenr_T lnum, int opening, int recurse, int *donep));
+static linenr_T setManualFoldWin __ARGS((win_T *wp, linenr_T lnum, int opening, int recurse, int *donep));
+static void foldOpenNested __ARGS((fold_T *fpr));
+static void deleteFoldEntry __ARGS((garray_T *gap, int idx, int recursive));
+static void foldMarkAdjustRecurse __ARGS((garray_T *gap, linenr_T line1, linenr_T line2, long amount, long amount_after));
+static int getDeepestNestingRecurse __ARGS((garray_T *gap));
+static int check_closed __ARGS((win_T *win, fold_T *fp, int *use_levelp, int level, int *maybe_smallp, linenr_T lnum_off));
+static void checkSmall __ARGS((win_T *wp, fold_T *fp, linenr_T lnum_off));
+static void setSmallMaybe __ARGS((garray_T *gap));
+static void foldCreateMarkers __ARGS((linenr_T start, linenr_T end));
+static void foldAddMarker __ARGS((linenr_T lnum, char_u *marker, int markerlen));
+static void deleteFoldMarkers __ARGS((fold_T *fp, int recursive, linenr_T lnum_off));
+static void foldDelMarker __ARGS((linenr_T lnum, char_u *marker, int markerlen));
+static void foldUpdateIEMS __ARGS((win_T *wp, linenr_T top, linenr_T bot));
+static void parseMarker __ARGS((win_T *wp));
+
+static char *e_nofold = N_("E490: No fold found");
+
+/*
+ * While updating the folds lines between invalid_top and invalid_bot have an
+ * undefined fold level.  Only used for the window currently being updated.
+ */
+static linenr_T invalid_top = (linenr_T)0;
+static linenr_T invalid_bot = (linenr_T)0;
+
+/*
+ * When using 'foldexpr' we sometimes get the level of the next line, which
+ * calls foldlevel() to get the level of the current line, which hasn't been
+ * stored yet.  To get around this chicken-egg problem the level of the
+ * previous line is stored here when available.  prev_lnum is zero when the
+ * level is not available.
+ */
+static linenr_T prev_lnum = 0;
+static int prev_lnum_lvl = -1;
+
+/* Flags used for "done" argument of setManualFold. */
+#define DONE_NOTHING	0
+#define DONE_ACTION	1	/* did close or open a fold */
+#define DONE_FOLD	2	/* did find a fold */
+
+static int foldstartmarkerlen;
+static char_u *foldendmarker;
+static int foldendmarkerlen;
+
+/* Exported folding functions. {{{1 */
+/* copyFoldingState() {{{2 */
+#if defined(FEAT_WINDOWS) || defined(PROTO)
+/*
+ * Copy that folding state from window "wp_from" to window "wp_to".
+ */
+    void
+copyFoldingState(wp_from, wp_to)
+    win_T	*wp_from;
+    win_T	*wp_to;
+{
+    wp_to->w_fold_manual = wp_from->w_fold_manual;
+    wp_to->w_foldinvalid = wp_from->w_foldinvalid;
+    cloneFoldGrowArray(&wp_from->w_folds, &wp_to->w_folds);
+}
+#endif
+
+/* hasAnyFolding() {{{2 */
+/*
+ * Return TRUE if there may be folded lines in the current window.
+ */
+    int
+hasAnyFolding(win)
+    win_T	*win;
+{
+    /* very simple now, but can become more complex later */
+    return (win->w_p_fen
+	    && (!foldmethodIsManual(win) || win->w_folds.ga_len > 0));
+}
+
+/* hasFolding() {{{2 */
+/*
+ * Return TRUE if line "lnum" in the current window is part of a closed
+ * fold.
+ * When returning TRUE, *firstp and *lastp are set to the first and last
+ * lnum of the sequence of folded lines (skipped when NULL).
+ */
+    int
+hasFolding(lnum, firstp, lastp)
+    linenr_T	lnum;
+    linenr_T	*firstp;
+    linenr_T	*lastp;
+{
+    return hasFoldingWin(curwin, lnum, firstp, lastp, TRUE, NULL);
+}
+
+/* hasFoldingWin() {{{2 */
+    int
+hasFoldingWin(win, lnum, firstp, lastp, cache, infop)
+    win_T	*win;
+    linenr_T	lnum;
+    linenr_T	*firstp;
+    linenr_T	*lastp;
+    int		cache;		/* when TRUE: use cached values of window */
+    foldinfo_T	*infop;		/* where to store fold info */
+{
+    int		had_folded = FALSE;
+    linenr_T	first = 0;
+    linenr_T	last = 0;
+    linenr_T	lnum_rel = lnum;
+    int		x;
+    fold_T	*fp;
+    int		level = 0;
+    int		use_level = FALSE;
+    int		maybe_small = FALSE;
+    garray_T	*gap;
+    int		low_level = 0;;
+
+    checkupdate(win);
+    /*
+     * Return quickly when there is no folding at all in this window.
+     */
+    if (!hasAnyFolding(win))
+    {
+	if (infop != NULL)
+	    infop->fi_level = 0;
+	return FALSE;
+    }
+
+    if (cache)
+    {
+	/*
+	 * First look in cached info for displayed lines.  This is probably
+	 * the fastest, but it can only be used if the entry is still valid.
+	 */
+	x = find_wl_entry(win, lnum);
+	if (x >= 0)
+	{
+	    first = win->w_lines[x].wl_lnum;
+	    last = win->w_lines[x].wl_lastlnum;
+	    had_folded = win->w_lines[x].wl_folded;
+	}
+    }
+
+    if (first == 0)
+    {
+	/*
+	 * Recursively search for a fold that contains "lnum".
+	 */
+	gap = &win->w_folds;
+	for (;;)
+	{
+	    if (!foldFind(gap, lnum_rel, &fp))
+		break;
+
+	    /* Remember lowest level of fold that starts in "lnum". */
+	    if (lnum_rel == fp->fd_top && low_level == 0)
+		low_level = level + 1;
+
+	    first += fp->fd_top;
+	    last += fp->fd_top;
+
+	    /* is this fold closed? */
+	    had_folded = check_closed(win, fp, &use_level, level,
+					       &maybe_small, lnum - lnum_rel);
+	    if (had_folded)
+	    {
+		/* Fold closed: Set last and quit loop. */
+		last += fp->fd_len - 1;
+		break;
+	    }
+
+	    /* Fold found, but it's open: Check nested folds.  Line number is
+	     * relative to containing fold. */
+	    gap = &fp->fd_nested;
+	    lnum_rel -= fp->fd_top;
+	    ++level;
+	}
+    }
+
+    if (!had_folded)
+    {
+	if (infop != NULL)
+	{
+	    infop->fi_level = level;
+	    infop->fi_lnum = lnum - lnum_rel;
+	    infop->fi_low_level = low_level == 0 ? level : low_level;
+	}
+	return FALSE;
+    }
+
+    if (lastp != NULL)
+	*lastp = last;
+    if (firstp != NULL)
+	*firstp = first;
+    if (infop != NULL)
+    {
+	infop->fi_level = level + 1;
+	infop->fi_lnum = first;
+	infop->fi_low_level = low_level == 0 ? level + 1 : low_level;
+    }
+    return TRUE;
+}
+
+/* foldLevel() {{{2 */
+/*
+ * Return fold level at line number "lnum" in the current window.
+ */
+    int
+foldLevel(lnum)
+    linenr_T	lnum;
+{
+    /* While updating the folds lines between invalid_top and invalid_bot have
+     * an undefined fold level.  Otherwise update the folds first. */
+    if (invalid_top == (linenr_T)0)
+	checkupdate(curwin);
+    else if (lnum == prev_lnum && prev_lnum_lvl >= 0)
+	return prev_lnum_lvl;
+    else if (lnum >= invalid_top && lnum <= invalid_bot)
+	return -1;
+
+    /* Return quickly when there is no folding at all in this window. */
+    if (!hasAnyFolding(curwin))
+	return 0;
+
+    return foldLevelWin(curwin, lnum);
+}
+
+/* lineFolded()	{{{2 */
+/*
+ * Low level function to check if a line is folded.  Doesn't use any caching.
+ * Return TRUE if line is folded.
+ * Return FALSE if line is not folded.
+ * Return MAYBE if the line is folded when next to a folded line.
+ */
+    int
+lineFolded(win, lnum)
+    win_T	*win;
+    linenr_T	lnum;
+{
+    return foldedCount(win, lnum, NULL) != 0;
+}
+
+/* foldedCount() {{{2 */
+/*
+ * Count the number of lines that are folded at line number "lnum".
+ * Normally "lnum" is the first line of a possible fold, and the returned
+ * number is the number of lines in the fold.
+ * Doesn't use caching from the displayed window.
+ * Returns number of folded lines from "lnum", or 0 if line is not folded.
+ * When "infop" is not NULL, fills *infop with the fold level info.
+ */
+    long
+foldedCount(win, lnum, infop)
+    win_T	*win;
+    linenr_T	lnum;
+    foldinfo_T	*infop;
+{
+    linenr_T	last;
+
+    if (hasFoldingWin(win, lnum, NULL, &last, FALSE, infop))
+	return (long)(last - lnum + 1);
+    return 0;
+}
+
+/* foldmethodIsManual() {{{2 */
+/*
+ * Return TRUE if 'foldmethod' is "manual"
+ */
+    int
+foldmethodIsManual(wp)
+    win_T	*wp;
+{
+    return (wp->w_p_fdm[3] == 'u');
+}
+
+/* foldmethodIsIndent() {{{2 */
+/*
+ * Return TRUE if 'foldmethod' is "indent"
+ */
+    int
+foldmethodIsIndent(wp)
+    win_T	*wp;
+{
+    return (wp->w_p_fdm[0] == 'i');
+}
+
+/* foldmethodIsExpr() {{{2 */
+/*
+ * Return TRUE if 'foldmethod' is "expr"
+ */
+    int
+foldmethodIsExpr(wp)
+    win_T	*wp;
+{
+    return (wp->w_p_fdm[1] == 'x');
+}
+
+/* foldmethodIsMarker() {{{2 */
+/*
+ * Return TRUE if 'foldmethod' is "marker"
+ */
+    int
+foldmethodIsMarker(wp)
+    win_T	*wp;
+{
+    return (wp->w_p_fdm[2] == 'r');
+}
+
+/* foldmethodIsSyntax() {{{2 */
+/*
+ * Return TRUE if 'foldmethod' is "syntax"
+ */
+    int
+foldmethodIsSyntax(wp)
+    win_T	*wp;
+{
+    return (wp->w_p_fdm[0] == 's');
+}
+
+/* foldmethodIsDiff() {{{2 */
+/*
+ * Return TRUE if 'foldmethod' is "diff"
+ */
+    int
+foldmethodIsDiff(wp)
+    win_T	*wp;
+{
+    return (wp->w_p_fdm[0] == 'd');
+}
+
+/* closeFold() {{{2 */
+/*
+ * Close fold for current window at line "lnum".
+ * Repeat "count" times.
+ */
+    void
+closeFold(lnum, count)
+    linenr_T	lnum;
+    long	count;
+{
+    setFoldRepeat(lnum, count, FALSE);
+}
+
+/* closeFoldRecurse() {{{2 */
+/*
+ * Close fold for current window at line "lnum" recursively.
+ */
+    void
+closeFoldRecurse(lnum)
+    linenr_T	lnum;
+{
+    (void)setManualFold(lnum, FALSE, TRUE, NULL);
+}
+
+/* opFoldRange() {{{2 */
+/*
+ * Open or Close folds for current window in lines "first" to "last".
+ * Used for "zo", "zO", "zc" and "zC" in Visual mode.
+ */
+    void
+opFoldRange(first, last, opening, recurse, had_visual)
+    linenr_T	first;
+    linenr_T	last;
+    int		opening;	/* TRUE to open, FALSE to close */
+    int		recurse;	/* TRUE to do it recursively */
+    int		had_visual;	/* TRUE when Visual selection used */
+{
+    int		done = DONE_NOTHING;	/* avoid error messages */
+    linenr_T	lnum;
+    linenr_T	lnum_next;
+
+    for (lnum = first; lnum <= last; lnum = lnum_next + 1)
+    {
+	lnum_next = lnum;
+	/* Opening one level only: next fold to open is after the one going to
+	 * be opened. */
+	if (opening && !recurse)
+	    (void)hasFolding(lnum, NULL, &lnum_next);
+	(void)setManualFold(lnum, opening, recurse, &done);
+	/* Closing one level only: next line to close a fold is after just
+	 * closed fold. */
+	if (!opening && !recurse)
+	    (void)hasFolding(lnum, NULL, &lnum_next);
+    }
+    if (done == DONE_NOTHING)
+	EMSG(_(e_nofold));
+#ifdef FEAT_VISUAL
+    /* Force a redraw to remove the Visual highlighting. */
+    if (had_visual)
+	redraw_curbuf_later(INVERTED);
+#endif
+}
+
+/* openFold() {{{2 */
+/*
+ * Open fold for current window at line "lnum".
+ * Repeat "count" times.
+ */
+    void
+openFold(lnum, count)
+    linenr_T	lnum;
+    long	count;
+{
+    setFoldRepeat(lnum, count, TRUE);
+}
+
+/* openFoldRecurse() {{{2 */
+/*
+ * Open fold for current window at line "lnum" recursively.
