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Merge Risk: ⚪ Minimal · up to
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| Check name | Status | Explanation | Resolution |
|---|---|---|---|
| Out of Scope Changes check |  |
The change in zstd/src/decoding/simd_copy/tests.rs only changes how SIMD copy kernels are collected for tests. The diff does not connect this change to legacy frame parsing, dispatch, validation, or… |
Remove the unrelated zstd/src/decoding/simd_copy/tests.rs change, or provide evidence that the change is required for the legacy-frame implementation or its required CI coverage. |
| Docstring Coverage | |
Docstring coverage is 78.39% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 273 functions across 23 files. (1 skipped… | Write docstrings for the functions missing them to satisfy the coverage threshold. |
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Check name Status Explanation Description Check Check skipped - CodeRabbit’s high-level summary is enabled. Title check The title clearly and concisely identifies the main change: decoding v0.5, v0.6, and v0.7 frame formats. Linked Issues check Issue #131is open and directly linked. The PR adds default-enabledlegacydecoding for v0.5, v0.6, and v0.7. The reported implementation and tests cover Rust APIs, mixed streams, frame queries, C A…Full details: Linked Issues check
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Explanation
Issue
#131is open and directly linked. The PR adds default-enabledlegacydecoding for v0.5, v0.6, and v0.7. The reported implementation and tests cover Rust APIs, mixed streams, frame queries, C ABI entry points, CLI decoding and-lrefusal, dictionaries, malformed input, and feature-off refusal. The fuzz target compares whole-buffer and streaming decoding. The CI changes cover feature-on, feature-off, and no_std builds. The issue excludes v0.1-v0.4 decoding and legacy encoding, and the reported scope does not add them.
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Full details: Out of Scope Changes check
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Explanation
The change in
zstd/src/decoding/simd_copy/tests.rsonly changes how SIMD copy kernels are collected for tests. The diff does not connect this change to legacy frame parsing, dispatch, validation, or legacy test coverage. The remaining reported changes support Issue#131or its tests and documentation.Resolution
Remove the unrelated
zstd/src/decoding/simd_copy/tests.rschange, or provide evidence that the change is required for the legacy-frame implementation or its required CI coverage.
Full details: Docstring Coverage
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Explanation
Docstring coverage is 78.39% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 273 functions across 23 files. (1 skipped: 1 unsupported.)
Resolution
Write docstrings for the functions missing them to satisfy the coverage threshold.
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Actionable comments posted: 4
- 🪄 Fix comments: Fix CodeRabbit comments on this PR
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Review comments at @.github/workflows/ci.yml:
- Around line 1025-1027: Update the decode_legacy workflow step to replay
committed crash inputs from artifacts/decode_legacy before its fresh fuzz run,
skipping the replay when the directory has no inputs. Keep the existing corpus
and legacy-frame inputs in the fresh run unchanged.
Review comments at @zstd/src/decoding/frame_decoder.rs:
- Around line 1324-1330: Update decode_available so that after self.init, it
detects a started legacy stream and decodes the remaining input through that
stream, adding the bytes consumed while reading the header to the reported read
length; ensure this path returns before either state match can panic. Add a test
that calls decode_from_to on a fresh FrameDecoder with a legacy fixture.
- Around line 2735-2739: Pass the configured ContentChecksum mode into the
legacy decoder path so legacy v0.7 checksums are not hashed or verified when the
mode is None, while preserving verification for enabled modes. Update the legacy
checksum handling near the legacy_frame path; if that decoder cannot support
disabling checks, document the exception in the ContentChecksum contract
instead.
Review comments at @zstd/src/decoding/simd_copy/tests.rs:
- Around line 48-49: Remove the trivial function-pointer casts in the SSE2 and
AVX2 entries of the kernel selection code. Specify the tuple type on `then_some`
so each function item coerces to `CopyKernel` without a cast.
