81 lines
2.4 KiB
C
81 lines
2.4 KiB
C
/* Copyright (C) 1995, 1996 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 <errno.h>
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#include <stdlib.h>
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#include <limits.h>
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#include <sys/types.h>
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/* Global state for non-reentrant functions. */
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struct drand48_data __libc_drand48_data;
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int
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__drand48_iterate (xsubi, buffer)
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unsigned short int xsubi[3];
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struct drand48_data *buffer;
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{
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u_int64_t X, a, result;
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/* Initialize buffer, if not yet done. */
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if (!buffer->init)
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{
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#if (USHRT_MAX == 0xffffU)
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buffer->a[2] = 0x5;
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buffer->a[1] = 0xdeec;
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buffer->a[0] = 0xe66d;
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#else
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buffer->a[2] = 0x5deecUL;
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buffer->a[1] = 0xe66d0000UL;
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buffer->a[0] = 0;
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#endif
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buffer->c = 0xb;
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buffer->init = 1;
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}
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/* Do the real work. We choose a data type which contains at least
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48 bits. Because we compute the modulus it does not care how
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many bits really are computed. */
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if (sizeof (unsigned short int) == 2)
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{
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X = (u_int64_t)xsubi[2] << 32 | (u_int64_t)xsubi[1] << 16 | xsubi[0];
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a = ((u_int64_t)buffer->a[2] << 32 | (u_int64_t)buffer->a[1] << 16
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| buffer->a[0]);
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result = X * a + buffer->c;
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xsubi[0] = result & 0xffff;
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xsubi[1] = (result >> 16) & 0xffff;
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xsubi[2] = (result >> 32) & 0xffff;
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}
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else
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{
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X = (u_int64_t)xsubi[2] << 16 | xsubi[1] >> 16;
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a = (u_int64_t)buffer->a[2] << 16 | buffer->a[1] >> 16;
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result = X * a + buffer->c;
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xsubi[0] = result >> 16 & 0xffffffffl;
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xsubi[1] = result << 16 & 0xffff0000l;
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}
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return 0;
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}
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