77304153fc
Implements CIDToGIDMap resolver with Identity and stream forms: - Identity: zero-allocation short-circuit (GID == CID) - Stream: parses 2-byte big-endian GID values into Box<[u16]> - Emits CIDTOGIDMAP_TRUNCATED diagnostic on odd-byte-count input - Out-of-range CID returns GID 0 (notdef glyph) without panic Acceptance criteria: - Identity form: lookup of any CID returns same value as u16 - Stream form: synthetic 3-CID array decodes correctly [0, 5, 10] - Out-of-range CID returns GID 0 with no panic - Diagnostic CIDTOGIDMAP_TRUNCATED emitted on odd-byte-count input Refs: pdftract-5sh, Phase 2.1 line 1315
64 lines
2.5 KiB
Markdown
64 lines
2.5 KiB
Markdown
# pdftract-5sh: CIDToGIDMap resolver (Identity and stream forms)
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## Summary
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Implemented the CIDToGIDMap resolver for CIDFontType2 descendant fonts with:
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- `/Identity` name detection (zero-allocation short-circuit)
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- Stream form parsing into `Box<[u16]>` array (2-byte big-endian GID values)
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- `CIDTOGIDMAP_TRUNCATED` diagnostic for odd-byte-count input
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- Out-of-range CID returns GID 0 (notdef glyph)
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## Changes Made
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### 1. Added new diagnostic code (`diagnostics.rs`)
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- `DiagCode::FontCidtogidmapTruncated` - emitted when CIDToGIDMap stream has odd byte count
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- Added to category, name, severity (Warning), and catalog entries
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### 2. Updated `CIDToGIDMap` enum (`type0.rs`)
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Changed from `Custom(Vec<u8>)` to `Array(Box<[u16]>)`:
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- Pre-parsed u16 array instead of raw bytes
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- Single heap allocation, not per-lookup
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- `get()` method now uses `arr.get(cid as usize).copied().or(Some(0))`
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### 3. Updated `load_cid_to_gid_map()` function
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- Now parses decoded bytes into `Box<[u16]>` array
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- Emits `CIDTOGIDMAP_TRUNCATED` diagnostic on odd-length input
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- Truncates trailing byte instead of failing
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- Takes `diagnostics: &mut Vec<Diagnostic>` parameter
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### 4. Updated tests
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- `test_cid_to_gid_map_array` - tests Array variant with [0, 1, 2, 3]
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- `test_cid_to_gid_map_array_big_endian` - tests big-endian parsing
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- `test_cid_to_gid_map_out_of_range` - tests GID 0 return for out-of-range CID
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- `test_cid_to_gid_map_from_stream` - tests stream loading with [0, 5, 10] per acceptance criteria
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- `test_cid_to_gid_map_truncated` - tests odd-byte-count diagnostic emission
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## Acceptance Criteria - PASS
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- [PASS] Identity form: lookup of any CID returns same value as u16
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- [PASS] Stream form: synthetic 3-CID array decodes correctly [0, 5, 10]
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- [PASS] Out-of-range CID returns GID 0 with no panic
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- [PASS] Diagnostic `CIDTOGIDMAP_TRUNCATED` emitted on odd-byte-count input
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## Test Results
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```
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test font::type0::tests::test_cid_to_gid_map_array ... ok
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test font::type0::tests::test_cid_to_gid_map_array_big_endian ... ok
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test font::type0::tests::test_cid_to_gid_map_identity ... ok
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test font::type0::tests::test_cid_to_gid_map_out_of_range ... ok
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test font::type0::tests::test_cid_to_gid_map_truncated ... ok
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test font::type0::tests::test_cid_to_gid_map_from_stream ... ok
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test result: ok. 6 passed; 0 failed; 0 ignored
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```
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All 25 type0 tests pass.
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## Files Modified
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- `crates/pdftract-core/src/diagnostics.rs` - added FontCidtogidmapTruncated diagnostic
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- `crates/pdftract-core/src/font/type0.rs` - updated CIDToGIDMap enum and implementation
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