From 47cf98efcb88320f45b22a10677f434c51ea4e66 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Sat, 6 Mar 2010 01:31:17 +0000
Subject: [PATCH] Make trasher use a well defined random number generator and
 allow the seed to be specified on the cmd line.

Originally committed as revision 22228 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 tools/trasher.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/tools/trasher.c b/tools/trasher.c
index c7a0c7aa6a..12214f50ea 100644
--- a/tools/trasher.c
+++ b/tools/trasher.c
@@ -24,13 +24,18 @@
 #include <time.h>
 #include <inttypes.h>
 
+static uint32_t state;
+static uint32_t ran(void){
+    return state= state*1664525+1013904223;
+}
+
 int main(int argc, char** argv)
 {
     FILE *f;
     int count, maxburst, length;
 
-    if (argc < 4){
-        printf("USAGE: trasher <filename> <count> <maxburst>\n");
+    if (argc < 5){
+        printf("USAGE: trasher <filename> <count> <maxburst> <seed>\n");
         return 1;
     }
 
@@ -41,16 +46,15 @@ int main(int argc, char** argv)
     }
     count= atoi(argv[2]);
     maxburst= atoi(argv[3]);
-
-    srandom (time (0));
+    state= atoi(argv[4]);
 
     fseek(f, 0, SEEK_END);
     length= ftell(f);
     fseek(f, 0, SEEK_SET);
 
     while(count--){
-        int burst= 1 + random() * (uint64_t) (abs(maxburst)-1) / RAND_MAX;
-        int pos= random() * (uint64_t) length / RAND_MAX;
+        int burst= 1 + ran() * (uint64_t) (abs(maxburst)-1) / UINT32_MAX;
+        int pos= ran() * (uint64_t) length / UINT32_MAX;
         fseek(f, pos, SEEK_SET);
 
         if(maxburst<0) burst= -maxburst;
@@ -59,7 +63,7 @@ int main(int argc, char** argv)
             continue;
 
         while(burst--){
-            int val= random() * 256ULL / RAND_MAX;
+            int val= ran() * 256ULL / UINT32_MAX;
 
             if(maxburst<0) val=0;