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[libav.git] / libavcodec / mem.c
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1/*
2 * default memory allocator for libavcodec
3 * Copyright (c) 2002 Fabrice Bellard.
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 */
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19
20/**
21 * @file mem.c
22 * default memory allocator for libavcodec.
23 */
24
d01fe86d 25#include "avcodec.h"
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26
27/* here we can use OS dependant allocation functions */
28#undef malloc
29#undef free
30#undef realloc
31
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32#ifdef HAVE_MALLOC_H
33#include <malloc.h>
34#endif
35
36/* you can redefine av_malloc and av_free in your project to use your
37 memory allocator. You do not need to suppress this file because the
38 linker will do it automatically */
39
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40/**
41 * Memory allocation of size byte with alignment suitable for all
42 * memory accesses (including vectors if available on the
43 * CPU). av_malloc(0) must return a non NULL pointer.
44 */
18f77016 45void *av_malloc(unsigned int size)
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46{
47 void *ptr;
67725183 48
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49#ifdef MEMALIGN_HACK
50 int diff;
51 ptr = malloc(size+16+1);
52 diff= ((-(int)ptr - 1)&15) + 1;
53 ptr += diff;
54 ((char*)ptr)[-1]= diff;
55#elif defined (HAVE_MEMALIGN)
8f2b21a8 56 ptr = memalign(16,size);
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57 /* Why 64?
58 Indeed, we should align it:
59 on 4 for 386
60 on 16 for 486
61 on 32 for 586, PPro - k6-III
62 on 64 for K7 (maybe for P3 too).
63 Because L1 and L2 caches are aligned on those values.
64 But I don't want to code such logic here!
65 */
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66 /* Why 16?
67 because some cpus need alignment, for example SSE2 on P4, & most RISC cpus
68 it will just trigger an exception and the unaligned load will be done in the
69 exception handler or it will just segfault (SSE2 on P4)
70 Why not larger? because i didnt see a difference in benchmarks ...
71 */
72 /* benchmarks with p3
73 memalign(64)+1 3071,3051,3032
74 memalign(64)+2 3051,3032,3041
75 memalign(64)+4 2911,2896,2915
76 memalign(64)+8 2545,2554,2550
77 memalign(64)+16 2543,2572,2563
78 memalign(64)+32 2546,2545,2571
79 memalign(64)+64 2570,2533,2558
80
81 btw, malloc seems to do 8 byte alignment by default here
82 */
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83#else
84 ptr = malloc(size);
85#endif
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86 return ptr;
87}
88
b7a22d84 89/**
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90 * av_realloc semantics (same as glibc): if ptr is NULL and size > 0,
91 * identical to malloc(size). If size is zero, it is identical to
92 * free(ptr) and NULL is returned.
b7a22d84 93 */
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94void *av_realloc(void *ptr, unsigned int size)
95{
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96#ifdef MEMALIGN_HACK
97 //FIXME this isnt aligned correctly though it probably isnt needed
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98 int diff;
99 if(!ptr) return av_malloc(size);
100 diff= ((char*)ptr)[-1];
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101 return realloc(ptr - diff, size + diff) + diff;
102#else
8e1e6f31 103 return realloc(ptr, size);
da9b170c 104#endif
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105}
106
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107/* NOTE: ptr = NULL is explicetly allowed */
108void av_free(void *ptr)
109{
110 /* XXX: this test should not be needed on most libcs */
111 if (ptr)
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112#ifdef MEMALIGN_HACK
113 free(ptr - ((char*)ptr)[-1]);
114#else
d01fe86d 115 free(ptr);
da9b170c 116#endif
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117}
118