# HG changeset patch
# User mas01cr
# Date 1262702700 0
# Node ID 4c4389325ae445042b84fd52c3e57514167f0275
# Parent  b82b90c6445e427282ea0f4b9b694244f3852095
Better RNG initialization

On platforms where it's available, use gettimeofday() and mix in the ~20
bits that that gives to the high (slowly-changing) bits of the seconds
since the Epoch.

diff -r b82b90c6445e -r 4c4389325ae4 audioDB.h
--- a/audioDB.h	Tue Jan 05 14:09:43 2010 +0000
+++ b/audioDB.h	Tue Jan 05 14:45:00 2010 +0000
@@ -5,6 +5,7 @@
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/time.h>
 #if !defined(WIN32)
 #include <sys/mman.h>
 #endif
@@ -16,7 +17,7 @@
 #include <map>
 #include <string>
 #include <math.h>
-#include <sys/time.h>
+#include <time.h>
 #include <assert.h>
 #include <float.h>
 #include <signal.h>
diff -r b82b90c6445e -r 4c4389325ae4 common.cpp
--- a/common.cpp	Tue Jan 05 14:09:43 2010 +0000
+++ b/common.cpp	Tue Jan 05 14:45:00 2010 +0000
@@ -39,7 +39,21 @@
     error("could not allocate Random Number Generator");
   }
   /* FIXME: maybe we should use a real source of entropy? */
-  gsl_rng_set(rng, time(NULL));
+  uint32_t seed = 0;
+#ifdef WIN32
+  seed = time(NULL);
+#else
+  struct timeval tv;
+  if(gettimeofday(&tv, NULL) == -1) {
+    error("failed to get time of day");
+  }
+  /* usec field should be less than than 2^20.  We want to mix the
+     usec field, highly-variable, into the high bits of the seconds
+     field, which will be static between closely-spaced runs.  -- CSR,
+     2010-01-05 */
+  seed = tv.tv_sec ^ (tv.tv_usec << 12);
+#endif
+  gsl_rng_set(rng, seed);
 }
 
 void audioDB::initDBHeader(const char* dbName) {