Class: Omnizip::Implementations::XZUtils::LZMA2::Encoder

Inherits:
Base::LZMA2EncoderBase show all
Includes:
Algorithms::LZMA::Constants
Defined in:
lib/omnizip/implementations/xz_utils/lzma2/encoder.rb

Overview

XZ Utils LZMA2 encoder.

Constant Summary collapse

UNCOMPRESSED_MAX =

XZ Utils limits (from lzma2_encoder.h) Maximum UNCOMPRESSED size per chunk: 2MB

1 << 21
COMPRESSED_MAX =

Maximum COMPRESSED size per chunk: 64KB

1 << 16

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

Attributes inherited from Base::LZMA2EncoderBase

#dict_size, #lc, #lp, #pb

Instance Method Summary collapse

Methods inherited from Base::LZMA2EncoderBase

#standalone?

Constructor Details

#initialize(options = {}) ⇒ Encoder

Initialize the encoder

Parameters:

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

    Encoding options

Options Hash (options):

  • :dict_size (Integer) —

    Dictionary size (default: 8MB)

  • :lc (Integer) —

    Literal context bits (default: 3)

  • :lp (Integer) —

    Literal position bits (default: 0)

  • :pb (Integer) —

    Position bits (default: 2)

  • :standalone (Boolean) —

    If true, write property byte at start (default: true)



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# File 'lib/omnizip/implementations/xz_utils/lzma2/encoder.rb', line 70

def initialize(options = {})
  dict_size = options.fetch(:dict_size, 8 * 1024 * 1024)
  lc = options.fetch(:lc, 3)
  lp = options.fetch(:lp, 0)
  pb = options.fetch(:pb, 2)
  standalone = options.fetch(:standalone, true)

  super(
    dict_size: dict_size,
    lc: lc,
    lp: lp,
    pb: pb,
    standalone: standalone
  )

  # Shared state across all chunks
  @dictionary = Omnizip::Algorithms::LZMA::Dictionary.new(dict_size)
  @state = Omnizip::Algorithms::LZMA::LZMAState.new(0)
  @models = Omnizip::Algorithms::LZMA::XzProbabilityModels.new(lc,
                                                               lp, pb)
  @match_finder = Omnizip::Algorithms::LZMA::MatchFinder.new(@dictionary)
  @optimal = Omnizip::Algorithms::LZMA::OptimalEncoder.new(mode: :fast)

  # Track previous byte for literal context
  @prev_byte = 0

  # CRITICAL: For XZ Utils compatibility, first chunk MUST reset the dictionary
  # (matches XZ Utils behavior - see lzma2_encoder.c:334-336)
  # need_dictionary_reset is set to true for the first compressed chunk
  @need_properties = false # Properties will be written in first compressed chunk
  @need_state_reset = false
  @need_dictionary_reset = true # Always reset dictionary for first chunk (XZ Utils compatibility)
end

Instance Method Details

#encode(input_data) ⇒ Object 



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# File 'lib/omnizip/implementations/xz_utils/lzma2/encoder.rb', line 104

def encode(input_data)
  # CRITICAL: Reset match finder state for each encoding session
  # This ensures hash table and hash chain start fresh for each Xz.create call
  @match_finder.reset

  output = StringIO.new
  output.set_encoding(Encoding::BINARY)

  # Write property byte if standalone mode (for .lz2 files)
  # The property byte encodes dictionary size
  # Formula: For power-of-2 sizes, d = 2 * (log2_size - 12)
  if @standalone
    prop_byte = encode_dict_size(@dict_size)
    output.putc(prop_byte)
  end

  input = StringIO.new(input_data)
  input.set_encoding(Encoding::BINARY)

  # Process in chunks (UNCOMPRESSED_MAX = 2MB per chunk)
  while !input.eof?
    chunk_data = input.read(UNCOMPRESSED_MAX)
    break if chunk_data.nil? || chunk_data.empty?

    chunk = encode_chunk(chunk_data)
    output.write(chunk.to_bytes)

    @need_properties = false
    @need_state_reset = false
    @need_dictionary_reset = false
  end

  # End marker (0x00) is REQUIRED for all LZMA2 streams
  # The @standalone flag only controls whether a property byte is written
  # at the START (for raw LZMA2 format like .lz2), not the end marker.
  # XZ format requires the end marker to properly terminate the LZMA2 stream.
  output.write([0x00].pack("C"))

  output.string
end

#implementation_name ⇒ Symbol

Get implementation identifier.

Returns:

  • (Symbol) —

    :xz_utils



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# File 'lib/omnizip/implementations/xz_utils/lzma2/encoder.rb', line 148

def implementation_name
  :xz_utils
end