new file mode 100644
--- /dev/null
+++ b/src/memfile.c
@@ -0,0 +1,1312 @@
+/* vi:set ts=8 sts=4 sw=4:
+ *
+ * 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.
+ */
+
+/*
+ * memfile.c: Contains the functions for handling blocks of memory which can
+ * be stored in a file. This is the implementation of a sort of virtual memory.
+ *
+ * A memfile consists of a sequence of blocks. The blocks numbered from 0
+ * upwards have been assigned a place in the actual file. The block number
+ * is equal to the page number in the file. The
+ * blocks with negative numbers are currently in memory only. They can be
+ * assigned a place in the file when too much memory is being used. At that
+ * moment they get a new, positive, number. A list is used for translation of
+ * negative to positive numbers.
+ *
+ * The size of a block is a multiple of a page size, normally the page size of
+ * the device the file is on. Most blocks are 1 page long. A Block of multiple
+ * pages is used for a line that does not fit in a single page.
+ *
+ * Each block can be in memory and/or in a file. The block stays in memory
+ * as long as it is locked. If it is no longer locked it can be swapped out to
+ * the file. It is only written to the file if it has been changed.
+ *
+ * Under normal operation the file is created when opening the memory file and
+ * deleted when closing the memory file. Only with recovery an existing memory
+ * file is opened.
+ */
+
+#if defined MSDOS || defined(WIN32) || defined(_WIN64)
+# include <io.h>	/* for lseek(), must be before vim.h */
+#endif
+
+#include "vim.h"
+
+#ifdef HAVE_FCNTL_H
+# include <fcntl.h>
+#endif
+
+/*
+ * Some systems have the page size in statfs.f_bsize, some in stat.st_blksize
+ */
+#ifdef HAVE_ST_BLKSIZE
+# define STATFS stat
+# define F_BSIZE st_blksize
+# define fstatfs(fd, buf, len, nul) mch_fstat((fd), (buf))
+#else
+# ifdef HAVE_SYS_STATFS_H
+#  include <sys/statfs.h>
+#  define STATFS statfs
+#  define F_BSIZE f_bsize
+#  ifdef __MINT__		/* do we still need this? */
+#   define fstatfs(fd, buf, len, nul) mch_fstat((fd), (buf))
+#  endif
+# endif
+#endif
+
+/*
+ * for Amiga Dos 2.0x we use Flush
+ */
+#ifdef AMIGA
+# ifdef FEAT_ARP
+extern int dos2;			/* this is in os_amiga.c */
+# endif
+# ifdef SASC
+#  include <proto/dos.h>
+#  include <ios1.h>			/* for chkufb() */
+# endif
+#endif
+
+#define MEMFILE_PAGE_SIZE 4096		/* default page size */
+
+static long_u	total_mem_used = 0;	/* total memory used for memfiles */
+static int	dont_release = FALSE;	/* don't release blocks */
+
+static void mf_ins_hash __ARGS((memfile_T *, bhdr_T *));
+static void mf_rem_hash __ARGS((memfile_T *, bhdr_T *));
+static bhdr_T *mf_find_hash __ARGS((memfile_T *, blocknr_T));
+static void mf_ins_used __ARGS((memfile_T *, bhdr_T *));
+static void mf_rem_used __ARGS((memfile_T *, bhdr_T *));
+static bhdr_T *mf_release __ARGS((memfile_T *, int));
+static bhdr_T *mf_alloc_bhdr __ARGS((memfile_T *, int));
+static void mf_free_bhdr __ARGS((bhdr_T *));
+static void mf_ins_free __ARGS((memfile_T *, bhdr_T *));
+static bhdr_T *mf_rem_free __ARGS((memfile_T *));
+static int  mf_read __ARGS((memfile_T *, bhdr_T *));
+static int  mf_write __ARGS((memfile_T *, bhdr_T *));
+static int  mf_trans_add __ARGS((memfile_T *, bhdr_T *));
+static void mf_do_open __ARGS((memfile_T *, char_u *, int));
+
+/*
+ * The functions for using a memfile:
+ *
+ * mf_open()	    open a new or existing memfile
+ * mf_open_file()   open a swap file for an existing memfile
+ * mf_close()	    close (and delete) a memfile
+ * mf_new()	    create a new block in a memfile and lock it
+ * mf_get()	    get an existing block and lock it
+ * mf_put()	    unlock a block, may be marked for writing
+ * mf_free()	    remove a block
+ * mf_sync()	    sync changed parts of memfile to disk
+ * mf_release_all() release as much memory as possible
+ * mf_trans_del()   may translate negative to positive block number
+ * mf_fullname()    make file name full path (use before first :cd)
+ */
+
+/*
+ * Open an existing or new memory block file.
+ *
+ *  fname:	name of file to use (NULL means no file at all)
+ *		Note: fname must have been allocated, it is not copied!
+ *			If opening the file fails, fname is freed.
+ *  flags:	flags for open() call
+ *
+ *  If fname != NULL and file cannot be opened, fail.
+ *
+ * return value: identifier for this memory block file.
