Move LDM block-compressor strategy validation, selection ordering, and callback error propagation into Rust while retaining dictionary-mode lookup, MatchState mutation, and the actual codec callback in C. Invalid preflight inputs now use the existing generic error path, and valid strategies preserve the original optimal-parser boundary.
Test Plan: ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings; cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check; make -j1; ./tests/rustLibSmoke; make -j1 -C tests test (all shell tests, large streaming tests, native tester, fuzzer phases, and zstream tester passed).
Move the pure LDM parameter-defaulting policy behind the original
ZSTD_ldm_adjustParameters() ABI symbol. Rust now receives the existing C
parameter structs directly, applies the same 30/8/8 build constants, and
keeps the ASAN-sensitive table-size projection in C.
Test Plan:
- `cc -fsyntax-only -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -Ilib/legacy lib/compress/zstd_ldm.c` -- passed.
- `cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check` -- passed.
- `git diff --check` and `git diff --cached --check` -- passed.
- Heavy verification intentionally deferred until the combined seam set is ready.
The LDM sequence-space helper was already implemented in Rust, but C still
owned the public symbol and forwarded through a pointer-based Rust bridge.
Make the Rust parameter representation public and ABI-compatible for the
original by-value `ldmParams_t` call, then have Rust compare `enableLdm`
directly with `ZSTD_ps_enable` before applying the sequence bound. Remove only
the redundant C bridge declaration and wrapper; table sizing, state, and
sequence generation remain unchanged.
Test Plan:
- `git diff --check` -- passed.
- `git diff --cached --check` -- passed.
- `cc -std=c99 -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -fsyntax-only lib/compress/zstd_ldm.c` -- passed.
- `cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check` -- passed.
- Cargo build/test, make, and other heavy checks were intentionally not run per the requested lightweight-only scope.
Keep the existing internal ZSTD_ldm_* ABI names while making the two
sequence-store skip operations direct Rust exports. Remove only the C
forwarding declarations and bodies; LDM state projection, configuration
constants, and block-compressor adapters remain in C.
Test Plan:
- clang -fsyntax-only on lib/compress/zstd_ldm.c
- git diff --check
- Full capped native/upstream suite pending after this commit
Move the strategy classification that decides whether LDM preparation fills
fast or double-fast tables into Rust. C retains the private match-state,
configuration-specific table-fill leaves, and the existing excluded-DFAST
assertion. Add enum-value ABI checks plus focused tests for valid and invalid
strategy classifications.
Test Plan:
- `ulimit -v 41943040; cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check`
- `ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings`
- `ulimit -v 41943040; make -j1`
- `ulimit -v 41943040; make -j1 -C tests test`
- `ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/cli/Cargo.toml --all-targets -- -D warnings`
- `ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo test --manifest-path rust/cli/Cargo.toml --all-targets`
The integrated checks ran at the combined working-tree tip under a serial
40 GiB virtual-memory limit. Standalone root Rust unit linking remains
unavailable because the crate imports C-owned bridge symbols without a Cargo
build/link setup.
Move the scalar policy that selects the optimal parser for long-distance
matching into Rust. The C implementation continues to own match-state and
compressor dispatch, but the strategy threshold is now defined and tested at
the Rust seam.
Test Plan:
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo +nightly fmt --manifest-path rust/Cargo.toml -- --check
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo test --manifest-path rust/Cargo.toml --all-targets (775 passed)
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/cli/Cargo.toml --all-targets -- -D warnings
- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo test --manifest-path rust/cli/Cargo.toml --all-targets (179 passed)
- ulimit -v 41943040; make -j1
- ulimit -v 41943040; make -j1 -C tests test (all tests completed successfully)
Keep the LDM limit-table update on the Rust compression path while leaving
match-state ownership in C. Previously, the C block wrapper combined pointer
subtraction, match-state access, and the bounded scalar update. The wrapper
now computes `curr` from `anchor - window.base`, passes `curr` and
`nextToUpdate` through the narrow U32 ABI, and stores Rust's result before the
existing fast-table dispatch.
The Rust leaf uses explicit wrapping arithmetic to preserve the C U32 behavior:
the strict `curr > nextToUpdate + 1024` threshold and the `MIN(512, ...)`
clamp. Focused tests cover the threshold, one-step update, clamp, nonzero
starting point, and arithmetic wraparound.
Test Plan:
- `cargo test zstd_ldm` -- default-feature test-binary link failed because
existing dict-builder C symbols are not linked.
- `cargo test --no-default-features --features compression zstd_ldm` -- passed
(7 tests).
- `make lib-nomt` -- passed.
- `make lib-mt` -- passed.
- `make -C tests test-zstream` -- passed; it emitted the existing
`tests/zstreamtest.c` unterminated-string warning.
- `cargo clippy`, `cargo clippy --benches`, `cargo clippy --tests`,
`cargo +nightly fmt`, then the same clippy sequence -- passed.
Move long-distance matching and high-level decompression from C shims into
Rust. The decoder now owns context, dictionary, parameter, one-shot, and
buffered streaming state while C retains allocation/configuration, legacy,
and trace leaves.
