Fastest way to read a file line by line with an arbitrary number of characters in each

Question

Ok, I'm trying to figure out which way would be faster to read a text file that I'm working with. The contents of the file look like this

1982 3923 3542 4343
2344 3453 2
334 423423 32432 23423

They're basically just an arbitrary number of int numbers and I need to read line by line. Would it be better to use getline or the insertion (>>) operator? I, personally, think it would be a lot easier to implement by using the insertion operator but I don't know how I would make the program so that it reads all of the int numbers in the same line until it reaches the end. I was thinking of setting it up like the following:

ifstream input;
input.open("someFile.txt");
if (input) {
    char* ch;
    while (ch != '\n\)
        getline(input, buffer, ' ')

The only problem is that I have to do a conversion to an int, then put each int in an array. My desired end goal is to produce a two-dimensional array where each line of int's is an array of int's. Any suggestions as to the best implementation is appreciated!

Answer 1

I would keep it real simple:

ifstream in(...);
string line;
while (getline(in, line)) {
    istringstream line_in(line);
    while (line_in) {
        int val = 0;
        if (line_in >> val) {
            // Do something with val
        }
    }
    // eol
}

Answer 2

1. You'd have to benchmark to get a correct answer.
2. The speed of the two functions is implementation defined. You might get different results on different compilers.
3. Fastest way to do it would probably to use a custom-made finite state machine. But those are about as unreadable as you get.

Produce correct code first. Then fine tune it if you need to later.