[英]WriteFile and ReadFile on child process's stdio (using overlapped named pipe)
[英]ReadFile using NamedPipe blocks though using overlapped
我正在使用NamedPipes在Windows应用程序的不同模块之间进行通信。 有时,读操作可能会花费很长时间,因此我们想添加一个超时。 我这样添加了OVERLAPPED标志:
pipeHandle = CreateFile(
pipename,
PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED,
0,
nullptr,
OPEN_EXISTING,
0,
nullptr);
然后,读取操作如下所示:
OVERLAPPED overlapped;
ZeroMemory(&overlapped, sizeof(OVERLAPPED));
overlapped.hEvent = CreateEvent(nullptr, TRUE, FALSE, nullptr);
successful = ReadFile(
pipeHandle,
buffer,
4096 * sizeof(wchar_t),
&numBytesRead,
&overlapped
);
if (successful == FALSE)
{
LOG("Reading was not successful");
if (GetLastError() != ERROR_IO_PENDING)
{
// The function call failed. ToDo: recovery.
LOG_LAST_ERROR("Failed because of Error: ");
return ERROR_READ_FAULT;
}
else
{
// TODO: add a timeout...
successful = GetOverlappedResult(pipeHandle, &overlapped, &numBytesRead, TRUE);
}
}
else
{
LOG("Reading was successful");
// I/O completed:
return ERROR_SUCCESS;
}
现在,我希望对ReadFile的调用将立即返回,这样我就可以处理可能的超时,但是它将阻塞直到调用返回。
我究竟做错了什么?
在您的代码中, FILE_FLAG_OVERLAPPED
在dwDesiredAccess
参数中,但应在dwFlagsAndAttributes
参数中指定。
因此,这可能会更好:
pipeHandle = CreateFile(
pipename,
PIPE_ACCESS_DUPLEX,
0,
nullptr,
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
nullptr);
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