The v0.2 decoder implementation and C boundary were already Rust-owned, but
its public error predicate, frame-size sentinel behavior, and opaque streaming
context lifecycle lacked focused Rust coverage. Add tests for malformed input,
content-size error reporting, one-shot decoding, reset behavior, and idempotent
context release so future legacy changes are checked at the ABI boundary.
Test Plan:
- Focused v0.2 Cargo tests under both feature sets -- 6 passed each
- `make -C tests -j2 test-legacy` -- passed
- `cargo +nightly fmt --manifest-path rust/Cargo.toml -- --check` -- passed
- Scoped `git diff --check` -- passed
The frozen v0.7 decoder's two-state FSE tail must emit state 1, reload,
state 2, reload, and possibly a final state 1 symbol. The Rust port used
current-state and end-of-stream early exits, so historical Huffman headers
could stop one terminal weight short and corrupt a literal byte. The legacy
corpus exposed this as the UTF-8 apostrophe's first byte changing from e2 to
e0. Match the historical reload-driven tail and retain the exact v0.7 frame
as a regression test.
Test Plan:
- `cargo test --manifest-path rust/Cargo.toml --no-default-features --features decompression,legacy-v07 legacy::zstd_v07::tests` -- passed (6 tests)
- `cargo clippy --manifest-path rust/Cargo.toml --no-default-features --features decompression,legacy-v07 --lib -- -D warnings` -- passed
- `rustfmt +nightly --edition 2021 rust/src/legacy/zstd_v07.rs` -- passed
- `make -C tests -j2 legacy` -- blocked by the active dict-builder work's
unrelated full-feature compilation gap
Move the frozen v0.7 decoder, dictionary handling, bufferless streaming,
and buffered streaming implementation into the Rust legacy module. Keep
the historical C translation unit as a declaration-only ABI shim so the
existing C callers and build selection remain unchanged.
The port preserves the v0.7 entropy and frame boundaries, while fixing the
Rust-side literal-tail bookkeeping and making buffered header loading revisit
the complete frame header before sizing its rolling buffers.
Test Plan:
- cargo test --manifest-path rust/Cargo.toml --no-default-features --features decompression,legacy-v07 legacy::zstd_v07::tests
- cargo clippy --manifest-path rust/Cargo.toml -- -D warnings
- make -B -C programs zstd V=1
- decode a v0.7.5 fixture and compare its 200000-byte output
- make -C tests check V=1
Replace the v0.5 and v0.6 legacy decoder translation units with Rust modules
and keep only narrow C registration shims for the public legacy dispatch ABI.
Test Plan:
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo test --manifest-path rust/Cargo.toml --features compression,decompression,dict-builder,legacy-v05,legacy-v06,legacy-v07
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo clippy --manifest-path rust/Cargo.toml --all-targets --features compression,decompression,dict-builder,legacy-v05,legacy-v06,legacy-v07 -- -D warnings
- make -C tests check V=1
Move the frozen v0.4 frame, entropy, streaming, and dictionary decoder
implementation to Rust while retaining the C translation unit as an ABI
anchor. Register the decoder behind the matching legacy feature and keep its
historical behavior isolated from newer formats.
Test Plan:
- rustfmt +nightly --check --edition 2021 rust/src/legacy/zstd_v04.rs rust/src/legacy/mod.rs
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo test --manifest-path rust/Cargo.toml --no-default-features --features decompression,legacy-v04 legacy::zstd_v04
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo clippy --manifest-path rust/Cargo.toml --all-targets --no-default-features --features decompression,legacy-v04 -- -D warnings
- C/Rust v0.4 ABI and decompression build checks
- git diff --cached --check
Move the frozen v0.3 frame decoder, entropy tables, and streaming context
state into a feature-gated Rust module. Keep the historical C translation
unit as an ABI shim so existing C callers retain the opaque context and
error-code contracts while v0.4 and newer decoders remain unchanged.
