Use shared pointers to Backend classes

The schemarouter now uses shared pointers. This removes the need to copy
the class.

Following changes move the member variables inside the Backend class.

server/modules/routing/schemarouter/schemarouter.cc

@@ -0,0 +1,108 @@
+/*
+ * 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 "schemarouter.hh"
+
+#include <maxscale/protocol/mysql.h>
+
+using namespace schemarouter;
+
+Backend::Backend(SERVER_REF *ref):
+    m_backend(ref),
+    m_dcb(NULL),
+    m_map_queue(NULL),
+    m_mapped(false),
+    m_num_mapping_eof(0),
+    m_num_result_wait(0),
+    m_pending_cmd(NULL),
+    m_state(0)
+{
+}
+
+Backend::~Backend()
+{
+    gwbuf_free(m_map_queue);
+    gwbuf_free(m_pending_cmd);
+}
+
+
+bool Backend::execute_sescmd()
+{
+    if (BREF_IS_CLOSED(this))
+    {
+        return false;
+    }
+
+    CHK_DCB(m_dcb);
+
+    int rc = 0;
+
+    /** Return if there are no pending ses commands */
+    if (m_session_commands.size() == 0)
+    {
+        MXS_INFO("Cursor had no pending session commands.");
+        return false;
+    }
+
+    SessionCommandList::iterator iter = m_session_commands.begin();
+    GWBUF *buffer = iter->copy_buffer().release();
+
+    switch (iter->get_command())
+    {
+    case MYSQL_COM_CHANGE_USER:
+        /** This makes it possible to handle replies correctly */
+        gwbuf_set_type(buffer, GWBUF_TYPE_SESCMD);
+        rc = m_dcb->func.auth(m_dcb, NULL, m_dcb->session, buffer);
+        break;
+
+    case MYSQL_COM_QUERY:
+    default:
+        /**
+         * Mark session command buffer, it triggers writing
+         * MySQL command to protocol
+         */
+        gwbuf_set_type(buffer, GWBUF_TYPE_SESCMD);
+        rc = m_dcb->func.write(m_dcb, buffer);
+        break;
+    }
+
+    return rc == 1;
+}
+
+void Backend::clear_state(enum bref_state state)
+{
+    if (state != BREF_WAITING_RESULT)
+    {
+        m_state &= ~state;
+    }
+    else
+    {
+        /** Decrease global operation count */
+        ss_debug(int prev2 = )atomic_add(&m_backend->server->stats.n_current_ops, -1);
+        ss_dassert(prev2 > 0);
+    }
+}
+
+void Backend::set_state(enum bref_state state)
+{
+    if (state != BREF_WAITING_RESULT)
+    {
+        m_state |= state;
+    }
+    else
+    {
+        /** Increase global operation count */
+        ss_debug(int prev2 = )atomic_add(&m_backend->server->stats.n_current_ops, 1);
+        ss_dassert(prev2 >= 0);
+    }
+}