Niels Lohmann 31789f51cf Find the stop byte of a string run without a byte loop ...

find_string_special() and find_ascii_copyable_run() test eight bytes at a
time, but located the stopping byte inside a word with a byte loop. The
lowest flagged byte of the SWAR tests is always a true hit (the borrows of
the subtractions can only flag bytes above one), so its index is now the
trailing-zero count of the mask; words are read in little-endian order on
every platform, so this does not depend on the byte order.
scalar_string_bulk_run() validates a run of multi-byte UTF-8 sequences one
after another instead of searching for the next special byte in between,
which helps text in non-Latin scripts.

The kernels serve the lexer's contiguous fast path, the serializer, and the
binary formats. New tests compare all three with byte-by-byte reference
scans on 100,000 generated buffers at three alignments; the portable
fallback of count_trailing_zeros() was checked against the builtin.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

2026-09-29 03:49:26 +02:00

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nlohmann

Find the stop byte of a string run without a byte loop

2026-09-29 03:49:26 +02:00