Class: Mosaheh::Encoder

Inherits:
Object
  • Object
show all
Defined in:
lib/mosaheh/encoder.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Encoder

Initialize the encoder



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# File 'lib/mosaheh/encoder.rb', line 6

def initialize
  # UTF-8 bytes-sequences always begin with one of (0xD8 - 0xDB) for Arabic
  @utf_8_beginning_chars = [*216..219].map(&:chr).join.force_encoding('cp1252')

  # Misencoded sequences can be correctly re-encoded to utf-8, EXCEPT for one
  # charecter with gets replaced with a space (ASCII for it: 32)!
  @problem_char = 32.chr.force_encoding('cp1252')

  # The correct replacement for the problem charecter 
  @correct_char = 160.chr.force_encoding('cp1252')
end

Instance Method Details

#repair(str) ⇒ String

Repairs Arabic (U+0600 - U+06FF) data which has been misencoded from cp1252 to UTF-8 although the original data was UTF-8 encoded

Parameters:

  • Misencoded (String) —

    string

Returns:

  • (String) —

    Correctly encoded utf-8 string



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# File 'lib/mosaheh/encoder.rb', line 24

def repair(str)
  
  # Data buffers
  source = str.clone
  fixed  = ""
  
  # Each string needs a new converter instance
  ec  = Encoding::Converter.new('utf-8', 'cp1252')
  
  until source.empty?

    # Don't process correctly UTF-8 
    # encoded Arabic data
    if is_arabic?(source[0])
      fixed += source.shift!.force_encoding('cp1252')
      next
    end

    state = ec.primitive_convert(source, fixed, nil, nil, Encoding::Converter::AFTER_OUTPUT)

    # When an undefined sequence is found, we only move the
    # 2nd byte to the fixed data, as it will be valid in UTF-8.
    # For example: 129 is undefined in cp1252, but it is in UTF-8.
    #   If we get a sequence like:
    #   ec.last_error.error_char.unpack('C*') # => [194, 129]
    #   We just ignore the 194 and add the 129 to the fixed data
    if state == :undefined_conversion 
      c = ec.last_error.error_char.unpack('C*')[1].chr
      fixed += c.force_encoding('cp1252')
    end

    # After each byte gets converted, check for the problem charecter
    # and replace it if it's found
    if state == :after_output && ends_with_problem?(fixed)
      fixed.gsub!(/#{@problem_char}$/, @correct_char)
    end
  end

  fixed.force_encoding('utf-8')
end