libc/stdlib/rand.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2008  Tomas 'ZeXx86' Jedrzejek (zexx86@gmail.com)
   4  *
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19
  20 /* magic number */
  21 #define RAND_MAX        0x7fffffff
  22
  23 static unsigned long next = 1;
  24
  25
  26 static int do_rand (unsigned long *ctx)
  27 {
  28         return ((*ctx = *ctx * 1103515245 + 12345) % ((unsigned long) RAND_MAX + 1));
  29 }
  30
  31 int rand_r (unsigned int *ctx)
  32 {
  33         unsigned long val = (unsigned long) *ctx;
  34         *ctx = do_rand (&val);
  35
  36         return (int) *ctx;
  37 }
  38
  39 int rand ()
  40 {
  41         return do_rand (&next);
  42 }
  43
  44 void srand (unsigned int seed)
  45 {
  46         next = seed;
  47 }