Watch for modified files on Windows in Ruby

I'm writing a Windows service in ruby using the Win32-utils gems. The service currently works but a large part of it's function requires it to know when a file has been modified. I'm currently doing this with a large hash containing data about each file, which works great for relatively small directories, but when put into use on a folder containing ~50000 files this eats a lot of memory and takes a long time to check for updates.

The code looks like this:

First run (setting up the hash):

Find.find(@local_base) do |path|
  # Don't keep any directories in the hash
  if not FileTest.directory?(path)
    f = open(path)
    f.rewind
    @files[path.gsub(@local_base, "")] = DataFile.new(@local_base,
        path.gsub(@local_base, ""),
        Digest::MD5.hexdigest(f.read.gsub("\n", "\r\n")),
        f.mtime.to_i,
        @last_checked)
  end
end

Subsequent runs (checking for updates):

def check_for_updates
  # can't/shouldn't modified a hash while iterating, so set up temp storage
  tempHash = Hash.new

  Find.find(@local_base) do |path|

    # Ignore directories
    if not FileTest.directory?(path)
      File.open(path) do |f|
        #...and the file is already in the hash...
        if not @files[path.gsub(@local_base, "")].nil?
          # If it's been modified since the last scan...
          if f.mtime.to_i > @last_checked
            #...and the contents are modified...
            if @files[path.gsub(@local_base, "")].modified?
              #...update the hash with the new mtime and checksum
              @files[path.gsub(@local_base, "")].update
            end
          end # mtime check
        else
          # If it's a new file stick it in the temporary hash
          f.rewind
          tempHash[f.path] = DataFile.new(@local_base,
              path.gsub(@local_base, ""),
              Digest::MD5.hexdigest(f.read.gsub("\n", "\r\n")),
              f.mtime.to_i,
              @last_scan)
        end # nil check
      end # File.open block
    end # directory check
  end # Find.find block

  # If any new files are in the tempHash, add them to @files      
  if not tempHash.empty?
    tempHash.each do |k, v|
        开发者_如何转开发@files[k] = v
    end
  end

  # clear tempHash and update registry    
  tempHash = nil
  update_last_checked
end

Is there a faster/more efficient way to notify my program of modified files, even better if I can do it without recursively searching the whole directory.

You could leave it to Windows to warn you if the change journal is modified. There is a gem which "listens" to the service.

Check out rstakeout.rb. It will recursively watch directories, but it looks like it checks for the file modification criteria differently. I'm unsure of the speed on large file sets, but maybe it will give you some ideas.