[Piohrun]

What this changes

XRef::get_with (vendored hayro-syntax) parsed an object stream's whole index of objnum offset pairs again for every object it fetched from that stream, so reading all of a stream of N objects took N² steps. Most producers cap object streams at 100–200 objects (PdfCraft's own writer at 100), but some don't: the pdf.js corpus file bug1978317.pdf (Firefox, 65,542 objects in one stream) took 37 s to draw and 40 s to extract its text, and was a known timeout in the robustness baseline.

The parsed index is now kept per stream (ObjectStreamIndexes), beside the decoded stream data it indexes, and like that data never cleared (a repair keeps it too). A malformed index is remembered as malformed; /N or /First that can't be read (a reference that can't be followed while another stream loads) is not remembered. An offset past usize is now malformed instead of wrapping. Vendored hayro-syntax patch (22).

	Before	After
bug1978317.pdf render	37 s	0.5 s
bug1978317.pdf text	40 s	1.9 s
40,000 pages in one object stream, open	54 s	0.2 s

(Release build, Linux.) bug1978317.pdf now passes pdfcraft-cli check, so its timeout entry leaves xtask/baselines/pdfjs.json, as cargo xtask check asks for a newly fixed file.

How you verified it

• cargo fmt --check
• clippy with -D warnings on pdfcraft-render (through which the vendored crate builds)
• tests pass on pdfcraft-render
• cargo xtask layers and cargo xtask assets

Tests. raster::tests::objects_in_one_large_object_stream_are_read_in_linear_time builds a cross-reference-stream document whose 40,000 page dictionaries live in one object stream (opening it resolves the page tree, one fetch per page), renders the first page and checks its pixels, and renders the last page to check its index entry, at the end of the stream, is read from its own offset. With the xref.rs change reverted it times out at 20 s; with it, it passes in 0.2 s.

Never-crash

• No new unwrap/expect/panic!/unreachable!/todo!
• The index is bounded by the decoded data (each pair takes at least three bytes; /N is never used to pre-allocate); the offset addition is checked
• A poisoned lock is still used, as the dictionary cache beside it does: entries are complete Arcs inserted in one step; the lock is never held while parsing
• No unsafe

Provenance

• No assets, fonts or copied code; behaviour from ISO 32000-2 §7.5.7

Anything a reviewer should look at first

• The cache is never cleared, matching the decoded-data cache it sits beside; it holds at most one small Vec per object stream the document has.
• Noticed while here, not changed: the fallback trailer search in xref.rs (around line 212) slices &data.as_ref()[*offset..] with an offset read from the file. Worth its own fix.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Performance
  • PDFs with many objects stored in a shared object stream now render pages substantially faster. In a reported benchmark, drawing a page with 65,542 objects took about 0.5 seconds, compared with 37 seconds previously.
• Reliability
  • Malformed object-stream offsets are now rejected, helping prevent invalid document data from being processed as valid.

[itsF4LCON]

Looks good. The index is parsed once per object stream and cached under the mutex, a malformed index stays unreadable as before, and the offset overflow is now caught. Minor: the regression test gives 40,000 pages 20 s, which could get tight on a slow debug CI runner.

[FredApps]

Reviewed 93895a1. I found no blocking defect in the object-stream index cache. The cache follows the decoded-data lifetime, does not hold its mutex while parsing or following references, preserves failed-index results, and checks offset addition. The supplied regression checks both the first page's pixels and the last page's distinct dimensions.

Independent Linux validation at this exact head: the 40,000-page regression passed in 0.06 s; the render suite passed 299 tests with 1 ignored. Formatting, strict scoped Clippy, layers, assets and diff checks passed. Source hashes were unchanged through testing.

The standalone vendored xref concurrency tests were not executed because their dev-dependency md5 was absent from the offline cache. I did not run the real bug1978317.pdf corpus check because the pinned fixture was unavailable, so the reported real-file speedup and timeout-baseline removal are not independently reproduced here. Hosted CI's signing fixture failure is also present on current main; this is not a claim that full CI is green.

