libavutil/mem.c

   1 /*
   2  * default memory allocator for libavutil
   3  * Copyright (c) 2002 Fabrice Bellard.
   4  *
   5  * This file is part of FFmpeg.
   6  *
   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.
  11  *
  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.
  16  *
  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
  20  */
  21
  22 /**
  23  * @file mem.c
  24  * default memory allocator for libavutil.
  25  */
  26
  27 #include "common.h"
  28
  29 /* here we can use OS dependent allocation functions */
  30 #undef malloc
  31 #undef free
  32 #undef realloc
  33
  34 #ifdef HAVE_MALLOC_H
  35 #include <malloc.h>
  36 #endif
  37
  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 */
  41
  42 void *av_malloc(unsigned int size)
  43 {
  44     void *ptr;
  45 #ifdef CONFIG_MEMALIGN_HACK
  46     long diff;
  47 #endif
  48
  49     /* let's disallow possible ambiguous cases */
  50     if(size > (INT_MAX-16) )
  51         return NULL;
  52
  53 #ifdef CONFIG_MEMALIGN_HACK
  54     ptr = malloc(size+16);
  55     if(!ptr)
  56         return ptr;
  57     diff= ((-(long)ptr - 1)&15) + 1;
  58     ptr = (char*)ptr + diff;
  59     ((char*)ptr)[-1]= diff;
  60 #elif defined (HAVE_MEMALIGN)
  61     ptr = memalign(16,size);
  62     /* Why 64?
  63        Indeed, we should align it:
  64          on 4 for 386
  65          on 16 for 486
  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!
  70      */
  71      /* Why 16?
  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 did not see a difference in benchmarks ...
  76      */
  77      /* benchmarks with p3
  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
  85
  86         btw, malloc seems to do 8 byte alignment by default here
  87      */
  88 #else
  89     ptr = malloc(size);
  90 #endif
  91     return ptr;
  92 }
  93
  94 void *av_realloc(void *ptr, unsigned int size)
  95 {
  96 #ifdef CONFIG_MEMALIGN_HACK
  97     int diff;
  98 #endif
  99
 100     /* let's disallow possible ambiguous cases */
 101     if(size > (INT_MAX-16) )
 102         return NULL;
 103
 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 (char*)realloc((char*)ptr - diff, size + diff) + diff;
 109 #else
 110     return realloc(ptr, size);
 111 #endif
 112 }
 113
 114 void av_free(void *ptr)
 115 {
 116     /* XXX: this test should not be needed on most libcs */
 117     if (ptr)
 118 #ifdef CONFIG_MEMALIGN_HACK
 119         free((char*)ptr - ((char*)ptr)[-1]);
 120 #else
 121         free(ptr);
 122 #endif
 123 }
 124
 125 void av_freep(void *arg)
 126 {
 127     void **ptr= (void**)arg;
 128     av_free(*ptr);
 129     *ptr = NULL;
 130 }
 131
 132 void *av_mallocz(unsigned int size)
 133 {
 134     void *ptr = av_malloc(size);
 135     if (ptr)
 136         memset(ptr, 0, size);
 137     return ptr;
 138 }
 139
 140 char *av_strdup(const char *s)
 141 {
 142     char *ptr= NULL;
 143     if(s){
 144         int len = strlen(s) + 1;
 145         ptr = av_malloc(len);
 146         if (ptr)
 147             memcpy(ptr, s, len);
 148     }
 149     return ptr;
 150 }
 151