ThumbsRB: list and extract thumbnails in Thumbs.db

thumbs.rb

require 'optparse'
require 'fileutils'
require 'iconv'
require 'ole/storage'

# parsing code is taken from lf.win.shell.thumbsdb
#   http://libforensics.googlecode.com/

module ThumbsRB
  def self.main
    verbose = nil
    extract_all = nil
    output_dir = '.'
  
    ARGV.options do |o|
      o.banner = "Usage: #{File.basename $0} [options] thumbs.db [file-to-extract ..]"
      o.separator "Options:"

      o.on('-a', '--extract-all') { extract_all = true }
      o.on('-d DIR', '--output-dir=DIR') {|d| output_dir = d }
      o.on('-h', '--help') { abort o.to_s }

      ARGV.parse!
      
      abort o.to_s if ARGV.empty?
    end
    
    db, *names = ARGV

    db = File.join(db, "Thumbs.db") if File.directory?(db)
    File.exist?(db) or abort "no such file: '#{db}'"
    
    Thumbs.open(db) do |thumbs|
      if names.empty? && !extract_all
        puts thumbs.map {|e| e.name }.sort
        return
      end
      
      names = names.map {|n| n.downcase }

      FileUtils.mkdir_p(output_dir)
      thumbs.each do |e|
        next if !extract_all && !names.include?(e.name.downcase)
        
        path = File.join(output_dir, "#{e.name}.jpg")
        STDERR.print path if $DEBUG
        if File.exist?(path)
          warn "'#{path}' already exists. skipping"
          next
        end
        
        open(path, "wb") do |f|
          f << e.data
        end
        warn "." if $DEBUG
      end
    end
  end

  Thumb = Struct.new(:size, :id, :mtime, :name, :data_promise)

  class Thumb
    def data
      if data_promise.respond_to?(:call)
        self.data_promise = data_promise.call
      else
        data_promise
      end
    end
  end

  class Thumbs
    def self.open(path)
      Ole::Storage.open(path) do |db|
        yield new(db)
      end
    end

    include Enumerable

    def initialize(db)
      @db = db
      @entries = load_entries
    end

    def size
      @entries.size
    end

    def each(&blk)
      @entries.each(&blk)
    end

    private

    def load_entries
      @db.file.open("Catalog") do |f|
        f.seek 4
        size = f.read(4).unpack("V")[0]
        warn "#{size} items" if $DEBUG
        f.seek 16
        Array.new(size) { make_thumb(f) }
      end
    end

    def make_thumb(f)
      size, id, mtime = f.read(16).unpack("V3")
      rest = size - 16
      
      if rest > 0
        name = f.read(rest)
        name = Iconv.iconv('utf-8', 'utf-16le', name)[0]
        name.rstrip!
      end

      warn "##{id}: mtime #{mtime}, #{size} bytes, '#{name}'" if $DEBUG

      data_promise = proc do
        filename = id.to_s.reverse # WTF
        data = @db.file.read(filename)
        jpeg_header = "\xff\xd8"
        if data[12, 2] == jpeg_header
          data[12..-1]
        else
          warn "#{name}: no header found" unless data[16, 2] == jpeg_header if $DEBUG
          data[16..-1]
        end
      end

      Thumb.new(size, id, mtime, name, data_promise)
    end
  end
end

ThumbsRB.main if __FILE__ == $0