class Dir

# File lib/dirwalk.rb, line 9
def Dir.walk(top, topdown=true, onerror=nil, followlinks=false, &block)
  # yield 3-tuple, dirpath, dirnames, filenames
  dirs, nondirs = [], []
  Dir.chdir(top) do
    begin
      names = Dir.glob('*', File::FNM_DOTMATCH)
      names.shift(2)  # shift '.' and '..'
    rescue Exception => err
      onerror.call(err) if onerror
      return
    end

    names.each do |name|
      if File.directory?(name)
        dirs << name
      else
        nondirs << name
      end
    end
  end

  if topdown
    block.call(top, dirs, nondirs)
  end

  dirs.each do |name|
    new_path = File.join(top, name)
    if followlinks || !File.symlink?(new_path)
      walk(new_path, topdown, onerror, followlinks, &block)
    end
  end

  if !topdown
    block.call(top, dirs, nondirs)
  end
end