+ */
+    void
+openFoldRecurse(lnum)
+    linenr_T	lnum;
+{
+    (void)setManualFold(lnum, TRUE, TRUE, NULL);
+}
+
+/* foldOpenCursor() {{{2 */
+/*
+ * Open folds until the cursor line is not in a closed fold.
+ */
+    void
+foldOpenCursor()
+{
+    int		done;
+
+    checkupdate(curwin);
+    if (hasAnyFolding(curwin))
+	for (;;)
+	{
+	    done = DONE_NOTHING;
+	    (void)setManualFold(curwin->w_cursor.lnum, TRUE, FALSE, &done);
+	    if (!(done & DONE_ACTION))
+		break;
+	}
+}
+
+/* newFoldLevel() {{{2 */
+/*
+ * Set new foldlevel for current window.
+ */
+    void
+newFoldLevel()
+{
+    newFoldLevelWin(curwin);
+
+#ifdef FEAT_DIFF
+    if (foldmethodIsDiff(curwin) && curwin->w_p_scb)
+    {
+	win_T	    *wp;
+
+	/*
+	 * Set the same foldlevel in other windows in diff mode.
+	 */
+	FOR_ALL_WINDOWS(wp)
+	{
+	    if (wp != curwin && foldmethodIsDiff(wp) && wp->w_p_scb)
+	    {
+		wp->w_p_fdl = curwin->w_p_fdl;
+		newFoldLevelWin(wp);
+	    }
+	}
+    }
+#endif
+}
+
+    static void
+newFoldLevelWin(wp)
+    win_T	*wp;
+{
+    fold_T	*fp;
+    int		i;
+
+    checkupdate(wp);
+    if (wp->w_fold_manual)
+    {
+	/* Set all flags for the first level of folds to FD_LEVEL.  Following
+	 * manual open/close will then change the flags to FD_OPEN or
+	 * FD_CLOSED for those folds that don't use 'foldlevel'. */
+	fp = (fold_T *)wp->w_folds.ga_data;
+	for (i = 0; i < wp->w_folds.ga_len; ++i)
+	    fp[i].fd_flags = FD_LEVEL;
+	wp->w_fold_manual = FALSE;
+    }
+    changed_window_setting_win(wp);
+}
+
+/* foldCheckClose() {{{2 */
+/*
+ * Apply 'foldlevel' to all folds that don't contain the cursor.
+ */
+    void
+foldCheckClose()
+{
+    if (*p_fcl != NUL)	/* can only be "all" right now */
+    {
+	checkupdate(curwin);
+	if (checkCloseRec(&curwin->w_folds, curwin->w_cursor.lnum,
+							(int)curwin->w_p_fdl))
+	    changed_window_setting();
+    }
+}
+
+/* checkCloseRec() {{{2 */
+    static int
+checkCloseRec(gap, lnum, level)
+    garray_T	*gap;
+    linenr_T	lnum;
+    int		level;
+{
+    fold_T	*fp;
+    int		retval = FALSE;
+    int		i;
+
+    fp = (fold_T *)gap->ga_data;
+    for (i = 0; i < gap->ga_len; ++i)
+    {
+	/* Only manually opened folds may need to be closed. */
+	if (fp[i].fd_flags == FD_OPEN)
+	{
+	    if (level <= 0 && (lnum < fp[i].fd_top
+				      || lnum >= fp[i].fd_top + fp[i].fd_len))
+	    {
+		fp[i].fd_flags = FD_LEVEL;
+		retval = TRUE;
+	    }
+	    else
+		retval |= checkCloseRec(&fp[i].fd_nested, lnum - fp[i].fd_top,
+								   level - 1);
+	}
+    }
+    return retval;
+}
+
+/* foldCreateAllowed() {{{2 */
+/*
+ * Return TRUE if it's allowed to manually create or delete a fold.
+ * Give an error message and return FALSE if not.
+ */
+    int
+foldManualAllowed(create)
+    int		create;
+{
+    if (foldmethodIsManual(curwin) || foldmethodIsMarker(curwin))
+	return TRUE;
+    if (create)
+	EMSG(_("E350: Cannot create fold with current 'foldmethod'"));
+    else
+	EMSG(_("E351: Cannot delete fold with current 'foldmethod'"));
+    return FALSE;
+}
+
+/* foldCreate() {{{2 */
+/*
+ * Create a fold from line "start" to line "end" (inclusive) in the current
+ * window.
+ */
+    void
+foldCreate(start, end)
+    linenr_T	start;
+    linenr_T	end;
+{
+    fold_T	*fp;
+    garray_T	*gap;
+    garray_T	fold_ga;
+    int		i, j;
+    int		cont;
+    int		use_level = FALSE;
+    int		closed = FALSE;
+    int		level = 0;
+    linenr_T	start_rel = start;
+    linenr_T	end_rel = end;
+
+    if (start > end)
+    {
+	/* reverse the range */
+	end = start_rel;
+	start = end_rel;
+	start_rel = start;
+	end_rel = end;
+    }
+
+    /* When 'foldmethod' is "marker" add markers, which creates the folds. */
+    if (foldmethodIsMarker(curwin))
+    {
+	foldCreateMarkers(start, end);
+	return;
+    }
+
+    checkupdate(curwin);
+
+    /* Find the place to insert the new fold. */
+    gap = &curwin->w_folds;
+    for (;;)
+    {
+	if (!foldFind(gap, start_rel, &fp))
+	    break;
+	if (fp->fd_top + fp->fd_len > end_rel)
+	{
+	    /* New fold is completely inside this fold: Go one level deeper. */
+	    gap = &fp->fd_nested;
+	    start_rel -= fp->fd_top;
+	    end_rel -= fp->fd_top;
+	    if (use_level || fp->fd_flags == FD_LEVEL)
+	    {
+		use_level = TRUE;
+		if (level >= curwin->w_p_fdl)
+		    closed = TRUE;
+	    }
+	    else if (fp->fd_flags == FD_CLOSED)
+		closed = TRUE;
+	    ++level;
+	}
+	else
+	{
+	    /* This fold and new fold overlap: Insert here and move some folds
+	     * inside the new fold. */
+	    break;
+	}
+    }
+
+    i = (int)(fp - (fold_T *)gap->ga_data);
+    if (ga_grow(gap, 1) == OK)
+    {
+	fp = (fold_T *)gap->ga_data + i;
+	ga_init2(&fold_ga, (int)sizeof(fold_T), 10);
+
+	/* Count number of folds that will be contained in the new fold. */
+	for (cont = 0; i + cont < gap->ga_len; ++cont)
+	    if (fp[cont].fd_top > end_rel)
+		break;
+	if (cont > 0 && ga_grow(&fold_ga, cont) == OK)
+	{
+	    /* If the first fold starts before the new fold, let the new fold
+	     * start there.  Otherwise the existing fold would change. */
+	    if (start_rel > fp->fd_top)
+		start_rel = fp->fd_top;
+
+	    /* When last contained fold isn't completely contained, adjust end
+	     * of new fold. */
+	    if (end_rel < fp[cont - 1].fd_top + fp[cont - 1].fd_len - 1)
+		end_rel = fp[cont - 1].fd_top + fp[cont - 1].fd_len - 1;
+	    /* Move contained folds to inside new fold. */
+	    mch_memmove(fold_ga.ga_data, fp, sizeof(fold_T) * cont);
+	    fold_ga.ga_len += cont;
+	    fold_ga.ga_room -= cont;
+	    i += cont;
+
+	    /* Adjust line numbers in contained folds to be relative to the
+	     * new fold. */
+	    for (j = 0; j < cont; ++j)
+		((fold_T *)fold_ga.ga_data)[j].fd_top -= start_rel;
+	}
+	/* Move remaining entries to after the new fold. */
+	if (i < gap->ga_len)
+	    mch_memmove(fp + 1, (fold_T *)gap->ga_data + i,
+				     sizeof(fold_T) * (gap->ga_len - i));
+	gap->ga_len = gap->ga_len + 1 - cont;
+	gap->ga_room = gap->ga_room - 1 + cont;
+
+	/* insert new fold */
+	fp->fd_nested = fold_ga;
+	fp->fd_top = start_rel;
+	fp->fd_len = end_rel - start_rel + 1;
+
+	/* We want the new fold to be closed.  If it would remain open because
+	 * of using 'foldlevel', need to adjust fd_flags of containing folds.
+	 */
+	if (use_level && !closed && level < curwin->w_p_fdl)
+	    closeFold(start, 1L);
+	if (!use_level)
+	    curwin->w_fold_manual = TRUE;
+	fp->fd_flags = FD_CLOSED;
+	fp->fd_small = MAYBE;
+
+	/* redraw */
+	changed_window_setting();
+    }
+}
+
+/* deleteFold() {{{2 */
+/*
+ * Delete a fold at line "start" in the current window.
+ * When "end" is not 0, delete all folds from "start" to "end".
+ * When "recursive" is TRUE delete recursively.
+ */
+    void
+deleteFold(start, end, recursive, had_visual)
+    linenr_T	start;
+    linenr_T	end;
+    int		recursive;
+    int		had_visual;	/* TRUE when Visual selection used */
+{
+    garray_T	*gap;
+    fold_T	*fp;
+    garray_T	*found_ga;
+    fold_T	*found_fp = NULL;
+    linenr_T	found_off = 0;
+    int		use_level = FALSE;
+    int		maybe_small = FALSE;
+    int		level = 0;
+    linenr_T	lnum = start;
+    linenr_T	lnum_off;
+    int		did_one = FALSE;
+    linenr_T	first_lnum = MAXLNUM;
+    linenr_T	last_lnum = 0;
+
+    checkupdate(curwin);
+
+    while (lnum <= end)
+    {
+	/* Find the deepest fold for "start". */
+	gap = &curwin->w_folds;
+	found_ga = NULL;
+	lnum_off = 0;
+	for (;;)
+	{
+	    if (!foldFind(gap, lnum - lnum_off, &fp))
+		break;
+	    /* lnum is inside this fold, remember info */
+	    found_ga = gap;
+	    found_fp = fp;
+	    found_off = lnum_off;
+
+	    /* if "lnum" is folded, don't check nesting */
+	    if (check_closed(curwin, fp, &use_level, level,
+						      &maybe_small, lnum_off))
+		break;
+
+	    /* check nested folds */
+	    gap = &fp->fd_nested;
+	    lnum_off += fp->fd_top;
+	    ++level;
+	}
+	if (found_ga == NULL)
+	{
+	    ++lnum;
+	}
+	else
+	{
+	    lnum = found_fp->fd_top + found_fp->fd_len + found_off;
+	    did_one = TRUE;
+
+	    if (foldmethodIsManual(curwin))
+		deleteFoldEntry(found_ga,
+		    (int)(found_fp - (fold_T *)found_ga->ga_data), recursive);
+	    else
+	    {
+		if (found_fp->fd_top + found_off < first_lnum)
+		    first_lnum = found_fp->fd_top;
+		if (lnum > last_lnum)
+		    last_lnum = lnum;
+		parseMarker(curwin);
+		deleteFoldMarkers(found_fp, recursive, found_off);
+	    }
+
+	    /* redraw window */
+	    changed_window_setting();
+	}
+    }
+    if (!did_one)
+    {
+	EMSG(_(e_nofold));
+#ifdef FEAT_VISUAL
+	/* Force a redraw to remove the Visual highlighting. */
+	if (had_visual)
+	    redraw_curbuf_later(INVERTED);
+#endif
+    }
+    if (last_lnum > 0)
+	changed_lines(first_lnum, (colnr_T)0, last_lnum, 0L);
+}
+
+/* clearFolding() {{{2 */
+/*
+ * Remove all folding for window "win".
+ */
+    void
+clearFolding(win)
+    win_T	*win;
+{
+    deleteFoldRecurse(&win->w_folds);
+    win->w_foldinvalid = FALSE;
+}
+
+/* foldUpdate() {{{2 */
+/*
+ * Update folds for changes in the buffer of a window.
+ * Note that inserted/deleted lines must have already been taken care of by
+ * calling foldMarkAdjust().
+ * The changes in lines from top to bot (inclusive).
+ */
+    void
+foldUpdate(wp, top, bot)
+    win_T	*wp;
+    linenr_T	top;
+    linenr_T	bot;
+{
+    fold_T	*fp;
+
+    /* Mark all folds from top to bot as maybe-small. */
+    (void)foldFind(&curwin->w_folds, curwin->w_cursor.lnum, &fp);
+    while (fp < (fold_T *)curwin->w_folds.ga_data + curwin->w_folds.ga_len
+	    && fp->fd_top < bot)
+    {
+	fp->fd_small = MAYBE;
+	++fp;
+    }
+
+    if (foldmethodIsIndent(wp)
+	    || foldmethodIsExpr(wp)
+	    || foldmethodIsMarker(wp)
+#ifdef FEAT_DIFF
+	    || foldmethodIsDiff(wp)
+#endif
+	    || foldmethodIsSyntax(wp))
+	foldUpdateIEMS(wp, top, bot);
+}
+
+/* foldUpdateAll() {{{2 */
+/*
+ * Update all lines in a window for folding.
+ * Used when a fold setting changes or after reloading the buffer.
+ * The actual updating is postponed until fold info is used, to avoid doing
+ * every time a setting is changed or a syntax item is added.
