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/* Cairo - a vector graphics library with display and print output
*
* Copyright © 2007 Chris Wilson
* Copyright © 2009 Intel Corporation
* This library is free software; you can redistribute it and/or
* modify it either under the terms of the GNU Lesser General Public
* License version 2.1 as published by the Free Software Foundation
* (the "LGPL") or, at your option, under the terms of the Mozilla
* Public License Version 1.1 (the "MPL"). If you do not alter this
* notice, a recipoolent may use your version of this file under either
* the MPL or the LGPL.
* You should have received a copy of the LGPL along with this library
* in the file COPYING-LGPL-2.1; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
* You should have received a copy of the MPL along with this library
* in the file COPYING-MPL-1.1
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
* OF ANY KIND, either express or implied. See the LGPL or the MPL for
* the specific language governing rights and limitations.
* The Original Code is the cairo graphics library.
* The Initial Developer of the Original Code is Red Hat, Inc.
* Contributors(s):
* Chris Wilson <chris@chris-wilson.co.uk>
*/
#include "cairoint.h"
#include "cairo-mempool-private.h"
#include "cairo-list-inline.h"
/* a simple buddy allocator for memory pools
* XXX fragmentation? use Doug Lea's malloc?
#define BITTEST(p, n) ((p)->map[(n) >> 3] & (128 >> ((n) & 7)))
#define BITSET(p, n) ((p)->map[(n) >> 3] |= (128 >> ((n) & 7)))
#define BITCLEAR(p, n) ((p)->map[(n) >> 3] &= ~(128 >> ((n) & 7)))
static void
clear_bits (cairo_mempool_t *pool, size_t first, size_t last)
{
size_t i, n = last;
size_t first_full = (first + 7) & ~7;
size_t past_full = last & ~7;
size_t bytes;
if (n > first_full)
n = first_full;
for (i = first; i < n; i++)
BITCLEAR (pool, i);
if (past_full > first_full) {
bytes = past_full - first_full;
bytes = bytes >> 3;
memset (pool->map + (first_full >> 3), 0, bytes);
}
if (past_full < n)
past_full = n;
for (i = past_full; i < last; i++)
free_bits (cairo_mempool_t *pool, size_t start, int bits, cairo_bool_t clear)
struct _cairo_memblock *block;
if (clear)
clear_bits (pool, start, start + (((size_t) 1) << bits));
block = pool->blocks + start;
block->bits = bits;
cairo_list_add (&block->link, &pool->free[bits]);
pool->free_bytes += ((size_t) 1) << (bits + pool->min_bits);
if (bits > pool->max_free_bits)
pool->max_free_bits = bits;
/* Add a chunk to the free list */
free_blocks (cairo_mempool_t *pool,
size_t first,
size_t last,
cairo_bool_t clear)
size_t i, len;
int bits = 0;
for (i = first, len = 1; i < last; i += len) {
/* To avoid cost quadratic in the number of different
* blocks produced from this chunk of store, we have to
* use the size of the previous block produced from this
* chunk as the starting point to work out the size of the
* next block we can produce. If you look at the binary
* representation of the starting points of the blocks
* produced, you can see that you first of all increase the
* size of the blocks produced up to some maximum as the
* address dealt with gets offsets added on which zap out
* low order bits, then decrease as the low order bits of the
* final block produced get added in. E.g. as you go from
* 001 to 0111 you generate blocks
* of size 001 at 001 taking you to 010
* of size 010 at 010 taking you to 100
* of size 010 at 100 taking you to 110
* of size 001 at 110 taking you to 111
* So the maximum total cost of the loops below this comment
* is one trip from the lowest blocksize to the highest and
* back again.
