1  /* Reentrant random function from POSIX.1c.
       2     Copyright (C) 1996-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library 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 GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <stdlib.h>
      20  
      21  
      22  /* This algorithm is mentioned in the ISO C standard, here extended
      23     for 32 bits.  */
      24  int
      25  rand_r (unsigned int *seed)
      26  {
      27    unsigned int next = *seed;
      28    int result;
      29  
      30    next *= 1103515245;
      31    next += 12345;
      32    result = (unsigned int) (next / 65536) % 2048;
      33  
      34    next *= 1103515245;
      35    next += 12345;
      36    result <<= 10;
      37    result ^= (unsigned int) (next / 65536) % 1024;
      38  
      39    next *= 1103515245;
      40    next += 12345;
      41    result <<= 10;
      42    result ^= (unsigned int) (next / 65536) % 1024;
      43  
      44    *seed = next;
      45  
      46    return result;
      47  }