non-blocking std::getline, exit if no input

Question

Currently I have a program that reads from the standard input, occasionally the program needs to just keep running if no input is made, usually this is a test script there i

Answer 1

You can make a non-blocking equivalent to std::getline fairly easily using the istream::readsome() method. This reads available input up to a maximum buffer size, without blocking.

This function will always return instantly, but will capture a line if one is available on the stream. Partial lines are stored in a static variable until the next call.

bool getline_async(std::istream& is, std::string& str, char delim = '\n') {

    static std::string lineSoFar;
    char inChar;
    int charsRead = 0;
    bool lineRead = false;
    str = "";

    do {
        charsRead = is.readsome(&inChar, 1);
        if (charsRead == 1) {
            // if the delimiter is read then return the string so far
            if (inChar == delim) {
                str = lineSoFar;
                lineSoFar = "";
                lineRead = true;
            } else {  // otherwise add it to the string so far
                lineSoFar.append(1, inChar);
            }
        }
    } while (charsRead != 0 && !lineRead);

    return lineRead;
}