while (bits < pool->num_sizes - 1) {
size_t next_bits = bits + 1;
size_t next_len = len << 1;
if (i + next_bits > last) {
/* off end of chunk to be freed */
break;
if (i & (next_len - 1)) /* block would not be on boundary */
bits = next_bits;
len = next_len;
do {
if (i + len <= last && /* off end of chunk to be freed */
(i & (len - 1)) == 0) /* block would not be on boundary */
bits--; len >>=1;
} while (len);
if (len == 0)
free_bits (pool, i, bits, clear);
static struct _cairo_memblock *
get_buddy (cairo_mempool_t *pool, size_t offset, int bits)
if (offset + (((size_t) 1) << bits) >= pool->num_blocks)
return NULL; /* invalid */
if (BITTEST (pool, offset + (((size_t) 1) << bits) - 1))
return NULL; /* buddy is allocated */
block = pool->blocks + offset;
if (block->bits != bits)
return NULL; /* buddy is partially allocated */
return block;
merge_buddies (cairo_mempool_t *pool,
struct _cairo_memblock *block,
int max_bits)
size_t block_offset = block - pool->blocks;
int bits = block->bits;
while (bits < max_bits - 1) {
/* while you can, merge two blocks and get a legal block size */
size_t buddy_offset = block_offset ^ (((size_t) 1) << bits);
block = get_buddy (pool, buddy_offset, bits);
if (block == NULL)
cairo_list_del (&block->link);
/* Merged block starts at buddy */
if (buddy_offset < block_offset)
block_offset = buddy_offset;
bits++;
block = pool->blocks + block_offset;
/* attempt to merge all available buddies up to a particular size */
static int
merge_bits (cairo_mempool_t *pool, int max_bits)
struct _cairo_memblock *block, *buddy, *next;
int bits;
for (bits = 0; bits < max_bits - 1; bits++) {
cairo_list_foreach_entry_safe (block, next,
struct _cairo_memblock,
&pool->free[bits],
link)
size_t buddy_offset = (block - pool->blocks) ^ (((size_t) 1) << bits);
buddy = get_buddy (pool, buddy_offset, bits);
if (buddy == NULL)
continue;
if (buddy == next) {
next = cairo_container_of (buddy->link.next,
link);
merge_buddies (pool, block, max_bits);
return pool->max_free_bits;
/* find store for 1 << bits blocks */
static void *
buddy_malloc (cairo_mempool_t *pool, int bits)
size_t past, offset;
int b;
if (bits > pool->max_free_bits && bits > merge_bits (pool, bits))
return NULL;
/* Find a list with blocks big enough on it */
block = NULL;
for (b = bits; b <= pool->max_free_bits; b++) {
if (! cairo_list_is_empty (&pool->free[b])) {
block = cairo_list_first_entry (&pool->free[b],
assert (block != NULL);
while (cairo_list_is_empty (&pool->free[pool->max_free_bits])) {
if (--pool->max_free_bits == -1)
/* Mark end of allocated area */
offset = block - pool->blocks;
past = offset + (((size_t) 1) << bits);
BITSET (pool, past - 1);
/* If we used a larger free block than we needed, free the rest */
pool->free_bytes -= ((size_t) 1) << (b + pool->min_bits);
free_blocks (pool, past, offset + (((size_t) 1) << b), 0);
return pool->base + ((block - pool->blocks) << pool->min_bits);
cairo_status_t
_cairo_mempool_init (cairo_mempool_t *pool,
void *base, size_t bytes,
int min_bits, int num_sizes)
uintptr_t tmp;
int num_blocks;
int i;
/* Align the start to an integral chunk */
tmp = ((uintptr_t) base) & ((((size_t) 1) << min_bits) - 1);
if (tmp) {
tmp = (((size_t) 1) << min_bits) - tmp;
base = (char *)base + tmp;
bytes -= tmp;
assert ((((uintptr_t) base) & ((((size_t) 1) << min_bits) - 1)) == 0);
assert (num_sizes < ARRAY_LENGTH (pool->free));
pool->base = base;
pool->free_bytes = 0;
pool->max_bytes = bytes;
pool->max_free_bits = -1;
num_blocks = bytes >> min_bits;
pool->blocks = _cairo_calloc_ab (num_blocks, sizeof (struct _cairo_memblock));
if (pool->blocks == NULL)
return _cairo_error (CAIRO_STATUS_NO_MEMORY);
pool->num_blocks = num_blocks;
pool->min_bits = min_bits;
pool->num_sizes = num_sizes;
for (i = 0; i < ARRAY_LENGTH (pool->free); i++)
cairo_list_init (&pool->free[i]);
pool->map = _cairo_malloc ((num_blocks + 7) >> 3);
if (pool->map == NULL) {
free (pool->blocks);
memset (pool->map, -1, (num_blocks + 7) >> 3);
clear_bits (pool, 0, num_blocks);
/* Now add all blocks to the free list */
free_blocks (pool, 0, num_blocks, 1);
return CAIRO_STATUS_SUCCESS;
void *
_cairo_mempool_alloc (cairo_mempool_t *pool, size_t bytes)
size_t size;
size = ((size_t) 1) << pool->min_bits;
for (bits = 0; size < bytes; bits++)
size <<= 1;
if (bits >= pool->num_sizes)
return buddy_malloc (pool, bits);
void
_cairo_mempool_free (cairo_mempool_t *pool, void *storage)
size_t block_offset;
block_offset = ((char *)storage - pool->base) >> pool->min_bits;
BITCLEAR (pool, block_offset + ((((size_t) 1) << block->bits) - 1));
pool->free_bytes += ((size_t) 1) << (block->bits + pool->min_bits);
merge_buddies (pool, block, pool->num_sizes);
_cairo_mempool_fini (cairo_mempool_t *pool)
free (pool->map);