The CCtx workspace estimator still assembled its private sizing formula in C,
even though the match-state and component-sum leaves already lived in Rust.
That left buffering, LDM, static-context, and external-sequence sizing policy
outside the rewrite boundary.
Move the complete size_t formula into a Rust entry point. C now supplies only
private object sizes, sanitizer redzone policy, and LDM scalar fields through a
small ABI record. Rust retains the C wrapping/alignment behavior and focused
branch coverage while the C adapter preserves the existing public estimator
surface.
Test Plan:
- cargo fmt --manifest-path rust/Cargo.toml -- --check
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo test --manifest-path rust/Cargo.toml --release estimate_cctx_workspace_size
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo test --manifest-path rust/Cargo.toml --release (667 passed)
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --release --all-targets -- -D warnings
- ulimit -v 41943040; make -B -C programs -j1 zstd
- ulimit -v 41943040; make -C tests -j1 test-zstream ZSTREAM_TESTTIME=-T1s (84 tests and both short fuzzer rounds)
ddidderr
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