Optimize File.extname for common encodings#15912
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byroot merged 1 commit intoruby:masterfrom Jan 20, 2026
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Similar optimizations to the ones performed in rubyGH-15907. - Skip the expensive multi-byte encoding handling for the common encodings that are known to be safe. - Use `CheckPath` to save on copying the argument and only scan it for NULL bytes once. - Create the return string with rb_enc_str_new instead of rb_str_subseq as it's going to be a very small string anyway. This could be optimized a little bit further by searching for both `.` and `dirsep` in one pass, ``` compare-ruby: ruby 4.1.0dev (2026-01-19T03:51:30Z master 631bf19) +PRISM [arm64-darwin25] built-ruby: ruby 4.1.0dev (2026-01-20T07:33:42Z master 6fb5043) +PRISM [arm64-darwin25] ``` | |compare-ruby|built-ruby| |:----------|-----------:|---------:| |long | 3.606M| 22.229M| | | -| 6.17x| |long_name | 2.254M| 13.416M| | | -| 5.95x| |short | 16.488M| 29.969M| | | -| 1.82x|
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I tried it:
However there are many corner cases to consider, some of them being Windows only, so I'd rather ship the sure thing now and potentially come back to it later. |
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Similar optimizations to the ones performed in GH-15907.
CheckPathto save on copying the argument and only scan it for NULL bytes once.This could be optimized a little bit further by searching for both
.anddirsepin one pass,