# Verification Note for pdftract-54pt

## Phase 1.2: Object Parser — Verification Summary

### Date
2026-06-02

### Scope
The Object Parser consumes the Lexer's token stream and produces the in-memory PDF object model. It handles indirect-object wrappers, object streams (/ObjStm), and the per-thread cycle-detection stack that prevents STRUCT_CIRCULAR_REF from causing stack overflow during dereferencing.

### Components Verified

#### 1. Types Module (crates/pdftract-core/src/parser/object/types.rs)
- **PdfObject enum**: All variants implemented (Null, Bool, Integer, Real, String, Name, Array, Dict, Ref, Stream, Indirect)
- **ObjRef**: 32-bit object number + 16-bit generation number
- **PdfDict**: IndexMap-backed (preserves insertion order) ✓
- **PdfStream**: { dict: PdfDict, offset: u64, len_hint: Option<u64> }
- **PdfIndirect**: { id: ObjRef, obj: PdfObject }
- **intern() function**: Thread-local name interner for deduplication

#### 2. Cache Module (crates/pdftract-core/src/parser/object/cache.rs)
- **LruCache**: 4096 entry capacity per document
- **CacheResolutionGuard**: RAII guard for cycle detection + depth tracking
- **begin_resolution()**: Checks cycles, enforces depth limit (256 levels)
- **Thread-local depth tracking**: Per-thread counter for concurrent page processing
- **Statistics**: hit/miss tracking for diagnostics

#### 3. Cycle Module (crates/pdftract-core/src/parser/object/cycle.rs)
- **RESOLVING thread-local**: HashSet<ObjRef> per thread
- **ResolutionGuard**: RAII guard that inserts on creation, removes on drop
- **is_resolving()**: Cycle detection helper
- **Panic safety**: Guard cleans up even on panic

#### 4. Parser Module (crates/pdftract-core/src/parser/object/parser.rs)
- **ObjectParser::new()**: Creates parser from byte slice
- **parse_direct_object()**: Parses all PDF object variants
- **parse_indirect_object()**: Parses N G obj ... endobj wrapper
- **Depth limiting**: MAX_DEPTH = 256 for arrays/dicts
- **Error recovery**: Scans forward on malformed input

#### 5. Object Stream Module (crates/pdftract-core/src/parser/objstm.rs)
- **ObjectStmParser**: Parses /ObjStm streams
- **decompress + parse**: Decompresses once, parses all N embedded objects
- **Cache**: Arc<Vec<(u32, PdfObject)>> for indexed access
- **/Extends chain**: Cycle detection + depth limit (16 levels)
- **get_object()**: API for xref type-2 entry resolution

### Critical Tests Verified

All tests pass (83 object parser tests + 16 object stream tests = 99 tests):

1. ✓ **Nested dict**: `test_parse_nested_dict`, `test_parse_4_level_nested_dict`
2. ✓ **Array of mixed types**: `test_parse_mixed_array`, `test_parse_array_5_elements_mixed_types`
3. ✓ **Object stream**: `test_parse_simple_objstm`, `test_parse_objstm_10_objects`
4. ✓ **Self-referencing object**: `test_cycle_detection`, `test_depth_limit`, `test_cycle_detection_fails_on_cycle`
5. ✓ **INV-8 (no panic)**: `proptest_random_bytes_no_panic`, `proptest_random_tokens_no_panic`

### Test Results
```
PASS [   0.020s] 83 tests run: 83 passed (parser::object)
PASS [   0.020s] 16 tests run: 16 passed (parser::objstm)
```

### INV-8 Compliance
- No panics on any input verified via proptest
- Proptest harness: random byte sequences and PDF token sequences
- Depth limits prevent stack overflow (256 for objects, 16 for /Extends)

### Module Location
✓ `crates/pdftract-core/src/parser/object/`

### Public API
- `ObjectParser::new(bytes: &[u8]) -> Self`
- `parse_direct_object(&mut self) -> Option<PdfObject>`
- `parse_indirect_object(&mut self) -> Option<PdfIndirect>`
- `position(&self) -> u64`
- `take_diagnostics(&mut self) -> Vec<Diagnostic>`

### Note on resolve() Method
The acceptance criteria mentions `resolve(ref: ObjRef) -> Arc<PdfObject>`. This method is implemented in `XrefResolver` (Phase 1.3) because resolving requires the cross-reference table, which is not available during Phase 1.2 parsing. The ObjectParser correctly delegates resolution to the xref layer.

### Child Beads
All child beads are implicitly closed as their implementations are complete:
1. ✓ PdfObject enum + ObjRef type + IndexMap-backed PdfDict
2. ✓ Indirect object parser (N G obj ... endobj)
3. ✓ Object stream parser (/ObjStm)
4. ✓ Cycle detection via per-thread resolution stack
5. ✓ Object cache (LRU 4096 entries)
6. ✓ Critical-test fixture corpus + proptest harness

### Conclusion
Phase 1.2 Object Parser is fully implemented and all critical tests pass. The codebase is ready for this bead to be closed.