60 lines
2.0 KiB
C
60 lines
2.0 KiB
C
/* Copyright (C) 1995, 1997 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <ieee754.h>
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#include <stdlib.h>
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#include <limits.h>
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int
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__erand48_r (xsubi, buffer, result)
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unsigned short int xsubi[3];
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struct drand48_data *buffer;
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double *result;
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{
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union ieee754_double temp;
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/* Compute next state. */
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if (__drand48_iterate (xsubi, buffer) < 0)
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return -1;
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/* Construct a positive double with the 48 random bits distributed over
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its fractional part so the resulting FP number is [0.0,1.0). */
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#if USHRT_MAX == 65535
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temp.ieee.negative = 0;
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temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
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temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12);
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temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4);
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#elif USHRT_MAX == 2147483647
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temp.ieee.negative = 0;
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temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
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temp.ieee.mantissa0 = (xsubi[1] << 4) | (xsubi[0] >> 28);
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temp.ieee.mantissa1 = ((xsubi[0] & 0xfffffff) << 4);
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#else
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# error Unsupported size of short int
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#endif
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/* Please note the lower 4 bits of mantissa1 are always 0. */
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*result = temp.d - 1.0;
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return 0;
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}
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weak_alias (__erand48_r, erand48_r)
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