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The characters between two escapes (a quote, a backslash, a control character) are copied to the write buffer by memcpy with a length known only at run time. For a run of up to 16 characters that has 16 or more bytes in the string behind its start and in the buffer behind its end, a copy of a fixed block of 16 bytes does the same without the call; the surplus bytes in the buffer are overwritten by what follows. Apple M1, Apple clang, retired instructions per dump(), on top of the previous changes: JSON in JSON 8.32M -> 7.52M (-10 %) paths 8.17M -> 7.49M (-8 %) log lines 7.49M -> 7.14M (-5 %) cjk, emoji text (no escapes): +-1 % Linux x86-64 (callgrind), gcc 13 / clang 18: JSON in JSON -11 % / -10 %, paths -7 % / -6 %, log lines -5 % / -4 %. The branch is marked unlikely: text without escapes (CJK, accented Latin) has few short runs, and without the hint it paid up to 5 % for the check. Signed-off-by: Niels Lohmann <mail@nlohmann.me>