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Review comments at @zstd/src/decoding/legacy/tests.rs:
- Around line 1017-1072: Add coverage for the missing dictionary-ID reader error
in reader_errors_inside_the_header: reset the decoder with a v0.7 frame using
descriptor 0x01 and a complete window byte, then assert WouldBlock is wrapped as
ReadFrameHeaderError(DictionaryIdReadError). Preserve the existing descriptor,
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libzstd 1.5.7 reads these by default (legacy level 5 in every upstream build system and in the distributions), so the decoder needs them too. - decoding/legacy: one module per format plus the shared entropy layer (FSE tables up to 4096 states, the Huffman description with its weight-run header, one and four streams). Only the backward bit reader is shared with the RFC 8878 decoder; the formats differ from it and from each other in headers, literal and sequence coding, dictionaries and how an FSE string ends. - A block decodes to at most 128 KiB; a v0.7 content checksum is verified; the declared content size is not enforced, since the v0.6.2 command line declares its first chunk's size. - `legacy` feature, on by default. - scripts/legacy-fixtures.sh builds the v0.5.1, v0.6.2 and v0.7.5 command lines from digest-checked tags and writes zstd/legacy_frames, each frame checked to decode through libzstd 1.5.7 to its source. Part of #131
- read_frame_content_size, find_frame_compressed_size, find_decompressed_size and frame_decompressed_bound read these frames as libzstd does: the declared size or unknown, the length through the end block, and 128 KiB per block as the bound. The size walk reads the header's size fields only, as upstream's does. - is_frame: the codec's answer for ZSTD_isFrame, legacy magics included when the feature is on. - FrameDecoder::decode_all and its dictionary variants decode these frames straight into the caller's slice; a v0.7 frame naming a dictionary takes it from the handles given or from the registry. - A v0.7 frame takes its dictionary tables from the parsed Dictionary, so a handle serves both formats without a second copy of the dictionary bytes. Part of #131
- A Read-driven reset that meets a v0.5-v0.7 magic number reads the rest of that header from the same source and starts the frame on a LegacyStream; an RFC 8878 frame pays nothing, since the check sits on the bad-magic error the parser already returns. - The step interface follows: input_needed, decode_from_to, decode_blocks, collect, read, is_finished and the counters drive the stream, so StreamingDecoder and any caller of that interface decode these frames with no change of its own. The stream keeps the window plus a block of history and drops what lies out of reach once handed out. - read_to_end and concatenated frames decode them into the output vector; a forced dictionary applies as it does to RFC frames. - Dictionaries reach these frames only as parsed handles; the raw byte form and the v0.7 byte loader it needed are gone. - The bit-flip test now checks that a v0.7 frame decodes to other content only when that content matches the 22-bit checksum it carries; one fixture flip is such a collision. - simd_copy tests build their kernel list without a mut binding that a build without kernel features never pushes to. Part of #131
- LegacyVersion::header_size: a frame header's length from its size fields, for a caller that reads a header in pieces, as the C ABI stream does. - LegacyFrameError::WindowTooLarge is gone: a window past the ceiling is refused as FrameDecoderError::WindowSizeTooBig, as for RFC 8878 frames, and nothing built the variant. Part of #131
- ZSTD_isFrame answers through the codec's is_frame, these frames included, as libzstd 1.5.7 answers by default. - ZSTD_decompressStream measures such a header by its own size fields while it arrives in pieces, then starts the frame from the same reader; the frame queries and one-shot decoders already go through the codec. - The command line asks the codec whether input is a frame, so -d, -t and -c decode these frames; -l keeps refusing them, as the reference does. - Tests on the fixtures: the frame queries, ZSTD_decompress and _usingDict, the stream in 7-byte pieces with a DDict, a stream mixing them with RFC 8878 frames, and the command line. Part of #131
- The stream held its history in one vector and dropped what fell out of reach by moving the rest to the front, so every block past the window moved a whole window of bytes. It now writes in segments of at most the window and a block: a block that would not fit starts the next segment at the buffer's start, and a match reaching past that start reads from the segment before, which the new one has not overwritten yet, as upstream's buffered decoders wrap. No history is moved, and the buffer stays within the window and a block. - FSE and Huffman tables are rebuilt in the storage of the tables they replace, and the Huffman weight table is kept for the next description, instead of a fresh vector per block that sends one. - Fixtures: z000000 eight times over, from each command line, a frame several windows long whose matches cross the segment boundary; checked to decode through libzstd 1.5.7. - Tests: the stream reads those frames with the buffer bounded by the window and a block; a table rebuilt in place is a fresh one. Part of #131
