循环队列实现高速缓存的读写

// 循环队列实现高速缓存的读写// 教材上有对循环队列的讲解，不过头指针，尾指针重合的时候不好理解// 这里仿造标准库中的begin(),end()节点，使得头指针，为指针永远不重合，相对好理解点// 实现了对简单类型的数据的输入输出缓存，不支持CString，std::string等复杂类型，因为用的memcpy拷贝的数据template<class CType>class CInputOutputCache{public:CInputOutputCache(const int iCalcheSize){if (iCalcheSize < 1){return;}m_pCacheData = new CType[iCalcheSize+2];if (m_pCacheData == NULL){return;}m_pRead = m_pCacheData;m_pWrite = m_pCacheData+1;m_iCacheSize = iCalcheSize;};// 写iLen个数据，返回实际写的个数int Write(const CType* pBufWrite, const int iLen){if (m_pCacheData == NULL){return 0;}int iFreeSpace = GetFreeSpace();int iWriteLen = 0;if (iFreeSpace >= iLen){iWriteLen = iLen;}else{iWriteLen = iFreeSpace;}CType* pWritted = AddPoint(m_pWrite, iWriteLen);if (pWritted > m_pWrite){memcpy(m_pWrite, pBufWrite, iWriteLen);}else{int iFirstTimeWriteSize = m_pCacheData + m_iCacheSize + 2 - m_pWrite;memcpy(m_pWrite, pBufWrite, iFirstTimeWriteSize);memcpy(m_pCacheData, pBufWrite, iWriteLen-iFirstTimeWriteSize);}m_pWrite = pWritted;return iWriteLen;};// 读iLen个数据，返回实际读的个数int Read(CType* pBufRead, const int iLen){if (m_pCacheData == NULL){return 0;}int iValidLen = GetValidLen();int iReaded = 0;if (iValidLen >= iLen){iReaded = iLen;}else{iReaded = iValidLen;}CType* pReaded = AddPoint(m_pRead, iReaded);if (pReaded > m_pRead){memcpy(pBufRead, m_pRead+1, iReaded);}else{int iFirstTimeReadSize = m_pCacheData + m_iCacheSize + 2 - (m_pRead+1);memcpy(pBufRead, m_pRead+1, iFirstTimeReadSize);memcpy(pBufRead, m_pCacheData, iReaded-iFirstTimeReadSize);}m_pRead = pReaded;return iReaded;};int GetFreeSpace(){if (m_pCacheData == NULL){return 0;}return m_iCacheSize - GetValidLen();};int GetValidLen(){if (m_pCacheData == NULL){return 0;}if (m_pRead > m_pWrite){return m_iCacheSize - (m_pRead - m_pWrite -1);}else if (m_pRead < m_pWrite){return m_pWrite - m_pRead -1;}}private:CType* AddPoint(CType* pData, int iSize){int iOffset = pData - m_pCacheData;int iOffsetAdded = iOffset + iSize;if (iOffsetAdded >= m_iCacheSize+2){iOffsetAdded = iOffsetAdded - (m_iCacheSize + 2);}return m_pCacheData + iOffsetAdded;}CType* m_pCacheData; // 缓存int m_iCacheSize; // 缓存大小CType* m_pRead; // 读指针CType* m_pWrite; // 写指针};int _tmain(int argc, _TCHAR* argv[]){char sRead[20];CInputOutputCache<char> inputOutputCalche(10);int i = inputOutputCalche.Write("1234567890123", 12);inputOutputCalche.Read(sRead, 3);int iValidLen = inputOutputCalche.GetValidLen();int iFreeSpace = inputOutputCalche.GetFreeSpace();inputOutputCalche.Write("12345", 5);inputOutputCalche.Read(sRead, 3);}