db3234a3432ae86c89c5ec3d7980ffb2ca6a44a3
[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 mem.c
24 * default memory allocator for libavutil.
25 */
26
27 #include "common.h"
28
29 /* here we can use OS dependent allocation functions */
30 #undef malloc
31 #undef free
32 #undef realloc
33
34 #include <stdlib.h>
35 #if HAVE_MALLOC_H
36 #include <malloc.h>
37 #endif
38
39 /* you can redefine av_malloc and av_free in your project to use your
40 memory allocator. You do not need to suppress this file because the
41 linker will do it automatically */
42
43 void *av_malloc(unsigned int size)
44 {
45 void *ptr = NULL;
46 #if CONFIG_MEMALIGN_HACK
47 long diff;
48 #endif
49
50 /* let's disallow possible ambiguous cases */
51 if(size > (INT_MAX-16) )
52 return NULL;
53
54 #if CONFIG_MEMALIGN_HACK
55 ptr = malloc(size+16);
56 if(!ptr)
57 return ptr;
58 diff= ((-(long)ptr - 1)&15) + 1;
59 ptr = (char*)ptr + diff;
60 ((char*)ptr)[-1]= diff;
61 #elif HAVE_POSIX_MEMALIGN
62 posix_memalign(&ptr,16,size);
63 #elif HAVE_MEMALIGN
64 ptr = memalign(16,size);
65 /* Why 64?
66 Indeed, we should align it:
67 on 4 for 386
68 on 16 for 486
69 on 32 for 586, PPro - k6-III
70 on 64 for K7 (maybe for P3 too).
71 Because L1 and L2 caches are aligned on those values.
72 But I don't want to code such logic here!
73 */
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 did not see a difference in benchmarks ...
79 */
80 /* benchmarks with p3
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
88
89 btw, malloc seems to do 8 byte alignment by default here
90 */
91 #else
92 ptr = malloc(size);
93 #endif
94 return ptr;
95 }
96
97 void *av_realloc(void *ptr, unsigned int size)
98 {
99 #if CONFIG_MEMALIGN_HACK
100 int diff;
101 #endif
102
103 /* let's disallow possible ambiguous cases */
104 if(size > (INT_MAX-16) )
105 return NULL;
106
107 #if CONFIG_MEMALIGN_HACK
108 //FIXME this isn't aligned correctly, though it probably isn't needed
109 if(!ptr) return av_malloc(size);
110 diff= ((char*)ptr)[-1];
111 return (char*)realloc((char*)ptr - diff, size + diff) + diff;
112 #else
113 return realloc(ptr, size);
114 #endif
115 }
116
117 void av_free(void *ptr)
118 {
119 /* XXX: this test should not be needed on most libcs */
120 if (ptr)
121 #if CONFIG_MEMALIGN_HACK
122 free((char*)ptr - ((char*)ptr)[-1]);
123 #else
124 free(ptr);
125 #endif
126 }
127
128 void av_freep(void *arg)
129 {
130 void **ptr= (void**)arg;
131 av_free(*ptr);
132 *ptr = NULL;
133 }
134
135 void *av_mallocz(unsigned int size)
136 {
137 void *ptr = av_malloc(size);
138 if (ptr)
139 memset(ptr, 0, size);
140 return ptr;
141 }
142
143 char *av_strdup(const char *s)
144 {
145 char *ptr= NULL;
146 if(s){
147 int len = strlen(s) + 1;
148 ptr = av_malloc(len);
149 if (ptr)
150 memcpy(ptr, s, len);
151 }
152 return ptr;
153 }
154