| name | xz-lzma-format |
| description | Reference the XZ container format and LZMA/LZMA2 decoder behavior. Use when an AI agent needs to answer questions or make code changes involving XZ headers, blocks, indexes, checks, CRC64/XZ, LZMA2 chunks, LZMA end markers, corrupt .xz test files, or SharpCompress XZ/LZMA parsing and decompression behavior. |
XZ and LZMA Format
Use this skill for work at the boundary between the XZ container and the LZMA/LZMA2 compression streams. It captures the key details needed for SharpCompress XZ block parsing, XZ integrity checks, and LZMA2 decoder corruption handling.
Reference
- Read references/xz-lzma-format.md when the task depends on XZ binary layout, XZ block checks, CRC64/XZ parameters, LZMA2 chunk control bytes, LZMA end-of-payload markers, or XZ Utils bad-file expectations.
- Treat XZ as a container around filter chains. Do not assume raw LZMA/LZMA2 behavior is equivalent to XZ stream validation.
- Use the linked XZ Utils/liblzma sources in the reference when matching corruption behavior. The test corpus contains intentionally bad files that must throw even when they can produce all expected output bytes.
Workflow
- Identify the layer involved: XZ stream header/footer, block header, compressed data padding, block check, index, filter chain, LZMA2 chunk framing, or raw LZMA range decoding.
- Open
references/xz-lzma-format.md and cross-check the relevant spec/source section before changing parser or decoder code.
- For XZ checksum work, verify the stream check type from the XZ header. Use CRC32, CRC64/XZ, SHA-256, or no check according to the header, not according to a test fixture assumption.
- For LZMA2 corruption work, compare SharpCompress behavior against the XZ Utils test corpus notes and liblzma decoder state model.
- Test both sync and async paths. Relevant files are
XZBlock.cs, XZBlock.Async.cs, XZStream.cs, XZStream.Async.cs, LzmaStream.cs, LzmaStream.Async.cs, LzmaDecoder.cs, and LzmaDecoder.Async.cs.
