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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
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
22 * default memory allocator for libavcodec.
23 */
115329f1 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
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 */
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53 if(size > INT_MAX)
54 return NULL;
115329f1 55
da9b170c 56#ifdef MEMALIGN_HACK
da9b170c 57 ptr = malloc(size+16+1);
ed96aeea 58 diff= ((-(long)ptr - 1)&15) + 1;
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59 ptr += diff;
60 ((char*)ptr)[-1]= diff;
115329f1 61#elif defined (HAVE_MEMALIGN)
8f2b21a8 62 ptr = memalign(16,size);
115329f1 63 /* Why 64?
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64 Indeed, we should align it:
65 on 4 for 386
66 on 16 for 486
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67 on 32 for 586, PPro - k6-III
68 on 64 for K7 (maybe for P3 too).
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69 Because L1 and L2 caches are aligned on those values.
70 But I don't want to code such logic here!
71 */
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72 /* Why 16?
73 because some cpus need alignment, for example SSE2 on P4, & most RISC cpus
74 it will just trigger an exception and the unaligned load will be done in the
75 exception handler or it will just segfault (SSE2 on P4)
76 Why not larger? because i didnt see a difference in benchmarks ...
77 */
78 /* benchmarks with p3
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79 memalign(64)+1 3071,3051,3032
80 memalign(64)+2 3051,3032,3041
81 memalign(64)+4 2911,2896,2915
82 memalign(64)+8 2545,2554,2550
83 memalign(64)+16 2543,2572,2563
84 memalign(64)+32 2546,2545,2571
85 memalign(64)+64 2570,2533,2558
115329f1 86
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87 btw, malloc seems to do 8 byte alignment by default here
88 */
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89#else
90 ptr = malloc(size);
91#endif
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92 return ptr;
93}
94
b7a22d84 95/**
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96 * av_realloc semantics (same as glibc): if ptr is NULL and size > 0,
97 * identical to malloc(size). If size is zero, it is identical to
115329f1 98 * free(ptr) and NULL is returned.
b7a22d84 99 */
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100void *av_realloc(void *ptr, unsigned int size)
101{
88730be6 102#ifdef MEMALIGN_HACK
d5f121e2 103 int diff;
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104#endif
105
7d77d5f6 106 /* let's disallow possible ambiguous cases */
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107 if(size > INT_MAX)
108 return NULL;
109
da9b170c 110#ifdef MEMALIGN_HACK
7d77d5f6 111 //FIXME this isn't aligned correctly, though it probably isn't needed
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112 if(!ptr) return av_malloc(size);
113 diff= ((char*)ptr)[-1];
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114 return realloc(ptr - diff, size + diff) + diff;
115#else
8e1e6f31 116 return realloc(ptr, size);
da9b170c 117#endif
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118}
119
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120/**
121 * Free memory which has been allocated with av_malloc(z)() or av_realloc().
4f59b684 122 * NOTE: ptr = NULL is explicetly allowed
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123 * Note2: it is recommanded that you use av_freep() instead
124 */
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125void av_free(void *ptr)
126{
127 /* XXX: this test should not be needed on most libcs */
128 if (ptr)
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129#ifdef MEMALIGN_HACK
130 free(ptr - ((char*)ptr)[-1]);
131#else
d01fe86d 132 free(ptr);
da9b170c 133#endif
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134}
135