# File pstore.rb, line 22
  def initialize(file)
    dir = File::dirname(file)
    unless File::directory? dir
      raise PStore::Error, format("directory %s does not exist", dir)
    end
    if File::exist? file and not File::readable? file
      raise PStore::Error, format("file %s not readable", file)
    end
    @transaction = false
    @filename = file
    @abort = false
  end

# File pstore.rb, line 44
  def [](name)
    in_transaction
    @table[name]
  end

# File pstore.rb, line 58
  def []=(name, value)
    in_transaction_wr()
    @table[name] = value
  end

# File pstore.rb, line 84
  def abort
    in_transaction
    @abort = true
    throw :pstore_abort_transaction
  end

# File pstore.rb, line 79
  def commit
    in_transaction
    @abort = false
    throw :pstore_abort_transaction
  end

# File pstore.rb, line 62
  def delete(name)
    in_transaction_wr()
    @table.delete name
  end

# File pstore.rb, line 158
  def dump(table)
    Marshal::dump(table)
  end

# File pstore.rb, line 48
  def fetch(name, default=PStore::Error)
    unless @table.key? name
      if default==PStore::Error
        raise PStore::Error, format("undefined root name `%s'", name)
      else
        default
      end
    end
    self[name]
  end

# File pstore.rb, line 162
  def load(content)
    Marshal::load(content)
  end

# File pstore.rb, line 166
  def load_file(file)
    Marshal::load(file)
  end

# File pstore.rb, line 75
  def path
    @filename
  end

# File pstore.rb, line 71
  def root?(name)
    in_transaction
    @table.key? name
  end

# File pstore.rb, line 67
  def roots
    in_transaction
    @table.keys
  end

# File pstore.rb, line 90
  def transaction(read_only=false)
    raise PStore::Error, "nested transaction" if @transaction
    begin
      @rdonly = read_only
      @abort = false
      @transaction = true
      value = nil
      new_file = @filename + ".new"

      content = nil
      unless read_only
        file = File.open(@filename, File::RDWR | File::CREAT)
        file.binmode
        file.flock(File::LOCK_EX)
        commit_new(file) if FileTest.exist?(new_file)
        content = file.read()
      else
        begin
          file = File.open(@filename, File::RDONLY)
          file.binmode
          file.flock(File::LOCK_SH)
          content = (File.read(new_file) rescue file.read())
        rescue Errno::ENOENT
          content = ""
        end
      end

      if content != ""
        @table = load(content)
        if !read_only
          size = content.size
          md5 = Digest::MD5.digest(content)
        end
      else
        @table = {}
      end
      content = nil             # unreference huge data


      begin
        catch(:pstore_abort_transaction) do
          value = yield(self)
        end
      rescue Exception
        @abort = true
        raise
      ensure
        if !read_only and !@abort
          tmp_file = @filename + ".tmp"
          content = dump(@table)
          if !md5 || size != content.size || md5 != Digest::MD5.digest(content)
            File.open(tmp_file, "w") {|t|
              t.binmode
              t.write(content)
            }
            File.rename(tmp_file, new_file)
            commit_new(file)
          end
          content = nil         # unreference huge data

        end
      end
    ensure
      @table = nil
      @transaction = false
      file.close if file
    end
    value
  end