Return to memfile.c CVS log

Up to [local] / src / usr.bin / vim

Initial import of vim 4.2.

This is meant to replace nvi in the tree.  Vim, in general, works better,
provides more features, and does not suffer from the license problems
being imposed upon nvi.

On the other hand, vim lacks a non-visual ex mode, in addition to open mode.

This includes the GUI (X11) code, but doesn't try to compile it.

/*	$OpenBSD: memfile.c,v 1.1.1.1 1996/09/07 21:40:26 downsj Exp $	*/
/* vi:set ts=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.
 */

/* for debugging */
#define CHECK(c, s)	if (c) printf(s)

/*
 * 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
# include <io.h>		/* for lseek(), must be before vim.h */
#endif

#include "vim.h"
#include "globals.h"
#include "proto.h"
#include "option.h"
#ifdef HAVE_FCNTL_H
# include <fcntl.h>
#endif

/* 
 * Some systems have the page size in statfs, some in stat
 */
#ifdef HAVE_SYS_STATFS_H
# include <sys/statfs.h>
# define STATFS statfs
# define F_BSIZE f_bsize
# ifdef MINT
#  define fstatfs(fd, buf, len, nul) fstat((fd), (buf))
# endif
#else
# define STATFS stat
# define F_BSIZE st_blksize
# define fstatfs(fd, buf, len, nul) fstat((fd), (buf))
#endif

/*
 * for Amiga Dos 2.0x we use Flush
 */
#ifdef AMIGA
# ifndef NO_ARP
extern int dos2;						/* this is in 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 total_mem_used = 0;			/* total memory used for memfiles */

static void mf_ins_hash __ARGS((MEMFILE *, BHDR *));
static void mf_rem_hash __ARGS((MEMFILE *, BHDR *));
static BHDR *mf_find_hash __ARGS((MEMFILE *, blocknr_t));
static void mf_ins_used __ARGS((MEMFILE *, BHDR *));
static void mf_rem_used __ARGS((MEMFILE *, BHDR *));
static BHDR *mf_release __ARGS((MEMFILE *, int));
static BHDR *mf_alloc_bhdr __ARGS((MEMFILE *, int));
static void mf_free_bhdr __ARGS((BHDR *));
static void mf_ins_free __ARGS((MEMFILE *, BHDR *));
static BHDR *mf_rem_free __ARGS((MEMFILE *));
static int	mf_read __ARGS((MEMFILE *, BHDR *));
static int	mf_write __ARGS((MEMFILE *, BHDR *));
static int	mf_trans_add __ARGS((MEMFILE *, BHDR *));
static void mf_do_open __ARGS((MEMFILE *, 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)
 */

/*
 * mf_open: 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 NOT freed.
 *  trunc_file:		if TRUE: file should be truncated when opening
 *
 *  If fname != NULL and file cannot be opened, fail.
 *
 * return value: identifier for this memory block file.
 */
	MEMFILE *
mf_open(fname, trunc_file)
	char_u	*fname;
	int		trunc_file;
{
	MEMFILE			*mfp;
	int				i;
	long			size;
#ifdef UNIX
	struct STATFS 	stf;
#endif

	if ((mfp = (MEMFILE *)alloc((unsigned)sizeof(MEMFILE))) == NULL)
		return NULL;

	if (fname == NULL)		/* no file for this memfile, use memory only */
	{
		mfp->mf_fname = NULL;
		mfp->mf_xfname = NULL;
		mfp->mf_fd = -1;
	}
	else
	{
		mf_do_open(mfp, fname, trunc_file);		/* 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 UNIX
	/*
	 * Try to set the page size equal to the block size of the device.
	 * Speeds up I/O a lot.
	 * NOTE: minimal block size depends on size of block 0 data! It's not done
	 * with a sizeof(), because block 0 is defined in memline.c (Sorry).
	 * The maximal block size is arbitrary.
	 */
	if (mfp->mf_fd >= 0 &&
					fstatfs(mfp->mf_fd, &stf, sizeof(struct statfs), 0) == 0 &&
					stf.F_BSIZE >= 1048 && stf.F_BSIZE <= 50000)
		mfp->mf_page_size = stf.F_BSIZE;
#endif

	if (mfp->mf_fd < 0 || trunc_file ||
								(size = lseek(mfp->mf_fd, 0L, SEEK_END)) <= 0)
		mfp->mf_blocknr_max = 0;		/* no file or empty file */
	else
		mfp->mf_blocknr_max = size / mfp->mf_page_size;
	mfp->mf_blocknr_min = -1;
	mfp->mf_neg_count = 0;
	mfp->mf_infile_count = mfp->mf_blocknr_max;
	if (mfp->mf_fd < 0)
		mfp->mf_used_count_max = 0;			/* no limit */
	else
		mfp->mf_used_count_max = p_mm * 1024 / mfp->mf_page_size;

	return mfp;
}

/*
 * mf_open_file: open a file for an existing memfile. Used when updatecount
 *				 set from 0 to some value.
 *
 *	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 NOT freed.
 *
 * return value: FAIL if file could not be opened, OK otherwise
 */
	int
mf_open_file(mfp, fname)
	MEMFILE		*mfp;
	char_u		*fname;
{
	mf_do_open(mfp, fname, TRUE);				/* 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	*mfp;
	int		del_file;
{
	BHDR		*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("Close error on swap file");
	}
	if (del_file && mfp->mf_fname != NULL)
		vim_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_xfname);
	vim_free(mfp);
}

