Add session command class

The class abstracts the session commands and the lists of session commands
using standard library containers.

server/modules/routing/schemarouter/session_command.cc

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include "session_command.hh"
+#include <maxscale/modutil.h>
+
+void SessionCommand::mark_reply_received()
+{
+    m_replySent = true;
+}
+
+bool SessionCommand::is_reply_received() const
+{
+    return m_replySent;
+}
+
+Buffer SessionCommand::copy_buffer() const
+{
+    return m_buffer;
+}
+
+SessionCommand::SessionCommand(GWBUF *buffer):
+    m_buffer(buffer),
+    m_replySent(false)
+{
+}
+
+SessionCommand::~SessionCommand()
+{
+}
+
+std::string SessionCommand::to_string()
+{
+    std::string str;
+    
+    GWBUF **buf = &m_buffer;
+    char *sql;
+    int sql_len;
+
+    if (modutil_extract_SQL(*buf, &sql, &sql_len))
+    {
+        str.append(sql, sql_len);
+    }
+
+    return str;
+}