ZSTD_getCParamsFromCCtxParams previously kept its context-free selection,
LDM window override, nonzero-field override, and final adjustment orchestration
in C. Move that pipeline into a scalar Rust ABI leaf while keeping the private
ZSTD_CCtx_params snapshot in C. The ABI passes the compression parameters by
value, the source-size hint, mode switches, and the LDM default window log.
The active ZSTD_EXCLUDE_* definitions remain owned by the C preprocessor and
are encoded as a mask. Rust applies that mask before each adjustment stage,
including the existing standalone adjustment callers, so reduced compressor
builds retain the original fallback cascade without duplicating CCtx state or
compile-time configuration in Rust.
Test Plan:
- `cargo test --manifest-path rust/Cargo.toml --no-default-features --features compression`
-- passed, 337 tests.
- All three compression clippy commands passed before and after
`cargo +nightly fmt --manifest-path rust/Cargo.toml`.
- `make -C lib -j2 lib-mt` and `make -C lib -j2 lib-nomt` -- passed.
- `make -C tests -j2 test-zstream` -- passed 84 deterministic tests,
5,191 standard randomized cases, and 9,382 new-API randomized cases.
- `git diff --cached --check` -- passed.
ddidderr
837e4f0998