The worker context previously selected the cdict or raw-prefix initialization
path, applied non-first-job parameter updates, and published the frame-header
projection directly in C. That left the branch and failure order intertwined
with private CCtx and parameter layouts.
Project only the first-job and cdict flags into Rust. Rust now validates cdict
placement, selects the initialization path, stops on force-window or
prefix-policy errors, and publishes the header projection only after successful
initialization. C callbacks retain the private cdict, CCtx, parameter mutation,
and frame-header field operations, including the original pledged-size and
force-window behavior.
Focused tests cover cdict ordering, non-first parameter ordering, parameter and
initialization failures, header-publication suppression, and invalid cdict
placement.
Test Plan:
- `rustfmt +nightly --edition 2021 --check rust/src/zstdmt_compress.rs` -- passed.
- Capped GCC syntax-only check for `zstdmt_compress.c` -- passed.
- Capped Clang syntax-only check for `zstdmt_compress.c` -- passed.
- `git diff --cached --check` -- passed.
- Cargo, native builds, fuzzers, and large tests were not run per assignment.