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FFmpeg/libavutil/mem.c
Rémi Denis-Courmont 6039248018 mem: fix pointer pointer aliasing violations 
This uses explicit memory copying to read and write pointer to pointers
of arbitrary object types. This works provided that the architecture
uses the same representation for all pointer types (the previous code
made that assumption already anyway).

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
2015-02-01 02:28:40 +01:00

406 lines
8.8 KiB
C
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/*
* default memory allocator for libavutil
* Copyright (c) 2002 Fabrice Bellard
*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* default memory allocator for libavutil
*/
#include "config.h"
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#if HAVE_MALLOC_H
#include <malloc.h>
#endif
#include "avutil.h"
#include "common.h"
#include "intreadwrite.h"
#include "mem.h"
#ifdef MALLOC_PREFIX
#define malloc AV_JOIN(MALLOC_PREFIX, malloc)
#define memalign AV_JOIN(MALLOC_PREFIX, memalign)
#define posix_memalign AV_JOIN(MALLOC_PREFIX, posix_memalign)
#define realloc AV_JOIN(MALLOC_PREFIX, realloc)
#define free AV_JOIN(MALLOC_PREFIX, free)
void *malloc(size_t size);
void *memalign(size_t align, size_t size);
int posix_memalign(void **ptr, size_t align, size_t size);
void *realloc(void *ptr, size_t size);
void free(void *ptr);
#endif /* MALLOC_PREFIX */
/* You can redefine av_malloc and av_free in your project to use your
* memory allocator. You do not need to suppress this file because the
* linker will do it automatically. */
void *av_malloc(size_t size)
{
void *ptr = NULL;
#if CONFIG_MEMALIGN_HACK
long diff;
#endif
/* let's disallow possibly ambiguous cases */
if (size > (INT_MAX - 32) || !size)
return NULL;
#if CONFIG_MEMALIGN_HACK
ptr = malloc(size + 32);
if (!ptr)
return ptr;
diff = ((-(long)ptr - 1) & 31) + 1;
ptr = (char *)ptr + diff;
((char *)ptr)[-1] = diff;
#elif HAVE_POSIX_MEMALIGN
if (posix_memalign(&ptr, 32, size))
ptr = NULL;
#elif HAVE_ALIGNED_MALLOC
ptr = _aligned_malloc(size, 32);
#elif HAVE_MEMALIGN
ptr = memalign(32, size);
/* Why 64?
* Indeed, we should align it:
* on 4 for 386
* on 16 for 486
* on 32 for 586, PPro - K6-III
* on 64 for K7 (maybe for P3 too).
* Because L1 and L2 caches are aligned on those values.
* But I don't want to code such logic here!
*/
/* Why 32?
* For AVX ASM. SSE / NEON needs only 16.
* Why not larger? Because I did not see a difference in benchmarks ...
*/
/* benchmarks with P3
* memalign(64) + 1 3071, 3051, 3032
* memalign(64) + 2 3051, 3032, 3041
* memalign(64) + 4 2911, 2896, 2915
* memalign(64) + 8 2545, 2554, 2550
* memalign(64) + 16 2543, 2572, 2563
* memalign(64) + 32 2546, 2545, 2571
* memalign(64) + 64 2570, 2533, 2558
*
* BTW, malloc seems to do 8-byte alignment by default here.
*/
#else
ptr = malloc(size);
#endif
return ptr;
}
void *av_realloc(void *ptr, size_t size)
{
#if CONFIG_MEMALIGN_HACK
int diff;
#endif
/* let's disallow possibly ambiguous cases */
if (size > (INT_MAX - 16))
return NULL;
#if CONFIG_MEMALIGN_HACK
//FIXME this isn't aligned correctly, though it probably isn't needed
if (!ptr)
return av_malloc(size);
diff = ((char *)ptr)[-1];
return (char *)realloc((char *)ptr - diff, size + diff) + diff;
#elif HAVE_ALIGNED_MALLOC
return _aligned_realloc(ptr, size, 32);
#else
return realloc(ptr, size);
#endif
}
int av_reallocp(void *ptr, size_t size)
{
void *val;
if (!size) {
av_freep(ptr);
return 0;
}
memcpy(&val, ptr, sizeof(val));
val = av_realloc(val, size);
if (!val) {
av_freep(ptr);
return AVERROR(ENOMEM);
}
memcpy(ptr, &val, sizeof(val));
return 0;
