[CarolineW]

OK, I don't know what you mean by:

    > I can't see where that was written
                        ^^^^

To what exactly are you referring by the "that"?

    > Only that malicious users may read
    > past the end.

There's an entire section after that:

    Reducing complexity

    Improvement is not that much effective?
    Actually, we are optimizing the wrong way!
    Really ;)! When optimizing code, you have
    to, in order:

        reduce complexity;
        tune your compiler;
        optimize your code.

    So, how can we reduce complexity (Currently
    O(n) for both algorithms)? Simply by storing
    the string length somewhere! The complexity
    is then O(1)

etc.

But it's all there, and either you've read it and I don't know what you mean, or you haven't read it, and I've provided the pointer for you.