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 */
43 * Memory allocation of size byte with alignment suitable for all
44 * memory accesses (including vectors if available on the
45 * CPU). av_malloc(0) must return a non NULL pointer.
47 void *av_malloc(unsigned int size)
50 #ifdef CONFIG_MEMALIGN_HACK
54 /* let's disallow possible ambiguous cases */
55 if(size > (INT_MAX-16) )
58 #ifdef CONFIG_MEMALIGN_HACK
59 ptr = malloc(size+16);
62 diff= ((-(long)ptr - 1)&15) + 1;
64 ((char*)ptr)[-1]= diff;
65 #elif defined (HAVE_MEMALIGN)
66 ptr = memalign(16,size);
68 Indeed, we should align it:
71 on 32 for 586, PPro - k6-III
72 on 64 for K7 (maybe for P3 too).
73 Because L1 and L2 caches are aligned on those values.
74 But I don't want to code such logic here!
77 because some cpus need alignment, for example SSE2 on P4, & most RISC cpus
78 it will just trigger an exception and the unaligned load will be done in the
79 exception handler or it will just segfault (SSE2 on P4)
80 Why not larger? because i didnt see a difference in benchmarks ...
83 memalign(64)+1 3071,3051,3032
84 memalign(64)+2 3051,3032,3041
85 memalign(64)+4 2911,2896,2915
86 memalign(64)+8 2545,2554,2550
87 memalign(64)+16 2543,2572,2563
88 memalign(64)+32 2546,2545,2571
89 memalign(64)+64 2570,2533,2558
91 btw, malloc seems to do 8 byte alignment by default here
100 * av_realloc semantics (same as glibc): if ptr is NULL and size > 0,
101 * identical to malloc(size). If size is zero, it is identical to
102 * free(ptr) and NULL is returned.
104 void *av_realloc(void *ptr, unsigned int size)
106 #ifdef CONFIG_MEMALIGN_HACK
110 /* let's disallow possible ambiguous cases */
111 if(size > (INT_MAX-16) )
114 #ifdef CONFIG_MEMALIGN_HACK
115 //FIXME this isn't aligned correctly, though it probably isn't needed
116 if(!ptr) return av_malloc(size);
117 diff= ((char*)ptr)[-1];
118 return realloc(ptr - diff, size + diff) + diff;
120 return realloc(ptr, size);
125 * Free memory which has been allocated with av_malloc(z)() or av_realloc().
126 * NOTE: ptr = NULL is explicetly allowed
127 * Note2: it is recommended that you use av_freep() instead
129 void av_free(void *ptr)
131 /* XXX: this test should not be needed on most libcs */
133 #ifdef CONFIG_MEMALIGN_HACK
134 free(ptr - ((char*)ptr)[-1]);
141 * Frees memory and sets the pointer to NULL.
142 * @param arg pointer to the pointer which should be freed
144 void av_freep(void *arg)
146 void **ptr= (void**)arg;
151 void *av_mallocz(unsigned int size)
155 ptr = av_malloc(size);
157 memset(ptr, 0, size);
161 char *av_strdup(const char *s)
166 ptr = av_malloc(len);