diff --git a/Filelist b/Filelist
index 549eecc..3d67aff 100644
--- a/Filelist
+++ b/Filelist
@@ -39,6 +39,7 @@
 		src/mark.c \
 		src/mbyte.c \
 		src/memfile.c \
+		src/memfile_test.c \
 		src/memline.c \
 		src/menu.c \
 		src/message.c \
@@ -686,6 +687,8 @@
 		runtime/tutor/tutor.utf-8 \
 		runtime/tutor/tutor.?? \
 		runtime/tutor/tutor.??.* \
+		runtime/tutor/tutor.bar \
+		runtime/tutor/tutor.bar.* \
 		runtime/spell/README.txt \
 		runtime/spell/??/*.diff \
 		runtime/spell/??/main.aap \
diff --git a/src/Makefile b/src/Makefile
index 6d0e185..b154496 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -561,7 +561,7 @@
 #CFLAGS = -g -O2 '-DSTARTUPTIME="vimstartup"' -fno-strength-reduce -Wall -Wmissing-prototypes
 
 # Use this with GCC to check for mistakes, unused arguments, etc.
-#CFLAGS = -g -Wall -Wextra -Wmissing-prototypes -Wunreachable-code -D_FORTIFY_SOURCE=1 -DU_DEBUG
+#CFLAGS = -g -Wall -Wextra -Wmissing-prototypes -Wunreachable-code -D_FORTIFY_SOURCE=1
 #CFLAGS = -g -O2 -Wall -Wextra -Wmissing-prototypes -D_FORTIFY_SOURCE=1 -DU_DEBUG
 #PYTHON_CFLAGS_EXTRA = -Wno-missing-field-initializers
 #MZSCHEME_CFLAGS_EXTRA = -Wno-unreachable-code -Wno-unused-parameter
@@ -594,8 +594,9 @@
 
 # PROFILING - Uncomment the next two lines to do profiling with gcc and gprof.
 # Might not work with GUI or Perl.
-# For unknown reasons adding "-lc" fixes a linking problem with GCC.  That's
-# probably a bug in the "-pg" implementation.
+# For unknown reasons adding "-lc" fixes a linking problem with some versions
+# of GCC.  That's probably a bug in the "-pg" implementation.
+# After running Vim see the profile result with: gmon vim gmon.out | vim -
 # Need to recompile everything after changing this: "make clean" "make".
 #PROFILE_CFLAGS = -pg -g -DWE_ARE_PROFILING
 #PROFILE_LIBS = -pg
@@ -606,8 +607,8 @@
 # Configuration is in the .ccmalloc or ~/.ccmalloc file.
 # Doesn't work very well, since memory linked to from global variables
 # (in libraries) is also marked as leaked memory.
-#PROFILE_CFLAGS = -DEXITFREE
-#PROFILE_LIBS = -lccmalloc
+#LEAK_CFLAGS = -DEXITFREE
+#LEAK_LIBS = -lccmalloc
 
 #####################################################
 ###  Specific systems, check if yours is listed!  ### {{{
@@ -1329,7 +1330,7 @@
 PRE_DEFS = -Iproto $(DEFS) $(GUI_DEFS) $(GUI_IPATH) $(CPPFLAGS) $(EXTRA_IPATHS)
 POST_DEFS = $(X_CFLAGS) $(MZSCHEME_CFLAGS) $(TCL_CFLAGS) $(EXTRA_DEFS)
 
-ALL_CFLAGS = $(PRE_DEFS) $(CFLAGS) $(PROFILE_CFLAGS) $(POST_DEFS)
+ALL_CFLAGS = $(PRE_DEFS) $(CFLAGS) $(PROFILE_CFLAGS) $(LEAK_CFLAGS) $(POST_DEFS)
 
 # Exclude $CFLAGS for osdef.sh, for Mac 10.4 some flags don't work together
 # with "-E".
@@ -1358,7 +1359,8 @@
 	   $(PYTHON3_LIBS) \
 	   $(TCL_LIBS) \
 	   $(RUBY_LIBS) \
-	   $(PROFILE_LIBS)
+	   $(PROFILE_LIBS) \
+	   $(LEAK_LIBS)
 
 # abbreviations
 DEST_BIN = $(DESTDIR)$(BINDIR)
@@ -1480,8 +1482,15 @@
 	    if_python.c if_python3.c if_tcl.c if_ruby.c if_sniff.c \
 	    gui_beval.c workshop.c wsdebug.c integration.c netbeans.c
 
+# Unittest files
+MEMFILE_TEST_SRC = memfile_test.c
+MEMFILE_TEST_TARGET = memfile_test$(EXEEXT)
+
+UNITTEST_SRC = $(MEMFILE_TEST_SRC)
+UNITTEST_TARGETS = $(MEMFILE_TEST_TARGET)
+
 # All sources, also the ones that are not configured
-ALL_SRC = $(BASIC_SRC) $(ALL_GUI_SRC) $(EXTRA_SRC)
+ALL_SRC = $(BASIC_SRC) $(ALL_GUI_SRC) $(UNITTEST_SRC) $(EXTRA_SRC)
 
