xpact

xpact is an Eiffel XML parser project inspired by Finnian Reilly's Eiffel.org proposal, "Finding a billion-user project for Eiffel: How DbC catches the security flaws that Rust misses."

Tagline: XML parsing, by contract.

The project goal is to use libexpat as the public reference point while keeping the parser semantics owned by Eiffel. The C code in native/ is an ABI bridge: it exports libexpat-shaped symbols and delegates parsing to Eiffel classes. It is not intended to become a second C parser.

Current Status

This checkpoint is a Windows-only Phase 1 preview, not a final drop-in replacement for libexpat.

Implemented and verified now:

• Eiffel targets explicitly compile with void safety enabled (support="all" use="all"), using the safe Base precompile.
• Contract-backed temporary garbage-collection suspension for critical parse sections.
• XML 1.0 tokenization and entity handling in Eiffel.
• Capability-based external entity resolver policy: xpact does not open files, URLs, or sockets by itself.
• A libexpat 2.8.1 public API header surface in include/xpact.h.
• A Windows x64 Eiffel-backed xpact.dll build path.
• A finalized assertion-enabled xpact_assertions.dll tier for contract-audited validation runs.
• C ABI smoke tests for public callers and for the private Eiffel bridge.
• A native C benchmark path against the Windows Eiffel-backed DLL.
• A chunked XML_Parse CRC harness that compares event digests across buffer sizes and can be compiled against xpact or libexpat.
• An upstream libexpat test-suite adapter with explicit green/red parity rows.
• Published benchmark, performance-analysis, and parity documentation.
• An opt-in large XML benchmark runner for caller-supplied, pre-decompressed real corpora.

The upstream Expat 2.8.1 manifest currently has 399 START_TEST(...) entries. The expected-failure list expands to 86 rows:

• 86 allocator-injection tests are intentionally out of the current Eiffel release scope because they exercise libexpat's manual C allocation hook contract.

What Is Left

Before calling xpact a credible drop-in replacement, the project still needs:

• true incremental parsing in the Eiffel parser/session core; the current native adapter accepts chunks and now has CRC coverage for replayed character data, but it still relies on accumulated-buffer replay rather than a suspendable parser session;
• a stronger native-suite gate that reports actual unexpected failures by upstream test name, not only the current expected-failure manifest expansion;
• Phase 2 performance work: buffer-backed token slices, lazy materialization, string-pool recycling, and a native byte-buffer parse path;
• replacement testing in at least one public application that normally builds against libexpat;
• Linux/WSL packaging for an Eiffel-backed libxpact.so;
• broader consumer ABI coverage across compilers and build systems;
• a release decision on whether allocator-injection semantics are intentionally unsupported or emulated at the C ABI boundary.

Reading Order

Start here, then read:

1. docs/article-reading-guide.md for how the repository maps to the original Eiffel.org article and the Design by Contract argument.
2. docs/phase-1.md for the full Windows Phase 1 scope.
3. docs/test-matrix.md for assertion-on/assertion-off test lanes.
4. docs/platform-builds.md for Windows, Linux, and Eiffel .NET build preparation.
5. docs/design-overview.md and docs/bon/ for the design map and BON views.
6. docs/libexpat-api-compatibility.md for the public C API surface.
7. docs/libexpat-parity.md and adapters/libexpat/parity.tsv for green/red upstream test-suite status.
8. docs/chunked-parse-crc.md for incremental parsing verification through CRC-32 event digests across chunk sizes.
9. docs/incremental-shim-audit.md for the current accumulated-buffer replay baseline before the true incremental parser session.
10. docs/incremental-core-prototype.md for the isolated Eiffel session prototype that starts replacing replay with state-owned parsing.
11. docs/expat-port-spike.md for the isolated Expat-processor-style Eiffel port experiment.
12. docs/benchmarks.md for same-machine benchmark results.
13. docs/large-xml-benchmarks.md for opt-in real-corpus macro-benchmarking.
14. docs/performance-analysis.md for the current xpact-vs-libexpat performance gap analysis and next optimization priorities.
15. docs/drop-in-verification.md for the Jenkins and public-application replacement plan.

Build And Verify

Compile and run the Eiffel regression matrix, both with and without Eiffel runtime assertions:

.\scripts\run_eiffel_test_matrix.ps1 -AssertionMode All -BuildMode All

Build the Windows Eiffel-backed native DLL:

.\scripts\build_native_eiffel.ps1

Build the optimized assertion tier:

.\scripts\build_native_eiffel.ps1 -BuildTier Assertions

Run native ABI/link smoke tests:

.\scripts\run_native_abi_tests.ps1 -Target Windows

Run chunked XML_Parse CRC diagnostics:

.\scripts\run_chunked_crc_corpus.ps1 -Target Xpact -ParseMode All

Audit the current accumulated-buffer incremental shim:

.\scripts\run_incremental_shim_audit.ps1 -SkipBuild

Refresh the upstream Expat manifest and parity expansion:

.\scripts\run_libexpat_adapter.ps1 `
  -Mode Manifest `
  -ExpatSourceDir .\build\libexpat-R_2_8_1\libexpat-R_2_8_1\expat `
  -OutputDir .\build\libexpat-adapter-current `
  -XpactLibrary .\build\native-eiffel\xpact.lib `
  -SkipNativeBuild

Package the Windows x64 preview release:

.\scripts\package_windows_release.ps1

Run opt-in large XML benchmarks with pre-decompressed real XML files:

.\scripts\run_large_xml_benchmarks.ps1 -XmlFile C:\data\pubmed\pubmed25n0001.xml