getbits.hpp

一个用来实现偏微分方程中网格的计算库

/*
 * Copyright (C) 2006-2007 Chris Hamilton <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef _GETBITS_HPP_
#define _GETBITS_HPP_


#include <Hilbert/Common.hpp>
#include <Hilbert/BigBitVec.hpp>


namespace Hilbert
{
	template <class H,class I>
	H_INLINE
	void
	getBits(
		const H &h,	// bits to read
		int n,			// number of bits
		int i,			// bit index
		I &w				// destination
		)
	{
		// This is terribly inefficient.
		int j;
		for ( j = 0; j < n; j++ )
			w.setBit(j,h.getBit(i+j));
		return;
	}

	
	// <CBigBitVec,CBigBitVec>
	// #TODO

	// <CBigBitVec,CFixBitVec>
	template<>
	H_INLINE
	void
	getBits(
		const CBigBitVec &h,
		int n,
		int i,
		CFixBitVec &w
		)
	{
		int ir, ib, t;
		BBV_MODSPLIT(ir,ib,i);
		w.rack() = h.racks()[ir] >> ib;
		t = FBV_BITS - ib;
		if ( t < n )
		{
			w.rack() |= h.racks()[ir+1] >> (FBV_BITS-n);
		}
		w.truncate(n);
		return;
	}
	
	
	// <CFixBitVec,CFixBitVec>
	template<>
	H_INLINE
	void
	getBits(
		const CFixBitVec &h,
		int n,
		int i,
		CFixBitVec &w
		)
	{
		w = h >> i;
		w.truncate(n);
		return;
	}

}


#endif