bitset.cpp

clucene是c++版的全文检索引擎,完全移植于lucene,采用 stl 编写.

/*------------------------------------------------------------------------------
* Copyright (C) 2003-2006 Ben van Klinken and the CLucene Team
* 
* Distributable under the terms of either the Apache License (Version 2.0) or 
* the GNU Lesser General Public License, as specified in the COPYING file.
------------------------------------------------------------------------------*/
#include "CLucene/StdHeader.h"
#include "BitSet.h"
#include "CLucene/store/Directory.h"

CL_NS_USE(store)
CL_NS_DEF(util)

BitSet::BitSet( const BitSet& copy ) :
	_size( copy._size ),
	_count(-1)
{
	int32_t len = (_size >> 3) + 1;
	bits = _CL_NEWARRAY(uint8_t, len);
	memcpy( bits, copy.bits, len );
}

///Create a bitset with the specified size
BitSet::BitSet ( int32_t size ):
  _size(size),
  _count(-1)
{
	int32_t len = (_size >> 3) + 1;
	bits = _CL_NEWARRAY(uint8_t, len);
	memset(bits,0,len);
}

BitSet::BitSet(CL_NS(store)::Directory* d, const char* name) {
	_count=-1;
	CL_NS(store)::IndexInput* input = d->openInput( name );
	try {
		_size = input->readInt();			  // read size
	  	_count = input->readInt();			  // read count

		bits = _CL_NEWARRAY(uint8_t,(_size >> 3) + 1);		  // allocate bits
		input->readBytes(bits, (_size >> 3) + 1);	  // read bits
	} _CLFINALLY (
	    input->close();
	    _CLDELETE(input );
	);
}
	
void BitSet::write(CL_NS(store)::Directory* d, const char* name) {
	CL_NS(store)::IndexOutput* output = d->createOutput(name);
	try {
	  output->writeInt(size());			  // write size
	  output->writeInt(count());			  // write count
	  output->writeBytes(bits, (_size >> 3) + 1);	  // write bits
	} _CLFINALLY (
	    output->close();
	    _CLDELETE(output);
	);
}

///Destructor for the bit set
BitSet::~BitSet(){
	_CLDELETE_ARRAY(bits);
}
///set the value of the specified bit
void BitSet::set(const int32_t bit, bool val){
	_count = -1;

	if (val)
		bits[bit >> 3] |= 1 << (bit & 7);
	else
		bits[bit >> 3] &= ~(1 << (bit & 7));
	_count =-1;
}
///returns the size of the bitset
int32_t BitSet::size() const {
  return _size;
}
/// Returns the total number of one bits in this BitSet.  This is efficiently
///	computed and cached, so that, if the BitSet is not changed, no
///	recomputation is done for repeated calls. 
int32_t BitSet::count(){
	// if the BitSet has been modified
    if (_count == -1) {
      static const uint8_t BYTE_COUNTS[] = {  
            0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
            1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
            1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
            2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
            1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
            2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
            2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
            3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
            1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
            2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
            2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
            3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
            2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
            3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
            3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
            4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8};

      int32_t c = 0;
      int32_t end = (_size >> 3) + 1;
      for (int32_t i = 0; i < end; i++)
        c += BYTE_COUNTS[bits[i]];	  // sum bits per uint8_t
      _count = c;
    }
    return _count;
}
BitSet* BitSet::clone() const {
	return _CLNEW BitSet( *this );
}

CL_NS_END