git.zerfleddert.de Git - proxmark3-svn/blob - common/random.c

   1 #include "random.h"
   2
   3 static uint32_t g_nextrandom;
   4
   5 /* Generates a (non-cryptographically secure) 32-bit random number.
   6  *
   7  * We don't have an implementation of the "rand" function. Instead we use a
   8  * method of seeding with the time it took to call "autoseed" from first run.
   9  *
  10  * https://github.com/Proxmark/proxmark3/pull/209/commits/f9c1dcd9f6e68a8c07cffed697a9c4c8caed6015
  11  *
  12  * Iceman,  rand needs to be fast.
  13  * https://software.intel.com/en-us/articles/fast-random-number-generator-on-the-intel-pentiumr-4-processor/
  14  */
  15
  16 inline void fast_prand(){
  17         fast_prandEx(GetTickCount());
  18 }
  19 inline void fast_prandEx(uint32_t seed) {
  20         g_nextrandom = seed;
  21 }
  22
  23 uint32_t prand() {
  24 //      g_nextrandom *= 6364136223846793005;
  25 //      g_nextrandom += 1;
  26 //return (uint32_t)(g_nextrandom >> 32) % 0xffffffff;
  27         g_nextrandom = (214013 * g_nextrandom + 2531011);
  28         return (g_nextrandom>>16) & 0xFFFF;
  29 }
  30