Order multipart parser states by frequency in the dispatch ladder#303
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Kludex wants to merge 1 commit into
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Order multipart parser states by frequency in the dispatch ladder#303Kludex wants to merge 1 commit into
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The PART_DATA state machine walked its `if/elif state == ...` ladder in lifecycle order, so the hottest states (PART_DATA, the header states) sat near the bottom and paid a failed comparison for every state above them - ~84 state comparisons per part for a 100-field form. Reorder the branches by how often each state is actually active: boundary and part-data first, the once-per-stream START/END states last. The branches are mutually exclusive on `state`, so this is a pure reorder with no behavior change - verified byte-identical to the prior parser across ~135k differential comparisons (every chunk-split strategy incl. byte-by-byte and boundary-edge sweeps, crossed with callback subsets). large ~9% faster (400 to 363 us), simple ~7%, worstcase_crlf ~10%; file upload unchanged.
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What
The PART_DATA state machine walked its
if/elif state == ...ladder in lifecycle order, so the hottest states (PART_DATA, the header states) sat near the bottom and paid a failed comparison for every state above them - ~84state ==comparisons per part for a 100-field form.Reorder the branches by how often each state is actually active (measured): boundary and part-data states first, the once-per-stream
START/ENDstates last. The branches are mutually exclusive onstate, so this is a pure reorder - no branch body changes, no behavior change.Impact
This targets the per-part Python-level work that
simple/largeare bound by - the cases where this parser trailed the others - without touching the bulk paths where it already leads.Correctness
Verified byte-identical to the prior parser across ~135k differential comparisons of the full callback-event stream and error type/offset: every chunk-split strategy (whole, byte-by-byte, fixed-size, random) plus boundary-edge sweeps, crossed with enabled-callback subsets. Zero mismatches. 158 tests pass, 100% coverage. A content-level check confirms every non-comment line is unchanged - only the branch order and
if/elifkeywords differ.AI Disclaimer
This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.