I'm attempting to use overlapped IO to read input from the console by opening CONIN$ with the FILE_FLAG_OVERLAPPED flag. However, ReadFile blocks when I use it, even with an OVERLAPPED parameter.
I've read some posts reporting that this is a Windows 7 bug. I am using 7 so that could be possible.
Here's the code I'm using:
// Create a console window
AllocConsole();
AttachConsole(GetProcessId(GetModuleHandle(NULL)));
HANDLE overlappedConsoleIn = CreateFile(L"CONIN$",
GENERIC_READ,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED | FILE_FLAG_NO_BUFFERING,
NULL);
// Set up the console to work with stdio
FILE *consoleOut = _fdopen(_open_osfhandle((long)GetStdHandle(STD_OUTPUT_HANDLE), _O_TEXT), "w");
FILE *consoleIn = _fdopen(_open_osfhandle((long)overlappedConsoleIn, _O_TEXT), "r");
*stdout = *consoleOut;
*stdin = *consoleIn;
setvbuf(consoleOut, NULL, _IONBF, 0);
setvbuf(consoleIn, NULL, _IONBF, 0);
std::ios::sync_with_stdio();
// Create a completion event
HANDLE inputEvent = CreateEvent(NULL, true, false, NULL);
BYTE inputBuffer[128];
OVERLAPPED overlappedData;
overlappedData.Offset = 0;
overlappedData.OffsetHigh = 0;
overlappedData.hEvent = inputEvent;
DWORD numBytesRead = 0;
// Asynchronously read from console
ReadFile(overlappedConsoleIn, inputBuffer, 128, &numBytesRead, &overlappedData);
while(true)
{
if(WaitForSingleObject(inputEvent, 0) == WAIT_OBJECT_0)
{
std::cout << "input has been received" << std::endl;
}
std::cout << "doing something" << std::endl;
}