Mihaela Mihaljevic
41ca600d93
Plain scalars now suspend and resume mid-token instead of rolling back to a checkpoint and rescanning from the token's start on every chunk boundary inside them: scanPlainScalar's loop is an explicit PlainScalarPhase state machine that throws PlainScalarSuspended the moment a lookahead runs dry, and scanStep() resumes it directly from Scanner.suspendedPlainScalar. Getting this right took four rounds of bugs, each caught by the existing whole-suite streaming differential test: checking ranDry only once at the loop's end instead of after every peek-dependent decision, resuming a dry-interrupted content or break run through a pre-check meant only for a fresh entry point, trusting dispatchToken's own dry-fooled document-marker check, and a nested blankLineAhead() lookahead independently going dry before an outer check could catch it. A synthetic long-scalar test (needed since the real-world benchmark fixture's scalars are too short to exercise this) then caught a fifth, genuine bug: the first working resumePlainScalar took the whole suspended value by parameter, which kept a reference to its accumulated string alive for the entire resume call and defeated copy-on-write, copying the whole scalar on every resume. That is O(N^2) in the scalar's length, and measured 29x slower than not suspending at all at small chunk sizes. Passing state inout directly, with the alias broken at the call site before the call, fixed it to 3-4x, verified genuinely linear (not just a smaller quadratic constant) by a permanent test scaling scalar length 16x at a fixed chunk size. Also exposes this scanner as public API for the first time: scanStep() and everything around it were internal-only, so no consumer outside this module, including the separate PureYAMLStreaming package that actually wants a resumable token scanner, could call it. PureYAML.Streaming.Scanner wraps scanStep() directly with no independent logic, translating its tokens into public Streaming.Token/Kind/ScalarStyle types that don't leak the libyaml port's internal naming. Proven separately from the internal scanner with its own differential test, since a wrong case mapping in the translation layer wouldn't be caught by a proof that never looks at the public types. Stops short of rewiring PureYAMLStreaming's own document-boundary scanner onto this; that is separate, cross-repo work with its own build and CI cycle.
30 lines
1.0 KiB
Swift
30 lines
1.0 KiB
Swift
public extension PureYAML.Streaming.Token {
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/// A scanner token's kind, mirroring the internal libyaml-ported scanner's
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/// own token kinds (`yaml_token_type_t`) one for one, under public naming
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/// that does not leak the port's internal type names.
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enum Kind: Equatable, Sendable {
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case streamStart
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case streamEnd
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case documentStart
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case documentEnd
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case blockSequenceStart
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case blockMappingStart
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case blockEnd
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case blockEntry
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case flowSequenceStart
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case flowMappingStart
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case flowSequenceEnd
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case flowMappingEnd
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case flowEntry
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case key
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case value
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case versionDirective(major: Int, minor: Int)
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case tagDirective(handle: String, prefix: String)
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case reservedDirective
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case anchor(name: String)
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case alias(name: String)
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case tag(handle: String, suffix: String)
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case scalar(value: String, style: PureYAML.Streaming.Token.ScalarStyle)
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}
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}
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