2 * default memory allocator for libavutil
3 * Copyright (c) 2002 Fabrice Bellard
5 * This file is part of FFmpeg.
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.
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.
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
24 * default memory allocator for libavutil
39 /* here we can use OS-dependent allocation functions */
46 #define malloc AV_JOIN(MALLOC_PREFIX, malloc)
47 #define memalign AV_JOIN(MALLOC_PREFIX, memalign)
48 #define posix_memalign AV_JOIN(MALLOC_PREFIX, posix_memalign)
49 #define realloc AV_JOIN(MALLOC_PREFIX, realloc)
50 #define free AV_JOIN(MALLOC_PREFIX, free)
52 void *malloc(size_t size);
53 void *memalign(size_t align, size_t size);
54 int posix_memalign(void **ptr, size_t align, size_t size);
55 void *realloc(void *ptr, size_t size);
58 #endif /* MALLOC_PREFIX */
60 /* You can redefine av_malloc and av_free in your project to use your
61 memory allocator. You do not need to suppress this file because the
62 linker will do it automatically. */
64 void *av_malloc(unsigned int size)
67 #if CONFIG_MEMALIGN_HACK
71 /* let's disallow possible ambiguous cases */
72 if(size > (INT_MAX-16) )
75 #if CONFIG_MEMALIGN_HACK
76 ptr = malloc(size+16);
79 diff= ((-(long)ptr - 1)&15) + 1;
80 ptr = (char*)ptr + diff;
81 ((char*)ptr)[-1]= diff;
82 #elif HAVE_POSIX_MEMALIGN
83 if (posix_memalign(&ptr,16,size))
86 ptr = memalign(16,size);
88 Indeed, we should align it:
91 on 32 for 586, PPro - K6-III
92 on 64 for K7 (maybe for P3 too).
93 Because L1 and L2 caches are aligned on those values.
94 But I don't want to code such logic here!
97 Because some CPUs need alignment, for example SSE2 on P4, & most RISC CPUs
98 it will just trigger an exception and the unaligned load will be done in the
99 exception handler or it will just segfault (SSE2 on P4).
100 Why not larger? Because I did not see a difference in benchmarks ...
102 /* benchmarks with P3
103 memalign(64)+1 3071,3051,3032
104 memalign(64)+2 3051,3032,3041
105 memalign(64)+4 2911,2896,2915
106 memalign(64)+8 2545,2554,2550
107 memalign(64)+16 2543,2572,2563
108 memalign(64)+32 2546,2545,2571
109 memalign(64)+64 2570,2533,2558
111 BTW, malloc seems to do 8-byte alignment by default here.
119 void *av_realloc(void *ptr, unsigned int size)
121 #if CONFIG_MEMALIGN_HACK
125 /* let's disallow possible ambiguous cases */
126 if(size > (INT_MAX-16) )
129 #if CONFIG_MEMALIGN_HACK
130 //FIXME this isn't aligned correctly, though it probably isn't needed
131 if(!ptr) return av_malloc(size);
132 diff= ((char*)ptr)[-1];
133 return (char*)realloc((char*)ptr - diff, size + diff) + diff;
135 return realloc(ptr, size);
139 void av_free(void *ptr)
141 /* XXX: this test should not be needed on most libcs */
143 #if CONFIG_MEMALIGN_HACK
144 free((char*)ptr - ((char*)ptr)[-1]);
150 void av_freep(void *arg)
152 void **ptr= (void**)arg;
157 void *av_mallocz(unsigned int size)
159 void *ptr = av_malloc(size);
161 memset(ptr, 0, size);
165 char *av_strdup(const char *s)
169 int len = strlen(s) + 1;
170 ptr = av_malloc(len);