String#replace_invalid_bytes that replaces invalid bytes in a string

replace_invalid_bytes.rb

# -*- coding: utf-8 -*-

class String
  def replace_invalid_bytes(replace = nil)
    if block_given?
      if replace
        warn 'block not used' if $VERBOSE
      end
    elsif replace.nil?
      raise ArgumentError, 'an argument or a block must be given'
    end

    return self if valid_encoding?

    if replace
      r = String.try_convert(replace) or
        raise TypeError, "can't convert #{replace.class} into String"
      each_char.inject('') { |s, c|
        s << (c.valid_encoding? ? c : r)
      }
    else
      each_char.inject('') { |s, c|
        s << (c.valid_encoding? ? c : yield(*c.bytes))
      }
    end
  end
end

puts "あい\x80\xffう".replace_invalid_bytes('[?]')
#=> あい[?][?]う
puts "あい\x80\xffう".replace_invalid_bytes { |b| "<%02X>" % b }
#=> あい<80><FF>う