+ */
+    memfile_T *
+mf_open(fname, flags)
+    char_u	*fname;
+    int		flags;
+{
+    memfile_T		*mfp;
+    int			i;
+    off_t		size;
+#if defined(STATFS) && defined(UNIX) && !defined(__QNX__)
+# define USE_FSTATFS
+    struct STATFS	stf;
+#endif
+
+    if ((mfp = (memfile_T *)alloc((unsigned)sizeof(memfile_T))) == NULL)
+	return NULL;
+
+    if (fname == NULL)	    /* no file for this memfile, use memory only */
+    {
+	mfp->mf_fname = NULL;
+	mfp->mf_ffname = NULL;
+	mfp->mf_fd = -1;
+    }
+    else
+    {
+	mf_do_open(mfp, fname, flags);	/* try to open the file */
+
+	/* if the file cannot be opened, return here */
+	if (mfp->mf_fd < 0)
+	{
+	    vim_free(mfp);
+	    return NULL;
+	}
+    }
+
+    mfp->mf_free_first = NULL;		/* free list is empty */
+    mfp->mf_used_first = NULL;		/* used list is empty */
+    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 */
+    }
+    mfp->mf_page_size = MEMFILE_PAGE_SIZE;
+
+#ifdef USE_FSTATFS
+    /*
+     * Try to set the page size equal to the block size of the device.
+     * Speeds up I/O a lot.
+     * When recovering, the actual block size will be retrieved from block 0
+     * in ml_recover().  The size used here may be wrong, therefore
+     * mf_blocknr_max must be rounded up.
+     */
+    if (mfp->mf_fd >= 0
+	    && fstatfs(mfp->mf_fd, &stf, sizeof(struct statfs), 0) == 0
+	    && stf.F_BSIZE >= MIN_SWAP_PAGE_SIZE
+	    && stf.F_BSIZE <= MAX_SWAP_PAGE_SIZE)
+	mfp->mf_page_size = stf.F_BSIZE;
+#endif
+
+    if (mfp->mf_fd < 0 || (flags & (O_TRUNC|O_EXCL))
+		      || (size = lseek(mfp->mf_fd, (off_t)0L, SEEK_END)) <= 0)
+	mfp->mf_blocknr_max = 0;	/* no file or empty file */
+    else
+	mfp->mf_blocknr_max = (blocknr_T)((size + mfp->mf_page_size - 1)
+							 / mfp->mf_page_size);
+    mfp->mf_blocknr_min = -1;
+    mfp->mf_neg_count = 0;
+    mfp->mf_infile_count = mfp->mf_blocknr_max;
+    mfp->mf_used_count_max = p_mm * 1024 / mfp->mf_page_size;
+
+    return mfp;
+}
+
+/*
+ * Open a file for an existing memfile.  Used when updatecount set from 0 to
+ * some value.
+ * If the file already exists, this fails.
+ * "fname" is the name of file to use (NULL means no file at all)
+ * Note: "fname" must have been allocated, it is not copied!  If opening the
+ * file fails, "fname" is freed.
+ *
+ * return value: FAIL if file could not be opened, OK otherwise
+ */
+    int
+mf_open_file(mfp, fname)
+    memfile_T	*mfp;
+    char_u	*fname;
+{
+    mf_do_open(mfp, fname, O_RDWR|O_CREAT|O_EXCL); /* try to open the file */
+
+    if (mfp->mf_fd < 0)
+	return FAIL;
+
+    mfp->mf_dirty = TRUE;
+    return OK;
+}
+
+/*
+ * close a memory file and delete the associated file if 'del_file' is TRUE
+ */
+    void
+mf_close(mfp, del_file)
+    memfile_T	*mfp;
+    int		del_file;
+{
+    bhdr_T	*hp, *nextp;
+    NR_TRANS	*tp, *tpnext;
+    int		i;
+
+    if (mfp == NULL)		    /* safety check */
+	return;
+    if (mfp->mf_fd >= 0)
+    {
+	if (close(mfp->mf_fd) < 0)
+	    EMSG(_(e_swapclose));
+    }
+    if (del_file && mfp->mf_fname != NULL)
+	mch_remove(mfp->mf_fname);
+					    /* free entries in used list */
+    for (hp = mfp->mf_used_first; hp != NULL; hp = nextp)
+    {
+	total_mem_used -= hp->bh_page_count * mfp->mf_page_size;
+	nextp = hp->bh_next;
+	mf_free_bhdr(hp);
+    }
+    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);
+	}
+    vim_free(mfp->mf_fname);
+    vim_free(mfp->mf_ffname);
+    vim_free(mfp);
+}
+
+/*
+ * Close the swap file for a memfile.  Used when 'swapfile' is reset.
