bitset实现（转）

感觉bitset实现很漂亮--所以转载

转自：http://blog.sina.com.cn.sixxs.org/u/1282003632

感谢原作者！

为了区分C++标准库中的bitset数据结构，在本程序中使用_bitset。如果设置_bitset的长度为4，则可操作的位为0-3。//_bitset.h#ifndef _BITSET_H#define _BITSET_H#include <limits>#include <cstring>#include <iostream>using namespace std;class _bitset{ friend ostream & operator << (ostream & out,const _bitset & elem);   //重载输出操作符public: typedef unsigned long block_type;   //最小存储单元块的类型 typedef unsigned long size_type;    //最小存储单元块的大小类型private: enum {BLOCK_BYTES = sizeof(block_type)};     //最小存储单元块的字节数 enum {BLOCK_BITS = std::numeric_limits<block_type>::digits};  //最小单元存储块的位数，平台通用性，所以使用numeric_limitspublic: _bitset(); _bitset(size_type val); _bitset(const _bitset & val); _bitset & operator=(const _bitset & val); ~_bitset(); _bitset & operator <<= (size_type num);  //左移赋值操作 _bitset & operator >>= (size_type num);  //右移赋值操作 _bitset & set(size_type pos,bool tagSet = true); //设置bitset中的某一位的值 _bitset & clear(bool tagClear = true);    //使得bitset中每一位都为0 _bitset & flip();       //反转所有位操作 _bitset & operator ~();      //取反操作符 _bitset & flip(size_type pos);    //反转pos位的操作 bool test(size_type pos) const;    //测试相应位是1还是0 _bitset & operator &= (const _bitset & val); _bitset & operator |= (const _bitset & val); _bitset & operator ^= (const _bitset & val); bool operator == (const _bitset & val) const; size_type size() const;private: void leftShift(size_type num);   //左移操作 void rightShift(size_type num);   //右移操作private: size_type m_bitNum;   //bitset中位的个数 size_type m_size;     //block_type的个数 block_type * m_pBits; //存储bit位 block_type m_mask;    //假如bitset的位数是5，而m_pBits[0]=0xFFFFFFFF,m_mask用来表示                       //m_pBits[0]的后5位有效};_bitset operator << (const _bitset &,_bitset::size_type);_bitset operator >> (const _bitset &,_bitset::size_type);_bitset operator & (const _bitset &,const _bitset &);_bitset operator | (const _bitset &,const _bitset &);_bitset operator ^ (const _bitset &,const _bitset &);inline _bitset::_bitset(size_type bitNum){ m_bitNum = bitNum; size_type free_bits = (BLOCK_BITS - m_bitNum % BLOCK_BITS) % BLOCK_BITS; m_size = m_bitNum / BLOCK_BITS + (free_bits == 0 ? 0 : 1); m_pBits = new block_type[m_size]; if (m_pBits == NULL) {  cout << "no enough memorry!\n";  exit(0); } clear(); m_mask = ~block_type(0); m_mask >>= free_bits;}inline _bitset::_bitset(const _bitset &val){ m_size = val.m_size; m_pBits = new block_type[m_size]; if (m_pBits == NULL) {  cout << "no enough memorry!\n";  exit(0); } memcpy(m_pBits,val.m_pBits,m_size * BLOCK_BYTES); m_bitNum = val.m_bitNum; m_mask = val.m_mask;}inline _bitset & _bitset::operator =(const _bitset &val){ if (this == &val)  return (*this); if (m_size != val.m_size) {  delete [] m_pBits;  m_size = val.m_size;  m_pBits = new block_type[m_size];  if (m_pBits == NULL)  {   cout << "no enough memorry!\n";   exit(0);  } } memcpy(m_pBits,val.m_pBits,m_size * BLOCK_BYTES); m_bitNum = val.m_bitNum; m_mask = val.m_mask; return (*this);}inline _bitset::~_bitset(){ delete [] m_pBits;}inline _bitset & _bitset::operator <<=(_bitset::size_type num){ leftShift(num); return (*this);}inline _bitset & _bitset::operator >>=(_bitset::size_type num){ rightShift(num); return (*this);}inline _bitset::size_type _bitset::size() const{ return m_bitNum;}inline _bitset & _bitset::flip(){ for (size_type i=0;i<m_size;++i)  m_pBits[i] = ~m_pBits[i]; m_pBits[m_size-1] &= m_mask; return (*this);}inline _bitset & _bitset::operator~(){ return _bitset(*this).flip();}inline _bitset & _bitset::operator &=(const _bitset &val){ if (m_bitNum != val.m_bitNum) {  cout << "different length\n";  exit(0); } for (size_type i=0;i<m_size;i++)  m_pBits[i] &= val.m_pBits[i]; return (*this);}inline _bitset & _bitset::operator |=(const _bitset &val){ if (m_bitNum != val.m_bitNum) {  cout << "different length\n";  exit(0); } for (size_type i=0;i<m_size;i++)  m_pBits[i] |= val.m_pBits[i]; return (*this);}inline _bitset & _bitset::operator ^=(const _bitset &val){ if (m_bitNum != val.m_bitNum) {  cout << "different length\n";  exit(0); } for (size_type i=0;i<m_size;i++)  