+ */
+    void
+foldUpdateAll(win)
+    win_T	*win;
+{
+    win->w_foldinvalid = TRUE;
+    redraw_win_later(win, NOT_VALID);
+}
+
+/* foldMoveTo() {{{2 */
+/*
+ * If "updown" is FALSE: Move to the start or end of the fold.
+ * If "updown" is TRUE: move to fold at the same level.
+ * If not moved return FAIL.
+ */
+    int
+foldMoveTo(updown, dir, count)
+    int		updown;
+    int		dir;	    /* FORWARD or BACKWARD */
+    long	count;
+{
+    long	n;
+    int		retval = FAIL;
+    linenr_T	lnum_off;
+    linenr_T	lnum_found;
+    linenr_T	lnum;
+    int		use_level;
+    int		maybe_small;
+    garray_T	*gap;
+    fold_T	*fp;
+    int		level;
+    int		last;
+
+    /* Repeat "count" times. */
+    for (n = 0; n < count; ++n)
+    {
+	/* Find nested folds.  Stop when a fold is closed.  The deepest fold
+	 * that moves the cursor is used. */
+	lnum_off = 0;
+	gap = &curwin->w_folds;
+	use_level = FALSE;
+	maybe_small = FALSE;
+	lnum_found = curwin->w_cursor.lnum;
+	level = 0;
+	last = FALSE;
+	for (;;)
+	{
+	    if (!foldFind(gap, curwin->w_cursor.lnum - lnum_off, &fp))
+	    {
+		if (!updown)
+		    break;
+
+		/* When moving up, consider a fold above the cursor; when
+		 * moving down consider a fold below the cursor. */
+		if (dir == FORWARD)
+		{
+		    if (fp - (fold_T *)gap->ga_data >= gap->ga_len)
+			break;
+		    --fp;
+		}
+		else
+		{
+		    if (fp == (fold_T *)gap->ga_data)
+			break;
+		}
+		/* don't look for contained folds, they will always move
+		 * the cursor too far. */
+		last = TRUE;
+	    }
+
+	    if (!last)
+	    {
+		/* Check if this fold is closed. */
+		if (check_closed(curwin, fp, &use_level, level,
+						      &maybe_small, lnum_off))
+		    last = TRUE;
+
+		/* "[z" and "]z" stop at closed fold */
+		if (last && !updown)
+		    break;
+	    }
+
+	    if (updown)
+	    {
+		if (dir == FORWARD)
+		{
+		    /* to start of next fold if there is one */
+		    if (fp + 1 - (fold_T *)gap->ga_data < gap->ga_len)
+		    {
+			lnum = fp[1].fd_top + lnum_off;
+			if (lnum > curwin->w_cursor.lnum)
+			    lnum_found = lnum;
+		    }
+		}
+		else
+		{
+		    /* to end of previous fold if there is one */
+		    if (fp > (fold_T *)gap->ga_data)
+		    {
+			lnum = fp[-1].fd_top + lnum_off + fp[-1].fd_len - 1;
+			if (lnum < curwin->w_cursor.lnum)
+			    lnum_found = lnum;
+		    }
+		}
+	    }
+	    else
+	    {
+		/* Open fold found, set cursor to its start/end and then check
+		 * nested folds. */
+		if (dir == FORWARD)
+		{
+		    lnum = fp->fd_top + lnum_off + fp->fd_len - 1;
+		    if (lnum > curwin->w_cursor.lnum)
+			lnum_found = lnum;
+		}
+		else
+		{
+		    lnum = fp->fd_top + lnum_off;
+		    if (lnum < curwin->w_cursor.lnum)
+			lnum_found = lnum;
+		}
+	    }
+
+	    if (last)
+		break;
+
+	    /* Check nested folds (if any). */
+	    gap = &fp->fd_nested;
+	    lnum_off += fp->fd_top;
+	    ++level;
+	}
+	if (lnum_found != curwin->w_cursor.lnum)
+	{
+	    if (retval == FAIL)
+		setpcmark();
+	    curwin->w_cursor.lnum = lnum_found;
+	    curwin->w_cursor.col = 0;
+	    retval = OK;
+	}
+	else
+	    break;
+    }
+
+    return retval;
+}
+
+/* foldInitWin() {{{2 */
+/*
+ * Init the fold info in a new window.
+ */
+    void
+foldInitWin(newwin)
+    win_T	*newwin;
+{
+    ga_init2(&newwin->w_folds, (int)sizeof(fold_T), 10);
+}
+
+/* find_wl_entry() {{{2 */
+/*
+ * Find an entry in the win->w_lines[] array for buffer line "lnum".
+ * Only valid entries are considered (for entries where wl_valid is FALSE the
+ * line number can be wrong).
+ * Returns index of entry or -1 if not found.
+ */
+    int
+find_wl_entry(win, lnum)
+    win_T	*win;
+    linenr_T	lnum;
+{
+    int		i;
+
+    if (win->w_lines_valid > 0)
+	for (i = 0; i < win->w_lines_valid; ++i)
+	    if (win->w_lines[i].wl_valid)
+	    {
+		if (lnum < win->w_lines[i].wl_lnum)
+		    return -1;
+		if (lnum <= win->w_lines[i].wl_lastlnum)
+		    return i;
+	    }
+    return -1;
+}
+
+/* foldAdjustVisual() {{{2 */
+#ifdef FEAT_VISUAL
+/*
+ * Adjust the Visual area to include any fold at the start or end completely.
+ */
+    void
+foldAdjustVisual()
+{
+    pos_T	*start, *end;
+    char_u	*ptr;
+
+    if (!VIsual_active || !hasAnyFolding(curwin))
+	return;
+
+    if (ltoreq(VIsual, curwin->w_cursor))
+    {
+	start = &VIsual;
+	end = &curwin->w_cursor;
+    }
+    else
+    {
+	start = &curwin->w_cursor;
+	end = &VIsual;
+    }
+    if (hasFolding(start->lnum, &start->lnum, NULL))
+	start->col = 0;
+    if (hasFolding(end->lnum, NULL, &end->lnum))
+    {
+	ptr = ml_get(end->lnum);
+	end->col = (colnr_T)STRLEN(ptr);
+	if (end->col > 0 && *p_sel == 'o')
+	    --end->col;
+#ifdef FEAT_MBYTE
+	/* prevent cursor from moving on the trail byte */
+	if (has_mbyte)
+	    mb_adjust_cursor();
+#endif
+    }
+}
+#endif
+
+/* cursor_foldstart() {{{2 */
+/*
+ * Move the cursor to the first line of a closed fold.
+ */
+    void
+foldAdjustCursor()
+{
+    (void)hasFolding(curwin->w_cursor.lnum, &curwin->w_cursor.lnum, NULL);
+}
+
+/* Internal functions for "fold_T" {{{1 */
+/* cloneFoldGrowArray() {{{2 */
+/*
+ * Will "clone" (i.e deep copy) a garray_T of folds.
+ *
+ * Return FAIL if the operation cannot be completed, otherwise OK.
+ */
+    void
+cloneFoldGrowArray(from, to)
+    garray_T	*from;
+    garray_T	*to;
+{
+    int		i;
+    fold_T	*from_p;
+    fold_T	*to_p;
+
+    ga_init2(to, from->ga_itemsize, from->ga_growsize);
+    if (from->ga_len == 0 || ga_grow(to, from->ga_len) == FAIL)
+	return;
+
+    from_p = (fold_T *)from->ga_data;
+    to_p = (fold_T *)to->ga_data;
+
+    for (i = 0; i < from->ga_len; i++)
+    {
+	to_p->fd_top = from_p->fd_top;
+	to_p->fd_len = from_p->fd_len;
+	to_p->fd_flags = from_p->fd_flags;
+	to_p->fd_small = from_p->fd_small;
+	cloneFoldGrowArray(&from_p->fd_nested, &to_p->fd_nested);
+	++to->ga_len;
+	--to->ga_room;
+	++from_p;
+	++to_p;
+    }
+}
+
+/* foldFind() {{{2 */
+/*
+ * Search for line "lnum" in folds of growarray "gap".
+ * Set *fpp to the fold struct for the fold that contains "lnum" or
+ * the first fold below it (careful: it can be beyond the end of the array!).
+ * Returns FALSE when there is no fold that contains "lnum".
+ */
+    static int
+foldFind(gap, lnum, fpp)
+    garray_T	*gap;
+    linenr_T	lnum;
+    fold_T	**fpp;
+{
+    linenr_T	low, high;
+    fold_T	*fp;
+    int		i;
+
+    /*
+     * Perform a binary search.
+     * "low" is lowest index of possible match.
+     * "high" is highest index of possible match.
+     */
+    fp = (fold_T *)gap->ga_data;
+    low = 0;
+    high = gap->ga_len - 1;
+    while (low <= high)
+    {
+	i = (low + high) / 2;
+	if (fp[i].fd_top > lnum)
+	    /* fold below lnum, adjust high */
+	    high = i - 1;
+	else if (fp[i].fd_top + fp[i].fd_len <= lnum)
+	    /* fold above lnum, adjust low */
+	    low = i + 1;
+	else
+	{
+	    /* lnum is inside this fold */
+	    *fpp = fp + i;
+	    return TRUE;
+	}
+    }
+    *fpp = fp + low;
+    return FALSE;
+}
+
+/* foldLevelWin() {{{2 */
+/*
+ * Return fold level at line number "lnum" in window "wp".
+ */
+    static int
+foldLevelWin(wp, lnum)
+    win_T	*wp;
+    linenr_T	lnum;
+{
+    fold_T	*fp;
+    linenr_T	lnum_rel = lnum;
+    int		level =  0;
+    garray_T	*gap;
+
+    /* Recursively search for a fold that contains "lnum". */
+    gap = &wp->w_folds;
+    for (;;)
+    {
+	if (!foldFind(gap, lnum_rel, &fp))
+	    break;
+	/* Check nested folds.  Line number is relative to containing fold. */
+	gap = &fp->fd_nested;
+	lnum_rel -= fp->fd_top;
+	++level;
+    }
+
+    return level;
+}
+
+/* checkupdate() {{{2 */
+/*
+ * Check if the folds in window "wp" are invalid and update them if needed.
+ */
+    static void
+checkupdate(wp)
+    win_T	*wp;
+{
+    if (wp->w_foldinvalid)
+    {
+	foldUpdate(wp, (linenr_T)1, (linenr_T)MAXLNUM); /* will update all */
+	wp->w_foldinvalid = FALSE;
+    }
+}
+
+/* setFoldRepeat() {{{2 */
+/*
+ * Open or close fold for current window at line "lnum".
+ * Repeat "count" times.
+ */
+    static void
+setFoldRepeat(lnum, count, open)
+    linenr_T	lnum;
+    long	count;
+    int		open;
+{
+    int		done;
+    long	n;
+
+    for (n = 0; n < count; ++n)
+    {
+	done = DONE_NOTHING;
+	(void)setManualFold(lnum, open, FALSE, &done);
+	if (!(done & DONE_ACTION))
+	{
+	    /* Only give an error message when no fold could be opened. */
+	    if (n == 0 && !(done & DONE_FOLD))
+		EMSG(_(e_nofold));
+	    break;
+	}
+    }
+}
+
+/* setManualFold() {{{2 */
+/*
+ * Open or close the fold in the current window which contains "lnum".
+ * Also does this for other windows in diff mode when needed.
+ */
+    static linenr_T
+setManualFold(lnum, opening, recurse, donep)
+    linenr_T	lnum;
+    int		opening;    /* TRUE when opening, FALSE when closing */
+    int		recurse;    /* TRUE when closing/opening recursive */
+    int		*donep;
+{
+#ifdef FEAT_DIFF
+    if (foldmethodIsDiff(curwin) && curwin->w_p_scb)
+    {
+	win_T	    *wp;
+	linenr_T    dlnum;
+
+	/*
+	 * Do the same operation in other windows in diff mode.  Calculate the
+	 * line number from the diffs.
+	 */
+	FOR_ALL_WINDOWS(wp)
+	{
+	    if (wp != curwin && foldmethodIsDiff(wp) && wp->w_p_scb)
+	    {
+		dlnum = diff_lnum_win(curwin->w_cursor.lnum, wp);
+		if (dlnum != 0)
+		    (void)setManualFoldWin(wp, dlnum, opening, recurse, NULL);
+	    }
+	}
+    }
+#endif
+
+    return setManualFoldWin(curwin, lnum, opening, recurse, donep);
+}
+
+/* setManualFoldWin() {{{2 */
+/*
+ * Open or close the fold in window "wp" which contains "lnum".
+ * "donep", when not NULL, points to flag that is set to DONE_FOLD when some
+ * fold was found and to DONE_ACTION when some fold was opened or closed.
+ * When "donep" is NULL give an error message when no fold was found for
+ * "lnum", but only if "wp" is "curwin".
+ * Return the line number of the next line that could be closed.
+ * It's only valid when "opening" is TRUE!
+ */
+    static linenr_T
+setManualFoldWin(wp, lnum, opening, recurse, donep)
+    win_T	*wp;
+    linenr_T	lnum;
+    int		opening;    /* TRUE when opening, FALSE when closing */
+    int		recurse;    /* TRUE when closing/opening recursive */
+    int		*donep;
+{
+    fold_T	*fp;
+    fold_T	*fp2;
+    fold_T	*found = NULL;
+    int		j;
+    int		level = 0;
+    int		use_level = FALSE;
+    int		found_fold = FALSE;
+    garray_T	*gap;
+    linenr_T	next = MAXLNUM;
+    linenr_T	off = 0;
+    int		done = 0;
+
+    checkupdate(wp);
+
+    /*
+     * Find the fold, open or close it.