Test Plan:
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo test --manifest-path
rust/Cargo.toml --no-default-features --features legacy-v01,legacy-v02,
legacy-v03
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo test --manifest-path
rust/Cargo.toml --no-default-features --features compression,decompression,
dict-builder,legacy-v01,legacy-v02,legacy-v03
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= cargo clippy --manifest-path
rust/Cargo.toml --all-targets --no-default-features --features
compression,decompression,dict-builder,legacy-v01,legacy-v02,legacy-v03
-- -D warnings
- make -B -C lib libzstd.a ZSTD_LEGACY_SUPPORT=3 V=1
- git diff --cached --check
Translate the frozen v0.2 frame, entropy, block, frame-size, and streaming
decoder paths to Rust while preserving the opaque C context ABI. Replace the
3465-line historical C implementation with a declaration-only shim and enable
the Rust module for the legacy-v02 Cargo feature.
Test Plan:
- cargo test --manifest-path rust/Cargo.toml --no-default-features --features compression,decompression,dict-builder,legacy-v02
- make -B -C lib libzstd.a ZSTD_LEGACY_SUPPORT=2 V=1
- git diff --check
Refs: rust/src/legacy/zstd_v02.rs, lib/legacy/zstd_v02.c
Port lib/legacy/zstd_v01.c (the frozen zstd v0.1 decoder) to
rust/src/legacy/zstd_v01.rs as the first legacy-format port on the new
scaffolding, and reduce the C file to a declaration-only shim that
keeps its header includes for configuration and platform preprocessor
behavior.
Frozen-decoder policy: zstd_v01.c embeds its own v0.1-era FSE and
Huff0 snapshot, distinct from every other release. The Rust port is a
line-by-line translation with the same table layouts (FSE_DTable as a
u32 header word plus packed newState/symbol/nbBits entries, the Huff0
u16 DTable with byte/nbBits pairs), the same arithmetic including
wrap-around and pointer-comparison quirks (e.g. the offset-vs-base
address check in ZSTD_execSequence), the same internal FSE error space
(size_t)-1..-7, and the same public ZSTD error codes. It reuses no
modern Rust entropy module; its only crate dependency is `errors`,
matching the C file's error_private.h include. The 32-bit-only reload
points are kept as compile-time conditions on usize::BITS.
Symbol takeover boundary: all nine ZSTDv01_* entry points from
zstd_v01.h now come from Rust as context-free #[no_mangle] extern "C"
functions (isError, decompress, decompressDCtx,
findFrameSizeInfoLegacy, createDCtx, freeDCtx, resetDCtx,
nextSrcSizeToDecompress, decompressContinue). zstd_legacy.h only uses
the first four for v0.1; streaming for v0.1-v0.3 intentionally returns
version_unsupported there, unchanged. The ZSTDv01_Dctx struct
definition moves entirely into Rust: C code only ever holds an opaque
pointer (zstd_v01.h forward-declares the type), and the context is
malloc/free-allocated exactly like the C version so create/free may
pair across the language boundary.
Byte-identity verification against the pristine pre-migration C build
(f8745da6, pure C, ZSTD_LEGACY_SUPPORT=1):
- Real v0.1 frames were generated by building the v0.1.0 git tag and
compressing text, random, and 426 KB multi-block inputs. A one-shot
ZSTD_decompress harness linked once against the pristine C libzstd.a
and once against the Rust-backed libzstd.a produced bit-identical
outputs for all frames.
- A direct ZSTDv01_* probe (one-shot decode, dst-too-small, truncated
input, bad magic, findFrameSizeInfoLegacy, and the streaming
continue loop) printed identical results, including exact error
codes (-70 dstSize_tooSmall, -72 srcSize_wrong, -10 prefix_unknown)
and identical dBound values.
- zstd -l -v on v0.1 files matches the pristine binary; CLI streaming
decode of v0.1 fails with the same "Version not supported" in both,
by design of zstd_legacy.h.
Unit tests embed three v0.1.0-generated fixtures (entropy-coded,
raw-block, and four-block frames) plus the truncation, bad-magic,
small-destination, and streaming-API cases, all asserting the exact C
error codes above. Note that `make -C tests test-legacy` only covers
v0.4+ frames, so the embedded fixtures and the harness comparison are
the actual v0.1 coverage.
