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2 bj 1 
#ifndef __CGLA__BITMASK_H__
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#define __CGLA__BITMASK_H__
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#include "Vec3i.h"
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namespace CGLA
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{
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	const int MASKS[33] =
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		{
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			0x00000000,
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			0x00000001,
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			0x00000003,
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			0x00000007,
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			0x0000000f,
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			0x0000001f,
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			0x0000003f,
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			0x0000007f,
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			0x000000ff,
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			0x000001ff,
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			0x000003ff,
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			0x000007ff,
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			0x00000fff,
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			0x00001fff,
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			0x00003fff,
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			0x00007fff,
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			0x0000ffff,
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			0x0001ffff,
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			0x0003ffff,
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			0x0007ffff,
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			0x000fffff,
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			0x001fffff,
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			0x003fffff,
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			0x007fffff,
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			0x00ffffff,
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			0x01ffffff,
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			0x03ffffff,
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			0x07ffffff,
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			0x0fffffff,
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			0x1fffffff,
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			0x3fffffff,
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			0x7fffffff,
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			0xffffffff
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		};
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89 jab 45 
	/** \brief The BitMask class is mostly a utility class.
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2 bj 47 
			The main purpose is to be able to extract a set of bits from
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			an integer. For instance this can be useful if we traverse
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			some tree structure and the integer is the index. */
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	class BitMask
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	{
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		int fb, lb, bdiff;
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		int msk;
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	public:
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		/** Mask _fb-_lb+1 bits beginning from _fb. First bit is 0.
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				Say _fb=_lb=0. In this case, mask 1 bit namely 0.*/
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		BitMask(int _fb, int _lb):
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			fb(_fb), lb(_lb),
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			bdiff(lb-fb+1), msk(MASKS[bdiff]<<fb)
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		{}
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		/// first bit is 0 mask num bits.
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		BitMask(int num):
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			fb(0),lb(two_to_what_power(num)-1),
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			bdiff(lb-fb+1), msk(MASKS[bdiff]<<fb)
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		{}
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		/// Mask everything.
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		BitMask():
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			fb(0), lb(15),
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			bdiff(lb-fb+1), msk(MASKS[bdiff]<<fb)
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		{}
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		/// get number of first bit in mask
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		int first_bit() const {return fb;}
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		/// get number of last bit in mask
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 		int last_bit() const {return lb;}
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		/// Return number of masked bits
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		int no_bits() const {return bdiff;}
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		/// Mask a number
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		int mask(int var) const {return msk&var;}
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		/** Mask a number and shift back so the first bit inside
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				the mask becomes bit 0. */
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		int mask_shift(int var) const {return (msk&var)>>fb;}
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		/** Mask a vector by masking each coordinate. */
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		Vec3i mask(const Vec3i& v) const
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		{
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			return Vec3i(mask(v[0]),mask(v[1]),mask(v[2]));
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		}
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		/** Mask each coord of a vector and shift */
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		Vec3i maskshift(const Vec3i& v) const
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		{
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			return Vec3i(mask_shift(v[0]),mask_shift(v[1]),mask_shift(v[2]));
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		}
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	};
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}
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#endif