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get_generic_seed() for the cases without /dev/random and AV_READ_TIME

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Originally committed as revision 24102 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2010-07-07 23:47:48 +00:00
parent ce1cd1cba2
commit c84d5aa74f
1 changed files with 34 additions and 6 deletions
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40
libavutil/random_seed.c
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@ -21,6 +21,7 @@
#include <unistd.h>
#include <fcntl.h>
#include "timer.h"
#include "time.h"
#include "random_seed.h"
#include "avutil.h"
@ -37,6 +38,38 @@ static int read_random(uint32_t *dst, const char *file)
return err;
}
static uint32_t get_generic_seed(void)
{
int last_t=0;
int bits=0;
uint64_t random=0;
int i;
int s=0;
for(i=0;bits<64;i++){
int t= clock()>>s;
if(last_t && t != last_t){
if(i<10000U && s<24){
s++;
i=t=0;
}else{
random= 2*random + (i&1);
bits++;
}
}
last_t= t;
}
#ifdef AV_READ_TIME
random ^= AV_READ_TIME();
#else
random ^= clock();
#endif
random += random>>32;
return random;
}
uint32_t av_get_random_seed(void)
{
uint32_t seed;
@ -45,12 +78,7 @@ uint32_t av_get_random_seed(void)
return seed;
if (read_random(&seed, "/dev/random") == sizeof(seed))
return seed;
#ifdef AV_READ_TIME
seed = AV_READ_TIME();
#endif
// XXX what to do ?
return seed;
return get_generic_seed();
}
#if LIBAVUTIL_VERSION_MAJOR < 51