Class: Omnizip::Implementations::SevenZip::LZMA::Decoder

Inherits:
Object
  • Object
show all
Includes:
Algorithms::LZMA::Constants
Defined in:
lib/omnizip/implementations/seven_zip/lzma/decoder.rb

Overview

7-Zip SDK compatible LZMA decoder.

This decoder is designed to decode data encoded by the 7-Zip SDK encoder. Uses the same shared infrastructure (RangeDecoder, LengthCoder, DistanceCoder) to ensure model layout compatibility with the encoder.

Constant Summary collapse

MAX_DICT_SIZE =

Maximum dictionary size to prevent memory exhaustion 64MB is a reasonable practical limit

64 * 1024 * 1024

Constants included from Algorithms::LZMA::Constants

Algorithms::LZMA::Constants::BIT_MODEL_TOTAL, Algorithms::LZMA::Constants::COMPRESSION_LEVEL_DEFAULT, Algorithms::LZMA::Constants::COMPRESSION_LEVEL_MAX, Algorithms::LZMA::Constants::COMPRESSION_LEVEL_MIN, Algorithms::LZMA::Constants::DICT_SIZE_MAX, Algorithms::LZMA::Constants::DICT_SIZE_MIN, Algorithms::LZMA::Constants::DIST_ALIGN_BITS, Algorithms::LZMA::Constants::DIST_ALIGN_SIZE, Algorithms::LZMA::Constants::DIST_SLOT_FAST_LIMIT, Algorithms::LZMA::Constants::END_POS_MODEL_INDEX, Algorithms::LZMA::Constants::EOS_MARKER, Algorithms::LZMA::Constants::INIT_PROBS, Algorithms::LZMA::Constants::LEN_HIGH_SYMBOLS, Algorithms::LZMA::Constants::LEN_LOW_SYMBOLS, Algorithms::LZMA::Constants::LEN_MID_SYMBOLS, Algorithms::LZMA::Constants::LIT_SIZE_MAX, Algorithms::LZMA::Constants::MATCH_LEN_MAX, Algorithms::LZMA::Constants::MATCH_LEN_MIN, Algorithms::LZMA::Constants::MOVE_BITS, Algorithms::LZMA::Constants::NUM_DIRECT_BITS, Algorithms::LZMA::Constants::NUM_DIST_SLOTS, Algorithms::LZMA::Constants::NUM_DIST_SLOT_BITS, Algorithms::LZMA::Constants::NUM_FULL_DISTANCES, Algorithms::LZMA::Constants::NUM_LEN_HIGH_BITS, Algorithms::LZMA::Constants::NUM_LEN_LOW_BITS, Algorithms::LZMA::Constants::NUM_LEN_MID_BITS, Algorithms::LZMA::Constants::NUM_LEN_TO_POS_STATES, Algorithms::LZMA::Constants::NUM_LIT_CONTEXT_BITS_MAX, Algorithms::LZMA::Constants::NUM_LIT_POS_BITS_MAX, Algorithms::LZMA::Constants::NUM_POS_BITS_MAX, Algorithms::LZMA::Constants::NUM_STATES, Algorithms::LZMA::Constants::POS_STATES_MAX, Algorithms::LZMA::Constants::START_POS_MODEL_INDEX, Algorithms::LZMA::Constants::TOP

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(input, options = {}) ⇒ Decoder

Initialize 7-Zip LZMA decoder

Parameters:

  • input (IO) —

    Input stream with LZMA compressed data

  • options (Hash) (defaults to: {}) —

    Decoding options

Options Hash (options):

  • :raw_mode (Boolean) —

    Skip header parsing (for LZMA2)

  • :lc (Integer) —

    Literal context bits

  • :lp (Integer) —

    Literal position bits

  • :pb (Integer) —

    Position bits

  • :dict_size (Integer) —

    Dictionary size



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 50

def initialize(input, options = {})
  @input = input
  @raw_mode = options.fetch(:raw_mode, false)

  if @raw_mode
    @lc = options[:lc] || 3
    @lp = options[:lp] || 0
    @pb = options[:pb] || 2
    @dict_size = [[options[:dict_size] || (1 << 16), 1].max,
                  MAX_DICT_SIZE].min
    @uncompressed_size = options[:uncompressed_size]
  else
    parse_header
  end

  init_decoder
end

Instance Attribute Details

#dict_size ⇒ Object (readonly)

Returns the value of attribute dict_size.



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 39

def dict_size
  @dict_size
end

#lc ⇒ Object (readonly)

Returns the value of attribute lc.



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 39

def lc
  @lc
end

#lp ⇒ Object (readonly)

Returns the value of attribute lp.



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 39

def lp
  @lp
end

#pb ⇒ Object (readonly)

Returns the value of attribute pb.



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 39

def pb
  @pb
end

#uncompressed_size ⇒ Object (readonly)

Returns the value of attribute uncompressed_size.



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 39

def uncompressed_size
  @uncompressed_size
end

Instance Method Details

#decode_stream(output = nil, preserve_dict: false) ⇒ String, Integer

Decode LZMA stream

Parameters:

  • output (IO, nil) (defaults to: nil) —

    Output stream (if nil, returns String)

  • preserve_dict (Boolean) (defaults to: false) —

    Preserve dictionary for chunked decoding

Returns:

  • (String, Integer) —

    Decompressed data or bytes written



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 73

def decode_stream(output = nil, preserve_dict: false)
  @output_buffer = []
  unless preserve_dict && @dictionary
    @dictionary = Array.new(@dict_size,
                            0)
  end
  @dict_pos = 0
  @dict_full = false

  # Initialize range decoder (7-Zip SDK version)
  @range_decoder = RangeDecoder.new(@input)

  # Main decode loop
  loop do
    break if reached_end?

    # Track if we were using EOPM before decoding
    was_using_eopm = @allow_eopm

    decode_symbol

    # If we were using EOPM and now we're not, EOS was detected
    break if was_using_eopm && !@allow_eopm
  end

  result = @output_buffer.pack("C*").force_encoding(Encoding::BINARY)

  if output
    output.write(result)
    result.bytesize
  else
    result
  end
end

#reset(new_lc: nil, new_lp: nil, new_pb: nil, preserve_dict: false) ⇒ Object

Reset decoder state for new chunk (LZMA2)



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 109

def reset(new_lc: nil, new_lp: nil, new_pb: nil, preserve_dict: false)
  @lc = new_lc if new_lc
  @lp = new_lp if new_lp
  @pb = new_pb if new_pb

  unless preserve_dict
    @dictionary = Array.new(@dict_size, 0)
    @dict_pos = 0
    @dict_full = false
  end

  init_decoder
end

#set_input(new_input) ⇒ Object

Set new input stream (LZMA2)



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 124

def set_input(new_input)
  @input = new_input
end

#set_uncompressed_size(size, allow_eopm: true) ⇒ Object

Set uncompressed size (LZMA2)



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# File 'lib/omnizip/implementations/seven_zip/lzma/decoder.rb', line 129

def set_uncompressed_size(size, allow_eopm: true)
  @uncompressed_size = size
  @allow_eopm = allow_eopm
end