Class: Omnizip::Implementations::SevenZip::LZMA::Encoder

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

Overview

7-Zip LZMA SDK encoder implementation.

This is the original SdkEncoder moved from algorithms/lzma/sdk_encoder.rb to the new namespace structure.

Ported from 7-Zip LZMA SDK by Igor Pavlov.

Constant Summary

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(output, options = {}) ⇒ Encoder

Initialize the SDK-compatible encoder

Parameters:

  • output (IO) —

    Output stream for compressed data

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

    Encoding options

Options Hash (options):

  • :lc (Integer) —

    Literal context bits (0-8, default: 3)

  • :lp (Integer) —

    Literal position bits (0-4, default: 0)

  • :pb (Integer) —

    Position bits (0-4, default: 2)

  • :dict_size (Integer) —

    Dictionary size (default: 64KB)

  • :level (Integer) —

    Compression level (0-9, default: 5)

  • :raw_mode (Boolean) —

    Skip header and EOS marker for LZMA2 (default: false)



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# File 'lib/omnizip/implementations/seven_zip/lzma/encoder.rb', line 48

def initialize(output, options = {})
  @output = output
  @lc = options.fetch(:lc, 3)
  @lp = options.fetch(:lp, 0)
  @pb = options.fetch(:pb, 2)
  @dict_size = options.fetch(:dict_size, 1 << 16) # 64KB default
  @level = options.fetch(:level, 5)
  @raw_mode = options.fetch(:raw_mode, false) # NEW: skip header/EOS for LZMA2

  validate_parameters
  init_models
  init_coders
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/encoder.rb', line 36

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/encoder.rb', line 36

def lc
  @lc
end

#lp ⇒ Object (readonly)

Returns the value of attribute lp.



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# File 'lib/omnizip/implementations/seven_zip/lzma/encoder.rb', line 36

def lp
  @lp
end

#pb ⇒ Object (readonly)

Returns the value of attribute pb.



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# File 'lib/omnizip/implementations/seven_zip/lzma/encoder.rb', line 36

def pb
  @pb
end

Instance Method Details

#encode_stream(data) ⇒ Array<String, Integer>

Encode a stream of data

Main encoding loop following SDK's LzmaEnc_CodeOneBlock logic:

  1. Initialize match finder with data
  2. Process each position: find matches, encode literals/matches
  3. Write EOS marker
  4. Flush range encoder

Parameters:

  • data (String, IO) —

    Input data to compress

Returns:

  • (Array<String, Integer>) —

    Tuple of [compressed_data, decode_bytes]



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# File 'lib/omnizip/implementations/seven_zip/lzma/encoder.rb', line 72

def encode_stream(data)
  input_data = data.is_a?(String) ? data : data.read

  # Force binary encoding to handle binary data properly
  # Duplicate to avoid modifying frozen strings
  input_data = input_data.dup.force_encoding(Encoding::BINARY)

  # Write LZMA header
  write_header(input_data.bytesize) unless @raw_mode

  # Initialize range encoder (7-Zip SDK version)
  @range_encoder = RangeEncoder.new(@output)

  # Initialize match finder with SDK configuration
  match_finder_config = Omnizip::Algorithms::LZMA::MatchFinderConfig.sdk_config(
    dict_size: @dict_size,
    level: @level,
  )
  @match_finder = Omnizip::Algorithms::LZMA::MatchFinderFactory.create(match_finder_config)

  # Initialize state and dictionary
  @state = StateMachine.new
  @dict = +"" # Mutable string for dictionary
  @pos = 0

  # Initialize repeat distances (all 1 initially, as in SDK)
  @reps = [1, 1, 1, 1]

  # Main encoding loop
  while @pos < input_data.bytesize
    # Find best match at current position
    match = @match_finder.find_longest_match(input_data, @pos)

    # Decide: literal vs match
    if should_encode_match?(match)
      encode_match(match, input_data)
    else
      encode_literal(input_data[@pos].ord, input_data)
    end
  end

  # Write EOS marker and flush
  # For LZMA2: skip EOS marker but DO flush the range encoder
  # The range encoder flush outputs pending bytes needed by decoder
  # LZMA2 uses CONTROL_END (0x00) to signal end of stream instead of LZMA EOS
  encode_eos_marker unless @raw_mode # Skip EOS in raw mode
  @range_encoder.flush # Always flush to output pending range encoder bytes

  # Return tuple for LZMA2: [data, bytes_for_decode]
  # For raw mode, return actual decode bytes (excluding flush padding)
  if @raw_mode
    [@output.string, @range_encoder.bytes_for_decode]
  elsif @output.respond_to?(:string)
    # For File output, just return bytes written (don't try to read back)
    # For StringIO, return the string and its size
    [@output.string, @output.string.bytesize]
  else
    [@range_encoder.bytes_for_decode, @range_encoder.bytes_for_decode]
  end
end