- decode_legacy fuzz target: input kept on a v0.5-v0.7 magic number, decoded whole into a slice and through the stream, and the two outputs must agree; CI runs it 90 s seeded with zstd/legacy_frames. - CI: no_std clippy and the x86_64-unknown-none build with `legacy`, and the decoding and command-line tests again with the feature off. - Without `legacy` a v0.5-v0.7 frame is refused as an unknown prefix by the queries and the decoder (test); the command-line test of these frames runs with the feature only. - Crate docs and README: the `legacy` feature and what it reads; the README feature table also marks dict-builder as on by default, as the manifest has it. Part of #131
- decode_from_to on a fresh decoder hands a v0.5-v0.7 frame its header started to the frame's stream instead of panicking - the content checksum mode applies to v0.7's 22-bit checksum: None computes nothing, EmitOnly exposes both values, Verify refuses a mismatch; get_checksum_from_data / get_calculated_checksum report them - set_max_block_size holds these frames' blocks to the limit on every path, and a block its header rules out (past the limit, or RLE in v0.5 and v0.6, which reserve the type as upstream's decoders do) needs only its header - a window ceiling lowered under a started frame refuses its next step - content_size and blocks_decoded describe the frame in progress - a reader error inside the header is returned in the field it hit - the per-format decoder keeps its entropy tables and literal buffer across frames, whole-buffer ones too, and workspace_size counts them - CI replays committed decode_legacy crash inputs before the fresh run - simd_copy tests name the kernel type without a trivial cast Regression tests cover each of the above. Part of #131
- the caller-workspace decoder reports a v0.5-v0.7 frame as Unsupported::LegacyFrame rather than malformed: the owned decoders read it, and its decoders allocate, as upstream's static context refuses them - pinned dictionary IDs and window descriptors bind these frames on the streaming and whole-buffer paths: v0.7 carries both fields, v0.5 and v0.6 neither - per-block checksums cover their blocks on every path - after decode_all the accessors describe the frame decoded last, which stays current, finished, until the next header - find_decompressed_size refuses a v0.5-v0.7 tail shorter than a frame's first five bytes, as upstream does - the whole-buffer path borrows a held dictionary instead of counting a handle per frame - a new header ends any v0.5-v0.7 frame before it is read, so a header that fails to read leaves no stale frame behind - drop VecOutput's limit, which every caller set to usize::MAX, and the copy_match branches no output can reach, now a debug assertion Regression tests cover each fix; further tests cover the error codes, literal headers, one-symbol sequence tables, reader errors inside a block, held-back output, and arbitrary descriptions and overwritten frames, which must not panic. Part of #131
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- force_dict gives a started v0.5-v0.7 frame the registered dictionary, as it does an RFC 8878 frame: its tables, repeat offsets and content prime the blocks still to come; a v0.7 header naming another dictionary still refuses it - FrameDecoder::dictionary reports the handle such a frame decodes with - frame_header_size, and so ZSTD_frameHeaderSize, measures these headers by their own size fields instead of refusing the frames ZSTD_isFrame accepts - a reader failing inside a raw or RLE block's body names that block type in the error Each fix carries a regression test. Part of #131
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Summary
legacycargo feature, on by default; without it these frames are refused as an unknown prefix, as a libzstd built at legacy level 0 refuses them.Changes
decoding/legacy: one decoder per format over a shared entropy layer (FSE tables up to 4096 states, Huffman descriptions with the weight-run header, one and four streams), its tables and literal buffer reused from frame to frame. The declared content size is not enforced, since the v0.6.2 command line declares its first chunk's size; v0.5 and v0.6 refuse the RLE block type they reserve, as upstream's decoders do.force_dict,dictionary,content_size,blocks_decoded, the checksum accessors andworkspace_size.WorkspaceDecoderrefuses these frames asUnsupported::LegacyFrame: their decoders allocate, as upstream's static context refuses them too.read_frame_content_size,find_frame_compressed_size,find_decompressed_size,frame_decompressed_bound,frame_header_size, newis_frame) answer for these frames, a header measured by its own format's size fields.FrameDecoder::decode_all*decodes them into the caller's slice; aRead-driven reset that meets their magic number starts a stream, sodecode_blocks,decode_from_to,collect,read,StreamingDecoderand the C stream decode them unchanged. The stream keeps its history in segments of the window and a block, the previous segment read for matches that reach past the current one's start.DictionaryHandle, by ID or as given; v0.5 and v0.6 read a dictionary as its content.LegacyVersionnames the formats;LegacyVersion::header_sizemeasures a header arriving in pieces.ZSTD_isFrameandZSTD_decompressStreamaccept these frames; the queries and one-shot decoders go through the codec. No new exported symbols.-d,-t,-cand-Ddecode them;-lrefuses them, as the reference does.scripts/legacy-fixtures.shbuilds the v0.5.1, v0.6.2 and v0.7.5 command lines from digest-checked tags and writeszstd/legacy_frames; each frame decodes through libzstd 1.5.7 to its source.decode_legacyfuzz target: whole-buffer and streaming decodes of the same input must agree; CI replays its committed crash inputs before a seeded run.Testing
legacyincluded, x86 included), the full test suites of the codec, the C ABI crate and ffi-bench, doc tests and rustdoc. CI adds a no_std build withlegacy, the decoding and command-line tests with the feature off, and a seeded fuzz run ofdecode_legacy.Closes #131