src/compat-rand.h

   1 // SPDX-FileCopyrightText: 1996 Ulrich Drepper <drepper@cygnus.com>
   2 // SPDX-FileCopyrightText: 2013 Pierre-Luc St-Charles <pierre-luc.st-charles@polymtl.ca>
   3 //
   4 // SPDX-License-Identifier: LGPL-2.1-or-later
   5
   6 #ifndef _COMPAT_RAND_H
   7 #define _COMPAT_RAND_H
   8
   9 /*
  10  * Userspace RCU library - rand/rand_r Compatibility Header
  11  *
  12  * Note: this file is only used to simplify the code required to
  13  * use the 'rand_r(...)' system function across multiple platforms,
  14  * which might not always be referenced the same way.
  15  */
  16
  17 #ifndef HAVE_RAND_R
  18 /*
  19  * Reentrant random function from POSIX.1c.
  20  * Copyright (C) 1996, 1999 Free Software Foundation, Inc.
  21  * This file is part of the GNU C Library.
  22  * Contributed by Ulrich Drepper <drepper@cygnus.com <mailto:drepper@cygnus.com>>, 1996.
  23  */
  24 static inline int rand_r(unsigned int *seed)
  25 {
  26        unsigned int next = *seed;
  27        int result;
  28
  29        next *= 1103515245;
  30        next += 12345;
  31        result = (unsigned int) (next / 65536) % 2048;
  32
  33        next *= 1103515245;
  34        next += 12345;
  35        result <<= 10;
  36        result ^= (unsigned int) (next / 65536) % 1024;
  37
  38        next *= 1103515245;
  39        next += 12345;
  40        result <<= 10;
  41        result ^= (unsigned int) (next / 65536) % 1024;
  42
  43        *seed = next;
  44
  45        return result;
  46 }
  47 #endif /* HAVE_RAND_R */
  48
  49 #endif /* _COMPAT_RAND_H */