m_pBits[i] ^= val.m_pBits[i]; return (*this);}inline bool _bitset::operator ==(const _bitset &val) const{ if (m_bitNum != val.m_bitNum)  return false; for (size_type i=0;i < m_size;++i)  if (m_pBits[i] != val.m_pBits[i])   return false; return true;}inline _bitset operator << (const _bitset & val,_bitset::size_type num){ return _bitset(val) <<= num;}inline _bitset operator >> (const _bitset & val,_bitset::size_type num){ return _bitset(val) >>= num;}inline _bitset operator | (const _bitset & l,const _bitset & r){ return _bitset(l) |= r;}inline _bitset operator & (const _bitset & l,const _bitset & r){ return _bitset(l) &= r;}inline _bitset operator ^ (const _bitset & l,const _bitset & r){ return _bitset(l) ^= r;}inline _bitset & _bitset::clear(bool tagClear){ if (tagClear) {  memset(m_pBits,0,m_size * BLOCK_BYTES); } else {  memset(m_pBits,std::numeric_limits<unsigned char>::max(),m_size * BLOCK_BYTES);  m_pBits[m_size-1] &= m_mask; } return (*this);}#endif //_bitset.cpp#include "_bitset.h"void _bitset::leftShift(_bitset::size_type num){ if (num >= m_bitNum) {  clear();  return; } size_type eleNum = num / BLOCK_BITS; size_type bitNum = num % BLOCK_BITS; if (eleNum != 0) {  block_type * pTmp = new block_type[m_size];  if (pTmp == NULL)  {   cout << "no enough memory\n";   exit(0);  }  memcpy(pTmp,m_pBits,(m_size-eleNum)*BLOCK_BYTES);  memcpy(m_pBits+eleNum,pTmp,(m_size-eleNum)*BLOCK_BYTES);  memset(m_pBits,0,eleNum*BLOCK_BYTES);  delete [] pTmp; } if (bitNum != 0) {  block_type * pTmp = m_pBits + m_size -1;  for (;pTmp > m_pBits;--pTmp)  {   *pTmp = (*pTmp << bitNum) | (*(pTmp-1) >> (BLOCK_BITS - bitNum)); //*pTmp的地位或上(*(pTmp-1))的高位  }  *pTmp <<= bitNum; } m_pBits[m_size-1] &= m_mask;  //将数组最高位的元素无用位置0}void _bitset::rightShift(_bitset::size_type num){ if (num >= m_bitNum) {  clear();  return; } size_type eleNum = num / BLOCK_BITS; size_type bitNum = num % BLOCK_BITS; if (eleNum != 0) {  block_type * pTmp = new block_type[m_size];  if (pTmp == NULL)  {   cout << "no enough memory\n";   exit(0);  }  memcpy(pTmp,m_pBits+eleNum,(m_size-eleNum)*BLOCK_BYTES);  memcpy(m_pBits,pTmp,(m_size-eleNum)*BLOCK_BYTES);  memset(m_pBits+m_size-eleNum,0,eleNum * BLOCK_BYTES);  delete [] pTmp; } if (bitNum != 0) {  block_type * pTmp = m_pBits;  for (;pTmp < m_pBits + m_size -1;++pTmp)  {   *pTmp = (*pTmp >> bitNum) | (*(pTmp+1) << (BLOCK_BITS - bitNum));  }  *pTmp >>= bitNum; }}_bitset & _bitset::set(size_type pos,bool tagSet){ if (pos > m_bitNum || pos < 0) {  cout << "position is not right\n";  exit(0); }  size_type eleNum = pos / BLOCK_BITS; size_type bitNum = pos % BLOCK_BITS; block_type mask = 1; mask <<= bitNum; if (tagSet) {  m_pBits[eleNum] |= mask; } else {  m_pBits[eleNum] &= ~mask; } return (*this);}_bitset & _bitset::flip(_bitset::size_type pos){ if (pos > m_bitNum || pos < 0) {  cout << "position is not right\n";  exit(0); }  size_type eleNum = pos / BLOCK_BITS; size_type bitNum = pos % BLOCK_BITS; block_type mask = 1; mask <<= bitNum; m_pBits[eleNum] = m_pBits[eleNum] ^ mask; return (*this);}bool _bitset::test(_bitset::size_type pos) const{ if (pos > m_bitNum || pos < 0) {  cout << "position is not right\n";  exit(0); }  size_type eleNum = pos / BLOCK_BITS; size_type bitNum = pos % BLOCK_BITS; block_type mask = 1; mask <<= bitNum; return m_pBits[eleNum] & mask;}ostream & operator << (ostream & out,const _bitset & elem){ _bitset::size_type j = 0; _bitset::size_type mask = 1; mask <<= (elem.m_bitNum % _bitset::BLOCK_BITS-1); for (_bitset::size_type i = elem.m_bitNum-1;i>0;i--) {  if (i % (_bitset::BLOCK_BITS) == 0)  {   j++;   mask = 1;   mask <<= (_bitset::BLOCK_BITS-1);  }  if (elem.m_pBits[elem.m_size-j-1] & mask)  {   out << 1;  }  else  {   out << 0;  }  mask >>= 1; } return out;} //main 测试函数#include <iostream>#include <bitset>#include <limits>#include "_bitset.h"using namespace std;int main(){ bitset<4> mybits; //cout << mybits << endl; cout << mybits.set(3) << endl; _bitset bit(34); bit.set(33); //bit.rightShift(1); //bit <<= 1; cout << bit << endl;}

bitset数据结构能够有效的节约存储空间，在海量数据排序，海量数据检索中都有用处。