+ */
+    void
+mf_close_file(buf, getlines)
+    buf_T	*buf;
+    int		getlines;	/* get all lines into memory? */
+{
+    memfile_T	*mfp;
+    linenr_T	lnum;
+
+    mfp = buf->b_ml.ml_mfp;
+    if (mfp == NULL || mfp->mf_fd < 0)		/* nothing to close */
+	return;
+
+    if (getlines)
+    {
+	/* get all blocks in memory by accessing all lines (clumsy!) */
+	dont_release = TRUE;
+	for (lnum = 1; lnum <= buf->b_ml.ml_line_count; ++lnum)
+	    (void)ml_get_buf(buf, lnum, FALSE);
+	dont_release = FALSE;
+	/* TODO: should check if all blocks are really in core */
+    }
+
+    if (close(mfp->mf_fd) < 0)			/* close the file */
+	EMSG(_(e_swapclose));
+    mfp->mf_fd = -1;
+
+    if (mfp->mf_fname != NULL)
+    {
+	mch_remove(mfp->mf_fname);		/* delete the swap file */
+	vim_free(mfp->mf_fname);
+	vim_free(mfp->mf_ffname);
+	mfp->mf_fname = NULL;
+	mfp->mf_ffname = NULL;
+    }
+}
+
+/*
+ * Set new size for a memfile.  Used when block 0 of a swapfile has been read
+ * and the size it indicates differs from what was guessed.
+ */
+    void
+mf_new_page_size(mfp, new_size)
+    memfile_T	*mfp;
+    unsigned	new_size;
+{
+    /* Correct the memory used for block 0 to the new size, because it will be
+     * freed with that size later on. */
+    total_mem_used += new_size - mfp->mf_page_size;
+    mfp->mf_page_size = new_size;
+}
+
+/*
+ * get a new block
+ *
+ *   negative: TRUE if negative block number desired (data block)
+ */
+    bhdr_T *
+mf_new(mfp, negative, page_count)
+    memfile_T	*mfp;
+    int		negative;
+    int		page_count;
+{
+    bhdr_T    *hp;	    /* new bhdr_T */
+    bhdr_T    *freep;	    /* first block in free list */
+    char_u  *p;
+
+    /*
+     * If we reached the maximum size for the used memory blocks, release one
+     * If a bhdr_T is returned, use it and adjust the page_count if necessary.
+     */
+    hp = mf_release(mfp, page_count);
+
+/*
+ * Decide on the number to use:
+ * If there is a free block, use its number.
+ * Otherwise use mf_block_min for a negative number, mf_block_max for
+ * a positive number.
+ */
+    freep = mfp->mf_free_first;
+    if (!negative && freep != NULL && freep->bh_page_count >= page_count)
+    {
+	/*
+	 * If the block in the free list has more pages, take only the number
+	 * of pages needed and allocate a new bhdr_T with data
+	 *
+	 * If the number of pages matches and mf_release did not return a bhdr_T,
+	 * use the bhdr_T from the free list and allocate the data
+	 *
+	 * If the number of pages matches and mf_release returned a bhdr_T,
+	 * just use the number and free the bhdr_T from the free list
+	 */
+	if (freep->bh_page_count > page_count)
+	{
+	    if (hp == NULL && (hp = mf_alloc_bhdr(mfp, page_count)) == NULL)
+		return NULL;
+	    hp->bh_bnum = freep->bh_bnum;
+	    freep->bh_bnum += page_count;
+	    freep->bh_page_count -= page_count;
+	}
+	else if (hp == NULL)	    /* need to allocate memory for this block */
+	{
+	    if ((p = (char_u *)alloc(mfp->mf_page_size * page_count)) == NULL)
+		return NULL;
+	    hp = mf_rem_free(mfp);
+	    hp->bh_data = p;
+	}
+	else		    /* use the number, remove entry from free list */
+	{
+	    freep = mf_rem_free(mfp);
+	    hp->bh_bnum = freep->bh_bnum;
+	    vim_free(freep);
+	}
+    }
+    else	/* get a new number */
+    {
+	if (hp == NULL && (hp = mf_alloc_bhdr(mfp, page_count)) == NULL)
+	    return NULL;
+	if (negative)
+	{
+	    hp->bh_bnum = mfp->mf_blocknr_min--;
+	    mfp->mf_neg_count++;
+	}
+	else
+	{
+	    hp->bh_bnum = mfp->mf_blocknr_max;
+	    mfp->mf_blocknr_max += page_count;
+	}
+    }
+    hp->bh_flags = BH_LOCKED | BH_DIRTY;	/* new block is always dirty */
+    mfp->mf_dirty = TRUE;
+    hp->bh_page_count = page_count;
+    mf_ins_used(mfp, hp);
+    mf_ins_hash(mfp, hp);
+
+    /*
+     * Init the data to all zero, to avoid reading uninitialized data.
+     * This also avoids that the passwd file ends up in the swap file!
+     */
+    (void)vim_memset((char *)(hp->bh_data), 0, (size_t)mfp->mf_page_size);
+
+    return hp;
+}
+
+/*
+ * get existing block 'nr' with 'page_count' pages
+ *
+ * Note: The caller should first check a negative nr with mf_trans_del()
+ */
+    bhdr_T *
+mf_get(mfp, nr, page_count)
+    memfile_T	*mfp;
+    blocknr_T	nr;
+    int		page_count;
+{
+    bhdr_T    *hp;
+						/* doesn't exist */
+    if (nr >= mfp->mf_blocknr_max || nr <= mfp->mf_blocknr_min)
+	return NULL;
+
+    /*
+     * see if it is in the cache
+     */
+    hp = mf_find_hash(mfp, nr);
+    if (hp == NULL)	/* not in the hash list */
+    {
+	if (nr < 0 || nr >= mfp->mf_infile_count)   /* can't be in the file */
+	    return NULL;
+
+	/* could check here if the block is in the free list */
+
+	/*
+	 * Check if we need to flush an existing block.
