adding an initial prototype for a yotta-config based initialization for BLE transports

ble/BLE.h

@@ -154,6 +154,43 @@ public:
         transport->waitForEvent();
     }
 
+public:
+    typedef unsigned InstanceID_t;
+    static const InstanceID_t DEFAULT_INSTANCE = 0;
+#ifndef YOTTA_CFG_BLE_INSTANCES_COUNT
+    static const InstanceID_t NUM_INSTANCES = 1;
+#else
+    static const InstanceID_t NUM_INSTANCES = YOTTA_CFG_BLE_INSTANCES_COUNT;
+#endif
+
+    /**
+     * Get a reference to the BLE singleton corresponding to a given interface.
+     * There is a static array of BLE singletons.
+     *
+     * @Note: Calling Instance() is preferred over constructing a BLE object
+     * directly, as it returns references to singletons.
+     *
+     * @param[in] id
+     *              Instance-ID. This should be less than NUM_INSTANCES in order
+     *              for the returned BLE singleton to be useful.
+     *
+     * @return a reference to a single object
+     */
+    static BLE &Instance(InstanceID_t id = DEFAULT_INSTANCE);
+
+    /**
+     * Constructor for a handle to a BLE instance (i.e. BLE stack). BLE handles
+     * are thin wrappers around a transport object (i.e. ptr. to
+     * BLEInstanceBase).
+     *
+     * BLE objects are are better created as singletons accessed through the
+     * Instance() method. If multiple BLE handles are constructed for the same
+     * interface (using this constructor), they will share the same underlying
+     * transport object.
+     */
+    BLE(InstanceID_t instanceID = DEFAULT_INSTANCE);
+
+
     /*
      * Deprecation alert!
      * All of the following are deprecated and may be dropped in a future
@@ -1362,17 +1399,12 @@ public:
         return securityManager().onPasskeyDisplay(callback);
     }
 
-public:
-    BLE() : transport(createBLEInstance()) {
-        /* empty */
-    }
-
 private:
     BLE(const BLE&);
     BLE &operator=(const BLE &);
 
 private:
-    BLEInstanceBase *const transport; /* the device specific backend */
+    BLEInstanceBase *transport; /* the device specific backend */
 };
 
 typedef BLE BLEDevice; /* DEPRECATED. This type alias is retained for the sake of compatibility with older

source/BLE.cpp

@@ -36,3 +36,76 @@ BLE::init()
 
     return BLE_ERROR_NONE;
 }
+
+/**
+ * BLE::Instance() and BLE constructor rely upon a static array of initializers
+ * to create actual BLE transport instances. A description of these instances
+ * and initializers is supposed to be put in some .json file contributing to
+ * yotta's configuration (typically the target.json). Here's a sample:
+ *
+ *  "config": {
+ *    ...
+ *    "ble_instances": {
+ *      "count": 1,
+ *      "0" : {
+ *        "initializer" : "createBLEInstance"
+ *      }
+ *    }
+ *  }
+ *
+ * The following macros result in translating the above config into a static
+ * array: instanceConstructors.
+ */
+#ifdef YOTTA_CFG_BLE_INSTANCES_COUNT
+#define CONCATENATE(A, B) A ## B
+#define EXPAND(X) X /* this adds a level of indirection needed to allow macro-expansion following a token-paste operation (see use of CONCATENATE() below). */
+
+#define INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_1 YOTTA_CFG_BLE_INSTANCES_0_INITIALIZER
+#define INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_2 INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_1, YOTTA_CFG_BLE_INSTANCES_1_INITIALIZER
+#define INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_3 INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_2, YOTTA_CFG_BLE_INSTANCES_2_INITIALIZER
+#define INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_4 INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_3, YOTTA_CFG_BLE_INSTANCES_3_INITIALIZER
+#define INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_5 INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_4, YOTTA_CFG_BLE_INSTANCES_4_INITIALIZER
+/* ... add more of the above if ever needed */
+
+#define INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS(N) EXPAND(CONCATENATE(INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS_, N))
+#endif /* YOTTA_CFG_BLE_INSTANCES_COUNT */
+
+typedef BLEInstanceBase *(*InstanceConstructor_t)(void);
+static const InstanceConstructor_t instanceConstructors[BLE::NUM_INSTANCES] = {
+#ifndef YOTTA_CFG_BLE_INSTANCES_COUNT
+    createBLEInstance
+#else
+    INITIALIZER_LIST_FOR_INSTANCE_CONSTRUCTORS(YOTTA_CFG_BLE_INSTANCES_COUNT)
+#endif
+};
+
+BLE::BLE &
+BLE::Instance(InstanceID_t id)
+{
+    static BLE *singletons[NUM_INSTANCES];
+    if (id < NUM_INSTANCES) {
+        if (singletons[id] == NULL) {
+            singletons[id] = new BLE(id); /* This object will never be freed. */
+        }
+
+        return *singletons[id];
+    }
+
+    /* we come here only in the case of a bad interfaceID. */
+    static BLE badSingleton(NUM_INSTANCES /* this is a bad index; and will result in a NULL transport. */);
+    return badSingleton;
+}
+
+BLE::BLE(InstanceID_t instanceID) : transport()
+{
+    static BLEInstanceBase *transportInstances[NUM_INSTANCES];
+
+    if (instanceID < NUM_INSTANCES) {
+        if (!transportInstances[instanceID]) {
+            transportInstances[instanceID] = instanceConstructors[instanceID](); /* Call the stack's initializer for the transport object. */
+        }
+        transport = transportInstances[instanceID];
+    } else {
+        transport = NULL;
+    }
+}