Fixed http::async_connection::write_first_line()

Use persistent buffer for boost::asio::async_write

Author: omalashenko

boost/network/protocol/http/server/async_connection.hpp

@@ -289,7 +289,7 @@ namespace boost { namespace network { namespace http {
         Handler & handler;
         utils::thread_pool & thread_pool_;
         volatile bool headers_already_sent, first_line_already_sent, headers_in_progress, first_line_in_progress;
-        asio::streambuf headers_buffer;
+        asio::streambuf headers_buffer, first_line_buffer;
 
         boost::recursive_mutex headers_mutex;
         buffer_type read_buffer_;
@@ -525,19 +525,18 @@ namespace boost { namespace network { namespace http {
             if (first_line_in_progress) return;
             first_line_in_progress = true;
 
-            std::vector<asio::const_buffer> buffers;
             typedef constants<Tag> consts;
-            typename ostringstream<Tag>::type first_line_stream;
-            first_line_stream 
+            first_line_buffer.consume(first_line_buffer.size());
+            std::ostream first_line_stream(&first_line_buffer);
+            first_line_stream
                 << consts::http_slash() << 1<< consts::dot() << 1 << consts::space()
                 << status << consts::space() << status_message(status)
                 << consts::crlf()
+                << std::flush
                 ;
-            std::string first_line = first_line_stream.str();
-            buffers.push_back(asio::buffer(first_line));
             asio::async_write(
                 socket()
-                , buffers
+                , first_line_buffer
                 , callback);
         }