+	 * If so, use that block.
+	 * If not, allocate a new block.
+	 */
+	hp = mf_release(mfp, page_count);
+	if (hp == NULL && (hp = mf_alloc_bhdr(mfp, page_count)) == NULL)
+	    return NULL;
+
+	hp->bh_bnum = nr;
+	hp->bh_flags = 0;
+	hp->bh_page_count = page_count;
+	if (mf_read(mfp, hp) == FAIL)	    /* cannot read the block! */
+	{
+	    mf_free_bhdr(hp);
+	    return NULL;
+	}
+    }
+    else
+    {
+	mf_rem_used(mfp, hp);	/* remove from list, insert in front below */
+	mf_rem_hash(mfp, hp);
+    }
+
+    hp->bh_flags |= BH_LOCKED;
+    mf_ins_used(mfp, hp);	/* put in front of used list */
+    mf_ins_hash(mfp, hp);	/* put in front of hash list */
+
+    return hp;
+}
+
+/*
+ * release the block *hp
+ *
+ *   dirty: Block must be written to file later
+ *   infile: Block should be in file (needed for recovery)
+ *
+ *  no return value, function cannot fail
+ */
+    void
+mf_put(mfp, hp, dirty, infile)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+    int		dirty;
+    int		infile;
+{
+    int		flags;
+
+    flags = hp->bh_flags;
+
+    if ((flags & BH_LOCKED) == 0)
+	EMSG(_("E293: block was not locked"));
+    flags &= ~BH_LOCKED;
+    if (dirty)
+    {
+	flags |= BH_DIRTY;
+	mfp->mf_dirty = TRUE;
+    }
+    hp->bh_flags = flags;
+    if (infile)
+	mf_trans_add(mfp, hp);	    /* may translate negative in positive nr */
+}
+
+/*
+ * block *hp is no longer in used, may put it in the free list of memfile *mfp
+ */
+    void
+mf_free(mfp, hp)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+{
+    vim_free(hp->bh_data);	/* free the memory */
+    mf_rem_hash(mfp, hp);	/* get *hp out of the hash list */
+    mf_rem_used(mfp, hp);	/* get *hp out of the used list */
+    if (hp->bh_bnum < 0)
+    {
+	vim_free(hp);		/* don't want negative numbers in free list */
+	mfp->mf_neg_count--;
+    }
+    else
+	mf_ins_free(mfp, hp);	/* put *hp in the free list */
+}
+
+#if defined(__MORPHOS__)
+/* function is missing in MorphOS libnix version */
+extern unsigned long *__stdfiledes;
+
+    static unsigned long
+fdtofh(int filedescriptor)
+{
+    return __stdfiledes[filedescriptor];
+}
+#endif
+
+/*
+ * Sync the memory file *mfp to disk.
+ * Flags:
+ *  MFS_ALL	If not given, blocks with negative numbers are not synced,
+ *		even when they are dirty!
+ *  MFS_STOP	Stop syncing when a character becomes available, but sync at
+ *		least one block.
+ *  MFS_FLUSH	Make sure buffers are flushed to disk, so they will survive a
+ *		system crash.
+ *  MFS_ZERO	Only write block 0.
+ *
+ * Return FAIL for failure, OK otherwise
+ */
+    int
+mf_sync(mfp, flags)
+    memfile_T	*mfp;
+    int		flags;
+{
+    int		status;
+    bhdr_T	*hp;
+#if defined(SYNC_DUP_CLOSE) && !defined(MSDOS)
+    int		fd;
+#endif
+    int		got_int_save = got_int;
+
+    if (mfp->mf_fd < 0)	    /* there is no file, nothing to do */
+    {
+	mfp->mf_dirty = FALSE;
+	return FAIL;
+    }
+
+    /* Only a CTRL-C while writing will break us here, not one typed
+     * previously. */
+    got_int = FALSE;
+
+    /*
+     * sync from last to first (may reduce the probability of an inconsistent
+     * file) If a write fails, it is very likely caused by a full filesystem.
+     * Then we only try to write blocks within the existing file. If that also
+     * fails then we give up.
+     */
+    status = OK;
+    for (hp = mfp->mf_used_last; hp != NULL; hp = hp->bh_prev)
+	if (((flags & MFS_ALL) || hp->bh_bnum >= 0)
+		&& (hp->bh_flags & BH_DIRTY)
+		&& (status == OK || (hp->bh_bnum >= 0
+		    && hp->bh_bnum < mfp->mf_infile_count)))
+	{
+	    if ((flags & MFS_ZERO) && hp->bh_bnum != 0)
+		continue;
+	    if (mf_write(mfp, hp) == FAIL)
+	    {
+		if (status == FAIL)	/* double error: quit syncing */
+		    break;
+		status = FAIL;
+	    }
+	    if (flags & MFS_STOP)
+	    {
+		/* Stop when char available now. */
+		if (ui_char_avail())
+		    break;
+	    }
+	    else
+		ui_breakcheck();
+	    if (got_int)
+		break;
+	}
+
+    /*
+     * If the whole list is flushed, the memfile is not dirty anymore.
