Faster reverse() string function for ASCII-only case #14195
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UBarney
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Jan 21, 2025
| // SAFETY: Since the original string was ASCII, reversing the bytes still results in valid UTF-8. | ||
| let reversed = unsafe { | ||
| // reverse bytes directly since ASCII characters are single bytes | ||
| String::from_utf8_unchecked(s.bytes().rev().collect::<Vec<u8>>()) |
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We could avoid a allocation here by copying into a Vec<u8> buffer
// slightly faster than using iterator `bytes`
bytes_buf.extend(s.as_bytes())
bytes_buf.reverse()
...
bytes_buf.clear()
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Got an improvement of ~30% at most after add bytes_buf
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Dandandan
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That is some sweet sweet performance |
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Thanks @UBarney and @Dandandan |
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Which issue does this PR close?
Closes #12445.
Rationale for this change
See the issue.
What changes are included in this PR?
gen_string_arrayinbenches/character_length.rsto helper.rsAre these changes tested?
Yes. Using existing unit test
bench result
Are there any user-facing changes?
No