The multithreaded compressor already uses Rust-owned buffer and CCtx pools,
but zstdmt_compress.c still allocated and freed its job table directly. Move
the raw table storage and power-of-two sizing behind Rust's custom allocator
ABI. Keep descriptor field access and platform mutex/condition initialization
in C because those layouts remain private and platform-specific. The C
wrapper initializes and destroys synchronization primitives around the Rust
storage calls, preserving failure cleanup while leaving worker job setup,
scheduling, and stream entry points in C as the fallback implementation.
Keep the Rust storage-only ABI free of MT-only C references so single-threaded
archives can omit zstdmt_compress.c without acquiring new unresolved symbols.
Test Plan:
- `cargo test --manifest-path rust/Cargo.toml --no-default-features
--features compression zstdmt_compress --lib` -- passed (5 tests).
- `make -B -C lib lib-mt` -- passed.
- `make -B -C tests -j2 fullbench zstreamtest poolTests` -- passed.
- `./poolTests` -- passed.
- `./fullbench -i1 -B1000 README.md` -- passed, including -T2 scenarios.
- Rebuilt `programs/zstd` and ran a `-T2` compress/decompress `cmp` round-trip
-- passed.
- `rustfmt` and `cargo +nightly fmt --manifest-path rust/Cargo.toml --all
-- --check` -- passed.
- Full `cargo clippy -D warnings` remains blocked by unrelated warnings in
the concurrent `rust/src/fileio_asyncio.rs` worktree changes.
- `./zstreamtest -T5s` reaches an unrelated single-thread maxBlockSize
assertion at `tests/zstreamtest.c:2157`; MT fullbench and CLI smoke pass.
ddidderr
a15bf1d375