Sevenzip Format

Sevenzip Format

Use this skill for 7z container-format work. It provides a local Markdown conversion of the LZMA SDK 7zFormat.txt reference.

Reference

• Read references/7z-format.md when the task depends on 7z binary layout, header property IDs, stream/folder relationships, metadata fields, or encoded headers.
• Treat the reference as the LZMA SDK 7z format description version 4.59. It describes the container grammar, not compression method internals; method-specific codec details are outside this skill.
• Preserve source field names and numeric IDs when mapping the spec to code. The converted reference keeps source spelling inside syntax blocks where exact matching may matter.

Workflow

1. Identify which part of the 7z container is involved: signature/start header, packed streams, coders/folders, substreams, files info, or encoded headers.
2. Open the relevant section in references/7z-format.md and use the table of contents to avoid loading unrelated details.
3. When implementing or reviewing parsing logic, pay special attention to optional blocks marked with [], 7z's variable-length UINT64 encoding, and little-endian REAL_UINT64 fields.
4. Cross-check behavior against SharpCompress tests and existing parser conventions before changing public API or stream behavior.