/*
 * get a new block
 *
 *   negative: TRUE if negative block number desired (data block)
 */
	BHDR *
mf_new(mfp, negative, page_count)
	MEMFILE		*mfp;
	int			negative;
	int			page_count;
{
	BHDR	*hp;			/* new BHDR */
	BHDR	*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 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 with data
		 *
		 * If the number of pages matches and mf_release did not return a BHDR,
		 * use the BHDR from the free list and allocate the data
		 *
		 * If the number of pages matches and mf_release returned a BHDR,
		 * just use the number and free the BHDR 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);

	return hp;
}

/*
 * get existing block 'nr' with 'page_count' pages
 *
 * Note: The caller should first check a negative nr with mf_trans_del()
 */
	BHDR *
mf_get(mfp, nr, page_count)
	MEMFILE		*mfp;
	blocknr_t	nr;
	int			page_count;
{
	BHDR	*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	*mfp;
	BHDR	*hp;
	int		dirty;
	int		infile;
{
	int		flags;

	flags = hp->bh_flags;
	CHECK((flags & BH_LOCKED) == 0, "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	*mfp;
	BHDR	*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 */
}

/*
 * sync the memory file *mfp to disk
 *	if 'all' is FALSE blocks with negative numbers are not synced, even when
 *  they are dirty!
 *  if 'check_char' is TRUE, stop syncing when a character becomes available,
 *  but sync at least one block.
 *  if 'do_fsync' is TRUE make sure buffers are flushed to disk, so they will
 *  survive a system crash.
 *
 * Return FAIL for failure, OK otherwise
 */
	int
mf_sync(mfp, all, check_char, do_fsync)
	MEMFILE	*mfp;
	int		all;
	int		check_char;
	int		do_fsync;
{
	int		status;
	BHDR	*hp;
#ifdef SYNC_DUP_CLOSE
	int		fd;
#endif

	if (mfp->mf_fd < 0)		/* there is no file, nothing to do */
	{
		mfp->mf_dirty = FALSE;
		return FAIL;
	}

	/*
	 * 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 ((all || hp->bh_bnum >= 0) && (hp->bh_flags & BH_DIRTY) &&
					(status == OK || (hp->bh_bnum >= 0 &&
						hp->bh_bnum < mfp->mf_infile_count)))
		{
			if (mf_write(mfp, hp) == FAIL)
			{
				if (status == FAIL)		/* double error: quit syncing */
					break;
				status = FAIL;
			}
			if (check_char && mch_char_avail())	/* char available now */
				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 (do_fsync && *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 conf_os2.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
			 sync();
#endif
#ifdef DJGPP
		if (_dos_commit(mfp->mf_fd))
			status = FAIL;
#else
# ifdef SYNC_DUP_CLOSE
		/*
		 * MSdos 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
		/*
		 * 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....
		 */
# ifndef NO_ARP
		if (dos2)
# endif
# ifdef SASC
		{
			struct UFB *fp = chkufb(mfp->mf_fd);

			if (fp != NULL)
				Flush(fp->ufbfh);
		}
# else
#  ifdef _DCC
		{
			BPTR fh = (BPTR)fdtofh(mfp->mf_fd);

			if (fh != 0)
				Flush(fh);
			}
#  else /* assume Manx */
			Flush(_devtab[mfp->mf_fd].fd);
#  endif
# endif
#endif /* AMIGA */
	}

	return status;
}

/*
 * insert block *hp in front of hashlist of memfile *mfp
 */
	static void
mf_ins_hash(mfp, hp)
	MEMFILE	*mfp;
	BHDR	*hp;
{
	BHDR	*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	*mfp;
	BHDR	*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 *
mf_find_hash(mfp, nr)
	MEMFILE		*mfp;
	blocknr_t	nr;
{
	BHDR		*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	*mfp;
	BHDR	*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	*mfp;
	BHDR	*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 *
mf_release(mfp, page_count)
	MEMFILE		*mfp;
	int			page_count;
{
	BHDR		*hp;

		/*
		 * don't release a block if
		 *		there is no file for this memfile
		 * or
		 * 		there is no limit to the number of blocks for this memfile or
		 *		the maximum is not reached yet
		 *    and
		 *		total memory used is not up to 'maxmemtot'
		 */
	if (mfp->mf_fd < 0 || ((mfp->mf_used_count < mfp->mf_used_count_max ||
						mfp->mf_used_count_max == 0) &&
						(total_mem_used >> 10) < p_mmt))
		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 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			*buf;
	MEMFILE		*mfp;
	BHDR		*hp;
	int			retval = FALSE;

	for (buf = firstbuf; buf != NULL; buf = buf->b_next)
	{
		mfp = buf->b_ml.ml_mfp;
		if (mfp != NULL && mfp->mf_fd >= 0)		/* only if there is a memfile with a file */
			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 *
mf_alloc_bhdr(mfp, page_count)
	MEMFILE		*mfp;
	int			page_count;
{
	BHDR	*hp;

	if ((hp = (BHDR *)alloc((unsigned)sizeof(BHDR))) != 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		*hp;
{
	vim_free(hp->bh_data);
	vim_free(hp);
}

