Module: Cabriolet::QuantumShared

Included in:
Compressors::Quantum, Decompressors::Quantum
Defined in:
lib/cabriolet/quantum_shared.rb

Overview

Shared Quantum compression constants and models Used by both Compressors::Quantum and Decompressors::Quantum

Defined Under Namespace

Classes: Model, ModelSymbol

Constant Summary collapse

FRAME_SIZE =

Frame size (32KB per frame)

32_768
MIN_MATCH =

Match constants

3
MAX_MATCH = 
259
POSITION_BASE =

Position slot tables (same as in qtmd.c)

[
  0, 1, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, 64, 96, 128, 192, 256, 384,
  512, 768, 1024, 1536, 2048, 3072, 4096, 6144, 8192, 12_288, 16_384,
  24_576, 32_768, 49_152, 65_536, 98_304, 131_072, 196_608, 262_144,
  393_216, 524_288, 786_432, 1_048_576, 1_572_864
].freeze
EXTRA_BITS = 
[
  0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8,
  9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16,
  17, 17, 18, 18, 19, 19
].freeze
LENGTH_BASE = 
[
  0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 18, 22, 26,
  30, 38, 46, 54, 62, 78, 94, 110, 126, 158, 190, 222, 254
].freeze
LENGTH_EXTRA = 
[
  0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
  3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
].freeze

Class Method Summary collapse

Class Method Details

.find_length_slot(length) ⇒ Integer

Find length slot for a given length

Parameters:

  • Match length

Returns:

  • Length slot index



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# File 'lib/cabriolet/quantum_shared.rb', line 86

def self.find_length_slot(length)
  return 0 if length < 4

  # Binary search through LENGTH_BASE
  low = 1
  high = LENGTH_BASE.size - 1

  while low < high
    mid = (low + high + 1) / 2
    if LENGTH_BASE[mid] <= length
      low = mid
    else
      high = mid - 1
    end
  end

  low
end

.find_position_slot(offset) ⇒ Integer

Find position slot for a given offset

Parameters:

  • Position offset

Returns:

  • Position slot index



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# File 'lib/cabriolet/quantum_shared.rb', line 63

def self.find_position_slot(offset)
  return 0 if offset < 4

  # Binary search through POSITION_BASE
  low = 1
  high = POSITION_BASE.size - 1

  while low < high
    mid = (low + high + 1) / 2
    if POSITION_BASE[mid] <= offset
      low = mid
    else
      high = mid - 1
    end
  end

  low
end