+     */
+    gap = &wp->w_folds;
+    for (;;)
+    {
+	if (!foldFind(gap, lnum, &fp))
+	{
+	    /* If there is a following fold, continue there next time. */
+	    if (fp < (fold_T *)gap->ga_data + gap->ga_len)
+		next = fp->fd_top + off;
+	    break;
+	}
+
+	/* lnum is inside this fold */
+	found_fold = TRUE;
+
+	/* If there is a following fold, continue there next time. */
+	if (fp + 1 < (fold_T *)gap->ga_data + gap->ga_len)
+	    next = fp[1].fd_top + off;
+
+	/* Change from level-dependent folding to manual. */
+	if (use_level || fp->fd_flags == FD_LEVEL)
+	{
+	    use_level = TRUE;
+	    if (level >= wp->w_p_fdl)
+		fp->fd_flags = FD_CLOSED;
+	    else
+		fp->fd_flags = FD_OPEN;
+	    fp2 = (fold_T *)fp->fd_nested.ga_data;
+	    for (j = 0; j < fp->fd_nested.ga_len; ++j)
+		fp2[j].fd_flags = FD_LEVEL;
+	}
+
+	/* Simple case: Close recursively means closing the fold. */
+	if (!opening && recurse)
+	{
+	    if (fp->fd_flags != FD_CLOSED)
+	    {
+		done |= DONE_ACTION;
+		fp->fd_flags = FD_CLOSED;
+	    }
+	}
+	else if (fp->fd_flags == FD_CLOSED)
+	{
+	    /* When opening, open topmost closed fold. */
+	    if (opening)
+	    {
+		fp->fd_flags = FD_OPEN;
+		done |= DONE_ACTION;
+		if (recurse)
+		    foldOpenNested(fp);
+	    }
+	    break;
+	}
+
+	/* fold is open, check nested folds */
+	found = fp;
+	gap = &fp->fd_nested;
+	lnum -= fp->fd_top;
+	off += fp->fd_top;
+	++level;
+    }
+    if (found_fold)
+    {
+	/* When closing and not recurse, close deepest open fold. */
+	if (!opening && found != NULL)
+	{
+	    found->fd_flags = FD_CLOSED;
+	    done |= DONE_ACTION;
+	}
+	wp->w_fold_manual = TRUE;
+	if (done & DONE_ACTION)
+	    changed_window_setting_win(wp);
+	done |= DONE_FOLD;
+    }
+    else if (donep == NULL && wp == curwin)
+	EMSG(_(e_nofold));
+
+    if (donep != NULL)
+	*donep |= done;
+
+    return next;
+}
+
+/* foldOpenNested() {{{2 */
+/*
+ * Open all nested folds in fold "fpr" recursively.
+ */
+    static void
+foldOpenNested(fpr)
+    fold_T	*fpr;
+{
+    int		i;
+    fold_T	*fp;
+
+    fp = (fold_T *)fpr->fd_nested.ga_data;
+    for (i = 0; i < fpr->fd_nested.ga_len; ++i)
+    {
+	foldOpenNested(&fp[i]);
+	fp[i].fd_flags = FD_OPEN;
+    }
+}
+
+/* deleteFoldEntry() {{{2 */
+/*
+ * Delete fold "idx" from growarray "gap".
+ * When "recursive" is TRUE also delete all the folds contained in it.
+ * When "recursive" is FALSE contained folds are moved one level up.
+ */
+    static void
+deleteFoldEntry(gap, idx, recursive)
+    garray_T	*gap;
+    int		idx;
+    int		recursive;
+{
+    fold_T	*fp;
+    int		i;
+    long	moved;
+    fold_T	*nfp;
+
+    fp = (fold_T *)gap->ga_data + idx;
+    if (recursive || fp->fd_nested.ga_len == 0)
+    {
+	/* recursively delete the contained folds */
+	deleteFoldRecurse(&fp->fd_nested);
+	--gap->ga_len;
+	++gap->ga_room;
+	if (idx < gap->ga_len)
+	    mch_memmove(fp, fp + 1, sizeof(fold_T) * (gap->ga_len - idx));
+    }
+    else
+    {
+	/* move nested folds one level up, to overwrite the fold that is
+	 * deleted. */
+	moved = fp->fd_nested.ga_len;
+	if (ga_grow(gap, (int)(moved - 1)) == OK)
+	{
+	    /* adjust fd_top and fd_flags for the moved folds */
+	    nfp = (fold_T *)fp->fd_nested.ga_data;
+	    for (i = 0; i < moved; ++i)
+	    {
+		nfp[i].fd_top += fp->fd_top;
+		if (fp->fd_flags == FD_LEVEL)
+		    nfp[i].fd_flags = FD_LEVEL;
+		if (fp->fd_small == MAYBE)
+		    nfp[i].fd_small = MAYBE;
+	    }
+
+	    /* move the existing folds down to make room */
+	    if (idx < gap->ga_len)
+		mch_memmove(fp + moved, fp + 1,
+					sizeof(fold_T) * (gap->ga_len - idx));
+	    /* move the contained folds one level up */
+	    mch_memmove(fp, nfp, (size_t)(sizeof(fold_T) * moved));
+	    vim_free(nfp);
+	    gap->ga_len += moved - 1;
+	    gap->ga_room -= moved - 1;
+	}
+    }
+}
+
+/* deleteFoldRecurse() {{{2 */
+/*
+ * Delete nested folds in a fold.
+ */
+    void
+deleteFoldRecurse(gap)
+    garray_T	*gap;
+{
+    int		i;
+
+    for (i = 0; i < gap->ga_len; ++i)
+	deleteFoldRecurse(&(((fold_T *)(gap->ga_data))[i].fd_nested));
+    ga_clear(gap);
+}
+
+/* foldMarkAdjust() {{{2 */
+/*
+ * Update line numbers of folds for inserted/deleted lines.
+ */
+    void
+foldMarkAdjust(wp, line1, line2, amount, amount_after)
+    win_T	*wp;
+    linenr_T	line1;
+    linenr_T	line2;
+    long	amount;
+    long	amount_after;
+{
+    /* If deleting marks from line1 to line2, but not deleting all those
+     * lines, set line2 so that only deleted lines have their folds removed. */
+    if (amount == MAXLNUM && line2 >= line1 && line2 - line1 >= -amount_after)
+	line2 = line1 - amount_after - 1;
+    /* If appending a line in Insert mode, it should be included in the fold
+     * just above the line. */
+    if ((State & INSERT) && amount == (linenr_T)1 && line2 == MAXLNUM)
+	--line1;
+    foldMarkAdjustRecurse(&wp->w_folds, line1, line2, amount, amount_after);
+}
+
+/* foldMarkAdjustRecurse() {{{2 */
+    static void
+foldMarkAdjustRecurse(gap, line1, line2, amount, amount_after)
+    garray_T	*gap;
+    linenr_T	line1;
+    linenr_T	line2;
+    long	amount;
+    long	amount_after;
+{
+    fold_T	*fp;
+    int		i;
+    linenr_T	last;
+    linenr_T	top;
+
+    /* In Insert mode an inserted line at the top of a fold is considered part
+     * of the fold, otherwise it isn't. */
+    if ((State & INSERT) && amount == (linenr_T)1 && line2 == MAXLNUM)
+	top = line1 + 1;
+    else
+	top = line1;
+
+    /* Find the fold containing or just below "line1". */
+    (void)foldFind(gap, line1, &fp);
+
+    /*
+     * Adjust all folds below "line1" that are affected.
+     */
+    for (i = (int)(fp - (fold_T *)gap->ga_data); i < gap->ga_len; ++i, ++fp)
+    {
+	/*
+	 * Check for these situations:
+	 *	  1  2	3
+	 *	  1  2	3
+	 * line1     2	3  4  5
+	 *	     2	3  4  5
+	 *	     2	3  4  5
+	 * line2     2	3  4  5
+	 *		3     5  6
+	 *		3     5  6
+	 */
+
+	last = fp->fd_top + fp->fd_len - 1; /* last line of fold */
+
+	/* 1. fold completely above line1: nothing to do */
+	if (last < line1)
+	    continue;
+
+	/* 6. fold below line2: only adjust for amount_after */
+	if (fp->fd_top > line2)
+	{
+	    if (amount_after == 0)
+		break;
+	    fp->fd_top += amount_after;
+	}
+	else
+	{
+	    if (fp->fd_top >= top && last <= line2)
+	    {
+		/* 4. fold completely contained in range */
+		if (amount == MAXLNUM)
+		{
+		    /* Deleting lines: delete the fold completely */
+		    deleteFoldEntry(gap, i, TRUE);
+		    --i;    /* adjust index for deletion */
+		    --fp;
+		}
+		else
+		    fp->fd_top += amount;
+	    }
+	    else
+	    {
+		/* 2, 3, or 5: need to correct nested folds too */
+		foldMarkAdjustRecurse(&fp->fd_nested, line1 - fp->fd_top,
+				  line2 - fp->fd_top, amount, amount_after);
+		if (fp->fd_top < top)
+		{
+		    if (last <= line2)
+		    {
+			/* 2. fold contains line1, line2 is below fold */
+			if (amount == MAXLNUM)
+			    fp->fd_len = line1 - fp->fd_top;
+			else
+			    fp->fd_len += amount;
+		    }
+		    else
+		    {
+			/* 3. fold contains line1 and line2 */
+			fp->fd_len += amount_after;
+		    }
+		}
+		else
+		{
+		    /* 5. fold is below line1 and contains line2 */
+		    if (amount == MAXLNUM)
+		    {
+			fp->fd_len -= line2 - fp->fd_top + 1;
+			fp->fd_top = line1;
+		    }
+		    else
+		    {
+			fp->fd_len += amount_after - amount;
+			fp->fd_top += amount;
+		    }
+		}
+	    }
+	}
+    }
+}
+
+/* getDeepestNesting() {{{2 */
+/*
+ * Get the lowest 'foldlevel' value that makes the deepest nested fold in the
+ * current window open.
+ */
+    int
+getDeepestNesting()
+{
+    checkupdate(curwin);
+    return getDeepestNestingRecurse(&curwin->w_folds);
+}
+
+    static int
+getDeepestNestingRecurse(gap)
+    garray_T	*gap;
+{
+    int		i;
+    int		level;
+    int		maxlevel = 0;
+    fold_T	*fp;
+
+    fp = (fold_T *)gap->ga_data;
+    for (i = 0; i < gap->ga_len; ++i)
+    {
+	level = getDeepestNestingRecurse(&fp[i].fd_nested) + 1;
+	if (level > maxlevel)
+	    maxlevel = level;
+    }
+
+    return maxlevel;
+}
+
+/* check_closed() {{{2 */
+/*
+ * Check if a fold is closed and update the info needed to check nested folds.
+ */
+    static int
+check_closed(win, fp, use_levelp, level, maybe_smallp, lnum_off)
+    win_T	*win;
+    fold_T	*fp;
+    int		*use_levelp;	    /* TRUE: outer fold had FD_LEVEL */
+    int		level;		    /* folding depth */
+    int		*maybe_smallp;	    /* TRUE: outer this had fd_small == MAYBE */
+    linenr_T	lnum_off;	    /* line number offset for fp->fd_top */
+{
+    int		closed = FALSE;
+
+    /* Check if this fold is closed.  If the flag is FD_LEVEL this
+     * fold and all folds it contains depend on 'foldlevel'. */
+    if (*use_levelp || fp->fd_flags == FD_LEVEL)
+    {
+	*use_levelp = TRUE;
+	if (level >= win->w_p_fdl)
+	    closed = TRUE;
+    }
+    else if (fp->fd_flags == FD_CLOSED)
+	closed = TRUE;
+
+    /* Small fold isn't closed anyway. */
+    if (fp->fd_small == MAYBE)
+	*maybe_smallp = TRUE;
+    if (closed)
+    {
+	if (*maybe_smallp)
+	    fp->fd_small = MAYBE;
+	checkSmall(win, fp, lnum_off);
+	if (fp->fd_small == TRUE)
+	    closed = FALSE;
+    }
+    return closed;
+}
+
+/* checkSmall() {{{2 */
+/*
+ * Update fd_small field of fold "fp".
+ */
+    static void
+checkSmall(wp, fp, lnum_off)
+    win_T	*wp;
+    fold_T	*fp;
+    linenr_T	lnum_off;	/* offset for fp->fd_top */
+{
+    int		count;
+    int		n;
+
+    if (fp->fd_small == MAYBE)
+    {
+	/* Mark any nested folds to maybe-small */
+	setSmallMaybe(&fp->fd_nested);
+
+	if (fp->fd_len > curwin->w_p_fml)
+	    fp->fd_small = FALSE;
+	else
+	{
+	    count = 0;
+	    for (n = 0; n < fp->fd_len; ++n)
+	    {
+		count += plines_win_nofold(wp, fp->fd_top + lnum_off + n);
+		if (count > curwin->w_p_fml)
+		{
+		    fp->fd_small = FALSE;
+		    return;
+		}
+	    }
+	    fp->fd_small = TRUE;
+	}
+    }
+}
+
+/* setSmallMaybe() {{{2 */
+/*
+ * Set small flags in "gap" to MAYBE.
