class Rack::Deflater::GzipStream

def each(&block)
  @writer = block
  gzip = ::Zlib::GzipWriter.new(self)
  gzip.mtime = @mtime if @mtime
  # @body.each is equivalent to @body.gets (slow)
  if @body.is_a? ::File # XXX: Should probably be ::IO
    while part = @body.read(BUFFER_LENGTH)
      gzip.write(part)
      gzip.flush if @sync
    end
  else
    @body.each { |part|
      # Skip empty strings, as they would result in no output,
      # and flushing empty parts would raise Zlib::BufError.
      next if part.empty?
      gzip.write(part)
      gzip.flush if @sync
    }
  end
ensure
  gzip.finish
end