Back to index

glibc  2.9
erand48_r.c
Go to the documentation of this file.
00001 /* Copyright (C) 1995, 1997, 2001 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <ieee754.h>
00021 #include <stdlib.h>
00022 #include <limits.h>
00023 
00024 
00025 int
00026 __erand48_r (xsubi, buffer, result)
00027      unsigned short int xsubi[3];
00028      struct drand48_data *buffer;
00029      double *result;
00030 {
00031   union ieee754_double temp;
00032 
00033   /* Compute next state.  */
00034   if (__drand48_iterate (xsubi, buffer) < 0)
00035     return -1;
00036 
00037   /* Construct a positive double with the 48 random bits distributed over
00038      its fractional part so the resulting FP number is [0.0,1.0).  */
00039 
00040   temp.ieee.negative = 0;
00041   temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
00042   temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12);
00043   temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4);
00044 
00045   /* Please note the lower 4 bits of mantissa1 are always 0.  */
00046   *result = temp.d - 1.0;
00047 
00048   return 0;
00049 }
00050 weak_alias (__erand48_r, erand48_r)