Changeset 1547Tweet

Timestamp:

Jan 3, 2007, 10:20:22 PM (14 years ago)

Author:

Sam Hocevar

Message:

• No longer use the OS's PRNG, we use our own (based on a Dr Dobbs article from November 1985, page 91).

File:

• zzuf/trunk/src/random.c (modified) (1 diff)

zzuf/trunk/src/random.c

@@ -28 +28 @@
 #include "random.h"
 
+static unsigned long ctx = 1;
+
 void _zz_srand(uint32_t seed)
 {
-    srand(seed ^ 0x12345678);
+    ctx = (seed ^ 0x12345678);
 }
 
 uint32_t _zz_rand(uint32_t max)
 {
-    if(max <= RAND_MAX)
-        return rand() % max;
+    /* Could be better, but do we care? */
+    long hi, lo, x;
 
-    /* Could be better, but do we care? */
-    return (uint32_t)((max * 1.0) * (rand() / (RAND_MAX + 1.0)));
+    hi = ctx / 12773L;
+    lo = ctx % 12773L;
+    x = 16807L * lo - 2836L * hi;
+    if(x <= 0)
+        x += 0x7fffffffL;
+    return (ctx = x) % (unsigned long)max;
 }