Statistics
| Branch: | Revision:

ffmpeg / libavcodec / mem.c @ 18f77016

History | View | Annotate | Download (2.52 KB)

1
/*
2
 * default memory allocator for libavcodec
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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18
 */
19
#include "avcodec.h"
20
#ifdef HAVE_MALLOC_H
21
#include <malloc.h>
22
#endif
23

    
24
/* you can redefine av_malloc and av_free in your project to use your
25
   memory allocator. You do not need to suppress this file because the
26
   linker will do it automatically */
27

    
28
/* memory alloc */
29
void *av_malloc(unsigned int size)
30
{
31
    void *ptr;
32
#if defined (HAVE_MEMALIGN)
33
    ptr = memalign(16,size);
34
    /* Why 64? 
35
       Indeed, we should align it:
36
         on 4 for 386
37
         on 16 for 486
38
         on 32 for 586, PPro - k6-III
39
         on 64 for K7 (maybe for P3 too).
40
       Because L1 and L2 caches are aligned on those values.
41
       But I don't want to code such logic here!
42
     */
43
     /* Why 16?
44
        because some cpus need alignment, for example SSE2 on P4, & most RISC cpus
45
        it will just trigger an exception and the unaligned load will be done in the
46
        exception handler or it will just segfault (SSE2 on P4)
47
        Why not larger? because i didnt see a difference in benchmarks ...
48
     */
49
     /* benchmarks with p3
50
        memalign(64)+1                3071,3051,3032
51
        memalign(64)+2                3051,3032,3041
52
        memalign(64)+4                2911,2896,2915
53
        memalign(64)+8                2545,2554,2550
54
        memalign(64)+16                2543,2572,2563
55
        memalign(64)+32                2546,2545,2571
56
        memalign(64)+64                2570,2533,2558
57
        
58
        btw, malloc seems to do 8 byte alignment by default here
59
     */
60
#else
61
    ptr = malloc(size);
62
#endif
63
    if (!ptr)
64
        return NULL;
65
//fprintf(stderr, "%X %d\n", (int)ptr, size);
66
    /* NOTE: this memset should not be present */
67
    memset(ptr, 0, size);
68
    return ptr;
69
}
70

    
71
/* NOTE: ptr = NULL is explicetly allowed */
72
void av_free(void *ptr)
73
{
74
    /* XXX: this test should not be needed on most libcs */
75
    if (ptr)
76
        free(ptr);
77
}
78