Avoid useless stream buffer copying and workaround with chunk_size manipulation.

Author: dstogov

ext/mysqlnd/mysqlnd_vio.c

@@ -79,14 +79,12 @@ MYSQLND_METHOD(mysqlnd_vio, network_read)(MYSQLND_VIO * const vio, zend_uchar *
 {
 	enum_func_status return_value = PASS;
 	php_stream * net_stream = vio->data->m.get_stream(vio);
-	size_t old_chunk_size = net_stream->chunk_size;
 	size_t to_read = count, ret;
 	zend_uchar * p = buffer;
 
 	DBG_ENTER("mysqlnd_vio::network_read");
 	DBG_INF_FMT("count="MYSQLND_SZ_T_SPEC, count);
 
-	net_stream->chunk_size = MIN(to_read, vio->data->options.net_read_buffer_size);
 	while (to_read) {
 		if (!(ret = php_stream_read(net_stream, (char *) p, to_read))) {
 			DBG_ERR_FMT("Error while reading header from socket");
@@ -97,7 +95,6 @@ MYSQLND_METHOD(mysqlnd_vio, network_read)(MYSQLND_VIO * const vio, zend_uchar *
 		to_read -= ret;
 	}
 	MYSQLND_INC_CONN_STATISTIC_W_VALUE(stats, STAT_BYTES_RECEIVED, count - to_read);
-	net_stream->chunk_size = old_chunk_size;
 	DBG_RETURN(return_value);
 }
 /* }}} */
@@ -265,6 +262,8 @@ MYSQLND_METHOD(mysqlnd_vio, post_connect_set_opt)(MYSQLND_VIO * const vio, const
 			/* TCP -> Set SO_KEEPALIVE */
 			mysqlnd_set_sock_keepalive(net_stream);
 		}
+
+		net_stream->chunk_size = vio->data->options.net_read_buffer_size;
 	}
 
 	DBG_VOID_RETURN;

main/streams/streams.c

@@ -624,7 +624,9 @@ PHPAPI void _php_stream_fill_read_buffer(php_stream *stream, size_t size)
 
 			/* reduce buffer memory consumption if possible, to avoid a realloc */
 			if (stream->readbuf && stream->readbuflen - stream->writepos < stream->chunk_size) {
-				memmove(stream->readbuf, stream->readbuf + stream->readpos, stream->readbuflen - stream->readpos);
+				if (stream->writepos > stream->readpos) {
+					memmove(stream->readbuf, stream->readbuf + stream->readpos, stream->writepos - stream->readpos);
+				}
 				stream->writepos -= stream->readpos;
 				stream->readpos = 0;
 			}