Method: Cosmos::Crc#initialize

Defined in:
lib/cosmos/utilities/crc.rb

#initialize(poly, seed, xor, reflect) ⇒ Crc

Creates a CRC algorithm instance.

Parameters:

  • poly (Integer) —

    Polynomial to use when calculating the CRC

  • seed (Integer) —

    Seed value to start the calculation

  • xor (Boolean) —

    Whether to XOR the CRC result with 0xFFFF

  • reflect (Boolean) —

    Whether to bit reverse each byte of data before calculating the CRC



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# File 'lib/cosmos/utilities/crc.rb', line 63

def initialize(poly, seed, xor, reflect)
  @poly = poly
  @seed = seed
  @xor = xor
  @reflect = reflect
  if RUBY_ENGINE == 'ruby' and !ENV['COSMOS_NO_EXT']
    @table = ''
  else
    @table = []
  end

  # Determine which class we're using: Crc16, Crc32, Crc64
  @bit_size = self.class.name[-2..-1].to_i
  case @bit_size
  when 16
    pack = 'S'
    filter_mask = 0xFFFF
  when 32
    pack = 'I'
    filter_mask = 0xFFFFFFFF
  when 64
    pack = 'Q'
    filter_mask = 0xFFFFFFFFFFFFFFFF
  end
  if RUBY_ENGINE == 'ruby' and !ENV['COSMOS_NO_EXT']
    (0..255).each do |index|
      @table << [compute_table_entry(index, @bit_size)].pack(pack)
    end
  else
    (0..255).each do |index|
      @table << (compute_table_entry(index, @bit_size) & filter_mask)
    end
  end
end