+ */
+    static void
+setSmallMaybe(gap)
+    garray_T	*gap;
+{
+    int		i;
+    fold_T	*fp;
+
+    fp = (fold_T *)gap->ga_data;
+    for (i = 0; i < gap->ga_len; ++i)
+	fp[i].fd_small = MAYBE;
+}
+
+/* foldCreateMarkers() {{{2 */
+/*
+ * Create a fold from line "start" to line "end" (inclusive) in the current
+ * window by adding markers.
+ */
+    static void
+foldCreateMarkers(start, end)
+    linenr_T	start;
+    linenr_T	end;
+{
+    if (!curbuf->b_p_ma)
+    {
+	EMSG(_(e_modifiable));
+	return;
+    }
+    parseMarker(curwin);
+
+    foldAddMarker(start, curwin->w_p_fmr, foldstartmarkerlen);
+    foldAddMarker(end, foldendmarker, foldendmarkerlen);
+
+    /* Update both changes here, to avoid all folds after the start are
+     * changed when the start marker is inserted and the end isn't. */
+    changed_lines(start, (colnr_T)0, end, 0L);
+}
+
+/* foldAddMarker() {{{2 */
+/*
+ * Add "marker[markerlen]" in 'commentstring' to line "lnum".
+ */
+    static void
+foldAddMarker(lnum, marker, markerlen)
+    linenr_T	lnum;
+    char_u	*marker;
+    int		markerlen;
+{
+    char_u	*cms = curbuf->b_p_cms;
+    char_u	*line;
+    int		line_len;
+    char_u	*newline;
+    char_u	*p = (char_u *)strstr((char *)curbuf->b_p_cms, "%s");
+
+    /* Allocate a new line: old-line + 'cms'-start + marker + 'cms'-end */
+    line = ml_get(lnum);
+    line_len = (int)STRLEN(line);
+
+    if (u_save(lnum - 1, lnum + 1) == OK)
+    {
+	newline = alloc((unsigned)(line_len + markerlen + STRLEN(cms) + 1));
+	if (newline == NULL)
+	    return;
+	STRCPY(newline, line);
+	if (p == NULL)
+	{
+	    STRNCPY(newline + line_len, marker, markerlen);
+	    newline[line_len + markerlen] = NUL;
+	}
+	else
+	{
+	    STRCPY(newline + line_len, cms);
+	    STRNCPY(newline + line_len + (p - cms), marker, markerlen);
+	    STRCPY(newline + line_len + (p - cms) + markerlen, p + 2);
+	}
+
+	ml_replace(lnum, newline, FALSE);
+    }
+}
+
+/* deleteFoldMarkers() {{{2 */
+/*
+ * Delete the markers for a fold, causing it to be deleted.
+ */
+    static void
+deleteFoldMarkers(fp, recursive, lnum_off)
+    fold_T	*fp;
+    int		recursive;
+    linenr_T	lnum_off;	/* offset for fp->fd_top */
+{
+    int		i;
+
+    if (recursive)
+	for (i = 0; i < fp->fd_nested.ga_len; ++i)
+	    deleteFoldMarkers((fold_T *)fp->fd_nested.ga_data + i, TRUE,
+						       lnum_off + fp->fd_top);
+    foldDelMarker(fp->fd_top + lnum_off, curwin->w_p_fmr, foldstartmarkerlen);
+    foldDelMarker(fp->fd_top + lnum_off + fp->fd_len - 1,
+					     foldendmarker, foldendmarkerlen);
+}
+
+/* foldDelMarker() {{{2 */
+/*
+ * Delete marker "marker[markerlen]" at the end of line "lnum".
+ * Delete 'commentstring' if it matches.
+ * If the marker is not found, there is no error message.  Could a missing
+ * close-marker.
+ */
+    static void
+foldDelMarker(lnum, marker, markerlen)
+    linenr_T	lnum;
+    char_u	*marker;
+    int		markerlen;
+{
+    char_u	*line;
+    char_u	*newline;
+    char_u	*p;
+    int		len;
+    char_u	*cms = curbuf->b_p_cms;
+    char_u	*cms2;
+
+    line = ml_get(lnum);
+    for (p = line; *p != NUL; ++p)
+	if (STRNCMP(p, marker, markerlen) == 0)
+	{
+	    /* Found the marker, include a digit if it's there. */
+	    len = markerlen;
+	    if (VIM_ISDIGIT(p[len]))
+		++len;
+	    if (*cms != NUL)
+	    {
+		/* Also delete 'commentstring' if it matches. */
+		cms2 = (char_u *)strstr((char *)cms, "%s");
+		if (p - line >= cms2 - cms
+			&& STRNCMP(p - (cms2 - cms), cms, cms2 - cms) == 0
+			&& STRNCMP(p + len, cms2 + 2, STRLEN(cms2 + 2)) == 0)
+		{
+		    p -= cms2 - cms;
+		    len += (int)STRLEN(cms) - 2;
+		}
+	    }
+	    if (u_save(lnum - 1, lnum + 1) == OK)
+	    {
+		/* Make new line: text-before-marker + text-after-marker */
+		newline = alloc((unsigned)(STRLEN(line) - len + 1));
+		if (newline != NULL)
+		{
+		    STRNCPY(newline, line, p - line);
+		    STRCPY(newline + (p - line), p + len);
+		    ml_replace(lnum, newline, FALSE);
+		}
+	    }
+	    break;
+	}
+}
+
+/* foldtext_cleanup() {{{2 */
+/*
+ * Remove 'foldmarker' and 'commentstring' from "str" (in-place).
+ */
+    void
+foldtext_cleanup(str)
+    char_u	*str;
+{
+    char_u	*cms_start;	/* first part or the whole comment */
+    int		cms_slen = 0;	/* length of cms_start */
+    char_u	*cms_end;	/* last part of the comment or NULL */
+    int		cms_elen = 0;	/* length of cms_end */
+    char_u	*s;
+    int		len;
+    int		did1 = FALSE;
+    int		did2 = FALSE;
+
+    /* Ignore leading and trailing white space in 'commentstring'. */
+    cms_start = skipwhite(curbuf->b_p_cms);
+    cms_slen = STRLEN(cms_start);
+    while (cms_slen > 0 && vim_iswhite(cms_start[cms_slen - 1]))
+	--cms_slen;
+
+    /* locate "%s" in 'commentstring', use the part before and after it. */
+    cms_end = (char_u *)strstr((char *)cms_start, "%s");
+    if (cms_end != NULL)
+    {
+	cms_elen = cms_slen - (cms_end - cms_start);
+	cms_slen = cms_end - cms_start;
+
+	/* exclude white space before "%s" */
+	while (cms_slen > 0 && vim_iswhite(cms_start[cms_slen - 1]))
+	    --cms_slen;
+
+	/* skip "%s" and white space after it */
+	s = skipwhite(cms_end + 2);
+	cms_elen -= s - cms_end;
+	cms_end = s;
+    }
+    parseMarker(curwin);
+
+    for (s = str; *s != NUL; )
+    {
+	len = 0;
+	if (STRNCMP(s, curwin->w_p_fmr, foldstartmarkerlen) == 0)
+	{
+	    len = foldstartmarkerlen;
+	    if (VIM_ISDIGIT(s[len]))
+		++len;
+	}
+	else if (STRNCMP(s, foldendmarker, foldendmarkerlen) == 0)
+	{
+	    len = foldendmarkerlen;
+	    if (VIM_ISDIGIT(s[len]))
+		++len;
+	}
+	else if (cms_end != NULL)
+	{
+	    if (!did1 && STRNCMP(s, cms_start, cms_slen) == 0)
+	    {
+		len = cms_slen;
+		did1 = TRUE;
+	    }
+	    else if (!did2 && STRNCMP(s, cms_end, cms_elen) == 0)
+	    {
+		len = cms_elen;
+		did2 = TRUE;
+	    }
+	}
+	if (len != 0)
+	{
+	    while (vim_iswhite(s[len]))
+		++len;
+	    mch_memmove(s, s + len, STRLEN(s + len) + 1);
+	}
+	else
+	{
+#ifdef FEAT_MBYTE
+	    if (has_mbyte)
+		s += (*mb_ptr2len_check)(s);
+	    else
+#endif
+		++s;
+	}
+    }
+}
+
+/* Folding by indent, expr, marker and syntax. {{{1 */
+/* Define "fline_T", passed to get fold level for a line. {{{2 */
+typedef struct
+{
+    win_T	*wp;		/* window */
+    linenr_T	lnum;		/* current line number */
+    linenr_T	off;		/* offset between lnum and real line number */
+    linenr_T	lnum_save;	/* line nr used by foldUpdateIEMSRecurse() */
+    int		lvl;		/* current level (-1 for undefined) */
+    int		lvl_next;	/* level used for next line */
+    int		start;		/* number of folds that are forced to start at
+				   this line. */
+    int		end;		/* level of fold that is forced to end below
+				   this line */
+    int		had_end;	/* level of fold that is forced to end above
+				   this line (copy of "end" of prev. line) */
+} fline_T;
+
+/* Flag is set when redrawing is needed. */
+static int fold_changed;
+
+/* Function declarations. {{{2 */
+static linenr_T foldUpdateIEMSRecurse __ARGS((garray_T *gap, int level, linenr_T startlnum, fline_T *flp, void (*getlevel)__ARGS((fline_T *)), linenr_T bot, int topflags));
+static int foldInsert __ARGS((garray_T *gap, int i));
+static void foldSplit __ARGS((garray_T *gap, int i, linenr_T top, linenr_T bot));
+static void foldRemove __ARGS((garray_T *gap, linenr_T top, linenr_T bot));
+static void foldMerge __ARGS((fold_T *fp1, garray_T *gap, fold_T *fp2));
+static void foldlevelIndent __ARGS((fline_T *flp));
+#ifdef FEAT_DIFF
+static void foldlevelDiff __ARGS((fline_T *flp));
+#endif
+static void foldlevelExpr __ARGS((fline_T *flp));
+static void foldlevelMarker __ARGS((fline_T *flp));
+static void foldlevelSyntax __ARGS((fline_T *flp));
+
+/* foldUpdateIEMS() {{{2 */
+/*
+ * Update the folding for window "wp", at least from lines "top" to "bot".
+ * Return TRUE if any folds did change.