+     * In case of an error this flag is also set, to avoid trying all the time.
+     */
+    if (hp == NULL || status == FAIL)
+	mfp->mf_dirty = FALSE;
+
+    if ((flags & MFS_FLUSH) && *p_sws != NUL)
+    {
+#if defined(UNIX)
+# ifdef HAVE_FSYNC
+	/*
+	 * most Unixes have the very useful fsync() function, just what we need.
+	 * However, with OS/2 and EMX it is also available, but there are
+	 * reports of bad problems with it (a bug in HPFS.IFS).
+	 * So we disable use of it here in case someone tries to be smart
+	 * and changes os_os2_cfg.h... (even though there is no __EMX__ test
+	 * in the #if, as __EMX__ does not have sync(); we hope for a timely
+	 * sync from the system itself).
+	 */
+#  if defined(__EMX__)
+   error "Dont use fsync with EMX! Read emxdoc.doc or emxfix01.doc for info."
+#  endif
+	if (STRCMP(p_sws, "fsync") == 0)
+	{
+	    if (fsync(mfp->mf_fd))
+		status = FAIL;
+	}
+	else
+# endif
+	    /* OpenNT is strictly POSIX (Benzinger) */
+	    /* Tandem/Himalaya NSK-OSS doesn't have sync() */
+# if defined(__OPENNT) || defined(__TANDEM)
+	    fflush(NULL);
+# else
+	    sync();
+# endif
+#endif
+#ifdef VMS
+	if (STRCMP(p_sws, "fsync") == 0)
+	{
+	    if (fsync(mfp->mf_fd))
+		status = FAIL;
+	}
+#endif
+#ifdef MSDOS
+	if (_dos_commit(mfp->mf_fd))
+	    status = FAIL;
+#else
+# ifdef SYNC_DUP_CLOSE
+	/*
+	 * Win32 is a bit more work: Duplicate the file handle and close it.
+	 * This should flush the file to disk.
+	 */
+	if ((fd = dup(mfp->mf_fd)) >= 0)
+	    close(fd);
+# endif
+#endif
+#ifdef AMIGA
+# ifdef __AROS__
+	if (fsync(mfp->mf_fd) != 0)
+	    status = FAIL;
+# else
+	/*
+	 * Flush() only exists for AmigaDos 2.0.
+	 * For 1.3 it should be done with close() + open(), but then the risk
+	 * is that the open() may fail and lose the file....
+	 */
+#  ifdef FEAT_ARP
+	if (dos2)
+#  endif
+#  ifdef SASC
+	{
+	    struct UFB *fp = chkufb(mfp->mf_fd);
+
+	    if (fp != NULL)
+		Flush(fp->ufbfh);
+	}
+#  else
+#   if defined(_DCC) || defined(__GNUC__) || defined(__MORPHOS__)
+	{
+#    if defined(__GNUC__) && !defined(__MORPHOS__)
+	    /* Have function (in libnix at least),
+	     * but ain't got no prototype anywhere. */
+	    extern unsigned long fdtofh(int filedescriptor);
+#    endif
+	    BPTR fh = (BPTR)fdtofh(mfp->mf_fd);
+
+	    if (fh != 0)
+		Flush(fh);
+	}
+#   else /* assume Manx */
+	    Flush(_devtab[mfp->mf_fd].fd);
+#   endif
+#  endif
+# endif
+#endif /* AMIGA */
+    }
+
+    got_int |= got_int_save;
+
+    return status;
+}
+
+/*
+ * insert block *hp in front of hashlist of memfile *mfp
+ */
+    static void
+mf_ins_hash(mfp, hp)
+    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;
+}
+
+/*
+ * remove block *hp from hashlist of memfile list *mfp
+ */
+    static void
+mf_rem_hash(mfp, hp)
+    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;
+}
+
+/*
+ * look in hash lists of memfile *mfp for block header with number 'nr'
+ */
+    static bhdr_T *
+mf_find_hash(mfp, nr)
+    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;
+}
+
+/*
+ * insert block *hp in front of used list of memfile *mfp
+ */
+    static void
+mf_ins_used(mfp, hp)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+{
+    hp->bh_next = mfp->mf_used_first;
+    mfp->mf_used_first = hp;
+    hp->bh_prev = NULL;
+    if (hp->bh_next == NULL)	    /* list was empty, adjust last pointer */
+	mfp->mf_used_last = hp;
+    else
+	hp->bh_next->bh_prev = hp;
+    mfp->mf_used_count += hp->bh_page_count;
+    total_mem_used += hp->bh_page_count * mfp->mf_page_size;
+}
+
+/*
+ * remove block *hp from used list of memfile *mfp
+ */
+    static void
+mf_rem_used(mfp, hp)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+{
+    if (hp->bh_next == NULL)	    /* last block in used list */
+	mfp->mf_used_last = hp->bh_prev;
+    else
+	hp->bh_next->bh_prev = hp->bh_prev;
+    if (hp->bh_prev == NULL)	    /* first block in used list */
+	mfp->mf_used_first = hp->bh_next;
+    else
+	hp->bh_prev->bh_next = hp->bh_next;
+    mfp->mf_used_count -= hp->bh_page_count;
+    total_mem_used -= hp->bh_page_count * mfp->mf_page_size;
+}
+
+/*
+ * Release the least recently used block from the used list if the number
+ * of used memory blocks gets to big.
