ext/standard: Optimize str_pad() using doubling copies - #23661
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I think it s correct. nice follow-up for you is applying the same sort of optimisation in mbstring (mb_str_pad)
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Yeah here are some benchmark results if anyone is curious (str_pad):
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LamentXU123
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Follow-up #23661. Use the same optimization on mb_str_pad. Co-authored-by: David CARLIER <devnexen@gmail.com>
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I was reading standard code recently. The implementation of
str_padhere is quite old that we make a loop to pad the strings. The loop goes on if the remaining padding length is smaller than padded-string's length. In modern implementations like OpenJDK for example, we use a doubling algo for this: https://github.com/openjdk/jdk/blob/jdk-21%2B35/src/java.base/share/classes/java/lang/String.java#L4682 This is way more faster than the original one. Let's say we want to pad "ab" for 1 MiB. With the original one we need ~52,000 times of memory copying but with this implementation we only need 20 times.