Introduce ChainableGapEventHandler subclass of ChainableEventHandler

The ChainableGapEventHandler enables chaining together Gap::EventHandlers so separate parts of an application can be notified of Gap events as needed. The application can register multiple Gap::EventHandler objects to one ChainableGapEventHandler and then set the global Gap::EventHandler to the ChainableGapEventHandler. All registered EventHandlers will then be called when a Gap Event occurs.

Author: AGlass0fMilk

connectivity/FEATURE_BLE/include/ble/Gap.h

@@ -598,6 +598,12 @@ class Gap {
      * module to signal events back to the application.
      *
      * @param handler Application implementation of an EventHandler.
+     *
+     * @note Multiple discrete EventHandler instances may be used by adding them
+     * to a ChainableGapEventHandler and then setting the chain as the primary
+     * Gap EventHandler using this function.
+     *
+     * @see ChainableGapEventHandler
      */
     void setEventHandler(EventHandler *handler);
 

connectivity/FEATURE_BLE/include/ble/GattServer.h

@@ -204,6 +204,12 @@ class GattServer {
      * module to signal events back to the application.
      *
      * @param handler Application implementation of an EventHandler.
+     *
+     * @note Multiple discrete EventHandler instances may be used by adding them
+     * to a ChainableGattServerEventHandler and then setting the chain as the primary
+     * GattServer EventHandler using this function.
+     *
+     * @see ChainableGattServerEventHandler
      */
     void setEventHandler(EventHandler *handler);
 

connectivity/FEATURE_BLE/include/ble/common/ChainableEventHandler.h

@@ -33,7 +33,7 @@ class ChainableEventHandler
 
     ChainableEventHandler() { }
 
-    virtual ~ChainableEventHandler() {
+    ~ChainableEventHandler() {
         // Clean up all nodes
         auto it = head;
         while(it) {
@@ -45,13 +45,15 @@ class ChainableEventHandler
 
     /**
      * Add an EventHandler to be notified of events sent to
-     * this ChainableGattServerEventHandler
+     * this ChainableEventHandler
      *
      * @param[in] event_handler Handler to add to chain
+     *
+     * @retval true if adding EventHandler was successful, false otherwise
      */
-    void addEventHandler(T* event_handler) {
+    bool addEventHandler(T* event_handler) {
         auto eh = new (std::nothrow) node_t { event_handler, nullptr };
-        if(!eh) { return; }
+        if(!eh) { return false; }
         if(!head) {
             head = eh;
         } else {
@@ -61,6 +63,7 @@ class ChainableEventHandler
             }
             it->next = eh;
         }
+        return true;
     }
 
     /**
@@ -93,10 +96,12 @@ class ChainableEventHandler
 
 protected:
 
-    template<typename... Args>
-    void execute_on_all(void (T::*fn)(Args...), Args&... args) {
+    template<typename... FnArgs, typename... Args>
+    void execute_on_all(void (T::*fn)(FnArgs...), Args&&... args) {
         auto it = head;
         while(it) {
+            // we do not use std::forward, args have to remain lvalues
+            // as they are passed to multiple handlers
             (it->eh->*fn)(args...);
             it = it->next;
         }

connectivity/FEATURE_BLE/include/ble/gap/ChainableGapEventHandler.h

@@ -0,0 +1,117 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2020 ARM Limited
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MBED_CHAINABLEGAPEVENTHANDLER_H_
+#define MBED_CHAINABLEGAPEVENTHANDLER_H_
+
+#include "ble/Gap.h"
+#include "ble/common/ChainableEventHandler.h"
+
+/**
+ * Gap::EventHandler implementation that allows the application
+ * to register multiple separate EventHandlers to be called when
+ * Gap events happen.
+ */
+class ChainableGapEventHandler : public ble::Gap::EventHandler,
+                                 public ChainableEventHandler<ble::Gap::EventHandler>
+{
+
+public:
+
+    ChainableGapEventHandler() { }
+
+    ~ChainableGapEventHandler() { }
+
+    void onScanRequestReceived(const ble::ScanRequestEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onScanRequestReceived, event);
+    }
+
+    void onAdvertisingEnd(const ble::AdvertisingEndEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onAdvertisingEnd, event);
+    }
+    
+    void onAdvertisingReport(const ble::AdvertisingReportEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onAdvertisingReport, event);
+    }
+
+    void onScanTimeout(const ble::ScanTimeoutEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onScanTimeout, event);
+    }
+
+    void onPeriodicAdvertisingSyncEstablished(
+        const ble::PeriodicAdvertisingSyncEstablishedEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onPeriodicAdvertisingSyncEstablished, event);
+    }
+    
+    void onPeriodicAdvertisingReport(
+        const ble::PeriodicAdvertisingReportEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onPeriodicAdvertisingReport, event);
+    }
+
+    void onPeriodicAdvertisingSyncLoss(
+        const ble::PeriodicAdvertisingSyncLoss &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onPeriodicAdvertisingSyncLoss, event);
+    }
+
+    void onConnectionComplete(const ble::ConnectionCompleteEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onConnectionComplete, event);
+    }
+
+    void onUpdateConnectionParametersRequest(
+        const ble::UpdateConnectionParametersRequestEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onUpdateConnectionParametersRequest, event);
+    }
+
+    void onConnectionParametersUpdateComplete(
+        const ble::ConnectionParametersUpdateCompleteEvent &event) override {
+        execute_on_all(&ble::Gap::EventHandler::onConnectionParametersUpdateComplete, event);
+    }
+
+    void onDisconnectionComplete(const ble::DisconnectionCompleteEvent &event) override {
+       execute_on_all(&ble::Gap::EventHandler::onDisconnectionComplete, event);
+    }
+
+    void onReadPhy(
+        ble_error_t status,
+        ble::connection_handle_t connectionHandle,
+        ble::phy_t txPhy,
+        ble::phy_t rxPhy) override {
+        execute_on_all(&ble::Gap::EventHandler::onReadPhy, status,
+                connectionHandle, txPhy, rxPhy);
+    }
+
+    void onPhyUpdateComplete(
+        ble_error_t status,
+        ble::connection_handle_t connectionHandle,
+        ble::phy_t txPhy,
+        ble::phy_t rxPhy) override {
+        execute_on_all(&ble::Gap::EventHandler::onPhyUpdateComplete, status,
+                connectionHandle, txPhy, rxPhy);
+    }
+
+    void onDataLengthChange(
+        ble::connection_handle_t connectionHandle,
+        uint16_t txSize,
+        uint16_t rxSize) override {
+        execute_on_all(&ble::Gap::EventHandler::onDataLengthChange,
+                connectionHandle, txSize, rxSize);
+    }
+
+};
+
+#endif /* MBED_CHAINABLEGAPEVENTHANDLER_H_ */