[Piohrun]

@itsF4LCON On the 20 s budget: with the fix, the 40,000-page test runs in 0.06–0.2 s (FredApps measured 0.06 s), roughly 100× headroom, and the tests build with the workspace's optimized dev profile. Without the fix it doesn't finish inside 20 s. If you'd still like more margin I can raise it to 60 s; that would still catch the slowdown coming back.

[itsF4LCON]

@Piohrun Thanks, with ~100× headroom 20 s is fine, no need to change it.

[FredApps]

Re-reviewed 5d29546 against the previously approved object-stream index-cache change. The rebase range-diff changes documentation context, with the implementation and regression unchanged. No new blocking issue found. The 20-second test budget discussion is now settled in the thread. This is a source/rebase review, not a fresh test run; the earlier focused results do not establish current-head full CI.

[FredApps]

The current Windows CI failure is files_and_quit_from_the_operating_system in crates/ui-egui/tests/ui.rs:843 (expected one view, got zero), not the earlier signing/save-fixture failures. The object-stream regression passed in the same job: https://github.com/storytold/pdfcraft/actions/runs/38862733453/job/116848512461 . I inspected the OS-open test: it deletes its temporary file immediately after the harness runs four frames, while native open_path can still be preparing the file on a worker. The entire ui.rs blob is identical to current main f0c9901. This timing race is already addressed by pending PRs #1916 and #1949, which wait for the opened view before deleting the fixture; #2186 also reports intermittent failures under load. I have not independently reproduced the current-main failure, and earlier main plus #2425 passed the test, so this is not a claim that every baseline run fails. The refresh retains the previously approved feature lines; no duplicate fix or unmerged dependency was imported. Please retain the failed-run evidence and land/rebase onto the existing test fix when accepted.

[Piohrun]

Rebased onto main (43550c4; it was 240 commits behind). Now 7bcec4ac.

Renumbered: hayro-syntax patch 18 is now patch 22. While this waited, main gave (18) to the Flate back-reference copy (#2035) and (19)–(21) to later patches. This patch is now (22) everywhere: the five PdfCraft patch: markers in xref.rs, the regression test's doc comment, both roadmap entries, the commit title and the register row in vendor/README.md. In that row it is appended after (21), in both the patch and the test columns.

Otherwise unchanged from the approved head: the range-diff of the implementation and the regression test is the renumbering alone. Conflicts were only in vendor/README.md (the register row) and the status-line stack at the top of docs/roadmap.md (all of main's lines kept). The auto-merged files differ from main by exactly this PR's change.

Checked locally on the rebased head:

• cargo fmt --check, clippy -D warnings on pdfcraft-render, cargo xtask layers and cargo xtask assets: all pass.
• cargo test -p pdfcraft-render: 316 passed, 1 ignored, including objects_in_one_large_object_stream_are_read_in_linear_time.
• cargo test --manifest-path vendor/hayro-syntax/Cargo.toml: 219 passed, including the xref concurrency tests that could not run offline in the earlier review. The 2 failures are pdf::tests::pdf_version_header and pdf_version_catalog, which read ../hayro-tests/downloads/ corpus files that are not vendored. They fail the same way without this change.

Separately, the vendor/README.md register still has four hayro-syntax rows on main. One of them describes two patches the long row does not, the same number-collision loss #3312 fixed for hayro-interpret. That cleanup belongs in its own PR; this one only appends (22) to the long row.

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• vendor/hayro-syntax/src/xref.rs

📝 Walkthrough

The change adds per-PDF caching for parsed object-stream indexes, with checked offset arithmetic. It adds a rendering regression test for a 40,000-page document, updates progress records, and removes a PDF.js baseline entry that expected a timeout.

