check_modeline

# File lib/rdoc/parser.rb, line 174
  def self.check_modeline file_name
    line = open file_name do |io|
      io.gets
    end

    /-\*-\s*(.*?\S)\s*-\*-/ =~ line

    return nil unless type = $1

    if /;/ =~ type then
      return nil unless /(?:\s|\A)mode:\s*([^\s;]+)/ =~ type
      type = $1
    end

    return nil if /coding:/ =~ type

    type.downcase
  rescue ArgumentError # invalid byte sequence, etc.
  end