+ *
+ * Return the block header to the caller, including the memory block, so
+ * it can be re-used. Make sure the page_count is right.
+ */
+    static bhdr_T *
+mf_release(mfp, page_count)
+    memfile_T	*mfp;
+    int		page_count;
+{
+    bhdr_T	*hp;
+    int		need_release;
+    buf_T	*buf;
+
+    /* don't release while in mf_close_file() */
+    if (dont_release)
+	return NULL;
+
+    /*
+     * Need to release a block if the number of blocks for this memfile is
+     * higher than the maximum or total memory used is over 'maxmemtot'
+     */
+    need_release = ((mfp->mf_used_count >= mfp->mf_used_count_max)
+				  || (total_mem_used >> 10) >= (long_u)p_mmt);
+
+    /*
+     * Try to create a swap file if the amount of memory used is getting too
+     * high.
+     */
+    if (mfp->mf_fd < 0 && need_release && p_uc)
+    {
+	/* find for which buffer this memfile is */
+	for (buf = firstbuf; buf != NULL; buf = buf->b_next)
+	    if (buf->b_ml.ml_mfp == mfp)
+		break;
+	if (buf != NULL && buf->b_may_swap)
+	    ml_open_file(buf);
+    }
+
+    /*
+     * don't release a block if
+     *	there is no file for this memfile
+     * or
+     *	the number of blocks for this memfile is lower than the maximum
+     *	  and
+     *	total memory used is not up to 'maxmemtot'
+     */
+    if (mfp->mf_fd < 0 || !need_release)
+	return NULL;
+
+    for (hp = mfp->mf_used_last; hp != NULL; hp = hp->bh_prev)
+	if (!(hp->bh_flags & BH_LOCKED))
+	    break;
+    if (hp == NULL)	/* not a single one that can be released */
+	return NULL;
+
+    /*
+     * If the block is dirty, write it.
+     * If the write fails we don't free it.
+     */
+    if ((hp->bh_flags & BH_DIRTY) && mf_write(mfp, hp) == FAIL)
+	return NULL;
+
+    mf_rem_used(mfp, hp);
+    mf_rem_hash(mfp, hp);
+
+    /*
+     * If a bhdr_T is returned, make sure that the page_count of bh_data is
+     * right
+     */
+    if (hp->bh_page_count != page_count)
+    {
+	vim_free(hp->bh_data);
+	if ((hp->bh_data = alloc(mfp->mf_page_size * page_count)) == NULL)
+	{
+	    vim_free(hp);
+	    return NULL;
+	}
+	hp->bh_page_count = page_count;
+    }
+    return hp;
+}
+
+/*
+ * release as many blocks as possible
+ * Used in case of out of memory
+ *
+ * return TRUE if any memory was released
+ */
+    int
+mf_release_all()
+{
+    buf_T	*buf;
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+    int		retval = FALSE;
+
+    for (buf = firstbuf; buf != NULL; buf = buf->b_next)
+    {
+	mfp = buf->b_ml.ml_mfp;
+	if (mfp != NULL)
+	{
+	    /* If no swap file yet, may open one */
+	    if (mfp->mf_fd < 0 && buf->b_may_swap)
+		ml_open_file(buf);
+
+	    /* only if there is a swapfile */
+	    if (mfp->mf_fd >= 0)
+	    {
+		for (hp = mfp->mf_used_last; hp != NULL; )
+		{
+		    if (!(hp->bh_flags & BH_LOCKED)
+			    && (!(hp->bh_flags & BH_DIRTY)
+				|| mf_write(mfp, hp) != FAIL))
+		    {
+			mf_rem_used(mfp, hp);
+			mf_rem_hash(mfp, hp);
+			mf_free_bhdr(hp);
+			hp = mfp->mf_used_last;	/* re-start, list was changed */
+			retval = TRUE;
+		    }
+		    else
+			hp = hp->bh_prev;
+		}
+	    }
+	}
+    }
+    return retval;
+}
+
+/*
+ * Allocate a block header and a block of memory for it
+ */
+    static bhdr_T *
+mf_alloc_bhdr(mfp, page_count)
+    memfile_T	*mfp;
+    int		page_count;
+{
+    bhdr_T	*hp;
+
+    if ((hp = (bhdr_T *)alloc((unsigned)sizeof(bhdr_T))) != NULL)
+    {
+	if ((hp->bh_data = (char_u *)alloc(mfp->mf_page_size * page_count))
+								      == NULL)
+	{
+	    vim_free(hp);	    /* not enough memory */
+	    return NULL;
+	}
+	hp->bh_page_count = page_count;
+    }
+    return hp;
+}
+
+/*
+ * Free a block header and the block of memory for it
+ */
+    static void
+mf_free_bhdr(hp)
+    bhdr_T	*hp;
+{
+    vim_free(hp->bh_data);
+    vim_free(hp);
+}
+
+/*
+ * insert entry *hp in the free list
+ */
+    static void
+mf_ins_free(mfp, hp)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+{
+    hp->bh_next = mfp->mf_free_first;
+    mfp->mf_free_first = hp;
+}
+
+/*
+ * remove the first entry from the free list and return a pointer to it
+ * Note: caller must check that mfp->mf_free_first is not NULL!
