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git-svn-id: file:///Users/olsen/Code/migration-svn-zu-git/logical-line-staging/clib2/trunk@14685 87f5fb63-7c3d-0410-a384-fd976d0f7a62
81 lines
2.3 KiB
C
81 lines
2.3 KiB
C
/*
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* $Id: amiga_rangerand.c,v 1.1.1.1 2004-07-26 16:30:21 obarthel Exp $
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*
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* :ts=4
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*
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* Portable ISO 'C' (1994) runtime library for the Amiga computer
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* Copyright (c) 2002-2004 by Olaf Barthel <olsen@sourcery.han.de>
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* All rights reserved.
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*
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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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*
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* - 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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*
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* - Neither the name of Olaf Barthel nor the names of contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <exec/types.h>
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/****************************************************************************/
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#include <clib/alib_protos.h>
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/****************************************************************************/
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ULONG RangeSeed;
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/****************************************************************************/
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UWORD
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RangeRand(ULONG max_value)
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{
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ULONG next_value;
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ULONG result;
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ULONG value;
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UWORD range;
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UWORD bits;
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range = (max_value & 0xFFFF);
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bits = range - 1;
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value = RangeSeed;
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do
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{
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next_value = value + value;
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if(next_value <= value)
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next_value ^= 0x1D872B41;
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value = next_value;
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bits = bits >> 1;
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}
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while(bits != 0);
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RangeSeed = value;
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if(range == 0)
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result = value & 0xFFFF;
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else
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result = (range * (value & 0xFFFF)) >> 16;
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return((UWORD)result);
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}
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