I don't see it as being that critical. First, I don't really see >2GB transfers as phpseclib's intended use-case but if we can accommodate people wanting to do that without too much effort we should. Second, at a certain point, you're liable to run into issues with the internal pointers of `fread` and `fwrite`. Calling `fpos` would cause a problem because `fpos` returns an int and not a float but phpseclib doesn't call `fpos`. That's not to say other problems can't arise though.

At best we could maybe make it so phpseclib takes in either ints or Math_BigIntegers (ie. not one or the other exclusively but both) for functions like truncate but... if someone wants a feature like that they can create an issue on github. We haven't gotten one yet.