Add C++ filter example

The filter example uses the C++ template which helps new filter creation
by showing the minimal implementation required for a filter.

examples/CMakeLists.txt

@@ -15,6 +15,10 @@ target_link_libraries(testfilter maxscale-common)
 set_target_properties(testfilter PROPERTIES VERSION "1.0.0")
 install_module(testfilter core)
 
+add_library(examplecppfilter SHARED examplefilter.cc examplefiltersession.cc)
+set_target_properties(examplecppfilter PROPERTIES VERSION "1.0.0")
+install_module(examplecppfilter core)
+
 add_library(testprotocol SHARED testprotocol.c)
 set_target_properties(testprotocol PROPERTIES VERSION "1.0.0")
 install_module(testprotocol core)

examples/examplefilter.cc

@@ -0,0 +1,78 @@
+/*
+ * 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: 2020-01-01
+ *
+ * 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.
+ */
+
+// All log messages from this module are prefixed with this
+#define MXS_MODULE_NAME "examplefilter"
+
+#include "examplefilter.hh"
+
+// This declares a module in MaxScale
+extern "C" MXS_MODULE* MXS_CREATE_MODULE()
+{
+    static MXS_MODULE info =
+    {
+        MXS_MODULE_API_FILTER,
+        MXS_MODULE_IN_DEVELOPMENT,
+        MXS_FILTER_VERSION,
+        "An example filter that does nothing",
+        "V1.0.0",
+        RCAP_TYPE_NONE,
+        &ExampleFilter::s_object, // This is defined in the MaxScale filter template
+        NULL, /* Process init. */
+        NULL, /* Process finish. */
+        NULL, /* Thread init. */
+        NULL, /* Thread finish. */
+        {
+            { "an_example_parameter", MXS_MODULE_PARAM_STRING, "a-default-value" },
+            { MXS_END_MODULE_PARAMS }
+        }
+    };
+
+    return &info;
+}
+
+ExampleFilter::ExampleFilter()
+{
+}
+
+ExampleFilter::~ExampleFilter()
+{
+}
+
+// static
+ExampleFilter* ExampleFilter::create(const char* zName, char** pzOptions, MXS_CONFIG_PARAMETER* pParams)
+{
+    return new ExampleFilter();
+}
+
+ExampleFilterSession* ExampleFilter::newSession(MXS_SESSION* pSession)
+{
+    return ExampleFilterSession::create(pSession, this);
+}
+
+// static
+void ExampleFilter::diagnostics(DCB* pDcb) const
+{
+}
+
+// static
+json_t* ExampleFilter::diagnostics_json() const
+{
+    return NULL;
+}
+
+// static
+uint64_t ExampleFilter::getCapabilities()
+{
+    return RCAP_TYPE_NONE;
+}

examples/examplefilter.hh

@@ -0,0 +1,46 @@
+#pragma once
+/*
+ * 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: 2020-01-01
+ *
+ * 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 <maxscale/cppdefs.hh>
+#include <maxscale/filter.hh>
+#include "examplefiltersession.hh"
+
+class ExampleFilter : public maxscale::Filter<ExampleFilter, ExampleFilterSession>
+{
+    // Prevent copy-constructor and assignment operator usage
+    ExampleFilter(const ExampleFilter&);
+    ExampleFilter& operator = (const ExampleFilter&);
+
+public:
+    ~ExampleFilter();
+
+    // Creates a new filter instance
+    static ExampleFilter* create(const char* zName, char** pzOptions, MXS_CONFIG_PARAMETER* ppParams);
+
+    // Creates a new session for this filter
+    ExampleFilterSession* newSession(MXS_SESSION* pSession);
+
+    // Print diagnostics to a DCB
+    void diagnostics(DCB* pDcb) const;
+
+    // Returns JSON form diagnostic data
+    json_t* diagnostics_json() const;
+
+    // Get filter capabilities
+    uint64_t getCapabilities();
+
+private:
+    // Used in the create function
+    ExampleFilter();
+};

examples/examplefiltersession.cc

@@ -0,0 +1,43 @@
+/*
+ * 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: 2020-01-01
+ *
+ * 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.
+ */
+
+// All log messages from this module are prefixed with this
+#define MXS_MODULE_NAME "examplefilter"
+
+#include "examplefiltersession.hh"
+#include "examplefilter.hh"
+
+ExampleFilterSession::ExampleFilterSession(MXS_SESSION* pSession)
+    : mxs::FilterSession(pSession)
+{
+}
+
+ExampleFilterSession::~ExampleFilterSession()
+{
+}
+
+//static
+ExampleFilterSession* ExampleFilterSession::create(MXS_SESSION* pSession, const ExampleFilter* pFilter)
+{
+    return new ExampleFilterSession(pSession);
+}
+
+int ExampleFilterSession::routeQuery(GWBUF* pPacket)
+{
+    return mxs::FilterSession::routeQuery(pPacket);
+}
+
+int ExampleFilterSession::clientReply(GWBUF* pPacket)
+{
+    return mxs::FilterSession::clientReply(pPacket);
+}

examples/examplefiltersession.hh

@@ -0,0 +1,44 @@
+#pragma once
+/*
+ * 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: 2020-01-01
+ *
+ * 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 <maxscale/cppdefs.hh>
+#include <maxscale/filter.hh>
+
+class ExampleFilter;
+
+class ExampleFilterSession : public maxscale::FilterSession
+{
+    // Prevent copy-constructor and assignment operator usage
+    ExampleFilterSession(const ExampleFilterSession&);
+    ExampleFilterSession& operator = (const ExampleFilterSession&);
+
+public:
+    ~ExampleFilterSession();
+
+    // Called when a client session has been closed
+    void close();
+
+    // Create a new filter session
+    static ExampleFilterSession* create(MXS_SESSION* pSession, const ExampleFilter* pFilter);
+
+    // Handle a query from the client
+    int routeQuery(GWBUF* pPacket);
+
+    // Handle a reply from server
+    int clientReply(GWBUF* pPacket);
+
+private:
+    // Used in the create function
+    ExampleFilterSession(MXS_SESSION* pSession);
+};