ecrust

Rust-native Python package that targets the low-level eccodes import surface for modern GRIB workflows.

Current benchmark and handoff state for follow-on work lives in AGENT_CONTEXT.md. The latest Windows HRRR benchmark there shows ecrust ahead of ecCodes on both the single-file end-to-end values path and the 4-copy multi-file run. GitHub CI for release verification now lives in .github/workflows/ci.yml.

Goal:

• replace import eccodes with import ecrust
• keep the common codes_* handle/get/release flow unchanged
• avoid a native ecCodes C-library dependency

For the supported GRIB workflows, ecrust is a pure-Rust path and does not require linking against the ecCodes C library.

Current implemented surface:

• codes_grib_new_from_file
• codes_new_from_file
• codes_any_new_from_file
• codes_count_in_file
• codes_get, codes_get_long, codes_get_double, codes_get_string
• codes_get_array, codes_get_double_array, codes_get_long_array
• codes_get_values
• codes_is_defined, codes_is_missing
• codes_get_size, codes_get_offset, codes_get_message_offset, codes_get_message_size
• codes_get_native_type
• codes_keys_iterator_*
• codes_skip_*
• codes_clone, codes_release

Performance note:

• codes_get_values and native/double "values" array access now return read-only NumPy arrays backed by Rust-owned memory to avoid an extra copy on the hot path.
• codes_get_version_info() and the benchmark scripts now report allocator and target metadata so performance reruns are attributable to a concrete build variant.

Windows dev note:

• Local Python tests and benchmarks load python\ecrust\_ecrust.cp313-win_amd64.pyd. After cargo build --release, copy target\release\_ecrust.dll over that file before rerunning Python-side checks.
• Plain Windows release builds now default to mimalloc because the system allocator was materially slower on the HRRR workload. Use cargo build --release --features system-allocator only for A/B comparison.

Linux / WSL dev note:

• For Linux validation, run benchmarks from the distro filesystem rather than /mnt/c, and pass explicit --source / --copy-dir paths to the benchmark scripts.
• Non-Windows builds still default to the system allocator. Use maturin develop --release --features mimalloc or cargo build --release --features mimalloc only when comparing allocators.
• On Ubuntu 24.04 WSL with Rust 1.94.1, maturin develop --release hit a rustc warning-emission ICE. RUSTFLAGS="-Awarnings" maturin develop --release worked around it.

Verification note:

• The local parity suite now includes focused drop-in API coverage in tests/test_dropin_surface.py, and the repository includes a Linux/Windows GitHub Actions workflow that builds the extension and runs pytest -q.
• The parity suite now also includes pinned official operational ECMWF, GFS, and RRFS near-surface GRIB2 subsets, assembled from published .idx / .index sidecars via HTTP range requests so CI verifies real model data without downloading full upstream files.

Current scope:

• GRIB1 and GRIB2 decode
• modern GRIB metadata and value access
• GRIB2 mutation and write-back for common sample and real-world workflows: codes_set_*, codes_get_message, and codes_write now repack common GRIB2 messages and patch original section metadata instead of only exposing shadow state through getters
• expanded real-world parity coverage against the cfgrib sample corpus plus pinned official ECMWF/GFS/RRFS operational subsets, with broad modern GRIB message compatibility checks and mutation round-trip tests
• pure-Rust decode path, including JPEG2000 and CCSDS/AEC support through Rust crates

Current non-goals:

• BUFR, METAR, and GTS support
• full GRIB write/repack parity across every grid/packing/template combination
• the full long-tail of every historical eccodes binding function

Release checklist:

1. Set the final GitHub repository URL in package metadata once the repo is online.
2. Push the branch and confirm .github/workflows/ci.yml is green on Linux and Windows.
3. Configure trusted publishing for this repo on TestPyPI and PyPI, or provide the equivalent publish credentials expected by .github/workflows/release.yml.
4. Run .github/workflows/release.yml with publish_to=testpypi for a dry-run package upload.
5. Verify pip install ecrust from the published TestPyPI build on Windows and Linux.
6. Push a vX.Y.Z tag that matches the package version to build Linux x86_64 manylinux wheels, Windows x64 wheels, and an sdist, upload them to the GitHub release, and publish to PyPI.

Known remaining GRIB gap:

• GRIB1 spectral-complex packing (spherical_harmonics.grib) is still not implemented