 # Which files to check with lint.  Select one of these three lines.  ALL_SRC
 # checks more, but may not work well for checking a GUI that wasn't configured.
@@ -1492,7 +1501,7 @@
 #LINT_SRC = $(ALL_SRC)
 #LINT_SRC = $(BASIC_SRC)
 
-OBJ = \
+OBJ_COMMON = \
 	objects/buffer.o \
 	objects/blowfish.o \
 	objects/charset.o \
@@ -1513,10 +1522,8 @@
 	$(HANGULIN_OBJ) \
 	objects/if_cscope.o \
 	objects/if_xcmdsrv.o \
-	objects/main.o \
 	objects/mark.o \
-	objects/memfile.o \
-	objects/memline.o \
+        objects/memline.o \
 	objects/menu.o \
 	objects/message.o \
 	objects/misc1.o \
@@ -1541,6 +1548,7 @@
 	objects/term.o \
 	objects/ui.o \
 	objects/undo.o \
+	objects/version.o \
 	objects/window.o \
 	$(GUI_OBJ) \
 	$(LUA_OBJ) \
@@ -1555,6 +1563,13 @@
 	$(NETBEANS_OBJ) \
 	$(WSDEBUG_OBJ)
 
+OBJ = $(OBJ_COMMON) \
+	objects/main.o \
+	objects/memfile.o \
+
+MEMFILE_TEST_OBJ = $(OBJ_COMMON) \
+        objects/memfile_test.o
+
 PRO_AUTO = \
 	blowfish.pro \
 	buffer.pro \
@@ -1700,7 +1715,7 @@
 $(VIMTARGET): auto/config.mk objects $(OBJ) version.c version.h
 	$(CCC) version.c -o objects/version.o
 	@LINK="$(PURIFY) $(SHRPENV) $(CClink) $(ALL_LIB_DIRS) $(LDFLAGS) \
-		-o $(VIMTARGET) $(OBJ) objects/version.o $(ALL_LIBS)" \
+		-o $(VIMTARGET) $(OBJ) $(ALL_LIBS)" \
 		MAKE="$(MAKE)" LINK_AS_NEEDED=$(LINK_AS_NEEDED) \
 		sh $(srcdir)/link.sh
 
@@ -1825,6 +1840,15 @@
 		ln -s $(VIMTARGET) vim; \
 	fi
 	cd testdir; $(MAKE) -f Makefile $(GUI_TESTTARGET) VIMPROG=../$(VIMTARGET) $(GUI_TESTARG)
+	$(MAKE) -f Makefile unittest
+
+unittesttargets:
+	$(MAKE) -f Makefile $(UNITTEST_TARGETS)
+
+unittest unittests: $(UNITTEST_TARGETS)
+	@for t in $(UNITTEST_TARGETS); do \
+		./$$t || exit 1; echo $$t passed; \
+	done
 
 testclean:
 	cd testdir; $(MAKE) -f Makefile clean
@@ -1832,6 +1856,17 @@
 		cd $(PODIR); $(MAKE) checkclean; \
 	fi
 
+# Unittests
+# It's build just like Vim to satisfy all dependencies.
+$(MEMFILE_TEST_TARGET): auto/config.mk objects $(MEMFILE_TEST_OBJ)
+	$(CCC) version.c -o objects/version.o
+	@LINK="$(PURIFY) $(SHRPENV) $(CClink) $(ALL_LIB_DIRS) $(LDFLAGS) \
+		-o $(MEMFILE_TEST_TARGET) $(MEMFILE_TEST_OBJ) $(ALL_LIBS)" \
+		MAKE="$(MAKE)" LINK_AS_NEEDED=$(LINK_AS_NEEDED) \
+		sh $(srcdir)/link.sh
+
+# install targets
+
 install: $(GUI_INSTALL)
 
 install_normal: installvim installtools $(INSTALL_LANGS) install-icons
@@ -2265,6 +2300,7 @@
 	-rm -f *.o objects/* core $(VIMTARGET).core $(VIMTARGET) vim xxd/*.o
 	-rm -f $(TOOLS) auto/osdef.h auto/pathdef.c auto/if_perl.c
 	-rm -f conftest* *~ auto/link.sed
+	-rm -f $(UNITTEST_TARGETS)
 	-rm -f runtime pixmaps
 	-rm -rf $(APPDIR)
 	-rm -rf mzscheme_base.c
@@ -2559,6 +2595,9 @@
 objects/memfile.o: memfile.c
 	$(CCC) -o $@ memfile.c
 
+objects/memfile_test.o: memfile_test.c
+	$(CCC) -o $@ memfile_test.c
+
 objects/memline.o: memline.c
 	$(CCC) -o $@ memline.c
 
