glibc/stdlib/erand48_r.c

/* Copyright (C) 1995 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <math.h>
#include <stdlib.h>

int
erand48_r (xsubi, buffer, result)
     unsigned short int xsubi[3];
     struct drand48_data *buffer;
     double *result;
{
  int i;

  /* Be generous for the arguments, detect some errors.  */
  if (result == NULL)
    {
      errno = EFAULT;
      return -1;
    }

  /* Compute next state.  */
  if (__drand48_iterate (xsubi, buffer) < 0)
    return -1;

  *result = 0.0;
  for (i = 4 / sizeof (unsigned short int); i >= 0; --i)
    {
      double factor = ldexp (1.0, (i - 6) * sizeof (unsigned short int));

      *result += factor * (double) xsubi[i];
    }

  return 0;
}