Class: Omnizip::Algorithms::PPMd8::Decoder

Inherits:
Object
  • Object
show all
Includes:
Constants, Omnizip::Algorithms::PPMdBase::BaseConstants
Defined in:
lib/omnizip/algorithms/ppmd8/decoder.rb

Overview

PPMd8 Decoder

Decodes streams compressed with PPMd8, maintaining synchronized model state with the encoder.

Constant Summary

Constants included from Constants

Constants::BIN_SCALE, Constants::DEFAULT_RESTORE_METHOD, Constants::GLUE_COUNT_THRESHOLD, Constants::INIT_ESCAPE_FREQ, Constants::INTERVAL, Constants::INT_BITS, Constants::MAX_FREQ, Constants::MAX_STATES, Constants::PERIOD_BITS, Constants::PROB_TOTAL, Constants::RESTORE_METHOD_CUT_OFF, Constants::RESTORE_METHOD_RESTART, Constants::SEE_CONTEXTS, Constants::SUFFIX_CONTEXTS, Constants::UNIT_ALLOC_SIZE, Constants::UNIT_SIZE

Constants included from Omnizip::Algorithms::PPMdBase::BaseConstants

Omnizip::Algorithms::PPMdBase::BaseConstants::ALPHABET_SIZE, Omnizip::Algorithms::PPMdBase::BaseConstants::BOT_VALUE, Omnizip::Algorithms::PPMdBase::BaseConstants::DEFAULT_MEM_SIZE, Omnizip::Algorithms::PPMdBase::BaseConstants::DEFAULT_ORDER, Omnizip::Algorithms::PPMdBase::BaseConstants::MAX_MEM_SIZE, Omnizip::Algorithms::PPMdBase::BaseConstants::MAX_ORDER, Omnizip::Algorithms::PPMdBase::BaseConstants::MIN_MEM_SIZE, Omnizip::Algorithms::PPMdBase::BaseConstants::MIN_ORDER, Omnizip::Algorithms::PPMdBase::BaseConstants::TOP_VALUE

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

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

Initialize the decoder

Parameters:

  • input (IO) —

    Input stream of compressed data

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

    Decoding options

Options Hash (options):

  • :model_order (Integer) —

    Maximum context order

  • :mem_size (Integer) —

    Memory size for model

  • :restore_method (Integer) —

    Restoration method



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# File 'lib/omnizip/algorithms/ppmd8/decoder.rb', line 43

def initialize(input, options = {})
  @input = input
  @model = Model.new(
    options[:model_order] || DEFAULT_ORDER,
    options[:mem_size] || DEFAULT_MEM_SIZE,
    options[:restore_method] || DEFAULT_RESTORE_METHOD,
  )
  @range_decoder = LZMA::RangeDecoder.new(input)
end

Instance Attribute Details

#model ⇒ Object (readonly)

Returns the value of attribute model.



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# File 'lib/omnizip/algorithms/ppmd8/decoder.rb', line 34

def model
  @model
end

Instance Method Details

#decode_stream ⇒ String

Decode a stream back to original bytes

Returns:

  • (String) —

    Decoded data

Raises:

  • (NotImplementedError) —

    PPMd8 is not yet fully implemented



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# File 'lib/omnizip/algorithms/ppmd8/decoder.rb', line 57

def decode_stream
  raise NotImplementedError,
        "PPMd8 decompression is not yet fully implemented. " \
        "The arithmetic coding integration requires completion. " \
        "Please use PPMd7 or other compression algorithms instead."
end