+ */
+    static void
+foldUpdateIEMS(wp, top, bot)
+    win_T	*wp;
+    linenr_T	top;
+    linenr_T	bot;
+{
+    linenr_T	start;
+    linenr_T	end;
+    fline_T	fline;
+    void	(*getlevel)__ARGS((fline_T *));
+    int		level;
+    fold_T	*fp;
+
+    /* Avoid problems when being called recursively. */
+    if (invalid_top != (linenr_T)0)
+	return;
+
+    if (wp->w_foldinvalid)
+    {
+	/* Need to update all folds. */
+	top = 1;
+	bot = wp->w_buffer->b_ml.ml_line_count;
+	wp->w_foldinvalid = FALSE;
+
+	/* Mark all folds a maybe-small. */
+	setSmallMaybe(&wp->w_folds);
+    }
+
+#ifdef FEAT_DIFF
+    /* add the context for "diff" folding */
+    if (foldmethodIsDiff(wp))
+    {
+	if (top > diff_context)
+	    top -= diff_context;
+	else
+	    top = 1;
+	bot += diff_context;
+    }
+#endif
+
+    /* When deleting lines at the end of the buffer "top" can be past the end
+     * of the buffer. */
+    if (top > wp->w_buffer->b_ml.ml_line_count)
+	top = wp->w_buffer->b_ml.ml_line_count;
+
+    fold_changed = FALSE;
+    fline.wp = wp;
+    fline.off = 0;
+    fline.lvl = 0;
+    fline.lvl_next = -1;
+    fline.start = 0;
+    fline.end = MAX_LEVEL + 1;
+    fline.had_end = MAX_LEVEL + 1;
+
+    invalid_top = top;
+    invalid_bot = bot;
+
+    if (foldmethodIsMarker(wp))
+    {
+	getlevel = foldlevelMarker;
+
+	/* Init marker variables to speed up foldlevelMarker(). */
+	parseMarker(wp);
+
+	/* Need to get the level of the line above top, it is used if there is
+	 * no marker at the top. */
+	if (top > 1)
+	{
+	    /* Get the fold level at top - 1. */
+	    level = foldLevelWin(wp, top - 1);
+
+	    /* The fold may end just above the top, check for that. */
+	    fline.lnum = top - 1;
+	    fline.lvl = level;
+	    getlevel(&fline);
+
+	    /* If a fold started here, we already had the level, if it stops
+	     * here, we need to use lvl_next.  Could also start and end a fold
+	     * in the same line. */
+	    if (fline.lvl > level)
+		fline.lvl = level - (fline.lvl - fline.lvl_next);
+	    else
+		fline.lvl = fline.lvl_next;
+	}
+	fline.lnum = top;
+	getlevel(&fline);
+    }
+    else
+    {
+	fline.lnum = top;
+	if (foldmethodIsExpr(wp))
+	{
+	    getlevel = foldlevelExpr;
+	    /* start one line back, because a "<1" may indicate the end of a
+	     * fold in the topline */
+	    if (top > 1)
+		--fline.lnum;
+	}
+	else if (foldmethodIsSyntax(wp))
+	    getlevel = foldlevelSyntax;
+#ifdef FEAT_DIFF
+	else if (foldmethodIsDiff(wp))
+	    getlevel = foldlevelDiff;
+#endif
+	else
+	    getlevel = foldlevelIndent;
+
+	/* Backup to a line for which the fold level is defined.  Since it's
+	 * always defined for line one, we will stop there. */
+	fline.lvl = -1;
+	for ( ; !got_int; --fline.lnum)
+	{
+	    /* Reset lvl_next each time, because it will be set to a value for
+	     * the next line, but we search backwards here. */
+	    fline.lvl_next = -1;
+	    getlevel(&fline);
+	    if (fline.lvl >= 0)
+		break;
+	}
+    }
+
+    start = fline.lnum;
+    end = bot;
+    /* Do at least one line. */
+    if (start > end && end < wp->w_buffer->b_ml.ml_line_count)
+	end = start;
+    while (!got_int)
+    {
+	/* Always stop at the end of the file ("end" can be past the end of
+	 * the file). */
+	if (fline.lnum > wp->w_buffer->b_ml.ml_line_count)
+	    break;
+	if (fline.lnum > end)
+	{
+	    /* For "marker", "expr"  and "syntax"  methods: If a change caused
+	     * a fold to be removed, we need to continue at least until where
+	     * it ended. */
+	    if (getlevel != foldlevelMarker
+		    && getlevel != foldlevelSyntax
+		    && getlevel != foldlevelExpr)
+		break;
+	    if ((start <= end
+			&& foldFind(&wp->w_folds, end, &fp)
+			&& fp->fd_top + fp->fd_len - 1 > end)
+		    || (fline.lvl == 0
+			&& foldFind(&wp->w_folds, fline.lnum, &fp)
+			&& fp->fd_top < fline.lnum))
+		end = fp->fd_top + fp->fd_len - 1;
+	    else if (getlevel == foldlevelSyntax
+		    && foldLevelWin(wp, fline.lnum) != fline.lvl)
+		/* For "syntax" method: Compare the foldlevel that the syntax
+		 * tells us to the foldlevel from the existing folds.  If they
+		 * don't match continue updating folds. */
+		end = fline.lnum;
+	    else
+		break;
+	}
+
+	/* A level 1 fold starts at a line with foldlevel > 0. */
+	if (fline.lvl > 0)
+	{
+	    invalid_top = fline.lnum;
+	    invalid_bot = end;
+	    end = foldUpdateIEMSRecurse(&wp->w_folds,
+				   1, start, &fline, getlevel, end, FD_LEVEL);
+	    start = fline.lnum;
+	}
+	else
+	{
+	    if (fline.lnum == wp->w_buffer->b_ml.ml_line_count)
+		break;
+	    ++fline.lnum;
+	    fline.lvl = fline.lvl_next;
+	    getlevel(&fline);
+	}
+    }
+
+    /* There can't be any folds from start until end now. */
+    foldRemove(&wp->w_folds, start, end);
+
+    /* If some fold changed, need to redraw and position cursor. */
+    if (fold_changed && wp->w_p_fen)
+	changed_window_setting();
+
+    /* If we updated folds past "bot", need to redraw more lines.  Don't do
+     * this in other situations, the changed lines will be redrawn anyway and
+     * this method can cause the whole window to be updated. */
+    if (end != bot)
+    {
+	if (wp->w_redraw_top == 0 || wp->w_redraw_top > top)
+	    wp->w_redraw_top = top;
+	if (wp->w_redraw_bot < end)
+	    wp->w_redraw_bot = end;
+    }
+
+    invalid_top = (linenr_T)0;
+}
+
+/* foldUpdateIEMSRecurse() {{{2 */
+/*
+ * Update a fold that starts at "flp->lnum".  At this line there is always a
+ * valid foldlevel, and its level >= "level".
+ * "flp" is valid for "flp->lnum" when called and it's valid when returning.
+ * "flp->lnum" is set to the lnum just below the fold, if it ends before
+ * "bot", it's "bot" plus one if the fold continues and it's bigger when using
+ * the marker method and a text change made following folds to change.
+ * When returning, "flp->lnum_save" is the line number that was used to get
+ * the level when the level at "flp->lnum" is invalid.
+ * Remove any folds from "startlnum" up to here at this level.
+ * Recursively update nested folds.
+ * Below line "bot" there are no changes in the text.
+ * "flp->lnum", "flp->lnum_save" and "bot" are relative to the start of the
+ * outer fold.
+ * "flp->off" is the offset to the real line number in the buffer.
+ *
+ * All this would be a lot simpler if all folds in the range would be deleted
+ * and then created again.  But we would loose all information about the
+ * folds, even when making changes that don't affect the folding (e.g. "vj~").
+ *
+ * Returns bot, which may have been increased for lines that also need to be
+ * updated as a result of a detected change in the fold.
+ */
+    static linenr_T
+foldUpdateIEMSRecurse(gap, level, startlnum, flp, getlevel, bot, topflags)
+    garray_T	*gap;
+    int		level;
+    linenr_T	startlnum;
+    fline_T	*flp;
+    void	(*getlevel)__ARGS((fline_T *));
+    linenr_T	bot;
+    int		topflags;	/* flags used by containing fold */
+{
+    linenr_T	ll;
+    fold_T	*fp = NULL;
+    fold_T	*fp2;
+    int		lvl = level;
+    linenr_T	startlnum2 = startlnum;
+    linenr_T	firstlnum = flp->lnum;	/* first lnum we got */
+    int		i;
+    int		finish = FALSE;
+    linenr_T	linecount = flp->wp->w_buffer->b_ml.ml_line_count - flp->off;
+    int		concat;
+
+    /*
+     * If using the marker method, the start line is not the start of a fold
+     * at the level we're dealing with and the level is non-zero, we must use
+     * the previous fold.  But ignore a fold that starts at or below
+     * startlnum, it must be deleted.
+     */
+    if (getlevel == foldlevelMarker && flp->start <= flp->lvl - level
+							      && flp->lvl > 0)
+    {
+	foldFind(gap, startlnum - 1, &fp);
+	if (fp >= ((fold_T *)gap->ga_data) + gap->ga_len
+						   || fp->fd_top >= startlnum)
+	    fp = NULL;
+    }
+
+    /*
+     * Loop over all lines in this fold, or until "bot" is hit.
+     * Handle nested folds inside of this fold.
+     * "flp->lnum" is the current line.  When finding the end of the fold, it
+     * is just below the end of the fold.
+     * "*flp" contains the level of the line "flp->lnum" or a following one if
+     * there are lines with an invalid fold level.  "flp->lnum_save" is the
+     * line number that was used to get the fold level (below "flp->lnum" when
+     * it has an invalid fold level).  When called the fold level is always
+     * valid, thus "flp->lnum_save" is equal to "flp->lnum".
+     */
+    flp->lnum_save = flp->lnum;
+    while (!got_int)
+    {
+	/* Updating folds can be slow, check for CTRL-C. */
+	line_breakcheck();
+
+	/* Set "lvl" to the level of line "flp->lnum".  When flp->start is set
+	 * and after the first line of the fold, set the level to zero to
+	 * force the fold to end.  Do the same when had_end is set: Previous
+	 * line was marked as end of a fold. */
+	lvl = flp->lvl;
+	if (lvl > MAX_LEVEL)
+	    lvl = MAX_LEVEL;
+	if (flp->lnum > firstlnum
+		&& (level > lvl - flp->start || level >= flp->had_end))
+	    lvl = 0;
+
+	if (flp->lnum > bot && !finish && fp != NULL)
+	{
+	    /* For "marker" and "syntax" methods:
+	     * - If a change caused a nested fold to be removed, we need to
+	     *   delete it and continue at least until where it ended.
+	     * - If a change caused a nested fold to be created, or this fold
+	     *   to continue below its original end, need to finish this fold.
+	     */
+	    if (getlevel != foldlevelMarker
+		    && getlevel != foldlevelExpr
+		    && getlevel != foldlevelSyntax)
+		break;
+	    i = 0;
+	    fp2 = fp;
+	    if (lvl >= level)
+	    {
+		/* Compute how deep the folds currently are, if it's deeper
+		 * than "lvl" then some must be deleted, need to update
+		 * at least one nested fold. */
+		ll = flp->lnum - fp->fd_top;
+		while (foldFind(&fp2->fd_nested, ll, &fp2))
+		{
+		    ++i;
+		    ll -= fp2->fd_top;
+		}
+	    }
+	    if (lvl < level + i)
+	    {
+		foldFind(&fp->fd_nested, flp->lnum - fp->fd_top, &fp2);
+		if (fp2 != NULL)
+		    bot = fp2->fd_top + fp2->fd_len - 1 + fp->fd_top;
+	    }
+	    else if (fp->fd_top + fp->fd_len <= flp->lnum && lvl >= level)
+		finish = TRUE;
+	    else
+		break;
+	}
+
+	/* At the start of the first nested fold and at the end of the current
+	 * fold: check if existing folds at this level, before the current
+	 * one, need to be deleted or truncated. */
+	if (fp == NULL
+		&& (lvl != level
+		    || flp->lnum_save >= bot
+		    || flp->start != 0
+		    || flp->had_end <= MAX_LEVEL
+		    || flp->lnum == linecount))
+	{
+	    /*
+	     * Remove or update folds that have lines between startlnum and
+	     * firstlnum.
+	     */
+	    while (!got_int)
+	    {
+		/* set concat to 1 if it's allowed to concatenated this fold
+		 * with a previous one that touches it. */
+		if (flp->start != 0 || flp->had_end <= MAX_LEVEL)
+		    concat = 0;
+		else
+		    concat = 1;
+
+		/* Find an existing fold to re-use.  Preferably one that
+		 * includes startlnum, otherwise one that ends just before
+		 * startlnum or starts after it. */
+		if (foldFind(gap, startlnum, &fp)
+			|| (fp < ((fold_T *)gap->ga_data) + gap->ga_len
+			    && fp->fd_top <= firstlnum)
+			|| foldFind(gap, firstlnum - concat, &fp)
+			|| (fp < ((fold_T *)gap->ga_data) + gap->ga_len
+			    && ((lvl < level && fp->fd_top < flp->lnum)
+				|| (lvl >= level
+					   && fp->fd_top <= flp->lnum_save))))
+		{
+		    if (fp->fd_top + fp->fd_len + concat > firstlnum)
+		    {
+			/* Use existing fold for the new fold.  If it starts
+			 * before where we started looking, extend it.  If it
+			 * starts at another line, update nested folds to keep
+			 * their position, compensating for the new fd_top. */
+			if (fp->fd_top >= startlnum && fp->fd_top != firstlnum)
+			{
+			    if (fp->fd_top > firstlnum)
+				/* like lines are inserted */
+				foldMarkAdjustRecurse(&fp->fd_nested,
+					(linenr_T)0, (linenr_T)MAXLNUM,
+					(long)(fp->fd_top - firstlnum), 0L);
+			    else
+				/* like lines are deleted */
+				foldMarkAdjustRecurse(&fp->fd_nested,
+					(linenr_T)0,
+					(long)(firstlnum - fp->fd_top - 1),
+					(linenr_T)MAXLNUM,
+					(long)(fp->fd_top - firstlnum));
+			    fp->fd_len += fp->fd_top - firstlnum;
+			    fp->fd_top = firstlnum;
+			    fold_changed = TRUE;
+			}
+			else if (flp->start != 0 && lvl == level
+						   && fp->fd_top != firstlnum)
+			{
+			    /* Existing fold that includes startlnum must stop
+			     * if we find the start of a new fold at the same
+			     * level.  Split it.  Delete contained folds at
+			     * this point to split them too. */
+			    foldRemove(&fp->fd_nested, flp->lnum - fp->fd_top,
+						      flp->lnum - fp->fd_top);
+			    i = (int)(fp - (fold_T *)gap->ga_data);
+			    foldSplit(gap, i, flp->lnum, flp->lnum - 1);
+			    fp = (fold_T *)gap->ga_data + i + 1;
+			    /* If using the "marker" or "syntax" method, we
+			     * need to continue until the end of the fold is
+			     * found. */
+			    if (getlevel == foldlevelMarker
+				    || getlevel == foldlevelExpr
+				    || getlevel == foldlevelSyntax)
+				finish = TRUE;
+			}
+			break;
+		    }
+		    if (fp->fd_top >= startlnum)
+		    {
+			/* A fold that starts at or after startlnum and stops
+			 * before the new fold must be deleted.  Continue
+			 * looking for the next one. */
+			deleteFoldEntry(gap,
+				     (int)(fp - (fold_T *)gap->ga_data), TRUE);
+		    }
+		    else
+		    {
+			/* A fold has some lines above startlnum, truncate it
+			 * to stop just above startlnum.  */
+			fp->fd_len = startlnum - fp->fd_top;
+			foldMarkAdjustRecurse(&fp->fd_nested,
+				(linenr_T)fp->fd_len, (linenr_T)MAXLNUM,
+						       (linenr_T)MAXLNUM, 0L);
+			fold_changed = TRUE;
+		    }
+		}
+		else
+		{
+		    /* Insert new fold.  Careful: ga_data may be NULL and it
+		     * may change! */
+		    i = (int)(fp - (fold_T *)gap->ga_data);
+		    if (foldInsert(gap, i) != OK)
+			return bot;
+		    fp = (fold_T *)gap->ga_data + i;
+		    /* The new fold continues until bot, unless we find the
+		     * end earlier. */
+		    fp->fd_top = firstlnum;
+		    fp->fd_len = bot - firstlnum + 1;
+		    /* When the containing fold is open, the new fold is open.