Changes: Object-stream index caching

Layer / File(s)	Summary
Parse and cache object-stream indexes vendor/hayro-syntax/src/xref.rs	XRef caches shared object-stream index pairs or parse failures. Cache misses parse the index and check offset addition for overflow before constructing an ObjectStream reader.
Validate and record object-stream behavior crates/render/src/raster.rs, vendor/README.md, xtask/baselines/pdfjs.json, ROADMAP.md, docs/roadmap.md	A generated PDF and test exercise first- and last-page rendering in a 40,000-page document. Roadmap records report parsing and timing results. The vendor patch list is updated, and the PDF.js timeout baseline entry is removed.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: echelon, mtlcl410

Merge Risk: ⚪ Minimal · up to 74500

The change addresses repeated object-stream index parsing and adds large-document regression coverage. The prior documentation concern is resolved in the reviewed head, leaving no identified merge-blocking risk.

Security architecture risk: 🔵 Low · up to 74500

The cache remains isolated to one PDF and does not expand privileges or external access. Risk is low, but cached results can preserve an obsolete interpretation after cross-reference repair and impede document recovery.

Retained concerns

• Low · reliability · inferred: Cached index results are not invalidated or versioned when repair replaces the cross-reference map. If an indirect /N or /First value successfully resolves before repair but resolves differently afterward, a cached failure or old offsets remain authoritative. For example, an initially excessive /N can produce a cached parse failure that survives repair even when the corrected value would parse the unchanged decoded bytes. The base reread this metadata on each lookup. Decoded bytes already survived repair before this PR, which limits the novelty, but does not establish stability of referenced metadata. This is an inferred document-local recovery and availability issue, not a demonstrated privilege escalation.

Security review details

Security Blast Radius

• inferred — Attacker-controlled PDF bytes and dictionary values influence cached offsets and parse failures. The affected state is confined to the parsed document and its resolver consumers; inspected paths do not add cross-document sharing or privileged capabilities. Aggregate resource impact across concurrent documents depends on hosting limits not established here.

Trust Boundaries and Controls

• observed — Untrusted index pairs remain subject to bounded input reads and now checked offset arithmetic. A successful cache entry contains immutable shared offsets; a cached malformed result causes lookup failure rather than acceptance of partial offsets.

Resilience and Maintainability Implications

• inferred — Reusing valid indexes removes repeated whole-index parsing, while retaining vectors increases document-lifetime memory relative to the base's temporary vectors. Entry production is constrained by available decoded bytes, but the cache has no independent eviction budget. The inspected source does not establish a new unbounded allocation mechanism.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 64.29% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely identifies the main change: caching each object stream index so it is read once. It also identifies the affected render path and vendored patch.
Description check		The description is complete and directly matches the changes. It explains the problem, implementation, performance impact, verification steps, regression tests, safety checks, provenance, and reviewer…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description is complete and directly matches the changes. It explains the problem, implementation, performance impact, verification steps, regression tests, safety checks, provenance, and reviewer focus. Security and parity sections are omitted, but the template allows non-applicable sections to be removed.

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Actionable comments posted: 2

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @vendor/hayro-syntax/src/xref.rs:
- Around line 652-675: Update repair() to clear both the decoded-data cache and
object_stream_indexes when publishing the replacement xref_map, so later lookups
cannot reuse entries from the previous map.

Review comments at @vendor/README.md:
- Line 18: Update the patch 7 description in the vendor table to include ASCII85
among the filters capped by decode_limit, preserving the existing filter list
and leaving patch 22 unchanged.

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📒 Files selected for processing: 6

• ROADMAP.md
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• vendor/README.md
• vendor/hayro-syntax/src/xref.rs
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• xtask/baselines/pdfjs.json

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[mtlcl410]

Thanks @Piohrun, this is a clean, contained fix. I checked it at 7bcec4ac on Windows. Tags: [spec] for ISO 32000-2 text I read, [code] for path:line@7bcec4ac, [test] for something I ran, [inference] for my reading only. The fixtures are synthetic; I can share them.

