741450b53faad14df4067cc3f232c98d6955f815
[libav.git] / libavutil / mem.c
1 /*
2 * default memory allocator for libavutil
3 * Copyright (c) 2002 Fabrice Bellard
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file libavutil/mem.c
24 * default memory allocator for libavutil
25 */
26
27 #include "config.h"
28
29 #include <limits.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #if HAVE_MALLOC_H
33 #include <malloc.h>
34 #endif
35
36 #include "mem.h"
37
38 /* here we can use OS-dependent allocation functions */
39 #undef free
40 #undef malloc
41 #undef realloc
42
43 /* You can redefine av_malloc and av_free in your project to use your
44 memory allocator. You do not need to suppress this file because the
45 linker will do it automatically. */
46
47 void *av_malloc(unsigned int size)
48 {
49 void *ptr = NULL;
50 #if CONFIG_MEMALIGN_HACK
51 long diff;
52 #endif
53
54 /* let's disallow possible ambiguous cases */
55 if(size > (INT_MAX-16) )
56 return NULL;
57
58 #if CONFIG_MEMALIGN_HACK
59 ptr = malloc(size+16);
60 if(!ptr)
61 return ptr;
62 diff= ((-(long)ptr - 1)&15) + 1;
63 ptr = (char*)ptr + diff;
64 ((char*)ptr)[-1]= diff;
65 #elif HAVE_POSIX_MEMALIGN
66 if (posix_memalign(&ptr,16,size))
67 ptr = NULL;
68 #elif HAVE_MEMALIGN
69 ptr = memalign(16,size);
70 /* Why 64?
71 Indeed, we should align it:
72 on 4 for 386
73 on 16 for 486
74 on 32 for 586, PPro - K6-III
75 on 64 for K7 (maybe for P3 too).
76 Because L1 and L2 caches are aligned on those values.
77 But I don't want to code such logic here!
78 */
79 /* Why 16?
80 Because some CPUs need alignment, for example SSE2 on P4, & most RISC CPUs
81 it will just trigger an exception and the unaligned load will be done in the
82 exception handler or it will just segfault (SSE2 on P4).
83 Why not larger? Because I did not see a difference in benchmarks ...
84 */
85 /* benchmarks with P3
86 memalign(64)+1 3071,3051,3032
87 memalign(64)+2 3051,3032,3041
88 memalign(64)+4 2911,2896,2915
89 memalign(64)+8 2545,2554,2550
90 memalign(64)+16 2543,2572,2563
91 memalign(64)+32 2546,2545,2571
92 memalign(64)+64 2570,2533,2558
93
94 BTW, malloc seems to do 8-byte alignment by default here.
95 */
96 #else
97 ptr = malloc(size);
98 #endif
99 return ptr;
100 }
101
102 void *av_realloc(void *ptr, unsigned int size)
103 {
104 #if CONFIG_MEMALIGN_HACK
105 int diff;
106 #endif
107
108 /* let's disallow possible ambiguous cases */
109 if(size > (INT_MAX-16) )
110 return NULL;
111
112 #if CONFIG_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 (char*)realloc((char*)ptr - diff, size + diff) + diff;
117 #else
118 return realloc(ptr, size);
119 #endif
120 }
121
122 void av_free(void *ptr)
123 {
124 /* XXX: this test should not be needed on most libcs */
125 if (ptr)
126 #if CONFIG_MEMALIGN_HACK
127 free((char*)ptr - ((char*)ptr)[-1]);
128 #else
129 free(ptr);
130 #endif
131 }
132
133 void av_freep(void *arg)
134 {
135 void **ptr= (void**)arg;
136 av_free(*ptr);
137 *ptr = NULL;
138 }
139
140 void *av_mallocz(unsigned int size)
141 {
142 void *ptr = av_malloc(size);
143 if (ptr)
144 memset(ptr, 0, size);
145 return ptr;
146 }
147
148 char *av_strdup(const char *s)
149 {
150 char *ptr= NULL;
151 if(s){
152 int len = strlen(s) + 1;
153 ptr = av_malloc(len);
154 if (ptr)
155 memcpy(ptr, s, len);
156 }
157 return ptr;
158 }
159