@@ -2877,7 +2916,7 @@
 objects/os_unix.o: os_unix.c vim.h auto/config.h feature.h os_unix.h auto/osdef.h \
  ascii.h keymap.h term.h macros.h option.h structs.h regexp.h gui.h \
  gui_beval.h proto/gui_beval.pro ex_cmds.h proto.h globals.h farsi.h \
- arabic.h if_mzsch.h os_unixx.h
+ arabic.h os_unixx.h
 objects/pathdef.o: auto/pathdef.c vim.h auto/config.h feature.h os_unix.h \
  auto/osdef.h ascii.h keymap.h term.h macros.h option.h structs.h \
  regexp.h gui.h gui_beval.h proto/gui_beval.pro ex_cmds.h proto.h \
@@ -3016,6 +3055,10 @@
 objects/pty.o: pty.c vim.h auto/config.h feature.h os_unix.h auto/osdef.h ascii.h \
  keymap.h term.h macros.h option.h structs.h regexp.h gui.h gui_beval.h \
  proto/gui_beval.pro ex_cmds.h proto.h globals.h farsi.h arabic.h
+objects/memfile_test.o: memfile_test.c main.c vim.h auto/config.h feature.h \
+ os_unix.h auto/osdef.h ascii.h keymap.h term.h macros.h option.h \
+ structs.h regexp.h gui.h gui_beval.h proto/gui_beval.pro ex_cmds.h \
+ proto.h globals.h farsi.h arabic.h farsi.c arabic.c memfile.c
 objects/hangulin.o: hangulin.c vim.h auto/config.h feature.h os_unix.h \
  auto/osdef.h ascii.h keymap.h term.h macros.h option.h structs.h \
  regexp.h gui.h gui_beval.h proto/gui_beval.pro ex_cmds.h proto.h \
@@ -3027,7 +3070,7 @@
 objects/if_mzsch.o: if_mzsch.c vim.h auto/config.h feature.h os_unix.h \
  auto/osdef.h ascii.h keymap.h term.h macros.h option.h structs.h \
  regexp.h gui.h gui_beval.h proto/gui_beval.pro ex_cmds.h proto.h \
- globals.h farsi.h arabic.h if_mzsch.h mzscheme_base.c
+ globals.h farsi.h arabic.h if_mzsch.h
 objects/if_perl.o: auto/if_perl.c vim.h auto/config.h feature.h os_unix.h \
  auto/osdef.h ascii.h keymap.h term.h macros.h option.h structs.h \
  regexp.h gui.h gui_beval.h proto/gui_beval.pro ex_cmds.h proto.h \
@@ -3048,7 +3091,7 @@
  ascii.h keymap.h term.h macros.h option.h structs.h regexp.h gui.h \
  gui_beval.h proto/gui_beval.pro ex_cmds.h proto.h globals.h farsi.h \
  arabic.h
-objects/if_ruby.o: if_ruby.c vim.h auto/config.h feature.h os_unix.h auto/osdef.h \
+objects/if_ruby.o: if_ruby.c auto/config.h vim.h feature.h os_unix.h auto/osdef.h \
  ascii.h keymap.h term.h macros.h option.h structs.h regexp.h gui.h \
  gui_beval.h proto/gui_beval.pro ex_cmds.h proto.h globals.h farsi.h \
  arabic.h version.h
diff --git a/src/main.c b/src/main.c
index c79d2b8..0527a91 100644
--- a/src/main.c
+++ b/src/main.c
@@ -92,37 +92,39 @@
 #define EDIT_TAG    3	    /* tag name argument given, use tagname */
 #define EDIT_QF	    4	    /* start in quickfix mode */
 
-#if defined(UNIX) || defined(VMS)
+#if (defined(UNIX) || defined(VMS)) && !defined(NO_VIM_MAIN)
 static int file_owned __ARGS((char *fname));
 #endif
 static void mainerr __ARGS((int, char_u *));
+#ifndef NO_VIM_MAIN
 static void main_msg __ARGS((char *s));
 static void usage __ARGS((void));
 static int get_number_arg __ARGS((char_u *p, int *idx, int def));
-#if defined(HAVE_LOCALE_H) || defined(X_LOCALE)
+# if defined(HAVE_LOCALE_H) || defined(X_LOCALE)
 static void init_locale __ARGS((void));
-#endif
+# endif
 static void parse_command_name __ARGS((mparm_T *parmp));
 static void early_arg_scan __ARGS((mparm_T *parmp));
 static void command_line_scan __ARGS((mparm_T *parmp));
 static void check_tty __ARGS((mparm_T *parmp));
 static void read_stdin __ARGS((void));
 static void create_windows __ARGS((mparm_T *parmp));
-#ifdef FEAT_WINDOWS
+# ifdef FEAT_WINDOWS
 static void edit_buffers __ARGS((mparm_T *parmp));
-#endif
+# endif
 static void exe_pre_commands __ARGS((mparm_T *parmp));
 static void exe_commands __ARGS((mparm_T *parmp));
 static void source_startup_scripts __ARGS((mparm_T *parmp));
 static void main_start_gui __ARGS((void));
-#if defined(HAS_SWAP_EXISTS_ACTION)
+# if defined(HAS_SWAP_EXISTS_ACTION)
 static void check_swap_exists_action __ARGS((void));
-#endif
-#ifdef FEAT_CLIENTSERVER
+# endif
+# if defined(FEAT_CLIENTSERVER) || defined(PROTO)
 static void exec_on_server __ARGS((mparm_T *parmp));
 static void prepare_server __ARGS((mparm_T *parmp));
 static void cmdsrv_main __ARGS((int *argc, char **argv, char_u *serverName_arg, char_u **serverStr));
 static char_u *serverMakeName __ARGS((char_u *arg, char *cmd));
+# endif
 #endif
 