Correctness: no behaviour change found

• [spec] §7.5.7 (printed p.62) defines the index as "N pairs of integers separated by white-space, where the first integer in each pair shall represent the object number of a compressed object and the second integer shall represent the byte offset in the decoded stream of that object, relative to the first object". That index depends only on the stream's own decoded data, so caching it per stream next to the decoded data is sound.
• [code] The cache is keyed by the stream's identifier and lives on the parsed XRef (xref.rs:335), as the decoded Data it indexes does. A later revision is a new parse, so it can't see an old index. The lock is not held while the stream is fetched (xref.rs:648-676), so /N or /First given as a reference into another object stream doesn't deadlock.
• [test] I built nine object-stream fixtures and compared page count and extracted text between main and this PR's pdfcraft-cli. All nine are identical.
  • The cases: three objects in one plain stream; the same Flate-compressed; /N larger than the pairs present; one offset past the data; an object number listed twice; two streams read interleaved; an odd number of integers; an offset beyond usize; and an incremental update that redefines the object stream itself (same id, pages 300 pt wide in the new revision; both builds render 300 × 100).
• [test] Performance: 20,000 page objects in one Flate object stream. pdfcraft-cli info takes 11.3 s on main (release build) and 275 ms with this PR (dev build).
• [test] Fails without the fix: with vendor/hayro-syntax/src/xref.rs reset to main, objects_in_one_large_object_stream_are_read_in_linear_time times out at its 20 s limit. With the PR it passes in 0.07 s.
• No new unsafe. The changed hunks contain no indexing on input, and the new checked_add removes an overflow that main had on a huge offset.

Mutation run (5 mutants)

• Killed by your test: the cache never hit, and the cache never stored.
• Not pinned by any test: first_offset.checked_add(relative_offset)? → first_offset + relative_offset. In a debug build that + panics on the input it guards against. This test kills it, and passes on your head:

  #[test]
  fn an_object_stream_offset_past_usize_is_malformed_not_a_panic() {
      assert_eq!(read_object_stream_index(1, usize::MAX, b"5 1"), None);
      assert_eq!(read_object_stream_index(1, 10, b"5 1"), Some(vec![(5, 11)]));
  }

  (in xref.rs's tests module; cargo test --manifest-path vendor/hayro-syntax/Cargo.toml --lib)
• Equivalent: re-parsing a stream whose pairs failed, and refusing a poisoned lock. Each only falls back to parsing without the cache, so it costs time but gives the same output.

Small points

• Patch number collision. vendor/README.md here adds hayro-syntax (22). #2483 (inline image EI) also claims hayro-syntax (22) after its rebase today. main's highest is (21), so whichever lands second needs to renumber.
• [inference] Dropping bug1978317.pdf: "timeout" from xtask/baselines/pdfjs.json fits the description: a pdf.js test file with tens of thousands of objects in one stream. I couldn't confirm that it is that file, because I don't have the corpus locally.
• The test is time-based (a 20 s limit, on a case that takes about a minute on main). That margin looks safe. A loaded CI runner would only make main slower, not this PR.
• Pre-existing, not changed by this PR (both builds agree, so out of scope here):
  • When /N claims more pairs than exist, or an integer is left over, the whole stream is unreadable and the document has no pages. MuPDF keeps two blank pages.
  • When an object number is listed twice, the page is blank; MuPDF shows it.

[Piohrun]

@mtlcl410 Thank you for the thorough check, and for the mutant. Your test is in as 745008e (xref::tests::an_object_stream_offset_past_usize_is_malformed_not_a_panic). With checked_add swapped for + it fails with "attempt to add with overflow"; on this branch it passes. The vendored crate's unit tests now show 220 passed; the 2 failures are the same corpus-file tests as before, which need ../hayro-tests/downloads/.

On the patch number: agreed. Whichever of this PR and #2483 lands second renumbers, so if #2483 goes first, this becomes (23).

The two pre-existing MuPDF differences are noted as separate follow-ups, outside this PR: an over-long /N or a leftover integer leaves the whole stream unreadable, and a duplicated object number blanks the page.