Method: Barcode1DTools::MSI.decode

Defined in:
lib/barcode1dtools/msi.rb

.decode(str, options = {}) ⇒ Object

Decode a string in rle format. This will return a MSI object.



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# File 'lib/barcode1dtools/msi.rb', line 171

def decode(str, options = {})
  if str =~ /[^1-3]/ && str =~ /[^wn]/
    raise UnencodableCharactersError, "Pattern must be rle or wn"
  end

  # ensure a wn string
  if str =~ /[1-3]/
    str = str.tr('123','nww')
  end

  if str.reverse =~ /\A#{GUARD_PATTERN_LEFT_WN}.*?#{GUARD_PATTERN_RIGHT_WN}\z/
    str.reverse!
  end

  unless str =~ /\A#{GUARD_PATTERN_LEFT_WN}(.*?)#{GUARD_PATTERN_RIGHT_WN}\z/
    raise UnencodableCharactersError, "Start/stop pattern is not detected."
  end

  wn_pattern = $1

  # Each pattern is 4 bars and 4 spaces, with a space between.
  unless wn_pattern.size % 8 == 0
    raise UnencodableCharactersError, "Wrong number of bars."
  end

  decoded_string = ''

  wn_pattern.scan(/.{8}/).each do |chunk|

    found = false

    PATTERNS.each do |char,hsh|
      if chunk == hsh['wn']
        decoded_string += char
        found = true
        break;
      end
    end

    raise UndecodableCharactersError, "Invalid sequence: #{chunk}" unless found

  end

  MSI.new(decoded_string, options)
end