Block splitting still estimated literal and sequence section sizes through
three C helpers. Move the pure estimator into zstd_compress_stats.rs so its
histogram, HUF, and FSE cost calculations use the Rust implementations already
behind the compression ABI. Preserve the original literal headers, multi-stream
Huffman surcharge, sequence additional-bit costs, entropy-header accounting,
and fallback estimates; leave C responsible for split recursion and table
ownership.
Test Plan:
- `cargo test --manifest-path rust/Cargo.toml --no-default-features --features compression` -- 229 passed
- `cargo clippy --manifest-path rust/Cargo.toml --no-default-features --features compression` plus benches/tests -- passed before and after formatting
- `cargo +nightly fmt --manifest-path rust/Cargo.toml --all` -- passed
- `make -B -C lib -j2 lib` -- passed
- `make -C tests -j2 test-zstream` -- passed, including 84 deterministic and 15,375 randomized cases
ddidderr
511882e213