This class is a wrapper around File IO and Encoding that helps RDoc load files and convert them to the correct encoding.

Methods
R
S
Class Public methods
read_file(filename, encoding, force_transcode = false)

Reads the contents of filename and handles any encoding directives in the file.

The content will be converted to the encoding. If the file cannot be converted a warning will be printed and nil will be returned.

If force_transcode is true the document will be transcoded and any unknown character in the target encoding will be replaced with '?'

Source: show | on GitHub 

# File ../ruby/lib/rdoc/encoding.rb, line 20
def self.read_file filename, encoding, force_transcode = false
  content = open filename, "rb" do |f| f.read end
  content.gsub!("\r\n", "\n") if RUBY_PLATFORM =~ /mswin|mingw/

  utf8 = content.sub!(/\A\xef\xbb\xbf/, '')

  RDoc::Encoding.set_encoding content

  if Object.const_defined? :Encoding then
    encoding ||= Encoding.default_external
    orig_encoding = content.encoding

    if utf8 then
      content.force_encoding Encoding::UTF_8
      content.encode! encoding
    else
      # assume the content is in our output encoding
      content.force_encoding encoding
    end

    unless content.valid_encoding? then
      # revert and try to transcode
      content.force_encoding orig_encoding
      content.encode! encoding
    end

    unless content.valid_encoding? then
      warn "unable to convert #{filename} to #{encoding}, skipping"
      content = nil
    end
  end

  content
rescue ArgumentError => e
  raise unless e.message =~ /unknown encoding name - (.*)/
  warn "unknown encoding name \"#{$1}\" for #{filename}, skipping"
  nil
rescue Encoding::UndefinedConversionError => e
  if force_transcode then
    content.force_encoding orig_encoding
    content.encode! encoding, :undef => :replace, :replace => '?'
    content
  else
    warn "unable to convert #{e.message} for #{filename}, skipping"
    nil
  end
rescue Errno::EISDIR, Errno::ENOENT
  nil
end
set_encoding(string)

Sets the encoding of string based on the magic comment

Source: show | on GitHub 

# File ../ruby/lib/rdoc/encoding.rb, line 73
def self.set_encoding string
  first_line = string[/\A(?:#!.*\n)?.*\n/]

  name = case first_line
         when /^<\?xml[^?]*encoding=(["'])(.*?)\1/ then $2
         when /\b(?:en)?coding[=:]\s*([^\s;]+)/i   then $1
         else                                           return
         end

  string.sub! first_line, ''

  return unless Object.const_defined? :Encoding

  enc = Encoding.find name
  string.force_encoding enc if enc
end