Replace raw GWBUF pointers with mxs::Buffer

Now that the query queue is stored in an actual container, it is only
logical to use mxs::Buffer instead of GWBUF as the stored type.

include/maxscale/buffer.hh

@@ -24,6 +24,11 @@
 
 class SERVER;
 
+namespace maxscale
+{
+class Buffer;
+}
+
 /**
  * Buffer properties - used to store properties related to the buffer
  * contents. This may be added at any point during the processing of the
@@ -404,6 +409,7 @@ extern void dprintAllBuffers(void* pdcb);
  * @param log_level Log priority where the message is written
  */
 void gwbuf_hexdump(GWBUF* buffer, int log_level);
+void gwbuf_hexdump(const mxs::Buffer& buffer, int log_level);
 
 /**
  * Return pointer of the byte at offset from start of chained buffer
@@ -1043,6 +1049,16 @@ public:
         return gwbuf_length(m_pBuffer);
     }
 
+    /**
+     * Whether the buffer is empty.
+     *
+     * @return True if the buffer is empty
+     */
+    bool empty() const
+    {
+        return m_pBuffer == nullptr;
+    }
+
     /**
      * Whether the buffer is contiguous.
      *

server/core/buffer.cc

@@ -783,3 +783,8 @@ void gwbuf_hexdump(GWBUF* buffer, int log_level)
 
     MXS_LOG_MESSAGE(log_level, "%.*s", n, ss.str().c_str());
 }
+
+void gwbuf_hexdump(const mxs::Buffer& buffer, int log_level)
+{
+    return gwbuf_hexdump(const_cast<mxs::Buffer&>(buffer).get(), log_level);
+}

server/modules/routing/readwritesplit/rwsplit_route_stmt.cc

@@ -339,7 +339,7 @@ bool RWSplitSession::route_single_stmt(GWBUF* querybuf)
             else if (target->has_session_commands())
             {
                 // We need to wait until the session commands are executed
-                m_query_queue.push_back(gwbuf_clone(querybuf));
+                m_query_queue.emplace_back(gwbuf_clone(querybuf));
                 MXS_INFO("Queuing query until '%s' completes session command", target->name());
             }
             else

server/modules/routing/readwritesplit/rwsplitsession.cc

@@ -98,7 +98,6 @@ void close_all_connections(PRWBackends& backends)
 
 void RWSplitSession::close()
 {
-    std::for_each(m_query_queue.begin(), m_query_queue.end(), gwbuf_free);
     close_all_connections(m_raw_backends);
     m_current_query.reset();
 
@@ -154,7 +153,7 @@ int32_t RWSplitSession::routeQuery(GWBUF* querybuf)
                  gwbuf_length(querybuf), GWBUF_DATA(querybuf)[4], m_expected_responses,
                  mxs::extract_sql(querybuf, 1024).c_str());
 
-        m_query_queue.push_back(querybuf);
+        m_query_queue.emplace_back(querybuf);
         querybuf = NULL;
         rval = 1;
 
@@ -193,13 +192,13 @@ bool RWSplitSession::route_stored_query()
     {
         MXS_INFO(">>> Routing stored queries");
 
-        GWBUF* query_queue = m_query_queue.front();
+        auto query = std::move(m_query_queue.front());
         m_query_queue.pop_front();
 
-        mxb_assert(query_queue);
+        mxb_assert(!query.empty());
-        mxb_assert_message(modutil_count_packets(query_queue) == 1, "Buffer must contain only one packet");
+        mxb_assert_message(modutil_count_packets(query.get()) == 1, "Buffer must contain only one packet");
 
-        if (query_queue == NULL)
+        if (query.empty())
         {
             MXS_ALERT("Queued query unexpectedly empty, dumping query queue contents");
             for (auto& a : m_query_queue)
@@ -216,10 +215,10 @@ bool RWSplitSession::route_stored_query()
 
         // TODO: Move the handling of queued queries to the client protocol
         // TODO: module where the command tracking is done automatically.
-        uint8_t cmd = mxs_mysql_get_command(query_queue);
+        uint8_t cmd = mxs_mysql_get_command(query.get());
         mysql_protocol_set_current_command(m_client, (mxs_mysql_cmd_t)cmd);
 
-        if (!routeQuery(query_queue))
+        if (!routeQuery(query.release()))
         {
             rval = false;
             MXS_ERROR("Failed to route queued query.");
@@ -235,7 +234,7 @@ bool RWSplitSession::route_stored_query()
         else
         {
             /** Routing was stopped, we need to wait for a response before retrying */
-            std::copy(m_query_queue.begin(), m_query_queue.end(), std::back_inserter(temp_storage));
+            temp_storage.push_front(std::move(m_query_queue.front()));
             m_query_queue = std::move(temp_storage);
             break;
         }

server/modules/routing/readwritesplit/rwsplitsession.hh

@@ -320,7 +320,7 @@ private:
     uint64_t         m_sescmd_count;            /**< Number of executed session commands (starts from 1) */
     int              m_expected_responses;      /**< Number of expected responses to the current
                                                  * query */
-    std::deque<GWBUF*>      m_query_queue;      /**< Queued commands waiting to be executed */
+    std::deque<mxs::Buffer> m_query_queue;      /**< Queued commands waiting to be executed */
     RWSplit*                m_router;           /**< The router instance */
     mxs::SessionCommandList m_sescmd_list;      /**< List of executed session commands */
     ResponseMap             m_sescmd_responses; /**< Response to each session command */