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rar-format

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Reference the RAR/RAR5 archive container format and UnRAR source behavior. Use when an AI agent needs to answer questions or make code changes involving RAR signatures, RAR5 vint fields, block headers, file/service headers, extra records, solid archives, multivolume parts, encryption headers, recovery records, quick-open data, or SharpCompress Rar parsing and extraction behavior.

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Source SKILL.md: https://github.com/adamhathcock/sharpcompress/blob/HEAD/.agents/skills/rar-format/SKILL.md

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Rar Format

Use this skill for RAR container-format work. It provides a local, SharpCompress-oriented reference for RAR 5.0 archive blocks, older RAR header compatibility, UnRAR source behavior, and current SharpCompress Rar implementation boundaries.

Reference

  • Read references/rar-format.md when the task depends on RAR binary layout, RAR4 vs RAR5 signatures, RAR5 vint encoding, block/header flags, file and service header fields, extra records, encrypted headers, solid archives, split volumes, redirection records, or current SharpCompress Rar support boundaries.
  • Treat the reference as an implementation guide, not a standards replacement. It summarizes reference/RAR 5.0 archive format.htm and selected files under reference/unrar/, especially headers5.hpp, headers.hpp, arcread.cpp, rawread.*, crypt*.cpp, qopen.*, volume.*, recvol*.cpp, unpack*.cpp, and blake2sp.*.
  • Prefer the SharpCompress support matrix in the reference over generic RAR assumptions when changing code. RAR is a read-only format in SharpCompress, and metadata/service-header support is intentionally partial.

Workflow

  1. Identify which layer is involved: signature detection, RAR4 headers, RAR5 headers, vint parsing, block flags, extra records, file/service metadata, encrypted headers, multivolume handling, decompression, reader/archive API behavior, or tests.
  2. Open the relevant section in references/rar-format.md and use the source-file pointers before changing code.
  3. For header parsing changes, cross-check sync and async implementations: MarkHeader.cs, RarHeader.cs, RarHeaderFactory.cs, FileHeader.cs, Flags.cs, and their async counterparts.
  4. For extraction changes, verify split and solid archive behavior with RarArchive, RarReader, RarStream, and the unpacker files under src/SharpCompress/Compressors/Rar/.
  5. For support claims, keep unsupported or partial features explicit: RAR writing, pre-RAR4 archives, complete service-header semantics, quick-open use, recovery reconstruction, and encryption/version constraints.