From c84d5aa74fcb99bf570f2891c381638744b5b289 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Wed, 7 Jul 2010 23:47:48 +0000
Subject: [PATCH] get_generic_seed() for the cases without /dev/random and
AV_READ_TIME
Originally committed as revision 24102 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
libavutil/random_seed.c | 40 ++++++++++++++++++++++++++++++++++------
1 file changed, 34 insertions(+), 6 deletions(-)
diff --git a/libavutil/random_seed.c b/libavutil/random_seed.c
index 86c60f3838e..f8e7f83d3cc 100644
--- a/libavutil/random_seed.c
+++ b/libavutil/random_seed.c
@@ -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
--
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