Test plan:
- cd rust && cargo fmt --check && cargo clippy --all-targets
--features legacy-v01 -- -D warnings && cargo test --all-targets
--features legacy-v01 (127 tests, 9 for v0.1)
- cargo clippy/test --no-default-features --features
decompression,legacy-v01 (module builds standalone)
- make -C tests fuzzer && ./tests/fuzzer -i1 --no-big-tests, also with
ZSTD_LEGACY_SUPPORT=1 (mixed Rust v0.1 + C v0.2-0.7 link)
- make -C tests test-rust-lib-smoke && make -C tests test-legacy
- make -C programs zstd (default and ZSTD_LEGACY_SUPPORT=1); nm shows
the nine ZSTDv01_* symbols provided by Rust at level 1
- make -C lib libzstd.a ZSTD_LEGACY_SUPPORT=0 (no legacy symbols) and
meson -Dlegacy_level=1 shared library exporting all nine
The legacy decoders (lib/legacy/zstd_v01.c .. zstd_v07.c) are next in
the Rust migration. Each of those files is a frozen snapshot of the
FSE/Huff0 entropy coders and frame logic of one historical release, so
their ports must not reuse the modern Rust entropy modules and must not
share code with each other: outputs and error codes have to stay
byte-identical to the frozen C forever. This commit installs the
build-system scaffolding so seven per-version ports can land
independently, each adding only its own module file plus a one-line
registration in rust/src/legacy/mod.rs.
Cargo grows features legacy-v01 .. legacy-v07. They are never default
features: the C build defaults differ per build system, so each build
system passes the list explicitly, derived from its own legacy
configuration:
- lib/Makefile and programs/Makefile map ZSTD_LEGACY_SUPPORT=N to the
features for versions N..7 (0 disables legacy), mirroring the
ZSTD_LEGACY_FILES selection in lib/libzstd.mk.
- tests/Makefile always enables all seven features because its
ZSTDLEGACY_FILES wildcard compiles every lib/legacy/*.c regardless of
the dispatch level.
- build/meson maps legacy_level exactly like the makefiles; build/cmake
enables all seven whenever ZSTD_LEGACY_SUPPORT is ON because it
always compiles all seven C files (ZSTD_LEGACY_LEVEL only selects the
C dispatch).
Every build system also encodes the legacy selection in the Rust target
directory name (e.g. c1-d1-default-legacy5), for the same reason the
HUF mode is encoded there: a cached archive built for one configuration
must never be linked into a build expecting another. In tests/Makefile
the legacy level additionally flows into the existing HUF C-mode stamp,
so the flat C test objects (which bake -DZSTD_LEGACY_SUPPORT into the
dispatch) are rebuilt whenever the level changes. In programs/Makefile
the compress-only, decompress-only, and CLI archives keep
level-independent directories (RUST_HUF_MODE) because they are only
linked into ZSTD_LEGACY_SUPPORT=0 program variants and carry no legacy
features.
A feature whose version has not been ported yet gates nothing: the
module registration in rust/src/legacy/mod.rs is added by each port,
so enabling e.g. legacy-v05 today simply leaves that decoder in C.
This is what makes mixed C/Rust legacy levels link cleanly while the
seven ports land in any order.
Test plan:
- cd rust && cargo fmt --check && cargo clippy --all-targets
-- -D warnings && cargo test --all-targets
- cargo clippy with --no-default-features --features
decompression,legacy-v01 and with all seven legacy features
- make -C tests fuzzer && ./tests/fuzzer -i1 --no-big-tests
- make -C tests test-rust-lib-smoke; make -C tests test-legacy
- make -C lib libzstd.a with ZSTD_LEGACY_SUPPORT=0, 1 and default (5)
- cmake configure and meson setup (including -Dlegacy_level=1) emit the
expected --features lists and legacy-suffixed target directories
ddidderr