 
@@ -145,7 +147,8 @@
 #define ME_INVALID_ARG		5
 };
 
-#ifndef PROTO	    /* don't want a prototype for main() */
+#ifndef NO_VIM_MAIN	/* skip this for unittests */
+#ifndef PROTO		/* don't want a prototype for main() */
     int
 # ifdef VIMDLL
 _export
@@ -966,6 +969,7 @@
     return 0;
 }
 #endif /* PROTO */
+#endif /* NO_VIM_MAIN */
 
 /*
  * Main loop: Execute Normal mode commands until exiting Vim.
@@ -1430,6 +1434,7 @@
     mch_exit(exitval);
 }
 
+#ifndef NO_VIM_MAIN
 /*
  * Get a (optional) count for a Vim argument.
  */
@@ -2994,6 +2999,8 @@
 #endif
 }
 
+#endif  /* NO_VIM_MAIN */
+
 /*
  * Get an environment variable, and execute it as Ex commands.
  * Returns FAIL if the environment variable was not executed, OK otherwise.
@@ -3033,7 +3040,7 @@
     return FAIL;
 }
 
-#if defined(UNIX) || defined(VMS)
+#if (defined(UNIX) || defined(VMS)) && !defined(NO_VIM_MAIN)
 /*
  * Return TRUE if we are certain the user owns the file "fname".
  * Used for ".vimrc" and ".exrc".
@@ -3091,6 +3098,7 @@
     mainerr(ME_ARG_MISSING, str);
 }
 
+#ifndef NO_VIM_MAIN
 /*
  * print a message with three spaces prepended and '\n' appended.
  */
@@ -3311,6 +3319,8 @@
 }
 #endif
 
+#endif
+
 #if defined(STARTUPTIME) || defined(PROTO)
 static void time_diff __ARGS((struct timeval *then, struct timeval *now));
 
@@ -3420,7 +3430,7 @@
 
 #endif
 
-#if defined(FEAT_CLIENTSERVER) || defined(PROTO)
+#if (defined(FEAT_CLIENTSERVER) && !defined(NO_VIM_MAIN)) || defined(PROTO)
 
 /*
  * Common code for the X command server and the Win32 command server.
@@ -3888,6 +3898,32 @@
 }
 
 /*
+ * Make our basic server name: use the specified "arg" if given, otherwise use
+ * the tail of the command "cmd" we were started with.
+ * Return the name in allocated memory.  This doesn't include a serial number.
+ */
+    static char_u *
+serverMakeName(arg, cmd)
+    char_u	*arg;
+    char	*cmd;
+{
+    char_u *p;
+
+    if (arg != NULL && *arg != NUL)
+	p = vim_strsave_up(arg);
+    else
+    {
+	p = vim_strsave_up(gettail((char_u *)cmd));
+	/* Remove .exe or .bat from the name. */
+	if (p != NULL && vim_strchr(p, '.') != NULL)
+	    *vim_strchr(p, '.') = NUL;
+    }
+    return p;
+}
+#endif /* FEAT_CLIENTSERVER */
+
+#if defined(FEAT_CLIENTSERVER) || defined(PROTO)
+/*
  * Replace termcodes such as <CR> and insert as key presses if there is room.
  */
     void
@@ -3998,32 +4034,7 @@
 # endif
     return res;
 }
-
-
-/*
- * Make our basic server name: use the specified "arg" if given, otherwise use
- * the tail of the command "cmd" we were started with.
- * Return the name in allocated memory.  This doesn't include a serial number.
- */
-    static char_u *
-serverMakeName(arg, cmd)
-    char_u	*arg;
-    char	*cmd;
-{
-    char_u *p;
-
-    if (arg != NULL && *arg != NUL)
-	p = vim_strsave_up(arg);
-    else
-    {
-	p = vim_strsave_up(gettail((char_u *)cmd));
-	/* Remove .exe or .bat from the name. */
-	if (p != NULL && vim_strchr(p, '.') != NULL)
-	    *vim_strchr(p, '.') = NUL;
-    }
-    return p;
-}
-#endif /* FEAT_CLIENTSERVER */
+#endif
 
 /*
  * When FEAT_FKMAP is defined, also compile the Farsi source code.
diff --git a/src/memfile.c b/src/memfile.c
index 2d83ce8..8769dbc 100644
--- a/src/memfile.c
+++ b/src/memfile.c
@@ -84,6 +84,13 @@
 static int  mf_write_block __ARGS((memfile_T *mfp, bhdr_T *hp, off_t offset, unsigned size));
 static int  mf_trans_add __ARGS((memfile_T *, bhdr_T *));
 static void mf_do_open __ARGS((memfile_T *, char_u *, int));
+static void mf_hash_init __ARGS((mf_hashtab_T *));
+static void mf_hash_free __ARGS((mf_hashtab_T *));
+static void mf_hash_free_all __ARGS((mf_hashtab_T *));
+static mf_hashitem_T *mf_hash_find __ARGS((mf_hashtab_T *, blocknr_T));
+static void mf_hash_add_item __ARGS((mf_hashtab_T *, mf_hashitem_T *));
+static void mf_hash_rem_item __ARGS((mf_hashtab_T *, mf_hashitem_T *));
+static int mf_hash_grow __ARGS((mf_hashtab_T *));
 
