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/indra/llmath/llmodularmath.h

https://bitbucket.org/lindenlab/viewer-beta/
C++ Header | 52 lines | 12 code | 4 blank | 36 comment | 0 complexity | 60644ba70eedd810cc6a7f657c22b64c MD5 | raw file
 1/** 
 2 * @file llmodularmath.h
 3 * @brief Useful modular math functions.
 4 *
 5 * $LicenseInfo:firstyear=2008&license=viewerlgpl$
 6 * Second Life Viewer Source Code
 7 * Copyright (C) 2010, Linden Research, Inc.
 8 * 
 9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation;
12 * version 2.1 of the License only.
13 * 
14 * This library is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * Lesser General Public License for more details.
18 * 
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
22 * 
23 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
24 * $/LicenseInfo$
25 */
26
27#ifndef LLMODULARMATH_H
28#define LLMODULARMATH_H
29
30namespace LLModularMath
31{
32    // Return difference between lhs and rhs
33    // treating the U32 operands and result
34    // as unsigned values of given width.
35	template<int width>
36	inline U32 subtract(U32 lhs, U32 rhs)
37	{
38		// Generate a bit mask which will truncate
39		// unsigned values to given width at compile time.
40		const U32 mask = (1 << width) - 1;
41		
42		// Operands are unsigned, so modular
43		// arithmetic applies. If lhs < rhs,
44		// difference will wrap in to lower
45		// bits of result, which is then masked
46		// to give a value that can be represented
47		// by an unsigned value of width bits.
48		return mask & (lhs - rhs);
49	}	
50}
51
52#endif