/* Copyright (C) 1995, 1996 Aladdin Enterprises.  All rights reserved.
  
  This file is part of Aladdin Ghostscript.
  
  Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
  or distributor accepts any responsibility for the consequences of using it,
  or for whether it serves any particular purpose or works at all, unless he
  or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
  License (the "License") for full details.
  
  Every copy of Aladdin Ghostscript must include a copy of the License,
  normally in a plain ASCII text file named PUBLIC.  The License grants you
  the right to copy, modify and redistribute Aladdin Ghostscript, but only
  under certain conditions described in the License.  Among other things, the
  License requires that the copyright notice and this notice be preserved on
  all copies.
*/

/* gxbcache.c */
/* 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);
}
