How can I reset the buffer of the readfile function?

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C++

timer

buffer

I am currently working on an idle timer that is designed to handle multiple I/O operations, and I partially made it work. However, I am encountering issues with the loop functionality; it tends to either enter an infinite loop (if I remove the break statement) or accept only a single input (if I keep the break statement). I suspect that the underlying issue lies with the ReadFile buffer (chBuffer in my program) not being reset after each input.

For more information here's my code:

#include <Windows.h>
#include <iostream>

DWORD waitThread(HANDLE hThread);

DWORD WINAPI threadFileOperations(LPVOID lpParam);

int main() {
    HANDLE  hThread{};
    LPDWORD dwThreadId{};
    CHAR chBuffer[251]{};

    // Create a thread to handle I/O operations
    hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)threadFileOperations, 
                   &chBuffer, 0, dwThreadId);

    if (hThread == NULL) {
        ExitProcess(2);
    }
    
    // While the function's return value is different from WAIT_TIMEOUT 
    // continue to wait on the thread
    while (!waitThread(hThread)) {
        switch (chBuffer[0]) {
        case '1': std::cout << "hello option 1" << std::endl;
            // Do something else...
            break;
        case '2': std::cout << "hello option 2" << std::endl;
            // Do something else...
            break;
        case '3': std::cout << "hello option 3" << std::endl;
            // Do something else...
            break;
        case '4': std::cout << "hello option 4" << std::endl;
            // Do something else...
            break;
        case '5': std::cout << "exit loop" << std::endl;
            break;
        default: std::cout << "invalid option" << std::endl;
            break;
        }
        // We get stuck in an infinite loop if we erase the break below
        break;
    }

    CloseHandle(hThread);

    return 0;
}

DWORD waitThread(HANDLE hThread) {
    DWORD dwTimeOut{ 10'000 };
   
    switch (WaitForSingleObject(hThread, dwTimeOut)) {
    case WAIT_TIMEOUT:
        break;
    case WAIT_OBJECT_0: // return WaitForSingleObject(hThread, dwTimeOut) == WAIT_OBJECT_0;
        break;
    case WAIT_ABANDONED: std::cout << 
         "WaitForSingleObject: Error WAIT_ABANDONED" << std::endl;
        return FALSE;
    case WAIT_FAILED: std::cout << 
          "WaitForSingleObject: Error WAIT_FAILED" << std::endl;
        return FALSE;
    }
}

DWORD WINAPI threadFileOperations(LPVOID lpParam) {
    HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
    HANDLE hStdIn = GetStdHandle(STD_INPUT_HANDLE);
    
    LPCSTR lpszPrompt1{ "Option: " };
    DWORD dwBytesWritten{ 0 };
    DWORD dwBytesRead{ 0 };
    
    // Initialize the lpParam to chBuffer[251]
    CHAR* readBuffer;
    readBuffer = static_cast<CHAR*>(lpParam);

    if (hStdOut == INVALID_HANDLE_VALUE || hStdIn == INVALID_HANDLE_VALUE) {
        std::cout << "I/O Handles: Error " << GetLastError() << std::endl;
        return 1;
    }

    if (!WriteFile(
        hStdOut,
        lpszPrompt1,
        lstrlenA(lpszPrompt1),
        &dwBytesWritten,
        NULL)) {
        std::cout << "WriteFile: Error " << GetLastError() << std::endl;
        return 1;
    }

    if (!ReadFile(
        hStdIn,
        readBuffer,
        250,
        &dwBytesRead,
        NULL)) {
        std::cout << "ReadFile: Error " << GetLastError() << std::endl;
        return 1;
    }
    else {
        return readBuffer[0];
    }
}

What I have tried:

I searched for ways to reset the ReadFile buffer; however, I was unable to find any meaningful or practical answers. The closest solution that I found was the FlushFileBuffers function (https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-flushfilebuffers), but when I tried to use it, it didn't work (perhaps I failed to implement it correctly.)

Any recommendations for resetting the buffer are greatly appreciated.