mirror of https://code.videolan.org/videolan/vlc
63 lines
1.9 KiB
C
63 lines
1.9 KiB
C
/*****************************************************************************
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* nrand48.c: POSIX erand48(), jrand48() and nrand48() replacements
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*****************************************************************************
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* Copyright © 2010 Rémi Denis-Courmont
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*
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* This program 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
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
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*****************************************************************************/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <inttypes.h>
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static uint64_t iterate48 (unsigned short subi[3])
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{
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const uint64_t a = UINT64_C(0x5DEECE66D);
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const unsigned c = 13;
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const uint64_t mask = UINT64_C(0xFFFFFFFFFFFF); // 48 bits
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uint64_t x = ((uint64_t)subi[0] << 32)
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| ((uint32_t)subi[1] << 16)
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| subi[2];
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x *= a;
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x += c;
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x &= mask;
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subi[0] = (x >> 32) & 0xFFFF;
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subi[1] = (x >> 16) & 0xFFFF;
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subi[2] = (x >> 0) & 0XFFFF;
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return x;
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}
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double erand48 (unsigned short subi[3])
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{
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uint64_t r = iterate48 (subi);
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return ((double)r) / 281474976710655.;
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}
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long jrand48 (unsigned short subi[3])
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{
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return ((int64_t)iterate48 (subi)) >> 16;
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}
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long nrand48 (unsigned short subi[3])
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{
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return iterate48 (subi) >> 17;
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}
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