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, version 3 of the License ONLY.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15  */
  16 #include <fcntl.h>
  17 #include <stdlib.h>
  18 #include <time.h>
  19 #include <unistd.h>
  20
  21 #include <sys/stat.h>
  22 #include <sys/types.h>
  23
  24 #include "bjprng.h"
  25
  26
  27 static inline uint32_t hashint (uint32_t a) {
  28   a -= (a<<6);
  29   a ^= (a>>17);
  30   a -= (a<<9);
  31   a ^= (a<<4);
  32   a -= (a<<3);
  33   a ^= (a<<10);
  34   a ^= (a>>15);
  35   return a;
  36 }
  37
  38
  39 void bjprngRandomize (BJRandCtx *rng) {
  40 #ifndef OS_NT
  41   uint32_t res0, res1;
  42   int fd = open("/dev/urandom", O_RDONLY);
  43   if (fd >= 0) {
  44     read(fd, &res0, sizeof(res0));
  45     read(fd, &res1, sizeof(res1));
  46     close(fd);
  47   } else {
  48     res0 = hashint((uint32_t)getpid()^(uint32_t)time(NULL));
  49     res1 = hashint((uint32_t)getpid())^hashint((uint32_t)time(NULL));
  50   }
  51 #else
  52   uint32_t res0 = hashint((uint32_t)GetTickCount()^(uint32_t)GetCurrentProcessId());
  53   uint32_t res1 = hashint((uint32_t)GetTickCount())^hashint((uint32_t)GetCurrentProcessId());
  54 #endif
  55   rng->state = (((uint64_t)res0)<<32)|res1;
  56   rng->inc = 1;
  57   for (res0 = 16; res0 > 0; --res0) bjprngRand(rng);
  58 }
  59
  60
  61 // *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
  62 // Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
  63 uint32_t bjprngRand (BJRandCtx *rng) {
  64   uint64_t oldstate = rng->state;
  65   // advance internal state
  66   rng->state = oldstate*6364136223846793005ULL+(rng->inc|1);
  67   // calculate output function (XSH RR), uses old state for max ILP
  68   uint32_t xorshifted = ((oldstate>>18u)^oldstate)>>27u;
  69   uint32_t rot = oldstate>>59u;
  70   return (xorshifted>>rot)|(xorshifted<<((-rot)&31));
  71 }