+		     * The new fold is closed if the fold above it is closed.
+		     * The first fold depends on the containing fold. */
+		    if (topflags == FD_OPEN)
+		    {
+			flp->wp->w_fold_manual = TRUE;
+			fp->fd_flags = FD_OPEN;
+		    }
+		    else if (i <= 0)
+		    {
+			fp->fd_flags = topflags;
+			if (topflags != FD_LEVEL)
+			    flp->wp->w_fold_manual = TRUE;
+		    }
+		    else
+			fp->fd_flags = (fp - 1)->fd_flags;
+		    fp->fd_small = MAYBE;
+		    /* If using the "marker", "expr" or "syntax" method, we
+		     * need to continue until the end of the fold is found. */
+		    if (getlevel == foldlevelMarker
+			    || getlevel == foldlevelExpr
+			    || getlevel == foldlevelSyntax)
+			finish = TRUE;
+		    fold_changed = TRUE;
+		    break;
+		}
+	    }
+	}
+
+	if (lvl < level || flp->lnum > linecount)
+	{
+	    /*
+	     * Found a line with a lower foldlevel, this fold ends just above
+	     * "flp->lnum".
+	     */
+	    break;
+	}
+
+	/*
+	 * The fold includes the line "flp->lnum" and "flp->lnum_save".
+	 */
+	if (lvl > level)
+	{
+	    /*
+	     * There is a nested fold, handle it recursively.
+	     */
+	    /* At least do one line (can happen when finish is TRUE). */
+	    if (bot < flp->lnum)
+		bot = flp->lnum;
+
+	    /* Line numbers in the nested fold are relative to the start of
+	     * this fold. */
+	    flp->lnum = flp->lnum_save - fp->fd_top;
+	    flp->off += fp->fd_top;
+	    i = (int)(fp - (fold_T *)gap->ga_data);
+	    bot = foldUpdateIEMSRecurse(&fp->fd_nested, level + 1,
+				       startlnum2 - fp->fd_top, flp, getlevel,
+					      bot - fp->fd_top, fp->fd_flags);
+	    fp = (fold_T *)gap->ga_data + i;
+	    flp->lnum += fp->fd_top;
+	    flp->lnum_save += fp->fd_top;
+	    flp->off -= fp->fd_top;
+	    bot += fp->fd_top;
+	    startlnum2 = flp->lnum;
+
+	    /* This fold may end at the same line, don't incr. flp->lnum. */
+	}
+	else
+	{
+	    /*
+	     * Get the level of the next line, then continue the loop to check
+	     * if it ends there.
+	     * Skip over undefined lines, to find the foldlevel after it.
+	     * For the last line in the file the foldlevel is always valid.
+	     */
+	    flp->lnum = flp->lnum_save;
+	    ll = flp->lnum + 1;
+	    while (!got_int)
+	    {
+		/* Make the previous level available to foldlevel(). */
+		prev_lnum = flp->lnum;
+		prev_lnum_lvl = flp->lvl;
+
+		if (++flp->lnum > linecount)
+		    break;
+		flp->lvl = flp->lvl_next;
+		getlevel(flp);
+		if (flp->lvl >= 0 || flp->had_end <= MAX_LEVEL)
+		    break;
+	    }
+	    prev_lnum = 0;
+	    if (flp->lnum > linecount)
+		break;
+
+	    /* leave flp->lnum_save to lnum of the line that was used to get
+	     * the level, flp->lnum to the lnum of the next line. */
+	    flp->lnum_save = flp->lnum;
+	    flp->lnum = ll;
+	}
+    }
+
+    if (fp == NULL)	/* only happens when got_int is set */
+	return bot;
+
+    /*
+     * Get here when:
+     * lvl < level: the folds ends just above "flp->lnum"
+     * lvl >= level: fold continues below "bot"
+     */
+
+    /* Current fold at least extends until lnum. */
+    if (fp->fd_len < flp->lnum - fp->fd_top)
+    {
+	fp->fd_len = flp->lnum - fp->fd_top;
+	fold_changed = TRUE;
+    }
+
+    /* Delete contained folds from the end of the last one found until where
+     * we stopped looking. */
+    foldRemove(&fp->fd_nested, startlnum2 - fp->fd_top,
+						  flp->lnum - 1 - fp->fd_top);
+
+    if (lvl < level)
+    {
+	/* End of fold found, update the length when it got shorter. */
+	if (fp->fd_len != flp->lnum - fp->fd_top)
+	{
+	    if (fp->fd_top + fp->fd_len > bot + 1)
+	    {
+		/* fold coninued below bot */
+		if (getlevel == foldlevelMarker
+			|| getlevel == foldlevelExpr
+			|| getlevel == foldlevelSyntax)
+		{
+		    /* marker method: truncate the fold and make sure the
+		     * previously included lines are processed again */
+		    bot = fp->fd_top + fp->fd_len - 1;
+		    fp->fd_len = flp->lnum - fp->fd_top;
+		}
+		else
+		{
+		    /* indent or expr method: split fold to create a new one
+		     * below bot */
+		    i = (int)(fp - (fold_T *)gap->ga_data);
+		    foldSplit(gap, i, flp->lnum, bot);
+		    fp = (fold_T *)gap->ga_data + i;
+		}
+	    }
+	    else
+		fp->fd_len = flp->lnum - fp->fd_top;
+	    fold_changed = TRUE;
+	}
+    }
+
+    /* delete following folds that end before the current line */
+    for (;;)
+    {
+	fp2 = fp + 1;
+	if (fp2 >= (fold_T *)gap->ga_data + gap->ga_len
+						  || fp2->fd_top > flp->lnum)
+	    break;
+	if (fp2->fd_top + fp2->fd_len > flp->lnum)
+	{
+	    if (fp2->fd_top < flp->lnum)
+	    {
+		/* Make fold that includes lnum start at lnum. */
+		foldMarkAdjustRecurse(&fp2->fd_nested,
+			(linenr_T)0, (long)(flp->lnum - fp2->fd_top - 1),
+			(linenr_T)MAXLNUM, (long)(fp2->fd_top - flp->lnum));
+		fp2->fd_len -= flp->lnum - fp2->fd_top;
+		fp2->fd_top = flp->lnum;
+		fold_changed = TRUE;
+	    }
+
+	    if (lvl >= level)
+	    {
+		/* merge new fold with existing fold that follows */
+		foldMerge(fp, gap, fp2);
+	    }
+	    break;
+	}
+	fold_changed = TRUE;
+	deleteFoldEntry(gap, (int)(fp2 - (fold_T *)gap->ga_data), TRUE);
+    }
+
+    /* Need to redraw the lines we inspected, which might be further down than
+     * was asked for. */
+    if (bot < flp->lnum - 1)
+	bot = flp->lnum - 1;
+
+    return bot;
+}
+
+/* foldInsert() {{{2 */
+/*
+ * Insert a new fold in "gap" at position "i".
+ * Returns OK for success, FAIL for failure.
+ */
+    static int
+foldInsert(gap, i)
+    garray_T	*gap;
+    int		i;
+{
+    fold_T	*fp;
+
+    if (ga_grow(gap, 1) != OK)
+	return FAIL;
+    fp = (fold_T *)gap->ga_data + i;
+    if (i < gap->ga_len)
+	mch_memmove(fp + 1, fp, sizeof(fold_T) * (gap->ga_len - i));
+    ++gap->ga_len;
+    --gap->ga_room;
+    ga_init2(&fp->fd_nested, (int)sizeof(fold_T), 10);
+    return OK;
+}
+
+/* foldSplit() {{{2 */
+/*
+ * Split the "i"th fold in "gap", which starts before "top" and ends below
+ * "bot" in two pieces, one ending above "top" and the other starting below
+ * "bot".
+ * The caller must first have taken care of any nested folds from "top" to
+ * "bot"!
+ */
+    static void
+foldSplit(gap, i, top, bot)
+    garray_T	*gap;
+    int		i;
+    linenr_T	top;
+    linenr_T	bot;
+{
+    fold_T	*fp;
+    fold_T	*fp2;
+    garray_T	*gap1;
+    garray_T	*gap2;
+    int		idx;
+    int		len;
+
+    /* The fold continues below bot, need to split it. */
+    if (foldInsert(gap, i + 1) == FAIL)
+	return;
+    fp = (fold_T *)gap->ga_data + i;
+    fp[1].fd_top = bot + 1;
+    fp[1].fd_len = fp->fd_len - (fp[1].fd_top - fp->fd_top);
+    fp[1].fd_flags = fp->fd_flags;
+
+    /* Move nested folds below bot to new fold.  There can't be
+     * any between top and bot, they have been removed by the caller. */
+    gap1 = &fp->fd_nested;
+    gap2 = &fp[1].fd_nested;
+    (void)(foldFind(gap1, bot + 1 - fp->fd_top, &fp2));
+    len = (int)((fold_T *)gap1->ga_data + gap1->ga_len - fp2);
+    if (len > 0 && ga_grow(gap2, len) == OK)
+    {
+	for (idx = 0; idx < len; ++idx)
+	{
+	    ((fold_T *)gap2->ga_data)[idx] = fp2[idx];
+	    ((fold_T *)gap2->ga_data)[idx].fd_top
+						 -= fp[1].fd_top - fp->fd_top;
+	}
+	gap2->ga_len = len;
+	gap2->ga_room -= len;
+	gap1->ga_len -= len;
+	gap1->ga_room += len;
+    }
+    fp->fd_len = top - fp->fd_top;
+    fold_changed = TRUE;
+}
+
+/* foldRemove() {{{2 */
+/*
+ * Remove folds within the range "top" to and including "bot".
+ * Check for these situations:
+ *      1  2  3
+ *      1  2  3
+ * top     2  3  4  5
+ *	   2  3  4  5
+ * bot	   2  3  4  5
+ *	      3     5  6
+ *	      3     5  6
+ *
+ * 1: not changed
+ * 2: trunate to stop above "top"
+ * 3: split in two parts, one stops above "top", other starts below "bot".
+ * 4: deleted
+ * 5: made to start below "bot".
+ * 6: not changed
+ */
+    static void
+foldRemove(gap, top, bot)
+    garray_T	*gap;
+    linenr_T	top;
+    linenr_T	bot;
+{
+    fold_T	*fp = NULL;
+
+    if (bot < top)
+	return;		/* nothing to do */
+
+    for (;;)
+    {
+	/* Find fold that includes top or a following one. */
+	if (foldFind(gap, top, &fp) && fp->fd_top < top)
+	{
+	    /* 2: or 3: need to delete nested folds */
+	    foldRemove(&fp->fd_nested, top - fp->fd_top, bot - fp->fd_top);
+	    if (fp->fd_top + fp->fd_len > bot + 1)
+	    {
+		/* 3: need to split it. */
+		foldSplit(gap, (int)(fp - (fold_T *)gap->ga_data), top, bot);
+	    }
+	    else
+	    {
+		/* 2: truncate fold at "top". */
+		fp->fd_len = top - fp->fd_top;
+	    }
+	    fold_changed = TRUE;
+	    continue;
+	}
+	if (fp >= (fold_T *)(gap->ga_data) + gap->ga_len
+		|| fp->fd_top > bot)
+	{
+	    /* 6: Found a fold below bot, can stop looking. */
+	    break;
+	}
+	if (fp->fd_top >= top)
+	{
+	    /* Found an entry below top. */
+	    fold_changed = TRUE;
+	    if (fp->fd_top + fp->fd_len > bot)
+	    {
+		/* 5: Make fold that includes bot start below bot. */
+		foldMarkAdjustRecurse(&fp->fd_nested,
+			(linenr_T)0, (long)(bot - fp->fd_top),
+			(linenr_T)MAXLNUM, (long)(fp->fd_top - bot - 1));
+		fp->fd_len -= bot - fp->fd_top + 1;
+		fp->fd_top = bot + 1;
+		break;
+	    }
+
+	    /* 4: Delete completely contained fold. */
+	    deleteFoldEntry(gap, (int)(fp - (fold_T *)gap->ga_data), TRUE);
+	}
+    }
+}
+
+/* foldMerge() {{{2 */
+/*
+ * Merge two adjecent folds (and the nested ones in them).
+ * This only works correctly when the folds are really adjecent!  Thus "fp1"
+ * must end just above "fp2".
+ * The resulting fold is "fp1", nested folds are moved from "fp2" to "fp1".
+ * Fold entry "fp2" in "gap" is deleted.
+ */
+    static void
+foldMerge(fp1, gap, fp2)
+    fold_T	*fp1;
+    garray_T	*gap;
+    fold_T	*fp2;
+{
+    fold_T	*fp3;
+    fold_T	*fp4;
+    int		idx;
+    garray_T	*gap1 = &fp1->fd_nested;
+    garray_T	*gap2 = &fp2->fd_nested;
+
+    /* If the last nested fold in fp1 touches the first nested fold in fp2,
+     * merge them recursively. */
+    if (foldFind(gap1, fp1->fd_len - 1L, &fp3) && foldFind(gap2, 0L, &fp4))
+	foldMerge(fp3, gap2, fp4);
+
+    /* Move nested folds in fp2 to the end of fp1. */
+    if (gap2->ga_len > 0 && ga_grow(gap1, gap2->ga_len) == OK)
+    {
+	for (idx = 0; idx < gap2->ga_len; ++idx)
+	{
+	    ((fold_T *)gap1->ga_data)[gap1->ga_len]
+					= ((fold_T *)gap2->ga_data)[idx];
+	    ((fold_T *)gap1->ga_data)[gap1->ga_len].fd_top += fp1->fd_len;
+	    ++gap1->ga_len;
+	    --gap1->ga_room;
+	}
+	gap2->ga_len = 0;
+	/* fp2->fd_nested.ga_room isn't updated, we delete it below */
+    }
+
+    fp1->fd_len += fp2->fd_len;
+    deleteFoldEntry(gap, (int)(fp2 - (fold_T *)gap->ga_data), TRUE);
+    fold_changed = TRUE;
+}
+
+/* foldlevelIndent() {{{2 */
+/*
+ * Low level function to get the foldlevel for the "indent" method.
