[Velli20]

Summary

• Dictionary stores its entries in a private Vec<(PdfName, ObjectVariant)> sorted by key, instead of a public BTreeMap<Vec<u8>, ObjectVariant>. Lookups use binary search, and iteration stays in key order.
• PdfName stores names of up to 22 bytes inline, so dictionary keys no longer allocate. Longer names use a shared Arc<[u8]>. parse_name returns a PdfName and only allocates when the name contains # escapes.
• Dictionary::new and its sort-and-dedup pass are removed:
  • the parser inserts each entry as it reads it, so a repeated key keeps its last value, as with the old BTreeMap;
  • decryption decrypts values in place through the new iter_mut();
  • inline-image normalization builds its dictionary directly; the abbreviated key still wins.
  • Callers with loose entries, mostly tests, use the new FromIterator impl.
• optional_entries and lenient_entries borrow the resolved sub-dictionary instead of cloning it.
• Name values are still PdfString { bytes: Arc<[u8]> }, so the 73 read::<Arc<[u8]>> sites still only clone an Arc and allocate nothing.

Benchmarks

document_open on the shipped profile (opt-level "z", fat LTO). Medians of 5 interleaved rounds against main, run before the parser switched to inserting keys as it reads them:

Document	main	this PR (sort once)
Gradients.pdf	34.69 ms	−3.2%
W3Schools.pdf	3.63 ms	−4.6%
dd5cf1a7….pdf	74.83 ms	−3.9%
RadialGradientFills.pdf	5.52 ms	−2.7%
PlaygroundMDN.pdf	4.38 ms	−2.4%
test6.pdf	0.27 ms	−2.6%
webgl.pdf	107.65 ms	−1.3%
is.pdf	292.61 ms	+0.4% (noise)

Inserting each key in sorted position as the parser reads it, instead of sorting once at the end, measured 0.2–2% slower on six documents and slightly faster on two, close to the noise floor. The final code was not benchmarked against main directly.

Inline keys compared with Arc<[u8]> keys, everything else identical: −1.8% to −3.1% on four documents, within noise on the rest.

Test plan

• cargo test --workspace --exclude pdf-graphics-skia --exclude pdf-conformance
• cargo clippy --workspace --all-targets --exclude pdf-graphics-skia --exclude pdf-conformance -- -D warnings
• cargo fmt --all --check, minimal-feature check
• Skia crates and the conformance tool were not built locally (Skia binaries can't be downloaded here); CI covers them

🤖 Generated with Claude Code