引用计数简单实现
延迟销毁资源，不具备写时复制功能，贴出代码
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class DataSource{private:volatile unsigned int *m_pICount;double *m_pData;public:DataSource(double *pData);~DataSource();DataSource(const DataSource &ds);DataSource& operator =(const DataSource &ds);bool operator ==(const DataSource &ds) const;bool operator !=(const DataSource &ds) const;private:void release();};?
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DataSource::DataSource(double *pData): m_pICount(new unsigned int(1)), m_pData(pData){}DataSource::~DataSource(){release();}DataSource::DataSource(const DataSource &ds): m_pICount(ds.m_pICount), m_pData(ds.m_pData){if(*this == ds)return;++(*m_pICount);}DataSource& DataSource::operator =(const DataSource &ds){if(*this == ds)return *this;this->release();m_pData = ds.m_pData;m_pICount = ds.m_pICount;++(*m_pICount);return *this;}bool DataSource::operator ==(const DataSource &ds) const{return (m_pICount == ds.m_pICount && m_pData == ds.m_pData);}bool DataSource::operator !=(const DataSource &ds) const{return (m_pICount != ds.m_pICount);}void DataSource::release(){if(0 == --(*m_pICount)){delete m_pICount;delete m_pData;m_pICount = NULL;m_pData = NULL;}}