mozilla/rust — pull request #2062 by grahame (2012-03-28 18:37:31+00:00)
Title: Rewrite str::push_char in rust.

Avoid crossing to C to reallocate underlying vec when possible,
if we must we now only cross once per char (not once per byte.)
As str::from_chars calls this method, but first reserves space in the
underlying vec, str::from_chars becomes significantly quicker.

From my testing this is a decent performance win.