Files

T

Move ZSTD_DDict allocation, ownership, construction, and public ABI exports
into Rust. The C decoder keeps ZSTD_loadDEntropy until its table loader moves.

The C shim now exposes C-computed DCtx field offsets. This keeps dictionary
state correct across conditional C layouts, including fuzz fields and 32-bit
static-BMI2 builds, without duplicating decoder-context layout in Rust.

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
- C fuzzer, zstreamtest, invalidDictionaries, and fuzzer32 smoke runs
- fuzz-enabled and i686 -mbmi2 C/Rust dictionary roundtrip harnesses

Refs: rust/README.md

2026-07-10 21:20:50 +02:00

src

feat(rust): port decode dictionaries

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Cargo.lock

feat(rust): add common primitive compatibility layer

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Cargo.toml

build(rust): select archives by target and HUF mode

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README.md

feat(rust): port decode dictionaries

2026-07-10 21:20:50 +02:00

README.md

Rust rewrite

This directory contains the in-progress Rust replacement for the zstd library and command-line program. During the migration, the crate is built as a static library and linked into the original C test programs. Production C translation units become declaration-only shims as their implementations move to Rust; the original C tests remain unchanged and provide compatibility coverage.

Component map

The crate is organized from low-level representation helpers toward the public zstd ABI:

Common primitives
- mem, bits, bitstream, and cpu implement byte-order, bitstream, and target-feature operations used by the codecs.
- errors, debug, xxhash, and zstd_common provide common exported ABI functions and state.
- common contains shared frame constants and internal data types.
Entropy coding
- entropy_common reads FSE normalized counts and Huffman statistics.
- fse_decompress builds FSE decoding tables and decodes FSE streams.
- fse_compress normalizes counts, writes FSE headers, builds compression tables, and encodes FSE streams.
- huf_decompress builds Huffman decoding tables and decodes X1 and X2 Huffman streams.
Compression primitives
- hist counts byte frequencies for FSE and Huffman compression.
Runtime support
- threading provides platform pthread wrappers required by zstd headers.
- pool implements the bounded worker pool used by multithreaded compression.
Dictionary support
- zstd_ddict owns, loads, copies, and references decode dictionaries.

The remaining block compression, general decompression, dictionary-building, legacy, and CLI translation units are still C. They must move before the rewrite is complete. Keeping that boundary explicit prevents a passing hybrid build from being mistaken for the final all-Rust result.

Compatibility boundary

The public ABI continues to come from the existing headers under lib/. Exported Rust functions therefore use C layout and calling conventions. A C source file whose implementation has moved to Rust remains in the original makefile source list as a small shim so header configuration and platform preprocessor behavior stay available during the transition.

The test and program makefiles select an archive directory for the active C configuration: default, forced HUF X1/X2, and the matching Rust target for 32-bit C binaries. When the HUF mode changes, they also rebuild cached C outputs before linking. This prevents original C tests from using a stale or configuration-incompatible implementation.

Validation

Run focused Rust checks from this directory:

cargo fmt --check
cargo clippy --all-targets -- -D warnings
cargo test --all-targets
cargo build --release

Then run original compatibility tests from the repository root, starting with the narrow target for the component being migrated. For example:

make -C tests fuzzer
./tests/fuzzer -i1 --no-big-tests

Broader tests/Makefile targets remain the authoritative integration gates as more of the library and CLI are rewritten.