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.
29 /* here we can use OS dependent allocation functions */
38 /* you can redefine av_malloc and av_free in your project to use your
39 memory allocator. You do not need to suppress this file because the
40 linker will do it automatically */
42 void *av_malloc(unsigned int size)
45 #ifdef CONFIG_MEMALIGN_HACK
49 /* let's disallow possible ambiguous cases */
50 if(size > (INT_MAX-16) )
53 #ifdef CONFIG_MEMALIGN_HACK
54 ptr = malloc(size+16);
57 diff= ((-(long)ptr - 1)&15) + 1;
59 ((char*)ptr)[-1]= diff;
60 #elif defined (HAVE_MEMALIGN)
61 ptr = memalign(16,size);
63 Indeed, we should align it:
66 on 32 for 586, PPro - k6-III
67 on 64 for K7 (maybe for P3 too).
68 Because L1 and L2 caches are aligned on those values.
69 But I don't want to code such logic here!
72 because some cpus need alignment, for example SSE2 on P4, & most RISC cpus
73 it will just trigger an exception and the unaligned load will be done in the
74 exception handler or it will just segfault (SSE2 on P4)
75 Why not larger? because i didnt see a difference in benchmarks ...
78 memalign(64)+1 3071,3051,3032
79 memalign(64)+2 3051,3032,3041
80 memalign(64)+4 2911,2896,2915
81 memalign(64)+8 2545,2554,2550
82 memalign(64)+16 2543,2572,2563
83 memalign(64)+32 2546,2545,2571
84 memalign(64)+64 2570,2533,2558
86 btw, malloc seems to do 8 byte alignment by default here
94 void *av_realloc(void *ptr, unsigned int size)
96 #ifdef CONFIG_MEMALIGN_HACK
100 /* let's disallow possible ambiguous cases */
101 if(size > (INT_MAX-16) )
104 #ifdef CONFIG_MEMALIGN_HACK
105 //FIXME this isn't aligned correctly, though it probably isn't needed
106 if(!ptr) return av_malloc(size);
107 diff= ((char*)ptr)[-1];
108 return realloc(ptr - diff, size + diff) + diff;
110 return realloc(ptr, size);
115 * Free memory which has been allocated with av_malloc(z)() or av_realloc().
116 * NOTE: ptr = NULL is explicetly allowed
117 * Note2: it is recommended that you use av_freep() instead
119 void av_free(void *ptr)
121 /* XXX: this test should not be needed on most libcs */
123 #ifdef CONFIG_MEMALIGN_HACK
124 free(ptr - ((char*)ptr)[-1]);
131 * Frees memory and sets the pointer to NULL.
132 * @param arg pointer to the pointer which should be freed
134 void av_freep(void *arg)
136 void **ptr= (void**)arg;
141 void *av_mallocz(unsigned int size)
145 ptr = av_malloc(size);
147 memset(ptr, 0, size);
151 char *av_strdup(const char *s)
156 ptr = av_malloc(len);