memfile.c

VIM文本编辑器

/* 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.
 */

/*
 * 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"

#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) 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) fstat((fd), (buf))
#  endif
# endif
#endif

/*
 * for Amiga Dos 2.0x we use Flush
 */
#ifdef AMIGA
# ifndef NO_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 *, 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 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;
    off_t	    size;
#if defined(STATFS) && defined(UNIX) && !defined(__QNX__)
# define USE_FSTATFS
    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_ffname = 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 USE_FSTATFS
    /*
     * 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, (off_t)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;
    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 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)
	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)
    BUF		*buf;
{
    MEMFILE	*mfp;
    linenr_t	lnum;

    mfp = buf->b_ml.ml_mfp;
    if (mfp == NULL || mfp->mf_fd < 0)		/* nothing to close */
	return;

    /* 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("Close error on swap file");
    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;
    }
}

/*
 * 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);

    /*
     * 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 *
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 */
    {