mem.c
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1 /*
2  * default memory allocator for libavutil
3  * Copyright (c) 2002 Fabrice Bellard
4  *
5  * This file is part of Libav.
6  *
7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
27 #include "config.h"
28 
29 #include <limits.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #if HAVE_MALLOC_H
33 #include <malloc.h>
34 #endif
35 
36 #include "avutil.h"
37 #include "mem.h"
38 
39 /* here we can use OS-dependent allocation functions */
40 #undef free
41 #undef malloc
42 #undef realloc
43 
44 #ifdef MALLOC_PREFIX
45 
46 #define malloc AV_JOIN(MALLOC_PREFIX, malloc)
47 #define memalign AV_JOIN(MALLOC_PREFIX, memalign)
48 #define posix_memalign AV_JOIN(MALLOC_PREFIX, posix_memalign)
49 #define realloc AV_JOIN(MALLOC_PREFIX, realloc)
50 #define free AV_JOIN(MALLOC_PREFIX, free)
51 
52 void *malloc(size_t size);
53 void *memalign(size_t align, size_t size);
54 int posix_memalign(void **ptr, size_t align, size_t size);
55 void *realloc(void *ptr, size_t size);
56 void free(void *ptr);
57 
58 #endif /* MALLOC_PREFIX */
59 
60 /* You can redefine av_malloc and av_free in your project to use your
61  memory allocator. You do not need to suppress this file because the
62  linker will do it automatically. */
63 
64 void *av_malloc(size_t size)
65 {
66  void *ptr = NULL;
67 #if CONFIG_MEMALIGN_HACK
68  long diff;
69 #endif
70 
71  /* let's disallow possible ambiguous cases */
72  if(size > (INT_MAX-32) )
73  return NULL;
74 
75 #if CONFIG_MEMALIGN_HACK
76  ptr = malloc(size+32);
77  if(!ptr)
78  return ptr;
79  diff= ((-(long)ptr - 1)&31) + 1;
80  ptr = (char*)ptr + diff;
81  ((char*)ptr)[-1]= diff;
82 #elif HAVE_POSIX_MEMALIGN
83  if (posix_memalign(&ptr,32,size))
84  ptr = NULL;
85 #elif HAVE_MEMALIGN
86  ptr = memalign(32,size);
87  /* Why 64?
88  Indeed, we should align it:
89  on 4 for 386
90  on 16 for 486
91  on 32 for 586, PPro - K6-III
92  on 64 for K7 (maybe for P3 too).
93  Because L1 and L2 caches are aligned on those values.
94  But I don't want to code such logic here!
95  */
96  /* Why 32?
97  For AVX ASM. SSE / NEON needs only 16.
98  Why not larger? Because I did not see a difference in benchmarks ...
99  */
100  /* benchmarks with P3
101  memalign(64)+1 3071,3051,3032
102  memalign(64)+2 3051,3032,3041
103  memalign(64)+4 2911,2896,2915
104  memalign(64)+8 2545,2554,2550
105  memalign(64)+16 2543,2572,2563
106  memalign(64)+32 2546,2545,2571
107  memalign(64)+64 2570,2533,2558
108 
109  BTW, malloc seems to do 8-byte alignment by default here.
110  */
111 #else
112  ptr = malloc(size);
113 #endif
114  return ptr;
115 }
116 
117 void *av_realloc(void *ptr, size_t size)
118 {
119 #if CONFIG_MEMALIGN_HACK
120  int diff;
121 #endif
122 
123  /* let's disallow possible ambiguous cases */
124  if(size > (INT_MAX-16) )
125  return NULL;
126 
127 #if CONFIG_MEMALIGN_HACK
128  //FIXME this isn't aligned correctly, though it probably isn't needed
129  if(!ptr) return av_malloc(size);
130  diff= ((char*)ptr)[-1];
131  return (char*)realloc((char*)ptr - diff, size + diff) + diff;
132 #else
133  return realloc(ptr, size);
134 #endif
135 }
136 
137 void av_free(void *ptr)
138 {
139 #if CONFIG_MEMALIGN_HACK
140  if (ptr)
141  free((char*)ptr - ((char*)ptr)[-1]);
142 #else
143  free(ptr);
144 #endif
145 }
146 
147 void av_freep(void *arg)
148 {
149  void **ptr= (void**)arg;
150  av_free(*ptr);
151  *ptr = NULL;
152 }
153 
154 void *av_mallocz(size_t size)
155 {
156  void *ptr = av_malloc(size);
157  if (ptr)
158  memset(ptr, 0, size);
159  return ptr;
160 }
161 
162 char *av_strdup(const char *s)
163 {
164  char *ptr= NULL;
165  if(s){
166  int len = strlen(s) + 1;
167  ptr = av_malloc(len);
168  if (ptr)
169  memcpy(ptr, s, len);
170  }
171  return ptr;
172 }
173