Remove 404 link.
[libav.git] / libavutil / mem.c
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d01fe86d 1/*
cea8f6f3 2 * default memory allocator for libavutil
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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
5509bffa 17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
d01fe86d 18 */
115329f1 19
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20/**
21 * @file mem.c
cea8f6f3 22 * default memory allocator for libavutil.
983e3246 23 */
115329f1 24
cea8f6f3 25#include "common.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
115329f1 40/**
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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;
88730be6 48#ifdef MEMALIGN_HACK
ed96aeea 49 long diff;
88730be6 50#endif
0ecca7a4 51
7d77d5f6 52 /* let's disallow possible ambiguous cases */
0a7c36af 53 if(size > (INT_MAX-16) )
0ecca7a4 54 return NULL;
115329f1 55
da9b170c 56#ifdef MEMALIGN_HACK
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57 ptr = malloc(size+16);
58 if(!ptr)
59 return ptr;
ed96aeea 60 diff= ((-(long)ptr - 1)&15) + 1;
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61 ptr += diff;
62 ((char*)ptr)[-1]= diff;
115329f1 63#elif defined (HAVE_MEMALIGN)
8f2b21a8 64 ptr = memalign(16,size);
115329f1 65 /* Why 64?
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66 Indeed, we should align it:
67 on 4 for 386
68 on 16 for 486
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69 on 32 for 586, PPro - k6-III
70 on 64 for K7 (maybe for P3 too).
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71 Because L1 and L2 caches are aligned on those values.
72 But I don't want to code such logic here!
73 */
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74 /* Why 16?
75 because some cpus need alignment, for example SSE2 on P4, & most RISC cpus
76 it will just trigger an exception and the unaligned load will be done in the
77 exception handler or it will just segfault (SSE2 on P4)
78 Why not larger? because i didnt see a difference in benchmarks ...
79 */
80 /* benchmarks with p3
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81 memalign(64)+1 3071,3051,3032
82 memalign(64)+2 3051,3032,3041
83 memalign(64)+4 2911,2896,2915
84 memalign(64)+8 2545,2554,2550
85 memalign(64)+16 2543,2572,2563
86 memalign(64)+32 2546,2545,2571
87 memalign(64)+64 2570,2533,2558
115329f1 88
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89 btw, malloc seems to do 8 byte alignment by default here
90 */
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91#else
92 ptr = malloc(size);
93#endif
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94 return ptr;
95}
96
b7a22d84 97/**
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98 * av_realloc semantics (same as glibc): if ptr is NULL and size > 0,
99 * identical to malloc(size). If size is zero, it is identical to
115329f1 100 * free(ptr) and NULL is returned.
b7a22d84 101 */
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102void *av_realloc(void *ptr, unsigned int size)
103{
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104#ifdef MEMALIGN_HACK
105 int diff;
106#endif
88730be6 107
7d77d5f6 108 /* let's disallow possible ambiguous cases */
a9493601 109 if(size > (INT_MAX-16) )
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110 return NULL;
111
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112#ifdef MEMALIGN_HACK
113 //FIXME this isn't aligned correctly, though it probably isn't needed
114 if(!ptr) return av_malloc(size);
115 diff= ((char*)ptr)[-1];
116 return realloc(ptr - diff, size + diff) + diff;
117#else
118 return realloc(ptr, size);
da9b170c 119#endif
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120}
121
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122/**
123 * Free memory which has been allocated with av_malloc(z)() or av_realloc().
4f59b684 124 * NOTE: ptr = NULL is explicetly allowed
da2e9781 125 * Note2: it is recommended that you use av_freep() instead
1499e0be 126 */
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127void av_free(void *ptr)
128{
129 /* XXX: this test should not be needed on most libcs */
130 if (ptr)
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131#ifdef MEMALIGN_HACK
132 free(ptr - ((char*)ptr)[-1]);
133#else
d01fe86d 134 free(ptr);
da9b170c 135#endif
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136}
137