1 /* Copyright (C) 1995, 1997, 2001 Free Software Foundation, Inc. 2 This file is part of the GNU C Library. 3 Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995. 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, write to the Free 17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 18 02111-1307 USA. */ 19 20 #include <ieee754.h> 21 #include <stdlib.h> 22 #include <limits.h> 23 24 25 int 26 __erand48_r (xsubi, buffer, result) 27 unsigned short int xsubi[3]; 28 struct drand48_data *buffer; 29 double *result; 30 { 31 union ieee754_double temp; 32 33 /* Compute next state. */ 34 if (__drand48_iterate (xsubi, buffer) < 0) 35 return -1; 36 37 /* Construct a positive double with the 48 random bits distributed over 38 its fractional part so the resulting FP number is [0.0,1.0). */ 39 40 temp.ieee.negative = 0; 41 temp.ieee.exponent = IEEE754_DOUBLE_BIAS; 42 temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12); 43 temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4); 44 45 /* Please note the lower 4 bits of mantissa1 are always 0. */ 46 *result = temp.d - 1.0; 47 48 return 0; 49 } 50 weak_alias (__erand48_r, erand48_r) 51