/** 
 * @file llmodularmath.h
 * @brief Useful modular math functions.
 *
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 * Copyright (c) 2008-2009, Linden Research, Inc.
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#ifndef LLMODULARMATH_H
#define LLMODULARMATH_H

namespace LLModularMath
{
    // Return difference between lhs and rhs
    // treating the U32 operands and result
    // as unsigned values of given width.
	template<int width>
	inline U32 subtract(U32 lhs, U32 rhs)
	{
		// Generate a bit mask which will truncate
		// unsigned values to given width at compile time.
		const U32 mask = (1 << width) - 1;
		
		// Operands are unsigned, so modular
		// arithmetic applies. If lhs < rhs,
		// difference will wrap in to lower
		// bits of result, which is then masked
		// to give a value that can be represented
		// by an unsigned value of width bits.
		return mask & (lhs - rhs);
	}	
}

#endif