+ */
+    static bhdr_T *
+mf_rem_free(mfp)
+    memfile_T	*mfp;
+{
+    bhdr_T	*hp;
+
+    hp = mfp->mf_free_first;
+    mfp->mf_free_first = hp->bh_next;
+    return hp;
+}
+
+/*
+ * read a block from disk
+ *
+ * Return FAIL for failure, OK otherwise
+ */
+    static int
+mf_read(mfp, hp)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+{
+    off_t	offset;
+    unsigned	page_size;
+    unsigned	size;
+
+    if (mfp->mf_fd < 0)	    /* there is no file, can't read */
+	return FAIL;
+
+    page_size = mfp->mf_page_size;
+    offset = (off_t)page_size * hp->bh_bnum;
+    size = page_size * hp->bh_page_count;
+    if (lseek(mfp->mf_fd, offset, SEEK_SET) != offset)
+    {
+	EMSG(_("E294: Seek error in swap file read"));
+	return FAIL;
+    }
+    if ((unsigned)vim_read(mfp->mf_fd, hp->bh_data, size) != size)
+    {
+	EMSG(_("E295: Read error in swap file"));
+	return FAIL;
+    }
+    return OK;
+}
+
+/*
+ * write a block to disk
+ *
+ * Return FAIL for failure, OK otherwise
+ */
+    static int
+mf_write(mfp, hp)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+{
+    off_t	offset;	    /* offset in the file */
+    blocknr_T	nr;	    /* block nr which is being written */
+    bhdr_T	*hp2;
+    unsigned	page_size;  /* number of bytes in a page */
+    unsigned	page_count; /* number of pages written */
+    unsigned	size;	    /* number of bytes written */
+
+    if (mfp->mf_fd < 0)	    /* there is no file, can't write */
+	return FAIL;
+
+    if (hp->bh_bnum < 0)	/* must assign file block number */
+	if (mf_trans_add(mfp, hp) == FAIL)
+	    return FAIL;
+
+    page_size = mfp->mf_page_size;
+
+    /*
+     * We don't want gaps in the file. Write the blocks in front of *hp
+     * to extend the file.
+     * If block 'mf_infile_count' is not in the hash list, it has been
+     * freed. Fill the space in the file with data from the current block.
+     */
+    for (;;)
+    {
+	nr = hp->bh_bnum;
+	if (nr > mfp->mf_infile_count)		/* beyond end of file */
+	{
+	    nr = mfp->mf_infile_count;
+	    hp2 = mf_find_hash(mfp, nr);	/* NULL catched below */
+	}
+	else
+	    hp2 = hp;
+
+	offset = (off_t)page_size * nr;
+	if (lseek(mfp->mf_fd, offset, SEEK_SET) != offset)
+	{
+	    EMSG(_("E296: Seek error in swap file write"));
+	    return FAIL;
+	}
+	if (hp2 == NULL)	    /* freed block, fill with dummy data */
+	    page_count = 1;
+	else
+	    page_count = hp2->bh_page_count;
+	size = page_size * page_count;
+	if ((unsigned)vim_write(mfp->mf_fd,
+	     (hp2 == NULL ? hp : hp2)->bh_data, size) != size)
+	{
+	    /*
+	     * Avoid repeating the error message, this mostly happens when the
+	     * disk is full. We give the message again only after a succesful
+	     * write or when hitting a key. We keep on trying, in case some
+	     * space becomes available.
+	     */
+	    if (!did_swapwrite_msg)
+		EMSG(_("E297: Write error in swap file"));
+	    did_swapwrite_msg = TRUE;
+	    return FAIL;
+	}
+	did_swapwrite_msg = FALSE;
+	if (hp2 != NULL)		    /* written a non-dummy block */
+	    hp2->bh_flags &= ~BH_DIRTY;
+					    /* appended to the file */
+	if (nr + (blocknr_T)page_count > mfp->mf_infile_count)
+	    mfp->mf_infile_count = nr + page_count;
+	if (nr == hp->bh_bnum)		    /* written the desired block */
+	    break;
+    }
+    return OK;
+}
+
+/*
+ * Make block number for *hp positive and add it to the translation list
+ *
+ * Return FAIL for failure, OK otherwise
+ */
+    static int
+mf_trans_add(mfp, hp)
+    memfile_T	*mfp;
+    bhdr_T	*hp;
+{
+    bhdr_T	*freep;
+    blocknr_T	new_bnum;
+    int		hash;
+    NR_TRANS	*np;
+    int		page_count;
+
+    if (hp->bh_bnum >= 0)		    /* it's already positive */
+	return OK;
+
+    if ((np = (NR_TRANS *)alloc((unsigned)sizeof(NR_TRANS))) == NULL)
+	return FAIL;
+
+/*
+ * get a new number for the block.
