mirror of
https://github.com/nlohmann/json.git
synced 2026-07-23 19:04:54 +00:00
Niels LohmannandClaude Opus 4.8
32c2b317af
When ensure_ascii is false, dump_escaped previously ran every byte of every string and object key through the UTF-8 DFA decoder, even for the common case of ordinary text with nothing to escape. This mirrors the per-byte cost the parser had before the contiguous fast paths. At a character boundary, bulk-copy the longest run of bytes that need no escaping using string_bulk_run() - the same SWAR scanner and UTF-8 bulk validator the lexer's contiguous path uses - and only fall back to the byte-at-a-time DFA loop for the first byte that needs individual handling (a quote, backslash, control character, or ill-formed/truncated UTF-8). Because every "hard" or invalid byte is still processed by the unchanged byte path, escaping output and error handling (including strict-mode error 316 position and message) are byte-identical to before. The ensure_ascii=true path is unchanged: it must escape non-ASCII and 0x7F, which string_bulk_run does not stop on, so a separate predicate would be needed for it. Verified byte-for-byte identical dump output against the pre-change implementation across ~20k randomized byte strings plus curated edge cases (all escapes, control chars, valid multibyte, surrogates, overlong, truncated sequences) for both ensure_ascii settings and all three error handlers, in C++11/17/20 at -O2/-O3. Throughput (g++ -O3, ensure_ascii=false, vs pre-change): long ASCII strings 4.2x twitter-like objects 2.3x dense CJK 1.4x (further headroom with JSON_USE_SIMDUTF) Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG Signed-off-by: Niels Lohmann <mail@nlohmann.me>