Resumable directory search like "find -depth"

dirdfs.rb

#! ruby19

DirDfs = Struct.new :root, :state_file do

  def self.resume(state_file)
    File.open(state_file, "rb") do |io|
      Marshal.load(io)
    end
  end

  def initialize(root, state_file)
    @stack = [[root]]
    self.state_file = state_file
  end

  def dfs
    until @stack.empty?
      while @stack.last.first
        f = File.join(*@stack.map(&:first))

        if test ?d, f
          @stack.push(Dir.entries(f).select {|s| /\A\.{1,2}\z/ !~ s})
        else
          yield f
          @stack.last.shift
        end

        save
      end

      @stack.pop
      d = File.join(*@stack.map(&:first))
      yield d
      @stack.last and @stack.last.shift
      save
    end

    File.delete(state_file) rescue nil

    self
  end

  def save
    File.open(state_file, "wb") do |io|
      Marshal.dump(self, io)
    end
  end
end

dd = if test ?f, 'c:/xxx.bin'
       DirDfs.resume 'c:/xxx.bin'
     else
       DirDfs.new 'c:/Temp', 'c:/xxx.bin'
     end

dd.dfs do |f|
  print(test(?d, f) ? "DIR " : "    ", f, "\n")
end