Move CLI parsing, safety policy, and dispatch into a separate Rust static
archive. Keeping it separate prevents library builds from retaining FIO
symbols, while C continues to own file opening, replacement, and I/O.
Program targets now select matching compression/decompression archives.
The remaining C boundary is intentional: high-level compression, optimal
parsing, dictionary building, legacy callbacks, and CLI file I/O still need
migration.
Test Plan:
- cargo test --all-targets (native and i686)
- cargo test --all-targets in rust/cli (native and i686)
- CLI crate compression-only and decompression-only feature tests
- native and i686 fuzzer/zstreamtest runs, plus legacy and dictionary tests
- ZSTD_C_PREDICT and ZSTD_HEAPMODE=0 fuzzer coverage
- library, dynamic-link, and program-target build/round-trip matrix
Refs: rust/README.md
* Remove all pointer-overflow suppressions from our UBSAN builds/tests.
* Add `ZSTD_ALLOW_POINTER_OVERFLOW_ATTR` macro to suppress
pointer-overflow at a per-function level. This is a superior approach
because it also applies to users who build zstd with UBSAN.
* Add `ZSTD_wrappedPtr{Diff,Add,Sub}()` that use these suppressions.
The end goal is to only tag these functions with
`ZSTD_ALLOW_POINTER_OVERFLOW`. But we can start by annoting functions
that rely on pointer overflow, and gradually transition to using
these.
* Add `ZSTD_maybeNullPtrAdd()` to simplify pointer addition when the
pointer may be `NULL`.
* Fix all the fuzzer issues that came up. I'm sure there will be a lot
more, but these are the ones that came up within a few minutes of
running the fuzzers, and while running GitHub CI.
```
for f in $(find . \( -path ./.git -o -path ./tests/fuzz/corpora \) -prune -o -type f);
do
sed -i 's/Facebook, Inc\./Meta Platforms, Inc. and affiliates./' $f;
done
```
* first attempt at fast DMS short cache
* significant wins for some scenarios
* fix all clang regressions
* nits
* fix 1.5% gcc11 regression on hot 110Kdict scenario
* fix CI
* nit
* Add tags to doublefast hash table
* use tags in doublefast DMS
* Fix CI
* Clean up some hardcoded logic / constants
* Switch forCCtx to an enum
* nit
* add short cache to ip+1 long search
* Move tag size into hashLog
* Minor nits
* Truncate dictionaries greater than 16MB in short cache mode
* Helper function for tag comparison
* Cap short cache hashLog at 24 to prevent overflow
* size_t dictTagsMatch -> int dictTagsMatch
* nit
* Clean up and comment dictionary truncation
* Move ZSTD_tableFillPurpose_e next to ZSTD_dictTableLoadMethod_e
* Comment and expand helper functions
* Asserts and documentation
* nit
this meant to abstract the sumtype representation required
to transfert `offcode` to `ZSTD_storeSeq()`.
Unfortunately, the sumtype numeric representation is currently a leaky abstraction
that has permeated many other parts of the code,
especially within `zstd_lazy.c` and also within `zstd_opt.c` and `zstd_compress.c`.
While this PR makes a good job a transfering a large nb of call sites
to using the new macros, there are still a few sites where this transformation is more complex,
or where the numeric representation itself it used "as is".
One of the problematics area is the decision to use the numeric format of the sumtype
within the match finders of `zstd_lazy`.
This commit doesn't change the behavior, it only introduces and employes the macros,
but eventually the resulting code remains identical.
At target, if the numeric representation of the sumtype can be completely abstracted
and no other part of the code depends on it,
it will be possible to move it towards something slightly more efficient.
LDM does especially poorly on repetitive data when that data's hash happens
to have `(hash & stopMask) == 0`. Either because the `stopMask == 0` or
random chance. Optimize this case by skipping over repetitive patterns.
The detection is very simplistic, but should catch most of the offending
cases.
```
head -c 1G /dev/zero | perf stat -- ./zstd -1 -o /dev/null -v --zstd=ldmHashRateLog=1 --long
21.187881087 seconds time elapsed
head -c 1G /dev/zero | perf stat -- ./zstd -1 -o /dev/null -v --zstd=ldmHashRateLog=1 --long
1.149707921 seconds time elapsed
```
* Fix overflow correction when `windowLog < cycleLog`. Previously, we
got the correction wrong in this case, and our chain tables and binary
trees would be corrupted. Now, we work as long as `maxDist` is a power
of two, by adding `MAX(maxDist, cycleSize)` to our indices.
* When `ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLY` is defined to non-zero
run overflow correction as frequently as allowed without impacting
compression ratio.
* Enable `ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLY` in `fuzzer` and
`zstreamtest` as well as all the OSS-Fuzz fuzzers. This has a 5-10%
speed penalty at most, which seems reasonable.
* Switch to yearless copyright per FB policy
* Fix up SPDX-License-Identifier lines in `contrib/linux-kernel` sources
* Add zstd copyright/license header to the `contrib/linux-kernel` sources
* Update the `tests/test-license.py` to check for yearless copyright
* Improvements to `tests/test-license.py`
* Check `contrib/linux-kernel` in `tests/test-license.py`
ddidderr
Yann Collet