iocp4如何取得IO返回的操作结果,并作处理.doc

如何取得IO返回的操作结果，并作处理在这一章中，我们的目标就集中在GetQueuedCompletionStatus。GetQueuedCompletionStatus 的作用就是从I/O出口队列中取得I/O操作结果。IOCP可以说是多入口（多种类型的函数可以提交I/O操作请求），单出口（一个函数就可以取得所有I/O操作的结果）。因此GetQueuedCompletionStatus 取得的结果将是复杂多样的。BOOL GetQueuedCompletionStatus( HANDLE CompletionPort, LPDWORD lpNumberOfBytes, PULONG_PTR lpCompletionKey, LPOVERLAPPED* lpOverlapped, DWORD dwMilliseconds);在GetQueuedCompletionStatus中要重点关注以下几点：（1） 返回的布尔值/ 操作成功与否的标志（2） lpCompletionKey 参数 / 标志那个socket的I/O操作结果（3） lpOverlapped 参数 / I/O操作得到的数据所在，看看I/O提交操作就知道了。接下来，看看一份测试数据，会明白很多 .各种情况下，返回值和其它参数的值得情况，如下表：Return valueCompletionPortlpNumberOfByteslpCompletionKeylpOverlappedWSAGetLastError()连接成功1 = TRUE1 = NOT NULL0（值为0 ）1 = NOT NULL1(NOT NULL) 0连接超时01011121对方拒绝010111225对方关闭110110断线01011数据111 = NOT NULL110未知情况11010本地关闭0101164说明：1 ConnectEx 对方之后，如果成功连接，返回值为TRUE，lpNumberOfBytes 为零，lpOverlapped 不为 0，lpCompletionKey 为绑定值2 对方关闭之后，返回值为TRUE，lpNumberOfBytes 为零，lpOverlapped 不为 0。3 如果对方关闭后，socket没有关闭，而且还投递WSARecv请求，那么GetQueuedCompletionStatus会立刻返回，回到步骤24 ConnectEx 对方之后，如果对方拒绝连接，返回值为FALSE，lpOverlapped 不为 0，lpNumberOfBytes 为零。5 假如ConnectEx的对方不存在（超时），那么返回值为FALSE，lpOverlapped 不为0，lpCompletionKey 为绑定的值，lpNumberOfBytes 为0，6任何情况下lpCompletionKey的值都是原先绑定的值7CompletionPort肯定不能为NULL，否则得到的值全部为空。有了以上的表，是不是比MSDN上说的明白多了呢。下面看看代码如何实现：void CIOCP_ClientDlg:IocpWorkerThread()MYOVERLAPPED *lpOverlapped = NULL;DWORDdwByteRecv = 0;ULONG_PTR *PerHandleKey = NULL;while (1) lpOverlapped = NULL;if(m_hIocp = NULL)break;/如果I/O 出口队列有结果，GetQueuedCompletionStatus则取得结果返回，否则等待 BOOL bResult = GetQueuedCompletionStatus( m_hIocp,/ 从这个IOCP中取得I/O操作结果 &dwByteRecv,/ 发送或是接收了多少字节 (PULONG_PTR)&PerHandleKey, (LPWSAOVERLAPPED*)&lpOverlapped, INFINITE); if (bResult = FALSE) / 对照表1.1，可能是连接超时、对方拒绝连接、断线 SOCKET socket = (SOCKET)PerHandleKey) ； / 转换，得到当初关联的socketclosesocket(SOCKET)PerHandleKey); / 出问题了，关闭socketdelete lpOverlapped ; / 释放OVERLAPPED if (lpOverlapped = NULL) / 根据MSDN的说法，会出现这种情况 / 根据MSDN的说法，会出现这种情况，但测试时都没发生过 TRACE(TEXT(did not dequeue a pack from iocp queue.error:%dn), GetLastError(); continue; else / ERROR TRACE(TEXT( dequeued a pack from a failure iocp queue.error:%dn), GetLastError(); continue; / end if(lpOverlapped = NULL) else ASSERT(lpOverlapped != NULL); / SOCKET socket = (SOCKET)PerHandleKey; / 取得关联的socketswitch (lpOverlapped-operateType) / 操作类型判别case OP_CONNECT: / 连接操作，是成功的。TRACE0(connected successfully!n);lpOverlapped-operateType = OP_RECV; /再次利用原有的OVERLAPPEDDWORDFlags = 0;/ 连接上之后，就要提交接收请求了，否则将收不到对方发过来的数据if (WSARecv(socket, &lpOverlapped-wsabuf, 1,&lpOverlapped-dwByteRecvSend, &Flags,( LPWSAOVERLAPPED )lpOverlapped, NULL) = SOCKET_ERROR) if (WSAGetLastError() = WSA_IO_PENDING)TRACE0(Error = WSA_IO_PENDINGn);elseTRACE0(Error occured at WSARecv()n);break;case OP_ACCEPT:/ 得到一已连接的socketSOCKET socketAccept = （SOCKET）lpOverlapped-pVoid; /接下来就应该：/ （1）将socketAccept关联到IOCP ，代码略/ （2）提交接收请求，代码略break;case OP_SEND:/ASSERT(dwByteRecv = lpOverlapped-wsabuf.len);if(dwByteRecv != lpOverlapped-wsabuf.len)ASSERT(FALSE); / 没实际用途，只做测试/ ./TRACE0(send completely!n);delete lpOverlapped; / 发送操作成功了，释放OVERLAPPED 结构break;case OP_RECV:TRACE0(recv completely!n);if(0 = dwByteRecv ) / 由表1.1知道对方已经关闭TRACE0(Peer have been closed , me clsoe too.);closesocket(socket); / 关闭socketdelete lpOverlapped ;continue;/ 处理数据，数据在lpOverlapped-wsabuf-buf中/ / 接下来，继续提交接受请求，且再次利用原来的OVERLAPPED结构lpOverlapped-operateType = OP_RECV;DWORDFlags = 0;if (WSARecv(socket, &lpOverlapped-wsabuf, 1,&lpOverlapped-dwByteRecvSend, &Flags,( LPWSAOVERLAPPED )lpOverlapped, NULL) = SOCKET_ERROR) if (WSAGetLastError() = WSA_IO_PENDING)TRACE0(Error = WSA_IO_PENDINGn);elseT