ERROR_IO_PENDING后的多个WriteFile
在我的应用程序中，当另一个Write操作在命名管道上挂起时，我正在测试WriteFile的行为。
管道处于消息模式（不是字节模式）。
为了使写入操作挂起，我保持命名管道的缓冲区非常小，并且客户端发送的数据多于缓冲区大小。 通过这种方式，我在客户端获得挂起的写操作。
我在服务器端面临以下问题：
使用ERROR_MORE_DATA失败ReadFile 。 它会更改缓冲区的内容，但不会更改接收的字节数。
服务器代码
//file server.cpp #include #include #include #include #define CONNECTING_STATE 0 #define READING_STATE 1 #define WRITING_STATE 2 #define INSTANCES 4 #define PIPE_TIMEOUT 5000 #define BUFSIZE 3 #define BUFSIZE2 1000 typedef struct { OVERLAPPED oOverlap; HANDLE hPipeInst; TCHAR chRequest[BUFSIZE2]; DWORD cbRead; DWORD cbReadSoFar; TCHAR chReply[BUFSIZE2]; DWORD cbToWrite; DWORD dwState; BOOL fPendingIO; } PIPEINST, *LPPIPEINST; VOID DisconnectAndReconnect(DWORD); BOOL ConnectToNewClient(HANDLE, LPOVERLAPPED); VOID GetAnswerToRequest(LPPIPEINST); PIPEINST Pipe[INSTANCES]; HANDLE hEvents[INSTANCES]; int _tmain(VOID) { DWORD i, dwWait, cbRet, dwErr; BOOL fSuccess; LPTSTR lpszPipename = TEXT("\\\\.\\pipe\\mynamedpipe"); for (i = 0; i < INSTANCES; i++) { hEvents[i] = CreateEvent(NULL, TRUE, TRUE, NULL); Pipe[i].oOverlap.hEvent = hEvents[i]; Pipe[i].hPipeInst = CreateNamedPipe(lpszPipename, PIPE_ACCESS_DUPLEX|FILE_FLAG_OVERLAPPED, PIPE_TYPE_MESSAGE|PIPE_READMODE_MESSAGE|PIPE_WAIT, INSTANCES, BUFSIZE*sizeof(TCHAR), BUFSIZE*sizeof(TCHAR), PIPE_TIMEOUT, NULL); if (Pipe[i].hPipeInst == INVALID_HANDLE_VALUE) { printf("CreateNamedPipe failed with %d.\n", GetLastError()); return 0; } Pipe[i].fPendingIO = ConnectToNewClient(Pipe[i].hPipeInst, &Pipe[i].oOverlap); Pipe[i].dwState = Pipe[i].fPendingIO ? CONNECTING_STATE : READING_STATE; } while (1) { dwWait = WaitForMultipleObjects(INSTANCES, hEvents, FALSE, INFINITE); i = dwWait - WAIT_OBJECT_0; // determines which pipe if (i (INSTANCES - 1)) { printf("Index out of range.\n"); return 0; } if (Pipe[i].fPendingIO) { fSuccess = GetOverlappedResult(Pipe[i].hPipeInst, &Pipe[i].oOverlap, &cbRet, FALSE); DWORD lasterror = GetLastError(); switch (Pipe[i].dwState) { case CONNECTING_STATE: if (! fSuccess) { printf("Error %d.\n", GetLastError()); return 0; } Pipe[i].dwState = READING_STATE; Pipe[i].cbReadSoFar = 0; break; case READING_STATE: if(ERROR_MORE_DATA == lasterror) { Pipe[i].cbReadSoFar += cbRet; break; } if(ERROR_IO_PENDING == lasterror) { continue; } if (! fSuccess || cbRet == 0) { DisconnectAndReconnect(i); continue; } Pipe[i].cbRead = cbRet; Pipe[i].cbReadSoFar = 0; printf("Message received: %s\n", Pipe[i].chRequest); break; default: { printf("Invalid pipe state.\n"); return 0; } } } switch (Pipe[i].dwState) { case READING_STATE: fSuccess = ReadFile( Pipe[i].hPipeInst, Pipe[i].chRequest + Pipe[i].cbReadSoFar, BUFSIZE*sizeof(TCHAR), &Pipe[i].cbRead, &Pipe[i].oOverlap); dwErr = GetLastError(); if (! fSuccess && (dwErr == ERROR_IO_PENDING)) { Pipe[i].fPendingIO = TRUE; continue; } if(!fSuccess && dwErr == ERROR_MORE_DATA) { Pipe[i].cbReadSoFar += Pipe[i].cbRead; continue; } if (fSuccess && Pipe[i].cbRead != 0) { Pipe[i].fPendingIO = FALSE; Pipe[i].cbReadSoFar = 0; //Log the message. printf("Message received: %s\n", Pipe[i].chRequest); continue; } // An error occurred; disconnect from the client. DisconnectAndReconnect(i); break; default: { printf("Invalid pipe state.\n"); return 0; } } } return 0; } VOID DisconnectAndReconnect(DWORD i) { if (! DisconnectNamedPipe(Pipe[i].hPipeInst) ) { printf("DisconnectNamedPipe failed with %d.