Add fast decode_lossy path for incomplete codepages#16
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Adds benchmark for decode_lossy with mostly ASCII input (90% ASCII, 10% extended) to measure performance on typical mixed-content data.
Use dual-table approach for incomplete codepages: - DECODE_TABLE: Option<UTF8Entry> with UTF8Len enum (niche-optimized) - DECODE_TABLE_LOSSY: CompleteEntry with branchless 4-byte writes decode_lossy uses the pre-filled lossy table with the fast complete decoder, achieving 1.5-2x speedup with no regression to decode_checked.
- Move CompleteEntry to decoder/complete.rs as Entry - Move UTF8Entry/UTF8Len to decoder/incomplete.rs as Entry/Len - Re-export with descriptive names: CompleteEntry, IncompleteEntry, IncompleteLen - Update codegen to use new naming convention
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Summary
DECODE_TABLE(withOption<Entry>) for checked decoding, andDECODE_TABLE_LOSSY(pre-filled with replacement chars) for lossy decodingdecode_lossynow uses the pre-filled table with the fast branchless 4-byte write path from complete decodersBenchmark Results
decode_lossy/all_bad/4096decode_lossy/all_bad/2048decode_lossy/all_bad/1024decode_lossy/mostly_ascii/4096decode_lossy/mostly_ascii/2048decode_lossy/mostly_ascii/1024No regression to
decode_checkedperformance.Test plan