Extension Mapping

Purpose

Reference for how file extensions map to extractors.

Simple Extensions

Extensions that map directly to a single extractor:

Extension	Extractor	Format
.7z	SevenZipExtractor	7-Zip
.cab	CabExtractor	Microsoft Cabinet
.cpio	CpioExtractor	CPIO
.gz	GzipExtractor	GZIP
.msi	OleExtractor	Windows Installer
.pkg	XarExtractor	macOS Package
.rpm	RpmExtractor	Red Hat Package
.tar	TarExtractor	TAR
.xar	XarExtractor	XAR
.xz	XzExtractor	XZ
.zip	ZipExtractor	ZIP

Compound Extensions

Extensions that trigger multiple extractors in sequence:

Extension	Extraction Chain	Result
.tar.gz	GzipExtractor → TarExtractor	Extracted TAR contents
.tgz	GzipExtractor → TarExtractor	Extracted TAR contents
.tar.xz	XzExtractor → TarExtractor	Extracted TAR contents
.txz	XzExtractor → TarExtractor	Extracted TAR contents

Special Cases

EXE Files

EXE files are handled with fallback logic:

# Order of attempts:
1. SevenZipExtractor  # Try 7-Zip self-extracting
2. CabExtractor       # Fall back to CAB self-extracting

Detection Logic

def extract(target)
  extension = File.extname(@archive).downcase

  case extension
  when '.exe'
    # Try 7-Zip first, then CAB
    begin
      SevenZipExtractor.new(@archive).extract(target)
    rescue
      CabExtractor.new(@archive).extract(target)
    end
  when '.gz'
    # Verify GZIP magic bytes
    if gzip_magic?(@archive)
      GzipExtractor.new(@archive).extract(target)
    else
      raise UnknownArchiveError
    end
  else
    # Standard extension mapping
    extractor = TYPES[extension]
    extractor.new(@archive).extract(target)
  end
end

Implementation

The TYPES hash maps extensions to extractors:

TYPES = {
  "cab"  => Extractors::CabExtractor,
  "cpio" => Extractors::CpioExtractor,
  "exe"  => Extractors::SevenZipExtractor,
  "gz"   => Extractors::GzipExtractor,
  "msi"  => Extractors::OleExtractor,
  "pkg"  => Extractors::XarExtractor,
  "rpm"  => Extractors::RpmExtractor,
  "tar"  => Extractors::TarExtractor,
  "xz"   => Extractors::XzExtractor,
  "zip"  => Extractors::ZipExtractor
}

Adding New Formats

To support a new format:

1. Create a new extractor class

2. Add mapping to TYPES hash

3. Handle compound extensions if needed

# 1. Create extractor
class Extractors::NewFormatExtractor < Extractor
  def extract(target)
    # Implementation
  end
end

# 2. Add to TYPES
TYPES["newfmt"] = Extractors::NewFormatExtractor