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rev: reverse by character in UTF-8 locales - #657
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SichenLiang wants to merge 1 commit into
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When the first nonempty value of LC_ALL, LC_CTYPE and LANG names a UTF-8 codeset, reverse valid UTF-8 records by code point. Keep byte reversal in other locales and for records that are not valid UTF-8.
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In a UTF-8 locale, reverse valid UTF-8 records by code point instead of by byte. Other locales keep the existing byte-reversal behavior.
The locale is taken from the first nonempty value of
LC_ALL,LC_CTYPE, andLANG. The manual now documents that rule.Records that are not valid UTF-8 are still reversed byte by byte and exit 0; util-linux reports an
fgetwc()error instead.On an x86_64 Linux machine, 64 MiB of records made entirely of multibyte characters took 5.9 to 7.2 times as much CPU as main, depending on code alignment, because they are now validated and reversed on character boundaries. Long ASCII records in a UTF-8 locale were 13% to 22% faster. In the C locale the code path is unchanged; a 7% difference there went away when both binaries were rebuilt with branch alignment. Short ASCII lines were about 3% slower.
Tests cover locale precedence, valid and invalid records, files, NUL-delimited input, and long records.
Fixes #656