/*
 * insert entry *hp in the free list
 */
	static void
mf_ins_free(mfp, hp)
	MEMFILE	*mfp;
	BHDR	*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 *
mf_rem_free(mfp)
	MEMFILE	*mfp;
{
	BHDR	*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		*mfp;
	BHDR		*hp;
{
	long_u		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 = page_size * hp->bh_bnum;
	size = page_size * hp->bh_page_count;
	if ((long_u)lseek(mfp->mf_fd, offset, SEEK_SET) != offset)
	{
		EMSG("Seek error in swap file read");
		return FAIL;
	}
	if ((unsigned)read(mfp->mf_fd, (char *)hp->bh_data, (size_t)size) != size)
	{
		EMSG("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		*mfp;
	BHDR		*hp;
{
	long_u		offset;		/* offset in the file */
	blocknr_t	nr;			/* block nr which is being written */
	BHDR		*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 = page_size * nr;
		if ((long_u)lseek(mfp->mf_fd, offset, SEEK_SET) != offset)
		{
			EMSG("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)write(mfp->mf_fd,
			 (char *)(hp2 == NULL ? hp : hp2)->bh_data, (size_t)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("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	*mfp;
	BHDR	*hp;
{
	BHDR		*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		*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_xfname according to mfp->mf_fname and some other things.
 * Don't get the full path name if did_cd is TRUE, then fname should
 * already be a full path name.
 */
	void
mf_set_xfname(mfp)
	MEMFILE		*mfp;
{
	mfp->mf_xfname = NULL;
	if (!did_cd)
		mfp->mf_xfname = FullName_save(mfp->mf_fname);
}

/*
 * Make the name of the file used for the memfile a full path.
 * Used before doing a :cd
 */
	void
mf_fullname(mfp)
	MEMFILE		*mfp;
{
	if (mfp != NULL && mfp->mf_fname != NULL && mfp->mf_xfname != NULL)
	{
		vim_free(mfp->mf_fname);
		mfp->mf_fname = mfp->mf_xfname;
		mfp->mf_xfname = NULL;
	}
}

/*
 * return TRUE if there are any translations pending for 'mfp'
 */
	int
mf_need_trans(mfp)
	MEMFILE		*mfp;
{
	return (mfp->mf_fname != NULL && mfp->mf_neg_count > 0);
}

#if 1			/* included for beta release, TODO: remove later */
/*
 * print statistics for a memfile (for debugging)
 */
	void
mf_statistics()
{
	MEMFILE		*mfp;
	BHDR		*hp;
	int			used = 0;
	int			locked = 0;
	int			dirty = 0;
	int			nfree = 0;
	int			negative = 0;

	mfp = curbuf->b_ml.ml_mfp;
	if (mfp == NULL)
		MSG("No memfile");
	else
	{
		for (hp = mfp->mf_used_first; hp != NULL; hp = hp->bh_next)
		{
			++used;
			if (hp->bh_flags & BH_LOCKED)
				++locked;
			if (hp->bh_flags & BH_DIRTY)
				++dirty;
			if (hp->bh_bnum < 0)
				++negative;
		}
		for (hp = mfp->mf_free_first; hp != NULL; hp = hp->bh_next)
			++nfree;
		sprintf((char *)IObuff, "%d used (%d locked, %d dirty, %d (%d) negative), %d free",
						used, locked, dirty, negative, (int)mfp->mf_neg_count, nfree);
		msg(IObuff);
		sprintf((char *)IObuff, "Total mem used is %ld bytes", total_mem_used);
		msg(IObuff);
	}
}
#endif

/*
 * open a swap file for a memfile
 */
	static void
mf_do_open(mfp, fname, trunc_file)
	MEMFILE		*mfp;
	char_u		*fname;
	int			trunc_file;
{
	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_xfname(mfp);

	/*
	 * try to open the file
	 */
	mfp->mf_fd = open((char *)fname,
			(trunc_file ? (O_CREAT | O_RDWR | O_TRUNC) : (O_RDONLY)) | O_EXTRA

#ifdef AMIGA				/* Amiga has no mode argument */
					);
#endif
#ifdef UNIX					/* open in rw------- mode */
					, (mode_t)0600);
#endif
#if defined(MSDOS) || defined(WIN32) || defined(__EMX__)
					, S_IREAD | S_IWRITE);         /* open read/write */
#endif
#ifdef VMS					/* open in rw------- mode */
					, 0600);
#endif

	/*
	 * If the file cannot be opened, use memory only
	 */
	if (mfp->mf_fd < 0)
	{
		vim_free(mfp->mf_xfname);
		mfp->mf_fname = NULL;
		mfp->mf_xfname = NULL;
	}
}