client/src/prng.c

   1 //-----------------------------------------------------------------------------
   2 //-----------------------------------------------------------------------------
   3 // Burtle Prng - Modified.   42iterations instead of 20.
   4 // ref: http://burtleburtle.net/bob/rand/smallprng.html
   5 //-----------------------------------------------------------------------------
   6 #include "prng.h"
   7
   8 #define rot(x,k) (((x)<<(k))|((x)>>(32-(k))))
   9 uint32_t burtle_get_mod(prng_ctx *x) {
  10     uint32_t e = x->a - rot(x->b, 21);
  11     x->a = x->b ^ rot(x->c, 19);
  12     x->b = x->c + rot(x->d, 6);
  13     x->c = x->d + e;
  14     x->d = e + x->a;
  15     return x->d;
  16 }
  17
  18 void burtle_init_mod(prng_ctx *x, uint32_t seed) {
  19     x->a = 0xf1ea5eed;
  20     x->b = x->c = x->d = seed;
  21     for (uint8_t i = 0; i < 42; ++i) {
  22         (void)burtle_get_mod(x);
  23     }
  24 }
  25
  26 void burtle_init(prng_ctx *x, uint32_t seed) {
  27     uint32_t i;
  28     x->a = 0xf1ea5eed, x->b = x->c = x->d = seed;
  29     for (i = 0; i < 20; ++i) {
  30         (void)burtle_get_mod(x);
  31     }
  32 }
  33
  34
  35 uint32_t GetSimplePrng(uint32_t seed) {
  36     seed *= 0x19660D;
  37     seed += 0x3C6EF35F;
  38     return seed;
  39 }