}
void *av_realloc_array(void *ptr, size_t nmemb, size_t size)
{
if (!size || nmemb >= INT_MAX / size)
return NULL;
return av_realloc(ptr, nmemb * size);
}
int av_reallocp_array(void *ptr, size_t nmemb, size_t size)
{
void *val;
if (!size || nmemb >= INT_MAX / size)
return AVERROR(ENOMEM);
if (!nmemb) {
av_freep(ptr);
return 0;
}
memcpy(&val, ptr, sizeof(val));
val = av_realloc(val, nmemb * size);
if (!val) {
av_freep(ptr);
return AVERROR(ENOMEM);
}
memcpy(ptr, &val, sizeof(val));
return 0;
}
void av_free(void *ptr)
{
#if CONFIG_MEMALIGN_HACK
if (ptr)
free((char *)ptr - ((char *)ptr)[-1]);
#elif HAVE_ALIGNED_MALLOC
_aligned_free(ptr);
#else
free(ptr);
#endif
}
void av_freep(void *arg)
{
void *val;
memcpy(&val, arg, sizeof(val));
memcpy(arg, &(void *){ NULL }, sizeof(val));
av_free(val);
}
void *av_mallocz(size_t size)
{
void *ptr = av_malloc(size);
if (ptr)
memset(ptr, 0, size);
return ptr;
}
char *av_strdup(const char *s)
{
char *ptr = NULL;
if (s) {
int len = strlen(s) + 1;
ptr = av_realloc(NULL, len);
if (ptr)
memcpy(ptr, s, len);
}
return ptr;
}
char *av_strndup(const char *s, size_t len)
{
char *ret = NULL, *end;
if (!s)
return NULL;
end = memchr(s, 0, len);
if (end)
len = end - s;
ret = av_realloc(NULL, len + 1);
if (!ret)
return NULL;
memcpy(ret, s, len);
ret[len] = 0;
return ret;
}
static void fill16(uint8_t *dst, int len)
{
uint32_t v = AV_RN16(dst - 2);
v |= v << 16;
while (len >= 4) {
AV_WN32(dst, v);
dst += 4;
len -= 4;
}
while (len--) {
*dst = dst[-2];
dst++;
}
}
static void fill24(uint8_t *dst, int len)
{
#if HAVE_BIGENDIAN
uint32_t v = AV_RB24(dst - 3);
uint32_t a = v << 8 | v >> 16;
uint32_t b = v << 16 | v >> 8;
uint32_t c = v << 24 | v;
#else
uint32_t v = AV_RL24(dst - 3);
uint32_t a = v | v << 24;
uint32_t b = v >> 8 | v << 16;
uint32_t c = v >> 16 | v << 8;
#endif
while (len >= 12) {
AV_WN32(dst, a);
AV_WN32(dst + 4, b);
AV_WN32(dst + 8, c);
dst += 12;
len -= 12;
}
if (len >= 4) {
AV_WN32(dst, a);
dst += 4;
len -= 4;
}
if (len >= 4) {
AV_WN32(dst, b);
dst += 4;
len -= 4;
}
while (len--) {
*dst = dst[-3];
dst++;
}
}
static void fill32(uint8_t *dst, int len)
{
uint32_t v = AV_RN32(dst - 4);
while (len >= 4) {
AV_WN32(dst, v);
dst += 4;
len -= 4;
}
while (len--) {
*dst = dst[-4];
dst++;
}
}
void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
{
const uint8_t *src = &dst[-back];
if (!back)
return;
if (back == 1) {
memset(dst, *src, cnt);
} else if (back == 2) {
fill16(dst, cnt);
} else if (back == 3) {
fill24(dst, cnt);
} else if (back == 4) {
fill32(dst, cnt);
} else {
if (cnt >= 16) {
int blocklen = back;
while (cnt > blocklen) {
memcpy(dst, src, blocklen);
dst += blocklen;
cnt -= blocklen;
blocklen <<= 1;
}
memcpy(dst, src, cnt);
return;
}
if (cnt >= 8) {
AV_COPY32U(dst, src);
AV_COPY32U(dst + 4, src + 4);
src += 8;
dst += 8;
cnt -= 8;
}
if (cnt >= 4) {
AV_COPY32U(dst, src);
src += 4;
dst += 4;
cnt -= 4;
}
if (cnt >= 2) {
AV_COPY16U(dst, src);
src += 2;
dst += 2;
cnt -= 2;
}
if (cnt)
*dst = *src;
}
}
void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
{
if (min_size < *size)
return ptr;
min_size = FFMAX(17 * min_size / 16 + 32, min_size);
ptr = av_realloc(ptr, min_size);
/* we could set this to the unmodified min_size but this is safer
* if the user lost the ptr and uses NULL now
*/
if (!ptr)
min_size = 0;
*size = min_size;
return ptr;
}
void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
{
void **p = ptr;
if (min_size < *size)
return;
min_size = FFMAX(17 * min_size / 16 + 32, min_size);
av_free(*p);
*p = av_malloc(min_size);
if (!*p)
min_size = 0;
*size = min_size;
}
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