Class: Omnizip::Formats::SevenZip::StreamDecompressor

Inherits:
Object
  • Object
show all
Defined in:
lib/omnizip/formats/seven_zip/stream_decompressor.rb

Overview

Decompresses .7z streams using coder chains Handles packed stream extraction and CRC validation

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(archive_io, folder, pack_pos, pack_size, header = nil) ⇒ StreamDecompressor

Initialize decompressor

Parameters:

  • archive_io (IO) —

    Archive file handle

  • folder (Models::Folder) —

    Folder specification

  • pack_pos (Integer) —

    Position of packed data

  • pack_size (Integer) —

    Size of packed data

  • header (Header, nil) (defaults to: nil) —

    Optional header for split archive handling



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# File 'lib/omnizip/formats/seven_zip/stream_decompressor.rb', line 20

def initialize(archive_io, folder, pack_pos, pack_size, header = nil)
  @archive_io = archive_io
  @folder = folder
  @pack_pos = pack_pos
  @pack_size = pack_size
  @header = header
  @chain_config = CoderChain.build_from_folder(folder)
end

Instance Attribute Details

#archive_io ⇒ Object (readonly)

Returns the value of attribute archive_io.



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# File 'lib/omnizip/formats/seven_zip/stream_decompressor.rb', line 11

def archive_io
  @archive_io
end

#chain_config ⇒ Object (readonly)

Returns the value of attribute chain_config.



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# File 'lib/omnizip/formats/seven_zip/stream_decompressor.rb', line 11

def chain_config
  @chain_config
end

#folder ⇒ Object (readonly)

Returns the value of attribute folder.



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# File 'lib/omnizip/formats/seven_zip/stream_decompressor.rb', line 11

def folder
  @folder
end

Instance Method Details

#decompress(size) ⇒ String

Decompress stream to output

Parameters:

  • size (Integer) —

    Expected uncompressed size

Returns:

  • (String) —

    Decompressed data

Raises:

  • (RuntimeError) —

    on decompression error



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# File 'lib/omnizip/formats/seven_zip/stream_decompressor.rb', line 34

def decompress(size)
  # Seek to packed data
  @archive_io.seek(@pack_pos)

  # For multi-volume archives, pack_size from stream_info may be incomplete.
  # For solid archives spanning volumes, the actual compressed data extends
  # from pack_pos to where the next header starts.
  if @archive_io.is_a?(SplitArchiveReader::MultiVolumeIO) && @header
    # next_header_offset is relative to start_pos_after_header
    # Actual packed data size is from pack_pos to next header position
    next_header_position = @header.start_pos_after_header + @header.next_header_offset
    actual_pack_size = next_header_position - @pack_pos
    packed_data = @archive_io.read(actual_pack_size)
  else
    # Regular single-file archive: use pack_size from stream info
    packed_data = @archive_io.read(@pack_size)
  end

  return packed_data if @chain_config.nil? # No compression

  # Get algorithm
  algo_sym = @chain_config[:algorithm]
  return packed_data unless algo_sym # Copy method

  # Get algorithm class
  algo_class = Omnizip::AlgorithmRegistry.get(algo_sym)
  raise "Algorithm not found: #{algo_sym}" unless algo_class

  # Decompress
  input_io = StringIO.new(packed_data)
  output_io = StringIO.new
  output_io.set_encoding("BINARY")

  # Build options from coder properties for 7-Zip format
  decoder_options = build_decoder_options

  decoder = algo_class.new(decoder_options)
  decoder.decompress(input_io, output_io, size: size)

  result = output_io.string

  # Apply filters if present
  if @chain_config[:filters] && !@chain_config[:filters].empty?
    @chain_config[:filters].reverse_each do |filter_sym|
      filter_class = Omnizip::FilterRegistry.get(filter_sym)
      next unless filter_class

      # BCJ2 requires special handling with multiple streams
      if filter_sym == :bcj2
        raise "BCJ2 archives require multi-stream decompression which is not yet implemented. " \
              "Please use the 7z command-line tool for this archive."
      end

      filter = filter_class.new
      filtered = StringIO.new
      filter.reverse(StringIO.new(result), filtered)
      result = filtered.string
    end
  end

  result
end

#decompress_and_verify(size, expected_crc = nil) ⇒ String

Decompress and verify CRC

Parameters:

  • size (Integer) —

    Expected uncompressed size

  • expected_crc (Integer, nil) (defaults to: nil) —

    Expected CRC32 value

Returns:

  • (String) —

    Decompressed data

Raises:

  • (RuntimeError) —

    if CRC mismatch



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# File 'lib/omnizip/formats/seven_zip/stream_decompressor.rb', line 103

def decompress_and_verify(size, expected_crc = nil)
  data = decompress(size)

  if expected_crc
    crc = Omnizip::Checksums::Crc32.new
    crc.update(data)
    actual_crc = crc.value

    unless actual_crc == expected_crc
      raise "CRC mismatch: expected 0x#{expected_crc.to_s(16)}, " \
            "got 0x#{actual_crc.to_s(16)}"
    end
  end

  data
end