\n", GetLastError()); } Pipe[i].fPendingIO = ConnectToNewClient( Pipe[i].hPipeInst, &Pipe[i].oOverlap); Pipe[i].dwState = Pipe[i].fPendingIO ? CONNECTING_STATE : // still connecting READING_STATE; // ready to read } BOOL ConnectToNewClient(HANDLE hPipe, LPOVERLAPPED lpo) { BOOL fConnected, fPendingIO = FALSE; fConnected = ConnectNamedPipe(hPipe, lpo); if (fConnected) { printf("ConnectNamedPipe failed with %d.\n", GetLastError()); return 0; } switch (GetLastError()) { case ERROR_IO_PENDING: fPendingIO = TRUE; break; case ERROR_PIPE_CONNECTED: if (SetEvent(lpo->hEvent)) break; default: { printf("ConnectNamedPipe failed with %d.\n", GetLastError()); return 0; } } return fPendingIO; } VOID GetAnswerToRequest(LPPIPEINST pipe) { _tprintf( TEXT("[%d] %s\n"), pipe->hPipeInst, pipe->chRequest); StringCchCopy( pipe->chReply, BUFSIZE, TEXT("Default answer from server") ); pipe->cbToWrite = (lstrlen(pipe->chReply)+1)*sizeof(TCHAR); }
客户端代码是
//file: client.cpp #include #include #include #include #define BUFSIZE 512 #define NUM_MESSAGE 4 int _tmain(int argc, TCHAR *argv[]) { HANDLE hPipe; LPTSTR lpvMessage=TEXT("Default message from the client."); TCHAR chBuf[NUM_MESSAGE+1][BUFSIZE]; BOOL fSuccess = FALSE; DWORD cbRead, cbToWrite, cbWritten, dwMode; LPTSTR lpszPipename = TEXT("\\\\.\\pipe\\mynamedpipe"); while (1) { hPipe = CreateFile(lpszPipename, GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL); if (hPipe != INVALID_HANDLE_VALUE) break; if (GetLastError() != ERROR_PIPE_BUSY) { _tprintf( TEXT("Could not open pipe. GLE=%d\n"), GetLastError() ); return -1; } if ( ! WaitNamedPipe(lpszPipename, 20000)) { printf("Could not open pipe: 20 second wait timed out."); return -1; } } dwMode = PIPE_READMODE_MESSAGE; fSuccess = SetNamedPipeHandleState(hPipe, &dwMode, NULL, NULL); if (!fSuccess) { _tprintf(TEXT("SetNamedPipeHandleState failed. GLE=%d\n"), GetLastError()); return -1; } cbToWrite = (lstrlen(lpvMessage)+1)*sizeof(TCHAR); _tprintf( TEXT("Sending %d byte message: \"%s\"\n"), cbToWrite, lpvMessage); OVERLAPPED woverlapped[NUM_MESSAGE]; HANDLE wevent[NUM_MESSAGE]; memset(woverlapped, 0, sizeof(woverlapped)); for(int i=0; i<NUM_MESSAGE; ++i) { wevent[i] = CreateEvent(NULL, 0, 0, NULL); woverlapped[i].hEvent = wevent[i]; } const int retrycount = NUM_MESSAGE; int numberofsend = retrycount; wretry: cbToWrite = _stprintf(chBuf[retrycount-numberofsend], TEXT("Message %d from Client"), retrycount - numberofsend + 1); cbToWrite *= sizeof(TCHAR); fSuccess = WriteFile(hPipe, chBuf[retrycount-numberofsend], cbToWrite, &cbWritten, &woverlapped[retrycount-numberofsend]); --numberofsend; if(!fSuccess) { _tprintf( TEXT("WriteFile to pipe failed. GLE=%d\n"), GetLastError() ); //return -1; if(GetLastError() != ERROR_IO_PENDING) return -1; } if(numberofsend) goto wretry; bool wait = true; while(wait) { DWORD retval = WaitForMultipleObjects(NUM_MESSAGE, wevent, FALSE, INFINITE); retval -= WAIT_OBJECT_0; DWORD cbret; DWORD success = ::GetOverlappedResult(hPipe, &woverlapped[retval], &cbret, FALSE); DWORD laserr = ::GetLastError(); ++numberofsend; if(numberofsend == retrycount) wait = false; } CloseHandle(hPipe); return 0; }
在这种情况下，我在服务器端做错了吗？ 还是预料到的？
引用MSDN ：
如果正在以消息模式读取命名管道，并且下一条消息的长度超过nNumberOfBytesToRead参数指定的值，则ReadFile返回FALSE，GetLastError返回ERROR_MORE_DATA。 可以通过随后调用ReadFile或PeekNamedPipefunction来读取消息的其余部分。