Make Source index-based instead of materializing a char list#489
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`Source.__init__` built `iter([(i, TOMLChar(c)) for i, c in enumerate(self)])`, allocating one tuple and one TOMLChar per character of the whole input up front. Track an integer index into the underlying string instead: `inc()` bumps the index and reads `self[idx]`, and state save/restore snapshots the index rather than copying an iterator. Construction is O(1) and per-character work is deferred to the read. No behaviour change (full suite incl. the toml-test conformance submodule passes); ~1.07-1.14x faster parsing across document sizes.
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This was referenced Jun 5, 2026
frostming
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Jun 8, 2026
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What
Source.__init__builtiter([(i, TOMLChar(c)) for i, c in enumerate(self)]), allocating one tuple and oneTOMLCharfor every character of the whole input before parsing even starts.This tracks an integer index over the underlying string instead:
inc()bumps the index and readsself[idx], and_Statesave/restore snapshots the index rather thancopy()-ing an iterator. Construction becomes O(1) and per-character work is deferred to the read.Benchmarks
Parsing speedup across document sizes/shapes (median, interleaved A/B vs
master):No regression on any shape (tiny inputs unchanged).
Tests
Full suite passes (972 tests, incl. the toml-test conformance submodule). No public API or behaviour change — round-trip output is byte-identical to
masteron a varied corpus.