revert aligned realloc() changesm this should be identical to r5784
[libav.git] / libavutil / mem.c
1 /*
2 * default memory allocator for libavutil
3 * Copyright (c) 2002 Fabrice Bellard.
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19
20 /**
21 * @file mem.c
22 * default memory allocator for libavutil.
23 */
24
25 #include "common.h"
26
27 /* here we can use OS dependant allocation functions */
28 #undef malloc
29 #undef free
30 #undef realloc
31
32 #ifdef HAVE_MALLOC_H
33 #include <malloc.h>
34 #endif
35
36 /* you can redefine av_malloc and av_free in your project to use your
37 memory allocator. You do not need to suppress this file because the
38 linker will do it automatically */
39
40 /**
41 * Memory allocation of size byte with alignment suitable for all
42 * memory accesses (including vectors if available on the
43 * CPU). av_malloc(0) must return a non NULL pointer.
44 */
45 void *av_malloc(unsigned int size)
46 {
47 void *ptr;
48 #ifdef MEMALIGN_HACK
49 long diff;
50 #endif
51
52 /* let's disallow possible ambiguous cases */
53 if(size > (INT_MAX-16) )
54 return NULL;
55
56 #ifdef MEMALIGN_HACK
57 ptr = malloc(size+16);
58 if(!ptr)
59 return ptr;
60 diff= ((-(long)ptr - 1)&15) + 1;
61 ptr += diff;
62 ((char*)ptr)[-1]= diff;
63 #elif defined (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 didnt 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 /**
98 * av_realloc semantics (same as glibc): if ptr is NULL and size > 0,
99 * identical to malloc(size). If size is zero, it is identical to
100 * free(ptr) and NULL is returned.
101 */
102 void *av_realloc(void *ptr, unsigned int size)
103 {
104 #ifdef 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 #ifdef 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 realloc(ptr - diff, size + diff) + diff;
117 #else
118 return realloc(ptr, size);
119 #endif
120 }
121
122 /**
123 * Free memory which has been allocated with av_malloc(z)() or av_realloc().
124 * NOTE: ptr = NULL is explicetly allowed
125 * Note2: it is recommended that you use av_freep() instead
126 */
127 void av_free(void *ptr)
128 {
129 /* XXX: this test should not be needed on most libcs */
130 if (ptr)
131 #ifdef MEMALIGN_HACK
132 free(ptr - ((char*)ptr)[-1]);
133 #else
134 free(ptr);
135 #endif
136 }
137