 /*
  * The functions for using a memfile:
@@ -119,7 +126,6 @@
     int		flags;
 {
     memfile_T		*mfp;
-    int			i;
     off_t		size;
 #if defined(STATFS) && defined(UNIX) && !defined(__QNX__)
 # define USE_FSTATFS
@@ -152,11 +158,8 @@
     mfp->mf_used_last = NULL;
     mfp->mf_dirty = FALSE;
     mfp->mf_used_count = 0;
-    for (i = 0; i < MEMHASHSIZE; ++i)
-    {
-	mfp->mf_hash[i] = NULL;		/* hash lists are empty */
-	mfp->mf_trans[i] = NULL;	/* trans lists are empty */
-    }
+    mf_hash_init(&mfp->mf_hash);
+    mf_hash_init(&mfp->mf_trans);
     mfp->mf_page_size = MEMFILE_PAGE_SIZE;
 #ifdef FEAT_CRYPT
     mfp->mf_old_key = NULL;
@@ -242,8 +245,6 @@
     int		del_file;
 {
     bhdr_T	*hp, *nextp;
-    NR_TRANS	*tp, *tpnext;
-    int		i;
 
     if (mfp == NULL)		    /* safety check */
 	return;
@@ -263,12 +264,8 @@
     }
     while (mfp->mf_free_first != NULL)	    /* free entries in free list */
 	vim_free(mf_rem_free(mfp));
-    for (i = 0; i < MEMHASHSIZE; ++i)	    /* free entries in trans lists */
-	for (tp = mfp->mf_trans[i]; tp != NULL; tp = tpnext)
-	{
-	    tpnext = tp->nt_next;
-	    vim_free(tp);
-	}
+    mf_hash_free(&mfp->mf_hash);
+    mf_hash_free_all(&mfp->mf_trans);	    /* free hashtable and its items */
     vim_free(mfp->mf_fname);
     vim_free(mfp->mf_ffname);
     vim_free(mfp);
@@ -743,16 +740,7 @@
     memfile_T	*mfp;
     bhdr_T	*hp;
 {
-    bhdr_T	*hhp;
-    int		hash;
-
-    hash = MEMHASH(hp->bh_bnum);
-    hhp = mfp->mf_hash[hash];
-    hp->bh_hash_next = hhp;
-    hp->bh_hash_prev = NULL;
-    if (hhp != NULL)
-	hhp->bh_hash_prev = hp;
-    mfp->mf_hash[hash] = hp;
+    mf_hash_add_item(&mfp->mf_hash, (mf_hashitem_T *)hp);
 }
 
 /*
@@ -763,13 +751,7 @@
     memfile_T	*mfp;
     bhdr_T	*hp;
 {
-    if (hp->bh_hash_prev == NULL)
-	mfp->mf_hash[MEMHASH(hp->bh_bnum)] = hp->bh_hash_next;
-    else
-	hp->bh_hash_prev->bh_hash_next = hp->bh_hash_next;
-
-    if (hp->bh_hash_next)
-	hp->bh_hash_next->bh_hash_prev = hp->bh_hash_prev;
+    mf_hash_rem_item(&mfp->mf_hash, (mf_hashitem_T *)hp);
 }
 
 /*
@@ -780,12 +762,7 @@
     memfile_T	*mfp;
     blocknr_T	nr;
 {
-    bhdr_T	*hp;
-
-    for (hp = mfp->mf_hash[MEMHASH(nr)]; hp != NULL; hp = hp->bh_hash_next)
-	if (hp->bh_bnum == nr)
-	    break;
-    return hp;
+    return (bhdr_T *)mf_hash_find(&mfp->mf_hash, nr);
 }
 
 /*
@@ -1187,7 +1164,6 @@
 {
     bhdr_T	*freep;
     blocknr_T	new_bnum;
-    int		hash;
     NR_TRANS	*np;
     int		page_count;
 
@@ -1235,12 +1211,8 @@
     hp->bh_bnum = new_bnum;
     mf_ins_hash(mfp, hp);		    /* insert in new hash list */
 
-    hash = MEMHASH(np->nt_old_bnum);	    /* insert in trans list */
-    np->nt_next = mfp->mf_trans[hash];
-    mfp->mf_trans[hash] = np;
-    if (np->nt_next != NULL)
-	np->nt_next->nt_prev = np;
-    np->nt_prev = NULL;
+    /* Insert "np" into "mf_trans" hashtable with key "np->nt_old_bnum" */
+    mf_hash_add_item(&mfp->mf_trans, (mf_hashitem_T *)np);
 
     return OK;
 }
@@ -1255,25 +1227,20 @@
     memfile_T	*mfp;
     blocknr_T	old_nr;
 {
-    int		hash;
     NR_TRANS	*np;
     blocknr_T	new_bnum;
 
