How to reliably PeekConsoleInput in a background thread while reading lines from stdin in main thread?

In order to reliably use PeekConsoleInput in a background thread while reading lines from stdin in the main thread, you will need to use synchronization primitives to ensure that both threads have access to the console input buffer without interfering with each other.

One way to achieve this is to use a named pipe to communicate between the two threads. Here are the steps to do this:

1. Create a named pipe using CreateNamedPipe in the background thread. This will be used to receive data from the main thread.
2. In the main thread, open the named pipe using CreateFile and set it up for asynchronous read operations using ReadFileEx.
3. In the background thread, use PeekConsoleInput to check for any input in the console input buffer. If there is input, read it using ReadConsoleInput.
4. If there is data in the ReadConsoleInput buffer, write it to the named pipe using WriteFile.
5. In the main thread, when the asynchronous read operation completes, process the data received from the named pipe and then initiate another read operation using ReadFileEx.

To ensure that the two threads don't interfere with each other, you will need to use synchronization primitives such as mutexes or semaphores to protect the shared resources (i.e., the console input buffer and the named pipe).

Here's some sample code to illustrate this approach:

scssCopy code
// In the background thread:

HANDLE hPipe = CreateNamedPipe(TEXT("\\\\.\\pipe\\MyPipe"),

                                PIPE_ACCESS_OUTBOUND,

                                PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT,

                                1,

                                0,

                                0,

                                NMPWAIT_USE_DEFAULT_WAIT,

                                NULL);

while (true) {

    if (WaitForSingleObject(hMutex, INFINITE) == WAIT_OBJECT_0) {

        // Check for input in console input buffer

        INPUT_RECORD inputBuffer[128];

        DWORD numEvents;

        PeekConsoleInput(hConsoleInput, inputBuffer, 128, &numEvents);

        if (numEvents > 0) {

            // Read console input buffer

            ReadConsoleInput(hConsoleInput, inputBuffer, 128, &numEvents);

            // Write to named pipe

            WriteFile(hPipe, inputBuffer, numEvents * sizeof(INPUT_RECORD), NULL, NULL);

        }

        ReleaseMutex(hMutex);

    }

    // Sleep for a short time to avoid busy-waiting

    Sleep(100);

}



// In the main thread:

HANDLE hPipe = CreateFile(TEXT("\\\\.\\pipe\\MyPipe"),

                           GENERIC_READ,

                           0,

                           NULL,

                           OPEN_EXISTING,

                           FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,

                           NULL);

OVERLAPPED overlapped = {};

overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

char buffer[1024];

while (true) {

    ReadFileEx(hPipe, buffer, 1024, &overlapped, [](DWORD dwErr, DWORD numBytes, LPOVERLAPPED lpOverlapped) {

        // Process data received from pipe

        // ...

        // Initiate another read operation

        ReadFileEx(hPipe, buffer, 1024, lpOverlapped, NULL);

    });

    // Wait for read operation to complete

    WaitForSingleObject(overlapped.hEvent, INFINITE);

}

Note that this is just a rough outline of the approach, and you will need to modify it to suit your specific needs. Additionally, you will need to handle error cases and ensure proper cleanup of resources.