Every append found the end of the buffer with strlen(), up to four
times per append and four appends per field, so building a response
cost the square of its size. /discovery fills a 4 KB buffer and spent
about 195 ms of its ~210 ms there (shades 126 ms, groups 69 ms), all on
the async_tcp task that serves every socket and web request.
Keep the length in the formatter and write every append at the end
through one helper. The web response and socket event subclasses and
ControllerChunker use the tracked length too. Output is unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
When something didn't fit, the formatters skipped it silently, closing
brackets included, and clients got malformed JSON. Two writes could
also go past the buffer:
- AsyncJsonResp flushed when full and then wrote the value without
checking again, so a value bigger than the whole buffer overflowed.
It is now streamed straight out instead.
- JsonSockEvent::closeEvent added the closing ] when only one byte was
left, putting the terminator one byte past the buffer.
The formatters now set an overflowed() flag and log an error, and a
socket event that overflowed is logged and not sent.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Tests BufferedJsonFormatter output: nesting and commas, number and bool
values, skipped null strings and escaping. A canary after the buffer
catches writes past its end.
Three fail: control characters other than \b\f\n\r\t aren't escaped,
calcEscapedLength skips the first character, and so a value starting
with an escaped character can be written one byte past the buffer.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