+ * If the first item in the free list has sufficient pages, use its number
+ * Otherwise use mf_blocknr_max.
+ */
+    freep = mfp->mf_free_first;
+    page_count = hp->bh_page_count;
+    if (freep != NULL && freep->bh_page_count >= page_count)
+    {
+	new_bnum = freep->bh_bnum;
+	/*
+	 * If the page count of the free block was larger, recude it.
+	 * If the page count matches, remove the block from the free list
+	 */
+	if (freep->bh_page_count > page_count)
+	{
+	    freep->bh_bnum += page_count;
+	    freep->bh_page_count -= page_count;
+	}
+	else
+	{
+	    freep = mf_rem_free(mfp);
+	    vim_free(freep);
+	}
+    }
+    else
+    {
+	new_bnum = mfp->mf_blocknr_max;
+	mfp->mf_blocknr_max += page_count;
+    }
+
+    np->nt_old_bnum = hp->bh_bnum;	    /* adjust number */
+    np->nt_new_bnum = new_bnum;
+
+    mf_rem_hash(mfp, hp);		    /* remove from old hash list */
+    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;
+
+    return OK;
+}
+
+/*
+ * Lookup a tranlation from the trans lists and delete the entry
+ *
+ * Return the positive new number when found, the old number when not found
+ */
+    blocknr_T
+mf_trans_del(mfp, old_nr)
+    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;
+    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;
+    vim_free(np);
+
+    return new_bnum;
+}
+
+/*
+ * Set mfp->mf_ffname according to mfp->mf_fname and some other things.
+ * Only called when creating or renaming the swapfile.	Either way it's a new
+ * name so we must work out the full path name.
+ */
+    void
+mf_set_ffname(mfp)
+    memfile_T	*mfp;
+{
+    mfp->mf_ffname = FullName_save(mfp->mf_fname, FALSE);
+}
+
+/*
+ * Make the name of the file used for the memfile a full path.
+ * Used before doing a :cd
+ */
+    void
+mf_fullname(mfp)
+    memfile_T	*mfp;
+{
+    if (mfp != NULL && mfp->mf_fname != NULL && mfp->mf_ffname != NULL)
+    {
+	vim_free(mfp->mf_fname);
+	mfp->mf_fname = mfp->mf_ffname;
+	mfp->mf_ffname = NULL;
+    }
+}
+
+/*
+ * return TRUE if there are any translations pending for 'mfp'
+ */
+    int
+mf_need_trans(mfp)
+    memfile_T	*mfp;
+{
+    return (mfp->mf_fname != NULL && mfp->mf_neg_count > 0);
+}
+
+/*
+ * Open a swap file for a memfile.
+ * The "fname" must be in allocated memory, and is consumed (also when an
+ * error occurs).
+ */
+    static void
+mf_do_open(mfp, fname, flags)
+    memfile_T	*mfp;
+    char_u	*fname;
+    int		flags;		/* flags for open() */
+{
+#ifdef HAVE_LSTAT
+    struct stat sb;
+#endif
+
+    mfp->mf_fname = fname;
+
+    /*
+     * Get the full path name before the open, because this is
+     * not possible after the open on the Amiga.
+     * fname cannot be NameBuff, because it must have been allocated.
+     */
+    mf_set_ffname(mfp);
+#if defined(MSDOS) || defined(MSWIN) || defined(RISCOS)
+    /*
+     * A ":!cd e:xxx" may change the directory without us knowning, use the
+     * full pathname always.  Careful: This frees fname!
+     */
+    mf_fullname(mfp);
+#endif
+
+#ifdef HAVE_LSTAT
+    /*
+     * Extra security check: When creating a swap file it really shouldn't
+     * exist yet.  If there is a symbolic link, this is most likely an attack.
+     */
+    if ((flags & O_CREAT) && mch_lstat((char *)mfp->mf_fname, &sb) >= 0)
+    {
+	mfp->mf_fd = -1;
+	EMSG(_("E300: Swap file already exists (symlink attack?)"));
+    }
+    else
+#endif
+    {
+	/*
+	 * try to open the file
+	 */
+	flags |= O_EXTRA;
+#ifdef WIN32
+	/* Prevent handle inheritance that cause problems with Cscope
+	 * (swap file may not be deleted if cscope connection was open after
+	 * the file) */
+	flags |= O_NOINHERIT;
+#endif
+	mfp->mf_fd = mch_open_rw((char *)mfp->mf_fname, flags);
+    }
+
+    /*
+     * If the file cannot be opened, use memory only
+     */
+    if (mfp->mf_fd < 0)
+    {
+	vim_free(mfp->mf_fname);
+	vim_free(mfp->mf_ffname);
+	mfp->mf_fname = NULL;
+	mfp->mf_ffname = NULL;
+    }
+    else
+	mch_hide(mfp->mf_fname);    /* try setting the 'hidden' flag */
+}