Class: Omnizip::Algorithms::LZMA::Lzma1Encoder

Inherits:
Implementations::XZUtils::LZMA2::Encoder show all
Defined in:
lib/omnizip/algorithms/lzma/lzma1_encoder.rb

Overview

Raw LZMA1 stream encoder (one continuous range-coded stream with the end-of-stream marker), reusing the XZ Utils symbol coders. This is the payload for the legacy .lzma container and the lzip member body.

Constant Summary collapse

UINT32_MAX = 
0xFFFFFFFF
REPS = 
4

Constants inherited from Implementations::XZUtils::LZMA2::Encoder

Implementations::XZUtils::LZMA2::Encoder::COMPRESSED_MAX, Implementations::XZUtils::LZMA2::Encoder::UNCOMPRESSED_CHUNK_MAX, Implementations::XZUtils::LZMA2::Encoder::UNCOMPRESSED_MAX

Constants included from Constants

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

Constants inherited from Implementations::Base::LZMA2EncoderBase

Implementations::Base::LZMA2EncoderBase::COMPRESSED_MAX, Implementations::Base::LZMA2EncoderBase::UNCOMPRESSED_MAX

Instance Attribute Summary

Attributes inherited from Implementations::Base::LZMA2EncoderBase

#dict_size, #lc, #lp, #pb

Instance Method Summary collapse

Methods inherited from Implementations::XZUtils::LZMA2::Encoder

#implementation_name, #initialize

Methods inherited from Implementations::Base::LZMA2EncoderBase

#implementation_name, #initialize, #standalone?

Constructor Details

This class inherits a constructor from Omnizip::Implementations::XZUtils::LZMA2::Encoder

Instance Method Details

#encode(input, emit_eopm: true) ⇒ String

Encode input as a complete standalone LZMA1 stream, terminated by the end-of-stream marker (dist = 0xFFFFFFFF, length 2) so decoders that do not know the size can stop.

rubocop:disable-next Metrics/MethodLength

Parameters:

  • input (String)
  • emit_eopm (Boolean) (defaults to: true) —

    omit when the container carries the uncompressed size (the legacy .lzma form)

Returns:

  • (String) —

    binary stream



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# File 'lib/omnizip/algorithms/lzma/lzma1_encoder.rb', line 45

def encode(input, emit_eopm: true)
  @match_finder.reset
  output_buffer = StringIO.new
  output_buffer.set_encoding(Encoding::BINARY)
  encoder = XzRangeEncoder.new(output_buffer)
  @match_finder.feed(input)
  @match_finder.skip(@match_finder.buffer.bytesize)

  start_pos = 0
  @current_start_pos = start_pos
  pos = 0
  while pos < input.bytesize
    encode_queued_symbols(encoder, output_buffer)

    match_pos = start_pos + pos
    distance, length = @optimal.find_optimal(
      match_pos, @match_finder, @state, @state.reps, @models
    )

    if distance == UINT32_MAX || length == 1
      encode_literal(input.getbyte(pos), encoder, match_pos)
      pos += 1
    elsif distance < REPS
      encode_repeated_match(distance, length, encoder, match_pos,
                            match_pos)
      pos += length
    else
      encode_match(distance - REPS, length, encoder, match_pos,
                   match_pos, input)
      pos += length
    end
  end

  encode_eopm(encoder, output_buffer, input.bytesize) if emit_eopm
  encode_queued_symbols(encoder, output_buffer)
  encoder.queue_flush
  encode_queued_symbols(encoder, output_buffer)
  output_buffer.string
end