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libavutil
mem.c
Go to the documentation of this file.
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/*
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* default memory allocator for libavutil
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* Copyright (c) 2002 Fabrice Bellard
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "
config.h
"
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#if HAVE_MALLOC_H
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#include <malloc.h>
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#endif
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#include "
avutil.h
"
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#include "
mem.h
"
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/* here we can use OS-dependent allocation functions */
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#undef free
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#undef malloc
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#undef realloc
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#ifdef MALLOC_PREFIX
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#define malloc AV_JOIN(MALLOC_PREFIX, malloc)
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#define memalign AV_JOIN(MALLOC_PREFIX, memalign)
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#define posix_memalign AV_JOIN(MALLOC_PREFIX, posix_memalign)
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#define realloc AV_JOIN(MALLOC_PREFIX, realloc)
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#define free AV_JOIN(MALLOC_PREFIX, free)
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void
*
malloc
(
size_t
size
);
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void
*memalign(
size_t
align,
size_t
size
);
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int
posix_memalign(
void
**ptr,
size_t
align,
size_t
size
);
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void
*
realloc
(
void
*ptr,
size_t
size
);
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void
free
(
void
*ptr);
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#endif
/* MALLOC_PREFIX */
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/* You can redefine av_malloc and av_free in your project to use your
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memory allocator. You do not need to suppress this file because the
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linker will do it automatically. */
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void
*
av_malloc
(
size_t
size
)
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{
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void
*ptr =
NULL
;
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#if CONFIG_MEMALIGN_HACK
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long
diff;
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#endif
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/* let's disallow possible ambiguous cases */
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if
(size > (INT_MAX-32) )
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return
NULL
;
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#if CONFIG_MEMALIGN_HACK
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ptr =
malloc
(size+32);
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if
(!ptr)
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return
ptr;
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diff= ((-(long)ptr - 1)&31) + 1;
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ptr = (
char
*)ptr + diff;
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((
char
*)ptr)[-1]= diff;
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#elif HAVE_POSIX_MEMALIGN
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if
(posix_memalign(&ptr,32,size))
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ptr =
NULL
;
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#elif HAVE_MEMALIGN
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ptr = memalign(32,size);
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/* Why 64?
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Indeed, we should align it:
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on 4 for 386
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on 16 for 486
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on 32 for 586, PPro - K6-III
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on 64 for K7 (maybe for P3 too).
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Because L1 and L2 caches are aligned on those values.
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But I don't want to code such logic here!
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*/
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/* Why 32?
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For AVX ASM. SSE / NEON needs only 16.
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Why not larger? Because I did not see a difference in benchmarks ...
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*/
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/* benchmarks with P3
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memalign(64)+1 3071,3051,3032
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memalign(64)+2 3051,3032,3041
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memalign(64)+4 2911,2896,2915
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memalign(64)+8 2545,2554,2550
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memalign(64)+16 2543,2572,2563
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memalign(64)+32 2546,2545,2571
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memalign(64)+64 2570,2533,2558
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BTW, malloc seems to do 8-byte alignment by default here.
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*/
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#else
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ptr =
malloc
(size);
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#endif
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return
ptr;
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}
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void
*
av_realloc
(
void
*ptr,
size_t
size
)
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{
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#if CONFIG_MEMALIGN_HACK
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int
diff;
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#endif
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/* let's disallow possible ambiguous cases */
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if
(size > (INT_MAX-16) )
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return
NULL
;
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#if CONFIG_MEMALIGN_HACK
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//FIXME this isn't aligned correctly, though it probably isn't needed
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if
(!ptr)
return
av_malloc
(size);
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diff= ((
char
*)ptr)[-1];
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return
(
char
*)
realloc
((
char
*)ptr - diff, size + diff) + diff;
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#else
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return
realloc
(ptr, size);
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#endif
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}
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void
av_free
(
void
*ptr)
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{
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#if CONFIG_MEMALIGN_HACK
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if
(ptr)
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free
((
char
*)ptr - ((
char
*)ptr)[-1]);
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#else
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free
(ptr);
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#endif
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}
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void
av_freep
(
void
*arg)
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{
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void
**ptr= (
void
**)arg;
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av_free
(*ptr);
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*ptr =
NULL
;
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}
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void
*
av_mallocz
(
size_t
size
)
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{
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void
*ptr =
av_malloc
(size);
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if
(ptr)
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memset(ptr, 0, size);
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return
ptr;
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}
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char
*
av_strdup
(
const
char
*s)
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{
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char
*ptr=
NULL
;
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if
(s){
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int
len
= strlen(s) + 1;
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ptr =
av_malloc
(len);
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if
(ptr)
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memcpy(ptr, s, len);
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}
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return
ptr;
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}
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