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Niels Lohmann
7db19dbf91
Under ensure_ascii, dump_escaped() calls find_ascii_copyable_run() at every character boundary. When the text is dense non-ASCII - CJK, where every byte is >= 0x80 - the scanner stops on its first byte and returns zero, so its SWAR block runs once per character and buys nothing, on top of the escaping that still has to happen afterwards. A run can only be non-empty when the first byte is one the scanner may copy, so test that single byte before calling it. Runs that do exist are found exactly as before, so the bulk-copy win is unchanged; only the calls that were always going to return zero are skipped. Output is unchanged: the dump digest over canada/citm/twitter, in compact, pretty and ensure_ascii form, matches develop byte for byte. dump(ensure_ascii=true) develop before after CJK text 3.54ms 4.25ms 3.36ms CJK, no ASCII at all 3.09ms 4.02ms 3.02ms Latin-1-ish text 4.39ms 3.04ms 2.93ms plain ASCII 3.92ms 0.80ms 0.79ms Signed-off-by: Niels Lohmann <mail@nlohmann.me>