gistfile1.rb

# -*- coding: utf-8 -*-
# Proposed solution to ruby 1.9's multibyte chars.
# -- just let ruby handle it, at least initially.
# -- not many that we're calling ActiveSupport methods
# -- on will have non-ascii characters anyway.

# useless performance metrics (on my macbook)
# ====================================+=======
# String#ascii_only?                  | 0.22µs
# String#force_encoding("ASCII-8BIT") | 0.60µs
# String#encoding==ASCII_ENCODING     | 0.26µs

# If we can safely do Encoding.default_external = Encoding.find("ASCII-8BIT"),
# then this only has 0.2µs overhead in string functions.

if '1.9'.respond_to?(:force_encoding)
  ASCII_ENCODING = Encoding.find("ASCII-8BIT")
  def do_something(str)
    if str.encoding == ASCII_ENCODING
      ::ActiveSupport::FFI.whatever_function(str)
    else
      do_the_existing_ruby_stuff()
    end
  end
else
  def do_something(str)
    ::ActiveSupport::FFI.whatever_function(str)
  end
end

# If we can't touch the default encoding, and know it isn't ASCII,
# then this will work, but it has about four times as much overhead, at 0.8µs.

if '1.9'.respond_to?(:force_encoding)
  def do_something(str)
    if str.ascii_only?
      ::ActiveSupport::FFI.whatever_function(str.force_encoding("ASCII-8BIT"))
    else
      do_the_existing_ruby_stuff()
    end
  end
else
  def do_something(str)
    ::ActiveSupport::FFI.whatever_function(str)
  end
end

# If we can't touch the encoding, but aren't sure what it is, then we can combine
# the two approaches above.

if '1.9'.respond_to?(:force_encoding)
  ASCII_ENCODING = Encoding.find("ASCII-8BIT")
  if Encoding.default_external == ASCII_ENCODING
    def do_something(str)
      if str.encoding == ASCII_ENCODING
        ::ActiveSupport::FFI.whatever_function(str)
      else
        do_the_existing_ruby_stuff()
      end
    end
  else
    def do_something(str)
      if str.ascii_only?
        ::ActiveSupport::FFI.whatever_function(str.force_encoding("ASCII-8BIT"))
      else
        do_the_existing_ruby_stuff()
      end
    end
  end
else
  def do_something(str)
    ::ActiveSupport::FFI.whatever_function(str)
  end
end