The WASM scanner could fill its fixed 4096-op buffer on large inputs (e.g. 5MB
of newlines or OSC traffic) and previously failed or appeared hung. ESC op
coalescing also corrupted the lengths field used for dispatch, causing millions
of redundant handler invocations on OSC benchmark data.
WASM scanner (parser.c / parser.h):
- Add scan_offset to ParserScanHeader; scan(offset, length) resumes after a
partial fill instead of returning -1 for the whole buffer.
- Return early from scan when the op buffer is full; all emit sites use
emit_or_stop() so scan_offset records where to continue.
- Coalesce consecutive OP_EXECUTE and OP_ESC ops with the same code/ident;
lengths holds repeat count, starts holds the input index for ESC.
- Keep CSI/DCS hook layout unchanged (lengths = final byte index, starts =
param arena offset).
TypeScript dispatch (EscapeSequenceParserWasm.ts):
- Drive parsing via runWasmScanChunks(): scan a slice, dispatch ops, advance
inputOffset to nextOffset until the chunk is consumed.
- Fix ESC dispatch: chunkPos uses starts (input index); escCount uses lengths
(repeat count). Avoid treating the CSI-style final-byte index as a loop bound.
- Throw if nextOffset does not advance to catch stuck scans.
EscapeSequenceParser.ts:
- Extend _scanCache for chunked scan state; reset() clears inputOffset and
cached scan data so later parses are not skipped.
Benchmarks:
- Import compiled modules from ../../out/common and ../../out/browser so
npm run benchmark works without NODE_PATH after path-mapping removal.
- Update benchmark skill notes accordingly.
Build:
- build_parser_wasm.sh selects a clang with wasm32 support (Homebrew LLVM on
macOS when Xcode clang lacks the target).
Co-authored-by: Cursor <cursoragent@cursor.com>
Daniel ImmsandCursor
