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/* 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.
*/

#include "vim.h"

/*
* 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 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_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:
*
* 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;
    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;
    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;
#endif

#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;

    /*
* Compute maximum number of pages ('maxmem' is in Kbyte):
* 'mammem' * 1Kbyte / page-size-in-bytes.
* Avoid overflow by first reducing page size as much as possible.
*/
    {
int shift = 10;
unsigned page_size = mfp->mf_page_size;

while (shift > 0 && (page_size & 1) == 0)
{
page_size = page_size >> 1;
--shift;
}
mfp->mf_used_count_max = (p_mm << shift) / page_size;
if (mfp->mf_used_count_max < 10)
mfp->mf_used_count_max = 10;
    }

    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;

    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));
    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);
}

/*
* 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!) */
mf_dont_release = TRUE;
for (lnum = 1; lnum <= buf->b_ml.ml_line_count; ++lnum)
(void)ml_get_buf(buf, lnum, FALSE);
mf_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 * page_count);

    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__) && defined(__libnix__)
/* 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
# if defined(__AROS__) || defined(__amigaos4__)
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__) && defined(__libnix__)
/* Have function (in libnix at least),
* but ain't got no prototype anywhere. */
extern unsigned long fdtofh(int filedescriptor);
# endif
# if !defined(__libnix__)
fflush(NULL);
# else
BPTR fh = (BPTR)fdtofh(mfp->mf_fd);

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

    got_int |= got_int_save;

    return status;
}

/*
* For all blocks in memory file *mfp that have a positive block number set
* the dirty flag. These are blocks that need to be written to a newly
* created swapfile.
*/
    void
mf_set_dirty(mfp)
    memfile_T *mfp;
{
    bhdr_T *hp;

    for (hp = mfp->mf_used_last; hp != NULL; hp = hp->bh_prev)
if (hp->bh_bnum > 0)
hp->bh_flags |= BH_DIRTY;
    mfp->mf_dirty = TRUE;
}

/*
* insert block *hp in front of hashlist of memfile *mfp
*/
    static void
mf_ins_hash(mfp, hp)
    memfile_T *mfp;
    bhdr_T *hp;
{
    mf_hash_add_item(&mfp->mf_hash, (mf_hashitem_T *)hp);
}

/*
* remove block *hp from hashlist of memfile list *mfp
*/
    static void
mf_rem_hash(mfp, hp)
    memfile_T *mfp;
    bhdr_T *hp;
{
    mf_hash_rem_item(&mfp->mf_hash, (mf_hashitem_T *)hp);
}

/*
* 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;
{
    return (bhdr_T *)mf_hash_find(&mfp->mf_hash, nr);
}

/*
* 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 (mf_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)
    {
PERROR(_("E294: Seek error in swap file read"));
return FAIL;
    }
    if ((unsigned)read_eintr(mfp->mf_fd, hp->bh_data, size) != size)
    {
PERROR(_("E295: Read error in swap file"));
return FAIL;
    }

#ifdef FEAT_CRYPT
    /* Decrypt if 'key' is set and this is a data block. */
    if (*mfp->mf_buffer->b_p_key != NUL)
ml_decrypt_data(mfp, hp->bh_data, offset, size);
#endif

    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)
{
PERROR(_("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 (mf_write_block(mfp, hp2 == NULL ? hp : hp2, offset, size) == FAIL)
{
/*
* Avoid repeating the error message, this mostly happens when the
* disk is full. We give the message again only after a successful
* 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;
}

/*
* Write block "hp" with data size "size" to file "mfp->mf_fd".
* Takes care of encryption.
* Return FAIL or OK.
*/
    static int
mf_write_block(mfp, hp, offset, size)
    memfile_T *mfp;
    bhdr_T *hp;
    off_t offset UNUSED;
    unsigned size;
{
    char_u *data = hp->bh_data;
    int result = OK;

#ifdef FEAT_CRYPT
    /* Encrypt if 'key' is set and this is a data block. */
    if (*mfp->mf_buffer->b_p_key != NUL)
    {
data = ml_encrypt_data(mfp, data, offset, size);
if (data == NULL)
return FAIL;
    }
#endif

    if ((unsigned)write_eintr(mfp->mf_fd, data, size) != size)
result = FAIL;

#ifdef FEAT_CRYPT
    if (data != hp->bh_data)
vim_free(data);
#endif

    return result;
}

/*
* 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;
    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 */

    /* 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;
}

/*
* Lookup a translation 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;
{
    NR_TRANS *np;
    blocknr_T new_bnum;

    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;

    /* remove entry from the trans list */
    mf_hash_rem_item(&mfp->mf_trans, (mf_hashitem_T *)np);

    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)
    /*
* 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 | O_NOFOLLOW;
#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
    {
#ifdef HAVE_FD_CLOEXEC
int fdflags = fcntl(mfp->mf_fd, F_GETFD);
if (fdflags >= 0 && (fdflags & FD_CLOEXEC) == 0)
fcntl(mfp->mf_fd, F_SETFD, fdflags | FD_CLOEXEC);
#endif
#ifdef HAVE_SELINUX
mch_copy_sec(fname, mfp->mf_fname);
#endif
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;
}
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