src/compat-rand.h

   1 #ifndef _COMPAT_RAND_H
   2 #define _COMPAT_RAND_H
   3
   4 /*
   5  * compat-rand.h
   6  *
   7  * Userspace RCU library - rand/rand_r Compatibility Header
   8  *
   9  * Copyright 1996 - Ulrich Drepper <drepper@cygnus.com >
  10  * Copyright 2013 - Pierre-Luc St-Charles <pierre-luc.st-charles@polymtl.ca>
  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  * This library is free software; you can redistribute it and/or
  17  * modify it under the terms of the GNU Lesser General Public
  18  * License as published by the Free Software Foundation; either
  19  * version 2.1 of the License, or (at your option) any later version.
  20  *
  21  * This library is distributed in the hope that it will be useful,
  22  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  23  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  24  * Lesser General Public License for more details.
  25  *
  26  * You should have received a copy of the GNU Lesser General Public
  27  * License along with this library; if not, write to the Free Software
  28  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  29  */
  30
  31 #ifndef HAVE_RAND_R
  32 /*
  33  * Reentrant random function from POSIX.1c.
  34  * Copyright (C) 1996, 1999 Free Software Foundation, Inc.
  35  * This file is part of the GNU C Library.
  36  * Contributed by Ulrich Drepper <drepper@cygnus.com <mailto:drepper@cygnus.com>>, 1996.
  37  */
  38 static inline int rand_r(unsigned int *seed)
  39 {
  40        unsigned int next = *seed;
  41        int result;
  42
  43        next *= 1103515245;
  44        next += 12345;
  45        result = (unsigned int) (next / 65536) % 2048;
  46
  47        next *= 1103515245;
  48        next += 12345;
  49        result <<= 10;
  50        result ^= (unsigned int) (next / 65536) % 1024;
  51
  52        next *= 1103515245;
  53        next += 12345;
  54        result <<= 10;
  55        result ^= (unsigned int) (next / 65536) % 1024;
  56
  57        *seed = next;
  58
  59        return result;
  60 }
  61 #endif /* HAVE_RAND_R */
  62
  63 #endif /* _COMPAT_RAND_H */