+ * Doesn't use any caching.
+ * Returns a level of -1 if the foldlevel depends on surrounding lines.
+ */
+    static void
+foldlevelIndent(flp)
+    fline_T	*flp;
+{
+    char_u	*s;
+    buf_T	*buf;
+    linenr_T	lnum = flp->lnum + flp->off;
+
+    buf = flp->wp->w_buffer;
+    s = skipwhite(ml_get_buf(buf, lnum, FALSE));
+
+    /* empty line or lines starting with a character in 'foldignore': level
+     * depends on surrounding lines */
+    if (*s == NUL || vim_strchr(flp->wp->w_p_fdi, *s) != NULL)
+    {
+	/* first and last line can't be undefined, use level 0 */
+	if (lnum == 1 || lnum == buf->b_ml.ml_line_count)
+	    flp->lvl = 0;
+	else
+	    flp->lvl = -1;
+    }
+    else
+	flp->lvl = get_indent_buf(buf, lnum) / buf->b_p_sw;
+    if (flp->lvl > flp->wp->w_p_fdn)
+	flp->lvl = flp->wp->w_p_fdn;
+}
+
+/* foldlevelDiff() {{{2 */
+#ifdef FEAT_DIFF
+/*
+ * Low level function to get the foldlevel for the "diff" method.
+ * Doesn't use any caching.
+ */
+    static void
+foldlevelDiff(flp)
+    fline_T	*flp;
+{
+    if (diff_infold(flp->wp, flp->lnum + flp->off))
+	flp->lvl = 1;
+    else
+	flp->lvl = 0;
+}
+#endif
+
+/* foldlevelExpr() {{{2 */
+/*
+ * Low level function to get the foldlevel for the "expr" method.
+ * Doesn't use any caching.
+ * Returns a level of -1 if the foldlevel depends on surrounding lines.
+ */
+    static void
+foldlevelExpr(flp)
+    fline_T	*flp;
+{
+#ifndef FEAT_EVAL
+    flp->start = FALSE;
+    flp->lvl = 0;
+#else
+    win_T	*win;
+    int		n;
+    int		c;
+    linenr_T	lnum = flp->lnum + flp->off;
+    int		save_keytyped;
+
+    win = curwin;
+    curwin = flp->wp;
+    curbuf = flp->wp->w_buffer;
+    set_vim_var_nr(VV_LNUM, lnum);
+
+    flp->start = 0;
+    flp->had_end = flp->end;
+    flp->end = MAX_LEVEL + 1;
+    if (lnum <= 1)
+	flp->lvl = 0;
+
+    /* KeyTyped may be reset to 0 when calling a function which invokes
+     * do_cmdline().  To make 'foldopen' work correctly restore KeyTyped. */
+    save_keytyped = KeyTyped;
+    n = eval_foldexpr(flp->wp->w_p_fde, &c);
+    KeyTyped = save_keytyped;
+
+    switch (c)
+    {
+	/* "a1", "a2", .. : add to the fold level */
+	case 'a': if (flp->lvl >= 0)
+		  {
+		      flp->lvl += n;
+		      flp->lvl_next = flp->lvl;
+		  }
+		  flp->start = n;
+		  break;
+
+	/* "s1", "s2", .. : subtract from the fold level */
+	case 's': if (flp->lvl >= 0)
+		  {
+		      if (n > flp->lvl)
+			  flp->lvl_next = 0;
+		      else
+			  flp->lvl_next = flp->lvl - n;
+		      flp->end = flp->lvl_next + 1;
+		  }
+		  break;
+
+	/* ">1", ">2", .. : start a fold with a certain level */
+	case '>': flp->lvl = n;
+		  flp->lvl_next = n;
+		  flp->start = 1;
+		  break;
+
+	/* "<1", "<2", .. : end a fold with a certain level */
+	case '<': flp->lvl_next = n - 1;
+		  flp->end = n;
+		  break;
+
+	/* "=": No change in level */
+	case '=': flp->lvl_next = flp->lvl;
+		  break;
+
+	/* "-1", "0", "1", ..: set fold level */
+	default:  if (n < 0)
+		      /* Use the current level for the next line, so that "a1"
+		       * will work there. */
+		      flp->lvl_next = flp->lvl;
+		  else
+		      flp->lvl_next = n;
+		  flp->lvl = n;
+		  break;
+    }
+
+    /* If the level is unknown for the first or the last line in the file, use
+     * level 0. */
+    if (flp->lvl < 0)
+    {
+	if (lnum <= 1)
+	{
+	    flp->lvl = 0;
+	    flp->lvl_next = 0;
+	}
+	if (lnum == curbuf->b_ml.ml_line_count)
+	    flp->lvl_next = 0;
+    }
+
+    curwin = win;
+    curbuf = curwin->w_buffer;
+#endif
+}
+
+/* parseMarker() {{{2 */
+/*
+ * Parse 'foldmarker' and set "foldendmarker", "foldstartmarkerlen" and
+ * "foldendmarkerlen".
+ * Relies on the option value to have been checked for correctness already.
+ */
+    static void
+parseMarker(wp)
+    win_T	*wp;
+{
+    foldendmarker = vim_strchr(wp->w_p_fmr, ',');
+    foldstartmarkerlen = (int)(foldendmarker++ - wp->w_p_fmr);
+    foldendmarkerlen = (int)STRLEN(foldendmarker);
+}
+
+/* foldlevelMarker() {{{2 */
+/*
+ * Low level function to get the foldlevel for the "marker" method.
+ * "foldendmarker", "foldstartmarkerlen" and "foldendmarkerlen" must have been
+ * set before calling this.
+ * Requires that flp->lvl is set to the fold level of the previous line!
+ * Careful: This means you can't call this function twice on the same line.
+ * Doesn't use any caching.
+ * Sets flp->start when a start marker was found.
+ */
+    static void
+foldlevelMarker(flp)
+    fline_T	*flp;
+{
+    char_u	*startmarker;
+    int		cstart;
+    int		cend;
+    int		start_lvl = flp->lvl;
+    char_u	*s;
+    int		n;
+
+    /* cache a few values for speed */
+    startmarker = flp->wp->w_p_fmr;
+    cstart = *startmarker;
+    ++startmarker;
+    cend = *foldendmarker;
+
+    /* Default: no start found, next level is same as current level */
+    flp->start = 0;
+    flp->lvl_next = flp->lvl;
+
+    s = ml_get_buf(flp->wp->w_buffer, flp->lnum + flp->off, FALSE);
+    while (*s)
+    {
+	if (*s == cstart
+		  && STRNCMP(s + 1, startmarker, foldstartmarkerlen - 1) == 0)
+	{
+	    /* found startmarker: set flp->lvl */
+	    s += foldstartmarkerlen;
+	    if (VIM_ISDIGIT(*s))
+	    {
+		n = atoi((char *)s);
+		if (n > 0)
+		{
+		    flp->lvl = n;
+		    flp->lvl_next = n;
+		    if (n <= start_lvl)
+			flp->start = 1;
+		    else
+			flp->start = n - start_lvl;
+		}
+	    }
+	    else
+	    {
+		++flp->lvl;
+		++flp->lvl_next;
+		++flp->start;
+	    }
+	}
+	else if (*s == cend
+	      && STRNCMP(s + 1, foldendmarker + 1, foldendmarkerlen - 1) == 0)
+	{
+	    /* found endmarker: set flp->lvl_next */
+	    s += foldendmarkerlen;
+	    if (VIM_ISDIGIT(*s))
+	    {
+		n = atoi((char *)s);
+		if (n > 0)
+		{
+		    flp->lvl = n;
+		    flp->lvl_next = n - 1;
+		    /* never start a fold with an end marker */
+		    if (flp->lvl_next > flp->lvl)
+			flp->lvl_next = flp->lvl;
+		}
+	    }
+	    else
+		--flp->lvl_next;
+	}
+	else
+	    ++s;
+    }
+
+    /* The level can't go negative, must be missing a start marker. */
+    if (flp->lvl_next < 0)
+	flp->lvl_next = 0;
+}
+
+/* foldlevelSyntax() {{{2 */
+/*
+ * Low level function to get the foldlevel for the "syntax" method.
+ * Doesn't use any caching.
+ */
+    static void
+foldlevelSyntax(flp)
+    fline_T	*flp;
+{
+#ifndef FEAT_SYN_HL
+    flp->start = 0;
+    flp->lvl = 0;
+#else
+    linenr_T	lnum = flp->lnum + flp->off;
+    int		n;
+
+    /* Use the maximum fold level at the start of this line and the next. */
+    flp->lvl = syn_get_foldlevel(flp->wp, lnum);
+    flp->start = 0;
+    if (lnum < flp->wp->w_buffer->b_ml.ml_line_count)
+    {
+	n = syn_get_foldlevel(flp->wp, lnum + 1);
+	if (n > flp->lvl)
+	{
+	    flp->start = n - flp->lvl;	/* fold(s) start here */
+	    flp->lvl = n;
+	}
+    }
+#endif
+}
+
+/* functions for storing the fold state in a View {{{1 */
+/* put_folds() {{{2 */
+#if defined(FEAT_SESSION) || defined(PROTO)
+static int put_folds_recurse __ARGS((FILE *fd, garray_T *gap, linenr_T off));
+static int put_foldopen_recurse __ARGS((FILE *fd, garray_T *gap, linenr_T off));
+
+/*
+ * Write commands to "fd" to restore the manual folds in window "wp".
+ * Return FAIL if writing fails.
+ */
+    int
+put_folds(fd, wp)
+    FILE	*fd;
+    win_T	*wp;
+{
+    if (foldmethodIsManual(wp))
+    {
+	if (put_line(fd, "silent! normal! zE") == FAIL
+		|| put_folds_recurse(fd, &wp->w_folds, (linenr_T)0) == FAIL)
+	    return FAIL;
+    }
+
+    /* If some folds are manually opened/closed, need to restore that. */
+    if (wp->w_fold_manual)
+	return put_foldopen_recurse(fd, &wp->w_folds, (linenr_T)0);
+
+    return OK;
+}
+
+/* put_folds_recurse() {{{2 */
+/*
+ * Write commands to "fd" to recreate manually created folds.
+ * Returns FAIL when writing failed.
+ */
+    static int
+put_folds_recurse(fd, gap, off)
+    FILE	*fd;
+    garray_T	*gap;
+    linenr_T	off;
+{
+    int		i;
+    fold_T	*fp;
+
+    fp = (fold_T *)gap->ga_data;
+    for (i = 0; i < gap->ga_len; i++)
+    {
+	/* Do nested folds first, they will be created closed. */
+	if (put_folds_recurse(fd, &fp->fd_nested, off + fp->fd_top) == FAIL)
+	    return FAIL;
+	if (fprintf(fd, "%ld,%ldfold", fp->fd_top + off,
+					fp->fd_top + off + fp->fd_len - 1) < 0
+		|| put_eol(fd) == FAIL)
+	    return FAIL;
+	++fp;
+    }
+    return OK;
+}
+
+/* put_foldopen_recurse() {{{2 */
+/*
+ * Write commands to "fd" to open and close manually opened/closed folds.
+ * Returns FAIL when writing failed.
+ */
+    static int
+put_foldopen_recurse(fd, gap, off)
+    FILE	*fd;
+    garray_T	*gap;
+    linenr_T	off;
+{
+    int		i;
+    fold_T	*fp;
+
+    fp = (fold_T *)gap->ga_data;
+    for (i = 0; i < gap->ga_len; i++)
+    {
+	if (fp->fd_flags != FD_LEVEL)
+	{
+	    if (fp->fd_nested.ga_len > 0)
+	    {
+		/* open/close nested folds while this fold is open */
+		if (fprintf(fd, "%ld", fp->fd_top + off) < 0
+			|| put_eol(fd) == FAIL
+			|| put_line(fd, "normal zo") == FAIL)
+		    return FAIL;
+		if (put_foldopen_recurse(fd, &fp->fd_nested, off + fp->fd_top)
+			== FAIL)
+		    return FAIL;
+	    }
+	    if (fprintf(fd, "%ld", fp->fd_top + off) < 0
+		    || put_eol(fd) == FAIL
+		    || fprintf(fd, "normal z%c",
+				    fp->fd_flags == FD_CLOSED ? 'c' : 'o') < 0
+		    || put_eol(fd) == FAIL)
+		return FAIL;
+	}
+	++fp;
+    }
+
+    return OK;
+}
+#endif /* FEAT_SESSION */
+
+/* }}}1 */
+#endif /* defined(FEAT_FOLDING) || defined(PROTO) */