file-compression

CODE SKILL — VERBATIM REQUIRED This skill targets multiple archive formats (TAR, GZIP, ZIP) with manual binary parsing. The Runnable Entry Point is the sole implementation. Adaptation is prohibited per C2-A Rule 3.

CRITICAL: Execution Constraints

The code below is the SOLE IMPLEMENTATION — it MUST NOT be replaced, simplified, or reimplemented.

Prohibited deviations:

• Do NOT write your own crc32() — use ONLY the one in Runnable Entry Point
• Do NOT write your own TAR header parser or builder — use ONLY the ones in Runnable Entry Point
• Do NOT write your own ZIP EOCD scanner or central directory parser — use ONLY the ones in Runnable Entry Point
• Do NOT skip any format-specific handling (.tar, .tar.gz, .tgz, .zip, .gz)
• Do NOT use shell tools (tar, gzip, unzip) — all operations are pure JavaScript in jsexec
• Do NOT alter the entry point dispatch logic (action === 'compress' / action === 'decompress')

Correct Invocation Pattern

1. Copy the complete script from ## Runnable Entry Point below
2. Replace ONLY {{action}}, {{input}}, {{output}}, {{format}} with actual values
3. Since the IIFE is large (370+ lines), persist to a temp file and execute via jsexec --file_path <file> — do NOT embed the entire IIFE inside another JS string
4. Execute with NO modifications to core logic

Argument Details

Arg	Type	Required	Default	Description
action	string	yes	—	compress or decompress
input	string	yes	—	Source file/directory (compress) or archive path (decompress)
output	string	no	auto	Output archive path (compress) or extract directory (decompress)
format	string	no	auto	tar / tar.gz / tgz / zip / gz (compress only). When both output and format are provided, format takes priority. When output is auto-generated, format determines the suffix.

⚠️ format vs output extension: When format is explicitly set, it overrides format detection from the output file extension. For example, format=zip + output=archive.tar still produces a valid ZIP. Without format, the extension determines the archive type.