Class: Omnizip::Algorithms::LZMA::LengthEncoder

Inherits:
Object
  • Object
show all
Includes:
Constants
Defined in:
lib/omnizip/algorithms/lzma/xz_probability_models.rb

Overview

Length encoder with probability models and price tables

Encodes match lengths using a 3-tier structure:

  • Low: lengths 2-9 (choice=0, 3 bits)
  • Mid: lengths 10-17 (choice=1, choice2=0, 3 bits)
  • High: lengths 18-273 (choice=1, choice2=1, 8 bits)

Constant Summary

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pb) ⇒ LengthEncoder

Initialize length encoder

Parameters:

  • pb (Integer) —

    Number of position bits



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 169

def initialize(pb)
  @pb = pb
  @num_pos_states = 1 << pb

  # Choice bits
  @choice = XzBufferedRangeEncoder::Probability.new
  @choice2 = XzBufferedRangeEncoder::Probability.new

  # Low lengths (per position state)
  @low = Array.new(@num_pos_states) do
    Array.new(LEN_LOW_SYMBOLS) { XzBufferedRangeEncoder::Probability.new }
  end

  # Mid lengths (per position state)
  @mid = Array.new(@num_pos_states) do
    Array.new(LEN_MID_SYMBOLS) { XzBufferedRangeEncoder::Probability.new }
  end

  # High lengths (shared across position states)
  @high = Array.new(LEN_HIGH_SYMBOLS) { XzBufferedRangeEncoder::Probability.new }

  # Price tables (updated incrementally)
  # prices[pos_state][length - MATCH_LEN_MIN]
  @prices = Array.new(@num_pos_states) do
    Array.new(MATCH_LEN_MAX - MATCH_LEN_MIN + 1, 0)
  end

  # Counters for price table updates
  @counters = Array.new(@num_pos_states, 0)
end

Instance Attribute Details

#choice ⇒ Object (readonly)

Returns the value of attribute choice.



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 164

def choice
  @choice
end

#choice2 ⇒ Object (readonly)

Returns the value of attribute choice2.



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 164

def choice2
  @choice2
end

#counters ⇒ Object (readonly)

Returns the value of attribute counters.



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 164

def counters
  @counters
end

#high ⇒ Object (readonly)

Returns the value of attribute high.



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 164

def high
  @high
end

#low ⇒ Object (readonly)

Returns the value of attribute low.



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 164

def low
  @low
end

#mid ⇒ Object (readonly)

Returns the value of attribute mid.



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 164

def mid
  @mid
end

#prices ⇒ Object (readonly)

Returns the value of attribute prices.



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 164

def prices
  @prices
end

Instance Method Details

#decrement_counter(pos_state) ⇒ Boolean

Decrement counter for position state

Parameters:

  • pos_state (Integer) —

    Position state

Returns:

  • (Boolean) —

    True if counter reached zero



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 243

def decrement_counter(pos_state)
  @counters[pos_state] -= 1
  @counters[pos_state] <= 0
end

#get_price(pos_state, length) ⇒ Integer

Get price for encoding length at position state

Parameters:

  • pos_state (Integer) —

    Position state (0 to 2^pb - 1)

  • length (Integer) —

    Match length (2 to 273)

Returns:

  • (Integer) —

    Price in price units



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 226

def get_price(pos_state, length)
  @prices[pos_state][length - MATCH_LEN_MIN]
end

#reset ⇒ Object

Reset all models to initial state



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 201

def reset
  @choice.value = BIT_MODEL_TOTAL >> 1
  @choice2.value = BIT_MODEL_TOTAL >> 1
  @low.each do |models|
    models.each do |prob|
      prob.value = BIT_MODEL_TOTAL >> 1
    end
  end
  @mid.each do |models|
    models.each do |prob|
      prob.value = BIT_MODEL_TOTAL >> 1
    end
  end
  @high.each { |prob| prob.value = BIT_MODEL_TOTAL >> 1 }

  # Reset price tables
  @prices.each { |pos_prices| pos_prices.fill(0) }
  @counters.fill(0)
end

#reset_counter(pos_state, value) ⇒ Object

Reset counter for position state

Parameters:

  • pos_state (Integer) —

    Position state

  • value (Integer) —

    Counter value



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 252

def reset_counter(pos_state, value)
  @counters[pos_state] = value
end

#set_price(pos_state, length, price) ⇒ Object

Set price for length at position state

Parameters:

  • pos_state (Integer) —

    Position state

  • length (Integer) —

    Match length

  • price (Integer) —

    Price value



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# File 'lib/omnizip/algorithms/lzma/xz_probability_models.rb', line 235

def set_price(pos_state, length, price)
  @prices[pos_state][length - MATCH_LEN_MIN] = price
end