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* default memory allocator for libavutil
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* Copyright (c) 2002 Fabrice Bellard.
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* This file is part of FFmpeg.
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* FFmpeg 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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* FFmpeg 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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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; 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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* default memory allocator for libavutil.
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/* here we can use OS dependent allocation functions */
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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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* Memory allocation of size byte with alignment suitable for all
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* memory accesses (including vectors if available on the
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* CPU). av_malloc(0) must return a non NULL pointer.
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void *av_malloc(unsigned int size)
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#ifdef CONFIG_MEMALIGN_HACK
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/* let's disallow possible ambiguous cases */
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if(size > (INT_MAX-16) )
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#ifdef CONFIG_MEMALIGN_HACK
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ptr = malloc(size+16);
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diff= ((-(long)ptr - 1)&15) + 1;
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((char*)ptr)[-1]= diff;
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#elif defined (HAVE_MEMALIGN)
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ptr = memalign(16,size);
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Indeed, we should align it:
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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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because some cpus need alignment, for example SSE2 on P4, & most RISC cpus
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it will just trigger an exception and the unaligned load will be done in the
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exception handler or it will just segfault (SSE2 on P4)
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Why not larger? because i didnt see a difference in benchmarks ...
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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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* av_realloc semantics (same as glibc): if ptr is NULL and size > 0,
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* identical to malloc(size). If size is zero, it is identical to
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* free(ptr) and NULL is returned.
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void *av_realloc(void *ptr, unsigned int size)
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#ifdef CONFIG_MEMALIGN_HACK
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/* let's disallow possible ambiguous cases */
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if(size > (INT_MAX-16) )
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#ifdef 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 realloc(ptr - diff, size + diff) + diff;
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return realloc(ptr, size);
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* Free memory which has been allocated with av_malloc(z)() or av_realloc().
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* NOTE: ptr = NULL is explicetly allowed
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* Note2: it is recommended that you use av_freep() instead
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void av_free(void *ptr)
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/* XXX: this test should not be needed on most libcs */
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#ifdef CONFIG_MEMALIGN_HACK
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free(ptr - ((char*)ptr)[-1]);
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* Frees memory and sets the pointer to NULL.
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* @param arg pointer to the pointer which should be freed
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void av_freep(void *arg)
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void **ptr= (void**)arg;
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void *av_mallocz(unsigned int size)
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ptr = av_malloc(size);
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memset(ptr, 0, size);
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char *av_strdup(const char *s)
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ptr = av_malloc(len);
added
removed
ffmpeg/libavutil/mem.c
