59 lines
2.0 KiB
C++
59 lines
2.0 KiB
C++
/**
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* @file llmodularmath.h
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* @brief Useful modular math functions.
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*
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* $LicenseInfo:firstyear=2008&license=viewergpl$
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*
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* Copyright (c) 2008-2009, Linden Research, Inc.
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*
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* Second Life Viewer Source Code
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* The source code in this file ("Source Code") is provided by Linden Lab
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* to you under the terms of the GNU General Public License, version 2.0
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* ("GPL"), unless you have obtained a separate licensing agreement
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* ("Other License"), formally executed by you and Linden Lab. Terms of
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* the GPL can be found in doc/GPL-license.txt in this distribution, or
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* online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
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*
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* There are special exceptions to the terms and conditions of the GPL as
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* it is applied to this Source Code. View the full text of the exception
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* in the file doc/FLOSS-exception.txt in this software distribution, or
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* online at
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* http://secondlifegrid.net/programs/open_source/licensing/flossexception
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*
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* By copying, modifying or distributing this software, you acknowledge
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* that you have read and understood your obligations described above,
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* and agree to abide by those obligations.
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*
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* ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
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* WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
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* COMPLETENESS OR PERFORMANCE.
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* $/LicenseInfo$
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*/
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#ifndef LLMODULARMATH_H
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#define LLMODULARMATH_H
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namespace LLModularMath
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{
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// Return difference between lhs and rhs
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// treating the U32 operands and result
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// as unsigned values of given width.
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template<int width>
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inline U32 subtract(U32 lhs, U32 rhs)
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{
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// Generate a bit mask which will truncate
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// unsigned values to given width at compile time.
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const U32 mask = (1 << width) - 1;
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// Operands are unsigned, so modular
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// arithmetic applies. If lhs < rhs,
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// difference will wrap in to lower
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// bits of result, which is then masked
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// to give a value that can be represented
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// by an unsigned value of width bits.
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return mask & (lhs - rhs);
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}
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}
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#endif
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