Blame stdlib/erand48_r.c

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/* Copyright (C) 1995-2018 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 Lesser General Public
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   License as published by the Free Software Foundation; either
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   version 2.1 of the 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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   Lesser General Public License for more details.
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   You should have received a copy of the GNU Lesser General Public
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   License along with the GNU C Library; if not, see
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   <http://www.gnu.org/licenses/>.  */
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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 (unsigned short int xsubi[3], 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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  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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  /* 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)