-    hash = MEMHASH(old_nr);
-    for (np = mfp->mf_trans[hash]; np != NULL; np = np->nt_next)
-	if (np->nt_old_bnum == old_nr)
-	    break;
+    np = (NR_TRANS *)mf_hash_find(&mfp->mf_trans, old_nr);
+
     if (np == NULL)		/* not found */
 	return old_nr;
 
     mfp->mf_neg_count--;
     new_bnum = np->nt_new_bnum;
-    if (np->nt_prev != NULL)		/* remove entry from the trans list */
-	np->nt_prev->nt_next = np->nt_next;
-    else
-	mfp->mf_trans[hash] = np->nt_next;
-    if (np->nt_next != NULL)
-	np->nt_next->nt_prev = np->nt_prev;
+
+    /* remove entry from the trans list */
+    mf_hash_rem_item(&mfp->mf_trans, (mf_hashitem_T *)np);
+
     vim_free(np);
 
     return new_bnum;
@@ -1397,3 +1364,207 @@
 	mch_hide(mfp->mf_fname);    /* try setting the 'hidden' flag */
     }
 }
+
+/*
+ * Implementation of mf_hashtab_T follows.
+ */
+
+/*
+ * The number of buckets in the hashtable is increased by a factor of
+ * MHT_GROWTH_FACTOR when the average number of items per bucket
+ * exceeds 2 ^ MHT_LOG_LOAD_FACTOR.
+ */
+#define MHT_LOG_LOAD_FACTOR 6
+#define MHT_GROWTH_FACTOR   2   /* must be a power of two */
+
+/*
+ * Initialize an empty hash table.
+ */
+    static void
+mf_hash_init(mht)
+    mf_hashtab_T *mht;
+{
+    vim_memset(mht, 0, sizeof(mf_hashtab_T));
+    mht->mht_buckets = mht->mht_small_buckets;
+    mht->mht_mask = MHT_INIT_SIZE - 1;
+}
+
+/*
+ * Free the array of a hash table.  Does not free the items it contains!
+ * The hash table must not be used again without another mf_hash_init() call.
+ */
+    static void
+mf_hash_free(mht)
+    mf_hashtab_T *mht;
+{
+    if (mht->mht_buckets != mht->mht_small_buckets)
+	vim_free(mht->mht_buckets);
+}
+
+/*
+ * Free the array of a hash table and all the items it contains.
+ */
+    static void
+mf_hash_free_all(mht)
+    mf_hashtab_T    *mht;
+{
+    long_u	    idx;
+    mf_hashitem_T   *mhi;
+    mf_hashitem_T   *next;
+
+    for (idx = 0; idx <= mht->mht_mask; idx++)
+	for (mhi = mht->mht_buckets[idx]; mhi != NULL; mhi = next)
+	{
+	    next = mhi->mhi_next;
+	    vim_free(mhi);
+	}
+
+    mf_hash_free(mht);
+}
+
+/*
+ * Find "key" in hashtable "mht".
+ * Returns a pointer to a mf_hashitem_T or NULL if the item was not found.
+ */
+    static mf_hashitem_T *
+mf_hash_find(mht, key)
+    mf_hashtab_T    *mht;
+    blocknr_T	    key;
+{
+    mf_hashitem_T   *mhi;
+
+    mhi = mht->mht_buckets[key & mht->mht_mask];
+    while (mhi != NULL && mhi->mhi_key != key)
+	mhi = mhi->mhi_next;
+
+    return mhi;
+}
+
+/*
+ * Add item "mhi" to hashtable "mht".
+ * "mhi" must not be NULL.
+ */
+    static void
+mf_hash_add_item(mht, mhi)
+    mf_hashtab_T    *mht;
+    mf_hashitem_T   *mhi;
+{
+    long_u	    idx;
+
+    idx = mhi->mhi_key & mht->mht_mask;
+    mhi->mhi_next = mht->mht_buckets[idx];
+    mhi->mhi_prev = NULL;
+    if (mhi->mhi_next != NULL)
+	mhi->mhi_next->mhi_prev = mhi;
+    mht->mht_buckets[idx] = mhi;
+
+    mht->mht_count++;
+
+    /*
+     * Grow hashtable when we have more thank 2^MHT_LOG_LOAD_FACTOR
+     * items per bucket on average
+     */
+    if (mht->mht_fixed == 0
+	&& (mht->mht_count >> MHT_LOG_LOAD_FACTOR) > mht->mht_mask)
+    {
+	if (mf_hash_grow(mht) == FAIL)
+	{
+	    /* stop trying to grow after first failure to allocate memory */
+	    mht->mht_fixed = 1;
+	}
+    }
+}
+
+/*
+ * Remove item "mhi" from hashtable "mht".
+ * "mhi" must not be NULL and must have been inserted into "mht".
+ */
+    static void
+mf_hash_rem_item(mht, mhi)
+    mf_hashtab_T    *mht;
+    mf_hashitem_T   *mhi;
+{
+    if (mhi->mhi_prev == NULL)
+	mht->mht_buckets[mhi->mhi_key & mht->mht_mask] = mhi->mhi_next;
+    else
+	mhi->mhi_prev->mhi_next = mhi->mhi_next;
+
+    if (mhi->mhi_next != NULL)
+	mhi->mhi_next->mhi_prev = mhi->mhi_prev;
+
+    mht->mht_count--;
+
+    /* We could shrink the table here, but it typically takes little memory,
+     * so why bother?  */
+}
+
+/*
+ * Increase number of buckets in the hashtable by MHT_GROWTH_FACTOR and
+ * rehash items.
+ * Returns FAIL when out of memory.
+ */
+    static int
+mf_hash_grow(mht)
+    mf_hashtab_T    *mht;
+{
+    long_u	    i, j;
+    int		    shift;
+    mf_hashitem_T   *mhi;
+    mf_hashitem_T   *tails[MHT_GROWTH_FACTOR];
+    mf_hashitem_T   **buckets;
+    size_t	    size;
+
+    size = (mht->mht_mask + 1) * MHT_GROWTH_FACTOR * sizeof(void *);
+    buckets = (mf_hashitem_T **)lalloc_clear(size, FALSE);
+    if (buckets == NULL)
+	return FAIL;
+
+    shift = 0;
+    while ((mht->mht_mask >> shift) != 0)
+	shift++;
+
+    for (i = 0; i <= mht->mht_mask; i++)
+    {
+	/*
+	 * Traverse the items in the i-th original bucket and move them into
+	 * MHT_GROWTH_FACTOR new buckets, preserving their relative order
+	 * within each new bucket.  Preserving the order is important because
+	 * mf_get() tries to keep most recently used items at the front of
+	 * each bucket.
+	 *
+	 * Here we strongly rely on the fact the hashes are computed modulo
+	 * a power of two.
+	 */
+
+	vim_memset(tails, 0, sizeof(tails));
+
+	for (mhi = mht->mht_buckets[i]; mhi != NULL; mhi = mhi->mhi_next)
+	{
+	    j = (mhi->mhi_key >> shift) & (MHT_GROWTH_FACTOR - 1);
+	    if (tails[j] == NULL)
+	    {
+		buckets[i + (j << shift)] = mhi;
+		tails[j] = mhi;
+		mhi->mhi_prev = NULL;
+	    }
+	    else
+	    {
+		tails[j]->mhi_next = mhi;
+		mhi->mhi_prev = tails[j];
+		tails[j] = mhi;
+	    }
+	}
+
+	for (j = 0; j < MHT_GROWTH_FACTOR; j++)
+	    if (tails[j] != NULL)
+		tails[j]->mhi_next = NULL;
+    }
+
+    if (mht->mht_buckets != mht->mht_small_buckets)
+	vim_free(mht->mht_buckets);
+
+    mht->mht_buckets = buckets;
+    mht->mht_mask = (mht->mht_mask + 1) * MHT_GROWTH_FACTOR - 1;
+
+    return OK;
+}
diff --git a/src/structs.h b/src/structs.h
index afc494e..b514c1e 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -378,6 +378,35 @@
 typedef long		    blocknr_T;
 