connectivity/FEATURE_BLE/include/ble/gatt/ChainableGattServerEventHandler.h

@@ -35,94 +35,37 @@ class ChainableGattServerEventHandler : public ble::GattServer::EventHandler,
 
     ChainableGattServerEventHandler() { }
 
-    virtual ~ChainableGattServerEventHandler() { }
-
-    /**
-     * Function invoked when the connections changes the ATT_MTU which controls
-     * the maximum size of an attribute that can be read in a single L2CAP packet
-     * which might be fragmented across multiple packets.
-     *
-     * @param connectionHandle The handle of the connection that changed the size.
-     * @param attMtuSize
-     */
+    ~ChainableGattServerEventHandler() { }
+
     void onAttMtuChange(ble::connection_handle_t connectionHandle, uint16_t attMtuSize) override {
         execute_on_all(&ble::GattServer::EventHandler::onAttMtuChange,
                 connectionHandle, attMtuSize);
     }
 
-    /**
-     * Function invoked when the server has sent data to a client as
-     * part of a notification/indication.
-     *
-     * @note params has a temporary scope and should be copied by the
-     * application if needed later
-     */
     void onDataSent(const GattDataSentCallbackParams* params) override {
         execute_on_all(&ble::GattServer::EventHandler::onDataSent, params);
     }
 
-    /**
-     * Function invoked when a client writes an attribute
-     *
-     * @note params has a temporary scope and should be copied by the
-     * application if needed later
-     */
     void onDataWritten(const GattWriteCallbackParams *params) override {
         execute_on_all(&ble::GattServer::EventHandler::onDataWritten, params);
     }
 
-    /**
-     * Function invoked when a client reads an attribute
-     *
-     * @note  This functionality may not be available on all underlying stacks.
-     * Application code may work around that limitation by monitoring read
-     * requests instead of read events.
-     *
-     * @note params has a temporary scope and should be copied by the
-     * application if needed later
-     *
-     * @see GattCharacteristic::setReadAuthorizationCallback()
-     * @see isOnDataReadAvailable().
-     */
     void onDataRead(const GattReadCallbackParams *params) override {
         execute_on_all(&ble::GattServer::EventHandler::onDataRead, params);
     }
 
-    /**
-     * Function invoked when the GattServer instance is about
-     * to be shut down. This can result in a call to reset() or BLE::reset().
-     */
     void onShutdown(const GattServer *server) override {
         execute_on_all(&ble::GattServer::EventHandler::onShutdown, server);
     }
 
-    /**
-     * Function invoked when the client has subscribed to characteristic updates
-     *
-     * @note params has a temporary scope and should be copied by the
-     * application if needed later
-     */
     void onUpdatesEnabled(const GattUpdatesEnabledCallbackParams* params) override {
         execute_on_all(&ble::GattServer::EventHandler::onUpdatesEnabled, params);
     }
 
-    /**
-     * Function invoked when the client has unsubscribed to characteristic updates
-     *
-     * @note params has a temporary scope and should be copied by the
-     * application if needed later
-     */
     void onUpdatesDisabled(const GattUpdatesDisabledCallbackParams* params) override {
         execute_on_all(&ble::GattServer::EventHandler::onUpdatesDisabled, params);
     }
 
-    /**
-     * Function invoked when an ACK has been received for an
-     * indication sent to the client.
-     *
-     * @note params has a temporary scope and should be copied by the
-     * application if needed later
-     */
     void onConfirmationReceived(const GattConfirmationReceivedCallbackParams* params) override {
         execute_on_all(&ble::GattServer::EventHandler::onConfirmationReceived, params);
     }