Decode legacy fixed-range TcfCaV1 (Canada) strings (backwards compatibility)#107
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chuff wants to merge 2 commits into
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Decode legacy fixed-range TcfCaV1 (Canada) strings (backwards compatibility)#107chuff wants to merge 2 commits into
chuff wants to merge 2 commits into
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Per the GPP Consent String Specification, the Canada section encodes several fields as OptimizedRange / N-ArrayOfRanges, both of which use Fibonacci coding. They were using fixed-integer encoders. - VendorExpressConsent, VendorImpliedConsent, DisclosedVendors (OptimizedRange): EncodableOptimizedFixedRange -> EncodableOptimizedFibonacciRange (new), backed by a new OptimizedFibonacciRangeEncoder. - PubRestrictions (N-ArrayOfRanges(6,2), whose ids are an OptimizedRange): EncodableArrayOfFixedIntegerRanges -> EncodableArrayOfOptimizedFibonacciRanges (new). The fixed variant is left untouched for TCF EU. Output is byte-identical to the master-based fix (PR IABTechLab#105): updated test vectors match (e.g. vendor section ...BhADVqxGAD0AILVgAA, PubRestrictions ...CCgAS7o). This PR is the encoding fix only; backwards-compatible decoding of pre-fix (fixed-range) strings follows in a separate PR stacked on this one. mvn test: 344 tests, 0 failures; spotless:check clean. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Strings produced by the previous encoder used fixed-integer ranges for the Canada OptimizedRange / N-ArrayOfRanges fields. Decode them by trying the spec-compliant (Fibonacci) interpretation first and, when the consumed bits do not re-encode to it, re-reading them under the legacy interpretation: - OptimizedFibonacciRangeEncoder.decode (VendorExpressConsent, VendorImpliedConsent, DisclosedVendors): in the range branch, fall back from a Fibonacci range to a fixed-integer range. - EncodableArrayOfOptimizedFibonacciRanges.decode (PubRestrictions): fall back from OptimizedRange ids to a plain fixed-integer range (the previous EncodableArrayOfFixedIntegerRanges layout). Adds BitString get/setReadIndex to mark/reset the read cursor for the round-trip check. Empty / bitfield-form data is unambiguous and unaffected. Tests decode real pre-fix strings: a fixed-range PubRestrictions string and a full real-world string whose vendor lists use fixed-integer ranges. Stacked on the encoding-fix PR; review/merge that first. mvn test: 346 tests, 0 failures; spotless:check clean. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Summary
Follow-up to #106 (the Canada OptimizedRange → Fibonacci encoding fix). This makes the decoder backwards compatible: strings produced by the previous encoder (fixed-integer ranges) still decode correctly.
Approach
Round-trip disambiguation at the datatype level — decode the spec-compliant (Fibonacci) way first and, if the consumed bits don't re-encode to it, reset the read cursor and re-read under the legacy interpretation:
OptimizedFibonacciRangeEncoder.decode(VendorExpressConsent,VendorImpliedConsent,DisclosedVendors): in the range branch, fall back from a Fibonacci range to a fixed-integer range.EncodableArrayOfOptimizedFibonacciRanges.decode(PubRestrictions): the whole ids structure changed (plain fixed range →OptimizedRange), so fall back fromOptimizedRangeids to a plain fixed-integer range (the previousEncodableArrayOfFixedIntegerRangeslayout).Adds
BitString#getReadIndex/setReadIndexto mark/reset the read cursor for the round-trip check. Empty / bitfield-form data is unambiguous and takes the fast path unchanged.Test plan
mvn test— 346 tests, 0 failuresmvn spotless:check— cleanPubRestrictionsstring, and a full real-world string whose vendor lists use fixed-integer ranges (14 express + 46 implied vendors)🤖 Generated with Claude Code