I am trying to inject a timestamp in each line of the GPS NMEA sentences being captured from the port in this case COM3.

My data currently looks like this:

#Example 1

EST: 2024-07-10 16:14:10
$GPSS ,,,,,,,,,,,
So on .....
......
...........
...........

EST: 2024-07-10 HH:MM:SS
$GPSS ,,,,,,,,,,,
So on .....
......
...........
...........

HH:MM:SS is arbitrary it means the next time stamp collected from the system.

However, I want the data to look like this:

EST: 2024-07-10 16:14:10 $GPSS ,,,,,,,,,,,
EST: 2024-07-10 HH:MM:SS So on .....
EST: 2024-07-10 HH:MM:SS So on .....
EST: 2024-07-10 HH:MM:SS So on .....
EST: 2024-07-10 HH:MM:SS So on .....
EST: 2024-07-10 HH:MM:SS So on .....
EST: 2024-07-10 HH:MM:SS So on .....
EST: 2024-07-10 HH:MM:SS So on .....
EST: 2024-07-10 HH:MM:SS So on .....

The code below produces example 1.

These are my imports as well:

#include <iostream>
#include <windows.h>
#include <chrono>
#include <stdlib.h>
#include <iomanip>

void readDataAndWriteToFile(HANDLE hSerial, const char* filePath) {
    DWORD bytesRead;
    char buffer[1024];
    DWORD dwBytesWritten = 0;
    HANDLE hFile;

    hFile = CreateFile(filePath, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == INVALID_HANDLE_VALUE) {
        std::cerr << "Error opening file for writing" << std::endl;
        return;
    }

    auto startTime = std::chrono::steady_clock::now();
    while (true) {
        auto currentTime = std::chrono::steady_clock::now();
        auto elapsedTime = std::chrono::duration_cast<std::chrono::minutes>(currentTime - startTime);
        if (elapsedTime.count() >= 2) {
            break;
        }
        std::chrono::time_point<std::chrono::_V2::system_clock> input = std::chrono::system_clock::now();
        ReadFile(hSerial, buffer, sizeof(buffer), &bytesRead, NULL);
        if (bytesRead > 0) {
            std::string timestamp = serial_TimePoint(input, "nEST: %Y-%m-%d %H:%M:%Sn");
            DWORD timestampLength = static_cast<DWORD>(timestamp.size());
            WriteFile(hFile, timestamp.c_str(),timestampLength,&dwBytesWritten, NULL);
            WriteFile(hFile, buffer, bytesRead, &dwBytesWritten, NULL);
        }
    }
    CloseHandle(hFile);
}

I am thinking whether if it were possible to concatenate timestamp.c_str(), and buffer. However, I feel this would still be a problem because buffer is a chunk of data read from the COM3 at a CBR_9600, which is 9600 bits per second. I don’t understand if the problem is that it’s too fast.