Module: Voltronic::Digest

Defined in:
lib/voltronic/digest.rb

Overview

:nodoc:

Defined Under Namespace

Classes: DigestMismatchError, MalformedInputError

Class Method Summary collapse

Class Method Details

.encode(input) ⇒ Object

:nodoc:



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# File 'lib/voltronic/digest.rb', line 39

def self.encode(input) #:nodoc:
  input = input.to_s
  crc = 0
  input.bytes.each do |byte|
    crc = ((@@crc_table[(((crc >> 8) ^ byte) & 0xff)] ^ (crc << 8)) & 0xffff)
  end

  first_byte = ((crc & 0xff00) >> 8)
  second_byte = (crc & 0xff)

  if ((0x28 == first_byte) || (0x0d == first_byte) || (0x0a == first_byte))
    first_byte += 1
  end
  if ((0x28 == second_byte) || (0x0d == second_byte) || (0x0a == second_byte))
    second_byte += 1
  end

  [input, first_byte.chr, second_byte.chr, @@termination_character.chr].join
end

.eos?(input) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/voltronic/digest.rb', line 59

def self.eos?(input) #:nodoc:
  input.to_s.bytes.any? { |byte| (@@termination_character == byte) }
end

.parse(input) ⇒ Object

:nodoc:



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# File 'lib/voltronic/digest.rb', line 3

def self.parse(input) #:nodoc:
  input = begin
    input_bytes = input.to_s.bytes
    end_index = input_bytes.length
    while(0 != end_index)
      if (@@termination_character == input_bytes[(end_index -= 1)])
        break
      end
    end
    input_bytes[0..end_index]
  end

  if (3 > input.length)
    raise MalformedInputError.new 'Input must be at at least 3 bytes in size'
  end

  input_crc = input[-3..-2]
  input = input[0..-4].map do |byte|
    if (128 > byte)
      byte.chr
    else
      raise MalformedInputError.new 'Input contained an unparsable character'
    end
  end.join

  calculated_crc = encode(input).to_s.bytes[-3..-2]
  if (calculated_crc == input_crc)
    return input
  end

  raise DigestMismatchError.new ['Device digest [',
    input_crc.first, ',', input_crc.last, '] != [',
    calculated_crc.first, ',', calculated_crc.last,
    '] calculated digest'].join
end