The advanced-CDict path previously kept a C callback that rebuilt the
ZSTD_rustCDictSizing projection and delegated the actual arithmetic back to
Rust. Replace that callback with a pointer to the explicit sizing projection,
so Rust owns the workspace-size policy while C continues to own private
zstd_cwksp allocation, object reservation, initialization, and teardown. The
projection replaces the old callback slot, preserving every later callback
offset and the synchronous lifetime of the C sizing values.
Update both sides' layout assertions, remove the redundant C helper, and make
the lifecycle tests assert that Rust's computed size reaches allocation and
workspace creation before the existing C-owned callbacks run. Custom-memory
validation and all other CDict callbacks remain unchanged.
Test Plan:
- `cc -fsyntax-only -Werror=incompatible-pointer-types -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -Ilib/legacy lib/compress/zstd_compress.c` -- passed.
- `rustfmt +nightly --edition 2021 --check rust/src/zstd_compress_dictionary.rs` -- passed.
- `git diff --check` and `git diff --cached --check` -- passed.
- Cargo build/test/clippy, Make, fuzzers, and other heavy verification were intentionally not run per request.
ddidderr
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