src/bjprng.c

   1 /* coded by Ketmar // Vampire Avalon (psyc://ketmar.no-ip.org/~Ketmar)
   2  * Understanding is not required. Only obedience.
   3  *
   4  * This program is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17 #include <fcntl.h>
  18 #include <stdlib.h>
  19 #include <time.h>
  20 #include <unistd.h>
  21
  22 #include <sys/stat.h>
  23 #include <sys/types.h>
  24
  25 #include "bjprng.h"
  26
  27
  28 ////////////////////////////////////////////////////////////////////////////////
  29 // by Bob Jenkins
  30 // public domain
  31 // http://burtleburtle.net/bob/rand/smallprng.html
  32 //
  33 ////////////////////////////////////////////////////////////////////////////////
  34 #define BJPRNG_ROT(x,k)  (((x)<<(k))|((x)>>(32-(k))))
  35
  36
  37 ////////////////////////////////////////////////////////////////////////////////
  38 uint32_t bjprngRand (BJRandCtx *x) {
  39   uint32_t e;
  40   /* original:
  41      e = x->a-BJPRNG_ROT(x->b, 27);
  42   x->a = x->b^BJPRNG_ROT(x->c, 17);
  43   x->b = x->c+x->d;
  44   x->c = x->d+e;
  45   x->d = e+x->a;
  46   */
  47   /* better, but slower at least in idiotic m$vc */
  48      e = x->a-BJPRNG_ROT(x->b, 23);
  49   x->a = x->b^BJPRNG_ROT(x->c, 16);
  50   x->b = x->c+BJPRNG_ROT(x->d, 11);
  51   x->c = x->d+e;
  52   x->d = e+x->a;
  53   //
  54   return x->d;
  55 }
  56
  57
  58 void bjprngInit (BJRandCtx *x, uint32_t seed) {
  59   x->a = 0xf1ea5eed;
  60   x->b = x->c = x->d = seed;
  61   for (int i = 0; i < 20; ++i) bjprngRand(x);
  62 }
  63
  64
  65 static inline uint32_t hashint (uint32_t a) {
  66   a -= (a<<6);
  67   a ^= (a>>17);
  68   a -= (a<<9);
  69   a ^= (a<<4);
  70   a -= (a<<3);
  71   a ^= (a<<10);
  72   a ^= (a>>15);
  73   return a;
  74 }
  75
  76
  77 uint32_t bjprngGenRandSeed (void) {
  78 #ifndef OS_NT
  79   uint32_t res = (uint32_t)getpid()^(uint32_t)time(NULL);
  80   int fd = open("/dev/urandom", O_RDONLY);
  81   if (fd >= 0) {
  82     read(fd, &res, sizeof(res));
  83     close(fd);
  84   }
  85 #else
  86   res = (uint32_t)GetTickCount()^(uint32_t)GetCurrentProcessId();
  87 #endif
  88   if ((res = hashint(res)) == 0) res = 45;
  89   return res;
  90 }