# File lib/ethon/easy/callbacks.rb, line 37
      def body_write_callback
        @body_write_callback ||= proc do |stream, size, num, object|
          headers
          result = body(chunk = stream.read_string(size * num))
          @response_body << chunk if result == :unyielded
          result != :abort ? size * num : -1
        end
      end