 /*
+ * mf_hashtab_T is a chained hashtable with blocknr_T key and arbitrary
+ * structures as items.  This is an intrusive data structure: we require
+ * that items begin with mf_hashitem_T which contains the key and linked
+ * list pointers.  List of items in each bucket is doubly-linked.
+ */
+
+typedef struct mf_hashitem_S mf_hashitem_T;
+
+struct mf_hashitem_S
+{
+    mf_hashitem_T   *mhi_next;
+    mf_hashitem_T   *mhi_prev;
+    blocknr_T	    mhi_key;
+};
+
+#define MHT_INIT_SIZE   64
+
+typedef struct mf_hashtab_S
+{
+    long_u	    mht_mask;	    /* mask used for hash value (nr of items
+				     * in array is "mht_mask" + 1) */
+    long_u	    mht_count;	    /* nr of items inserted into hashtable */
+    mf_hashitem_T   **mht_buckets;  /* points to mht_small_buckets or
+				     *dynamically allocated array */
+    mf_hashitem_T   *mht_small_buckets[MHT_INIT_SIZE];   /* initial buckets */
+    char	    mht_fixed;	    /* non-zero value forbids growth */
+} mf_hashtab_T;
+
+/*
  * for each (previously) used block in the memfile there is one block header.
  *
  * The block may be linked in the used list OR in the free list.
@@ -394,11 +423,11 @@
 
 struct block_hdr
 {
+    mf_hashitem_T bh_hashitem;      /* header for hash table and key */
+#define bh_bnum bh_hashitem.mhi_key /* block number, part of bh_hashitem */
+
     bhdr_T	*bh_next;	    /* next block_hdr in free or used list */
     bhdr_T	*bh_prev;	    /* previous block_hdr in used list */
-    bhdr_T	*bh_hash_next;	    /* next block_hdr in hash list */
-    bhdr_T	*bh_hash_prev;	    /* previous block_hdr in hash list */
-    blocknr_T	bh_bnum;	    /* block number */
     char_u	*bh_data;	    /* pointer to memory (for used block) */
     int		bh_page_count;	    /* number of pages in this block */
 
