Unicode string iterator performance

You probably saw that I have committed initial implementation of TextIterator. The impetus for this is that direct indexing of Unicode strings via [] operator is slow, very slow, at least currently. The reason is that [] cannot simply perform random-offset indexing into UCHar* strings. It needs to start from the beginning of the string and iterate forward until it reaches the desired offset, because our default unit is a codepoint, which can take up 1 or 2 UChar's. So here are some (rough) numbers on the relative performance of TextIterator vs. []. The script I used was a simple one (attached after the signature). Each test was 10000 runs over 500-character string. [] operator: 27.16373 s TextIterator: 1.89697 s (!) For comparison, running the same [] operator test on a 500-character binary (old-style) string gives me 9.11334 s. Quite interesting, I'd say. I am not sure how we can optimize [] to be faster than the iterator approach. Food for thought? - Andrei <?php $a = str_repeat('a\U010201bcß', 100); var_dump($a); /* warm up the engine */ for ($x = 0; $x < 100; $x++) { foreach (new TextIterator($a) as $c) { } } /* measure [] */ $start = microtime(true); for ($x = 0; $x < 10000; $x++) { $len = strlen($a); for ($i = 0; $i < $len; $i++) { $c = $a[$i]; } } $end = microtime(true); printf("[] run time: %.5f\n", $end - $start); /* measure iterator */ $start = microtime(true); for ($x = 0; $x < 10000; $x++) { foreach (new TextIterator($a) as $c) { } } $end = microtime(true); printf("iterator run time: %.5f\n", $end - $start); ?>