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Add av_compare_mod()

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Originally committed as revision 23551 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2010-06-09 17:27:42 +00:00
parent 130b096aea
commit 65db0587a8
2 changed files with 16 additions and 0 deletions
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7
libavutil/mathematics.c
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@ -144,6 +144,13 @@ int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b){
return 0; return 0;
} }
int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod){
int64_t c= (a-b) & (mod-1);
if(c > (mod>>1))
c-= mod;
return c;
}
#ifdef TEST #ifdef TEST
#include "integer.h" #include "integer.h"
#undef printf #undef printf

9
libavutil/mathematics.h
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@ -94,5 +94,14 @@ int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;
*/ */
int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b); int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b);
/**
* Compare 2 integers modulo mod.
* That is we compare integers a and b for which only the least significant log2(mod) bits are known
* @param mod must be a power of 2
* @returns a negative value if a is smaller than b
* a positiv value if a is greater than b
* 0 if a equals b
*/
int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod);
#endif /* AVUTIL_MATHEMATICS_H */ #endif /* AVUTIL_MATHEMATICS_H */