@@ -417,9 +446,9 @@
 
 struct nr_trans
 {
-    NR_TRANS	*nt_next;		/* next nr_trans in hash list */
-    NR_TRANS	*nt_prev;		/* previous nr_trans in hash list */
-    blocknr_T	nt_old_bnum;		/* old, negative, number */
+    mf_hashitem_T nt_hashitem;		/* header for hash table and key */
+#define nt_old_bnum nt_hashitem.mhi_key	/* old, negative, number */
+
     blocknr_T	nt_new_bnum;		/* new, positive, number */
 };
 
@@ -499,12 +528,6 @@
 
 typedef struct file_buffer buf_T;  /* forward declaration */
 
-/*
- * Simplistic hashing scheme to quickly locate the blocks in the used list.
- * 64 blocks are found directly (64 * 4K = 256K, most files are smaller).
- */
-#define MEMHASHSIZE	64
-#define MEMHASH(nr)	((nr) & (MEMHASHSIZE - 1))
 #define MF_SEED_LEN	8
 
 struct memfile
@@ -517,8 +540,8 @@
     bhdr_T	*mf_used_last;		/* lru block_hdr in used list */
     unsigned	mf_used_count;		/* number of pages in used list */
     unsigned	mf_used_count_max;	/* maximum number of pages in memory */
-    bhdr_T	*mf_hash[MEMHASHSIZE];	/* array of hash lists */
-    NR_TRANS	*mf_trans[MEMHASHSIZE];	/* array of trans lists */
+    mf_hashtab_T mf_hash;		/* hash lists */
+    mf_hashtab_T mf_trans;		/* trans lists */
     blocknr_T	mf_blocknr_max;		/* highest positive block number + 1*/
     blocknr_T	mf_blocknr_min;		/* lowest negative block number - 1 */
     blocknr_T	mf_neg_count;		/* number of negative blocks numbers */
diff --git a/src/testdir/Make_amiga.mak b/src/testdir/Make_amiga.mak
index c4a6c7f..4ca0594 100644
--- a/src/testdir/Make_amiga.mak
+++ b/src/testdir/Make_amiga.mak
@@ -28,7 +28,7 @@
 		test61.out test62.out test63.out test64.out test65.out \
 		test66.out test67.out test68.out test69.out test70.out \
 		test71.out test72.out test73.out test74.out test75.out \
-		test76.out
+		test76.out test77.out
 
 .SUFFIXES: .in .out
 
@@ -124,3 +124,4 @@
 test74.out: test74.in
 test75.out: test75.in
 test76.out: test76.in
+test77.out: test77.in
diff --git a/src/testdir/Make_dos.mak b/src/testdir/Make_dos.mak
index 3395c52..5cb220f 100644
--- a/src/testdir/Make_dos.mak
+++ b/src/testdir/Make_dos.mak
@@ -28,7 +28,7 @@
 		test37.out test38.out test39.out test40.out test41.out \
 		test42.out test52.out test65.out test66.out test67.out \
 		test68.out test69.out test71.out test72.out test73.out \
-		test74.out test75.out test76.out
+		test74.out test75.out test76.out test77.out
 
 SCRIPTS32 =	test50.out test70.out
 
diff --git a/src/testdir/Make_ming.mak b/src/testdir/Make_ming.mak
index 1d89dff..e2847d9 100644
--- a/src/testdir/Make_ming.mak
+++ b/src/testdir/Make_ming.mak
@@ -48,7 +48,7 @@
 		test37.out test38.out test39.out test40.out test41.out \
 		test42.out test52.out test65.out test66.out test67.out \
 		test68.out test69.out test71.out test72.out test73.out \
-		test74.out test75.out test76.out
+		test74.out test75.out test76.out test77.out
 
 SCRIPTS32 =	test50.out test70.out
 
diff --git a/src/testdir/Make_os2.mak b/src/testdir/Make_os2.mak
index 361e693..9bfd3b5 100644
--- a/src/testdir/Make_os2.mak
+++ b/src/testdir/Make_os2.mak
@@ -28,7 +28,7 @@
 		test61.out test62.out test63.out test64.out test65.out \
 		test66.out test67.out test68.out test69.out test70.out \
 		test71.out test72.out test73.out test74.out test75.out \
-		test76.out
+		test76.out test77.out
 
 .SUFFIXES: .in .out
 
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index 833a82a..b840a21 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -25,7 +25,7 @@
 		test59.out test60.out test61.out test62.out test63.out \
 		test64.out test65.out test66.out test67.out test68.out \
 		test69.out test70.out test71.out test72.out test73.out \
-		test74.out test75.out test76.out
+		test74.out test75.out test76.out test77.out
 
 SCRIPTS_GUI = test16.out
 
@@ -71,7 +71,7 @@
 		  fi \
 		else echo $* NO OUTPUT >>test.log; \
 		fi"
-	-rm -rf X* test.ok viminfo
+#	-rm -rf X* test.ok viminfo
 
 test49.out: test49.vim
 
diff --git a/src/version.c b/src/version.c
index 6b26600..bec8769 100644
--- a/src/version.c
+++ b/src/version.c
@@ -715,6 +715,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    143,
+/**/
     142,
 /**/
     141,