/* Copyright (C) 1995, 1996 Aladdin Enterprises.  All rights reserved.
  
  This file is part of GNU Ghostscript.
  
  GNU Ghostscript is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY.  No author or distributor accepts responsibility
  to anyone for the consequences of using it or for whether it serves any
  particular purpose or works at all, unless he says so in writing.  Refer
  to the GNU General Public License for full details.
  
  Everyone is granted permission to copy, modify and redistribute GNU
  Ghostscript, but only under the conditions described in the GNU General
  Public License.  A copy of this license is supposed to have been given
  to you along with GNU Ghostscript so you can know your rights and
  responsibilities.  It should be in a file named COPYING.  Among other
  things, the copyright notice and this notice must be preserved on all
  copies.
*/

/*$RCSfile: gxbcache.c,v $ $Revision: 1.2.2.1 $ */
/* Bitmap cache implementation */
#include "memory_.h"
#include "gx.h"
#include "gsmdebug.h"
#include "gxbcache.h"

/* ------ Entire cache ------ */

/* Initialize a cache.  The caller must allocate and initialize */
/* the first chunk. */
void
gx_bits_cache_init(gx_bits_cache * bc, gx_bits_cache_chunk * bck)
{
    bck->next = bck;
    bc->chunks = bck;
    bc->cnext = 0;
    bc->bsize = 0;
    bc->csize = 0;
}

/* ------ Chunks ------ */

/* Initialize a chunk.  The caller must allocate it and its data. */
void
gx_bits_cache_chunk_init(gx_bits_cache_chunk * bck, byte * data, uint size)
{
    bck->next = 0;
    bck->data = data;
    bck->size = size;
    bck->allocated = 0;
    if (data != 0) {
	gx_cached_bits_head *cbh = (gx_cached_bits_head *) data;

	cbh->size = size;
	cb_head_set_free(cbh);
    }
}

/* ------ Individual entries ------ */

/* Attempt to allocate an entry.  If successful, set *pcbh and return 0. */
/* If there isn't enough room, set *pcbh to an entry requiring freeing, */
/* or to 0 if we are at the end of the chunk, and return -1. */
int
gx_bits_cache_alloc(gx_bits_cache * bc, ulong lsize, gx_cached_bits_head ** pcbh)
{
#define ssize ((uint)lsize)
    ulong lsize1 = lsize + sizeof(gx_cached_bits_head);

#define ssize1 ((uint)lsize1)
    uint cnext = bc->cnext;
    gx_bits_cache_chunk *bck = bc->chunks;
    uint left = bck->size - cnext;
    gx_cached_bits_head *cbh;
    gx_cached_bits_head *cbh_next;
    uint fsize = 0;

    if (lsize1 > bck->size - cnext && lsize != left) {	/* Not enough room to allocate in this chunk. */
	*pcbh = 0;
	return -1;
    }
    /* Look for and/or free enough space. */
    cbh = cbh_next = (gx_cached_bits_head *) (bck->data + cnext);
    while (fsize < ssize1 && fsize != ssize) {
	if (!cb_head_is_free(cbh_next)) {	/* Ask the caller to free the entry. */
	    if (fsize)
		cbh->size = fsize;
	    *pcbh = cbh_next;
	    return -1;
	}
	fsize += cbh_next->size;
	if_debug2('K', "[K]merging free bits 0x%lx(%u)\n",
		  (ulong) cbh_next, cbh_next->size);
	cbh_next = (gx_cached_bits_head *) ((byte *) cbh + fsize);
    }
    if (fsize > ssize) {	/* fsize >= ssize1 */
	cbh_next = (gx_cached_bits_head *) ((byte *) cbh + ssize);
	cbh_next->size = fsize - ssize;
	cb_head_set_free(cbh_next);
	if_debug2('K', "[K]shortening bits 0x%lx by %u (initial)\n",
		  (ulong) cbh, fsize - ssize);
    }
    gs_alloc_fill(cbh, gs_alloc_fill_block, ssize);
    cbh->size = ssize;
    bc->bsize += ssize;
    bc->csize++;
    bc->cnext += ssize;
    bck->allocated += ssize;
    *pcbh = cbh;
    return 0;
#undef ssize
#undef ssize1
}

/* Shorten an entry by a given amount. */
void
gx_bits_cache_shorten(gx_bits_cache * bc, gx_cached_bits_head * cbh,
		      uint diff, gx_bits_cache_chunk * bck)
{
    gx_cached_bits_head *next;

    if ((byte *) cbh + cbh->size == bck->data + bc->cnext &&
	bck == bc->chunks
	)
	bc->cnext -= diff;
    bc->bsize -= diff;
    bck->allocated -= diff;
    cbh->size -= diff;
    next = (gx_cached_bits_head *) ((byte *) cbh + cbh->size);
    cb_head_set_free(next);
    next->size = diff;
}

/* Free an entry.  The caller is responsible for removing the entry */
/* from any other structures (like a hash table). */
void
gx_bits_cache_free(gx_bits_cache * bc, gx_cached_bits_head * cbh,
		   gx_bits_cache_chunk * bck)
{
    uint size = cbh->size;

    bc->csize--;
    bc->bsize -= size;
    bck->allocated -= size;
    gs_alloc_fill(cbh, gs_alloc_fill_deleted, size);
    cbh->size = size;		/* gs_alloc_fill may have overwritten */
    cb_head_set_free(cbh);
}
