tar-format

name	tar-format
description	Reference the Tar/USTAR/PAX/GNU tar archive container format. Use when an AI agent needs to answer questions or make code changes involving tar headers, 512-byte blocks, checksums, typeflags, USTAR prefixes, PAX local/global extended headers, GNU long names/links, sparse entries, wrapper compression, or SharpCompress Tar parsing and writing behavior.

Tar Format

Use this skill for tar container-format work. It provides a local, SharpCompress-oriented reference for POSIX USTAR, POSIX PAX, GNU tar extensions, and the current SharpCompress Tar implementation.

Reference

• Read references/tar-format.md when the task depends on tar binary layout, header field offsets, typeflag behavior, checksum rules, PAX records, GNU long-name/link records, wrapper compression support, or current SharpCompress Tar support boundaries.
• Treat the reference as an implementation guide, not a standards replacement. It cites POSIX and GNU tar sources, but it also documents SharpCompress-specific behavior and limitations.
• Prefer the SharpCompress support matrix in the reference over generic tar assumptions when changing code. Tar dialect support is intentionally partial in some areas.

Workflow

1. Identify which layer is involved: raw tar block/header parsing, POSIX USTAR fields, POSIX PAX metadata, GNU tar extensions, wrapper compression, reader/archive/writer API behavior, or tests.
2. Open the relevant section in references/tar-format.md and use the source-file pointers before changing code.
3. For parsing changes, cross-check TarHeader.cs, TarHeader.Async.cs, EntryType.cs, and matching sync/async tests.
4. For writer changes, verify both sync and async file/directory paths and TarWriterOptions.HeaderFormat behavior.
5. For support claims, keep unsupported features explicit: PAX write, sparse reconstruction, device/FIFO semantics, link-writing APIs, and writing tar.xz, tar.zst, or tar.Z.