C++版循环缓冲区类

// 声明 class CCycleBuffer { public: BOOL isFull(); BOOL isEmpty(); void Empty(); int GetLength(); CCycleBuffer(int size); virtual ~CCycleBuffer(); int Write(char* buf, int count); int Read(char* buf, int count); private: BOOL m_bEmpty, m_bFull; char * m_pBuf; int m_nBufSize; int m_nReadPos; int m_nWritePos; }; // 定义 CCycleBuffer::CCycleBuffer(int size) { m_nBufSize = size; m_nReadPos = 0; m_nWritePos = 0; m_pBuf = new char[m_nBufSize]; m_bEmpty = TRUE; m_bFull = FALSE; } CCycleBuffer::~CCycleBuffer() { delete[] m_pBuf; } /************************************************************************/ /* 向缓冲区写入数据，返回实际写入的字节数 */ /************************************************************************/ int CCycleBuffer::Write(char* buf, int count) { if(count <= 0) return 0; m_bEmpty = FALSE; // 缓冲区已满，不能继续写入 if(m_bFull) { return 0; } else if(m_nReadPos == m_nWritePos) // 缓冲区为空时 { /* == 内存模型 == (empty) m_nReadPos (empty) |----------------------------------|-----------------------------------------| m_nWritePos m_nBufSize */ int leftcount = m_nBufSize - m_nWritePos; if(leftcount > count) { CopyMemory(m_pBuf + m_nWritePos, buf, count); m_nWritePos += count; m_bFull = (m_nWritePos == m_nReadPos); return count; } else { CopyMemory(m_pBuf + m_nWritePos, buf, leftcount); m_nWritePos = (m_nReadPos > count - leftcount) ? count - leftcount : m_nWritePos; CopyMemory(m_pBuf, buf + leftcount, m_nWritePos); m_bFull = (m_nWritePos == m_nReadPos); return leftcount + m_nWritePos; } } else if(m_nReadPos < m_nWritePos) // 有剩余空间可写入 { /* == 内存模型 == (empty) (data) (empty) |-------------------|----------------------------|---------------------------| m_nReadPos m_nWritePos (leftcount) */ // 剩余缓冲区大小(从写入位置到缓冲区尾) int leftcount = m_nBufSize - m_nWritePos; if(leftcount > count) // 有足够的剩余空间存放 { CopyMemory(m_pBuf + m_nWritePos, buf, count); m_nWritePos += count; m_bFull = (m_nReadPos == m_nWritePos); ASSERT(m_nReadPos <= m_nBufSize); ASSERT(m_nWritePos <= m_nBufSize); return count; } else // 剩余空间不足 { // 先填充满剩余空间，再回头找空间存放 CopyMemory(m_pBuf + m_nWritePos, buf, leftcount); int m_nWritePos = (m_nReadPos >= count - leftcount) ? count - leftcount : m_nReadPos; CopyMemory(m_pBuf, buf + leftcount, m_nWritePos); m_bFull = (m_nReadPos == m_nWritePos); ASSERT(m_nReadPos <= m_nBufSize); ASSERT(m_nWritePos <= m_nBufSize); return leftcount + m_nWritePos; } } else { /* == 内存模型 == (unread) (read) (unread) |-------------------|----------------------------|---------------------------| m_nWritePos (leftcount) m_nReadPos */ int leftcount = m_nReadPos - m_nWritePos; if(leftcount > count) { // 有足够的剩余空间存放 CopyMemory(m_pBuf + m_nWritePos, buf, count); m_nWritePos += count; m_bFull = (m_nReadPos == m_nWritePos); ASSERT(m_nReadPos <= m_nBufSize); ASSERT(m_nWritePos <= m_nBufSize); return count; } else { // 剩余空间不足时要丢弃后面的数据 CopyMemory(m_pBuf + m_nWritePos, buf, leftcount); m_nWritePos += leftcount; m_bFull = (m_nReadPos == m_nWritePos); ASSERT(m_bFull); ASSERT(m_nReadPos <= m_nBufSize); ASSERT(m_nWritePos <= m_nBufSize); return leftcount; } } } /************************************************************************/ /* 从缓冲区读数据，返回实际读取的字节数 */ /************************************************************************/ int CCycleBuffer::Read(char* buf, int count) { if(count <= 0) return 0; m_bFull = FALSE; if(m_bEmpty) // 缓冲区空，不能继续读取数据 { return 0; } else if(m_nReadPos == m_nWritePos) // 缓冲区满时 { /* == 内存模型 == (data) m_nReadPos (data) |--------------------------------|--------------------------------------------| m_nWritePos m_nBufSize */ int leftcount = m_nBufSize - m_nReadPos; if(leftcount > count) { CopyMemory(buf, m_pBuf + m_nReadPos, count); m_nReadPos += count; m_bEmpty = (m_nReadPos == m_nWritePos); return count; } else { CopyMemory(buf, m_pBuf + m_nReadPos, leftcount); m_nReadPos = (m_nWritePos > count - leftcount) ? count - leftcount : m_nWritePos; CopyMemory(buf + leftcount, m_pBuf, m_nReadPos); m_bEmpty = (m_nReadPos == m_nWritePos); return leftcount + m_nReadPos; } } else if(m_nReadPos < m_nWritePos) // 写指针在前(未读数据是连接的) { /* == 内存模型 == (read) (unread) (read) |-------------------|----------------------------|---------------------------| m_nReadPos m_nWritePos m_nBufSize */ int leftcount = m_nWritePos - m_nReadPos; int c = (leftcount > count) ? count : leftcount; CopyMemory(buf, m_pBuf + m_nReadPos, c); m_nReadPos += c; m_bEmpty = (m_nReadPos == m_nWritePos); ASSERT(m_nReadPos <= m_nBufSize); ASSERT(m_nWritePos <= m_nBufSize); return c; } else // 读指针在前(未读数据可能是不连接的) { /* == 内存模型 == (unread) (read) (unread) |-------------------|----------------------------|---------------------------| m_nWritePos m_nReadPos m_nBufSize */ int leftcount = m_nBufSize - m_nReadPos; if(leftcount > count) // 未读缓冲区够大，直接读取数据 { CopyMemory(buf, m_pBuf + m_nReadPos, count); m_nReadPos += count; m_bEmpty = (m_nReadPos == m_nWritePos); ASSERT(m_nReadPos <= m_nBufSize); ASSERT(m_nWritePos <= m_nBufSize); return count; } else // 未读缓冲区不足，需回到缓冲区头开始读 { CopyMemory(buf, m_pBuf + m_nReadPos, leftcount); m_nReadPos = (m_nWritePos >= count - leftcount) ? count - leftcount : m_nWritePos; CopyMemory(buf, m_pBuf, m_nReadPos); m_bEmpty = (m_nReadPos == m_nWritePos); ASSERT(m_nReadPos <= m_nBufSize); ASSERT(m_nWritePos <= m_nBufSize); return leftcount + m_nReadPos; } } } /************************************************************************/ /* 获取缓冲区有效数据长度 */ /************************************************************************/ int CCycleBuffer::GetLength() { if(m_bEmpty) { return 0; } else if(m_bFull) { return m_nBufSize; } else if(m_nReadPos < m_nWritePos) { return m_nWritePos - m_nReadPos; } else { return m_nBufSize - m_nReadPos + m_nWritePos; } } void CCycleBuffer::Empty() { m_nReadPos = 0; m_nWritePos = 0; m_bEmpty = TRUE; m_bFull = FALSE; } BOOL CCycleBuffer::isEmpty() { return m_bEmpty; } BOOL CCycleBuffer::isFull() { return m_bFull; }