Comment by tspeterkim

  for (int i = 0; buffer[offset+i] != '\n'; i++) {

This would only process the current line, though. Here, each thread processes ~split_size bytes (multiple lines).

Even if were to read multiple lines, how would a thread know when to stop? (at which offset?)

And when it does, it should communicate where it stopped with the other threads to prevent re-reading the buffer. My brain's hurting now.