48 lines
1.8 KiB
C
48 lines
1.8 KiB
C
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/*
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Copyright (c) 2006-2020 Chung, Hyung-Hwan. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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1. Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR
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IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <hawk-utl.h>
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/* Park-Miller "minimal standard" 31 bit
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* pseudo-random number generator, implemented
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* with David G. Carta's optimisation: with
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* 32 bit math and without division.
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*/
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hawk_uint32_t hawk_rand31 (hawk_uint32_t seed)
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{
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hawk_uint32_t hi, lo;
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if (seed == 0) seed++;
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lo = 16807 * (seed & 0xFFFF);
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hi = 16807 * (seed >> 16);
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lo += (hi & 0x7FFF) << 16;
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lo += hi >> 15;
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if (lo > 0x7FFFFFFFul) lo -= 0x7FFFFFFFul;
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return lo;
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}
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