Move ZSTD_splitBlock into Rust while retaining its caller-owned workspace
contract. The implementation preserves the C fingerprint sampling heuristic
and calls the migrated histogram primitive without adding a hot-path
allocation.
Reference-vector and randomized differential tests compare every split level
with the original C translation unit. The C source remains as a declaration
shim so existing source lists resolve the Rust ABI during the migration.
Test Plan:
- cargo fmt, cargo clippy, cargo clippy --benches, cargo clippy --tests
- cargo test --all-targets and cargo build --release
- cargo test/build --target i686-unknown-linux-gnu
- 264-case original-C/Rust differential harness
- C fuzzer, zstreamtest, and fuzzer32 smoke runs
Refs: rust/README.md
so that it can be stored using standard alignment requirement (sizeof(void*)).
Distance function still requires 64-bit signed multiplication though,
so it won't change the issue regarding the bug in ubsan for clang 32-bit on github ci.
that samples 1 in 5 positions.
This variant is fast enough for lazy2 and btlazy2,
but it's less good in combination with post-splitter at higher levels (>= btopt).
ddidderr
Yann Collet