*/
/**
- * @file mem.c
- * default memory allocator for libavutil.
+ * @file libavutil/mem.c
+ * default memory allocator for libavutil
*/
#include "config.h"
#include "mem.h"
-/* here we can use OS dependent allocation functions */
+/* here we can use OS-dependent allocation functions */
#undef free
#undef malloc
#undef realloc
-/* you can redefine av_malloc and av_free in your project to use your
+/* You can redefine av_malloc and av_free in your project to use your
memory allocator. You do not need to suppress this file because the
- linker will do it automatically */
+ linker will do it automatically. */
void *av_malloc(unsigned int size)
{
ptr = (char*)ptr + diff;
((char*)ptr)[-1]= diff;
#elif HAVE_POSIX_MEMALIGN
- posix_memalign(&ptr,16,size);
+ if (posix_memalign(&ptr,16,size))
+ ptr = NULL;
#elif HAVE_MEMALIGN
ptr = memalign(16,size);
/* Why 64?
Indeed, we should align it:
on 4 for 386
on 16 for 486
- on 32 for 586, PPro - k6-III
+ on 32 for 586, PPro - K6-III
on 64 for K7 (maybe for P3 too).
Because L1 and L2 caches are aligned on those values.
But I don't want to code such logic here!
/* Why 16?
Because some CPUs need alignment, for example SSE2 on P4, & most RISC CPUs
it will just trigger an exception and the unaligned load will be done in the
- exception handler or it will just segfault (SSE2 on P4)
+ exception handler or it will just segfault (SSE2 on P4).
Why not larger? Because I did not see a difference in benchmarks ...
*/
- /* benchmarks with p3
+ /* benchmarks with P3
memalign(64)+1 3071,3051,3032
memalign(64)+2 3051,3032,3041
memalign(64)+4 2911,2896,2915
memalign(64)+32 2546,2545,2571
memalign(64)+64 2570,2533,2558
- btw, malloc seems to do 8 byte alignment by default here
+ BTW, malloc seems to do 8-byte alignment by default here.
*/
#else
ptr = malloc(size);