Fix decode_array double-reading length bytes for arrays with 24+ items#479
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cffls merged 1 commit intoPython-Cardano:mainfrom Feb 28, 2026
Merged
Fix decode_array double-reading length bytes for arrays with 24+ items#479cffls merged 1 commit intoPython-Cardano:mainfrom
cffls merged 1 commit intoPython-Cardano:mainfrom
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The custom decode_array override in serialization.py called _decode_length to check for indefinite-length arrays, then delegated to the original decode_array which called _decode_length again. For arrays with fewer than 24 items, the length is encoded directly in the subtype (no stream bytes consumed), so the double call was harmless. For 24+ items, CBOR uses multi-byte length encoding (e.g. 98 18 for 24 items) and _decode_length reads from the stream — the second call consumed actual array content as a length byte, corrupting the decode. Replace the _decode_length call with a simple subtype == 31 check, which is sufficient to detect indefinite-length arrays without consuming any bytes from the stream. This bug only affected cbor2pure, not the cbor2 C extension.
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## main #479 +/- ##
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- Coverage 90.61% 90.60% -0.01%
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Lines 5155 5154 -1
Branches 781 781
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The custom decode_array override in serialization.py called _decode_length to check for indefinite-length arrays, then delegated to the original decode_array which called _decode_length again. For arrays with fewer than 24 items, the length is encoded directly in the subtype (no stream bytes consumed), so the double call was harmless. For 24+ items, CBOR uses multi-byte length encoding (e.g. 98 18 for 24 items) and _decode_length reads from the stream — the second call consumed actual array content as a length byte, corrupting the decode.
Replace the _decode_length call with a simple subtype == 31 check, which is sufficient to detect indefinite-length arrays without consuming any bytes from the stream.
This bug only affected cbor2pure, not the cbor2 C extension.