stupid cross platform randomness issue, plus other fixes

include/jsw_rand.c

@@ -0,0 +1,73 @@
+#include <limits.h>
+#include <time.h>
+#include "jsw_rand.h"
+
+#define N 624
+#define M 397
+#define A 0x9908b0dfUL
+#define U 0x80000000UL
+#define L 0x7fffffffUL
+
+/* Internal state */
+static unsigned long x[N];
+static int next;
+
+/* Initialize internal state */
+void jsw_seed ( unsigned long s )
+{
+  int i;
+
+  x[0] = s & 0xffffffffUL;
+
+  for ( i = 1; i < N; i++ ) {
+    x[i] = ( 1812433253UL 
+      * ( x[i - 1] ^ ( x[i - 1] >> 30 ) ) + i );
+    x[i] &= 0xffffffffUL;
+  }
+}
+
+/* Mersenne Twister */
+unsigned long jsw_rand ( void )
+{
+  unsigned long y, a;
+  int i;
+
+  /* Refill x if exhausted */
+  if ( next == N ) {
+    next = 0;
+
+    for ( i = 0; i < N - 1; i++ ) {
+      y = ( x[i] & U ) | x[i + 1] & L;
+      a = ( y & 0x1UL ) ? A : 0x0UL;
+      x[i] = x[( i + M ) % N] ^ ( y >> 1 ) ^ a;
+    }
+
+    y = ( x[N - 1] & U ) | x[0] & L;
+    a = ( y & 0x1UL ) ? A : 0x0UL;
+    x[N - 1] = x[M - 1] ^ ( y >> 1 ) ^ a;
+  }
+
+  y = x[next++];
+
+  /* Improve distribution */
+  y ^= (y >> 11);
+  y ^= (y << 7) & 0x9d2c5680UL;
+  y ^= (y << 15) & 0xefc60000UL;
+  y ^= (y >> 18);
+
+  return y;
+}
+
+/* Portable time seed */
+unsigned jsw_time_seed()
+{
+  time_t now = time ( 0 );
+  unsigned char *p = (unsigned char *)&now;
+  unsigned seed = 0;
+  size_t i;
+
+  for ( i = 0; i < sizeof now; i++ )
+    seed = seed * ( UCHAR_MAX + 2U ) + p[i];
+
+  return seed;
+}

include/jsw_rand.h

@@ -0,0 +1,13 @@
+#ifndef JSW_RAND_H
+#define JSW_RAND_H
+
+/* Seed the RNG. Must be called first */
+void          jsw_seed ( unsigned long s );
+
+/* Return a 32-bit random number */
+unsigned long jsw_rand ( void );
+
+/* Seed with current system time */
+unsigned      jsw_time_seed();
+
+#endif