random.c

   1 #include <stdio.h>
   2
   3 #include "random.h"
   4
   5
   6 /* Simple Park-Miller */
   7
   8 static unsigned long pmseed = 29264;
   9
  10 void
  11 fast_srandom(unsigned long seed_)
  12 {
  13         pmseed = seed_;
  14 }
  15
  16 unsigned long
  17 fast_random(unsigned int max)
  18 {
  19         unsigned long hi, lo;
  20         lo = 16807 * (pmseed & 0xffff);
  21         hi = 16807 * (pmseed >> 16);
  22         lo += (hi & 0x7fff) << 16;
  23         lo += hi >> 15;
  24         pmseed = (lo & 0x7fffffff) + (lo >> 31);
  25         return ((pmseed & 0xffff) * max) >> 16;
  26 }