Add template casting to readValue and advertisement data (#52)

The value returned by reading a remote characteristic or by getting a notification for it is kept in the class instance of the NimBLERemoteCharacteristic. This value can be accessed as a std::string type using the getValue() function.

This adds templates to read the value in the type used by the peripheral. The same functionality is implemented for getting the manufacturer data or the service data of an advertised device.

src/NimBLEAdvertisedDevice.h

@@ -45,10 +45,28 @@ public:
     uint8_t         getAdvType();
     uint16_t        getAppearance();
     std::string     getManufacturerData();
+
+    template<typename T>
+    T               getManufacturerData(bool skipSizeCheck = false) {
+        std::string data = getManufacturerData();
+        if(!skipSizeCheck && data.size() < sizeof(T)) return T();
+        const char *pData = data.data();
+        return *((T *)pData);
+    }
+
     std::string     getName();
     int             getRSSI();
     NimBLEScan*     getScan();
     std::string     getServiceData();
+
+    template<typename T>
+    T               getServiceData(bool skipSizeCheck = false) {
+        std::string data = getServiceData();
+        if(!skipSizeCheck && data.size() < sizeof(T)) return T();
+        const char *pData = data.data();
+        return *((T *)pData);
+    }
+
     NimBLEUUID      getServiceDataUUID();
     NimBLEUUID      getServiceUUID();
     int8_t          getTXPower();

src/NimBLEClient.cpp

@@ -725,6 +725,7 @@ uint16_t NimBLEClient::getMTU() {
                         (*characteristic)->m_timestamp = time(nullptr);
                         (*characteristic)->m_semaphoreReadCharEvt.give();
                     }
+
                     if ((*characteristic)->m_notifyCallback != nullptr) {
                         NIMBLE_LOGD(LOG_TAG, "Invoking callback for notification on characteristic %s",
                                              (*characteristic)->toString().c_str());

src/NimBLERemoteCharacteristic.cpp

@@ -384,7 +384,7 @@ uint8_t NimBLERemoteCharacteristic::readUInt8() {
  * @brief Read the value of the remote characteristic.
  * @return The value of the remote characteristic.
  */
-std::string NimBLERemoteCharacteristic::readValue() {
+std::string NimBLERemoteCharacteristic::readValue(time_t *timestamp) {
     NIMBLE_LOGD(LOG_TAG, ">> readValue(): uuid: %s, handle: %d 0x%.2x",
                          getUUID().toString().c_str(), getHandle(), getHandle());
 
@@ -437,7 +437,15 @@ std::string NimBLERemoteCharacteristic::readValue() {
     } while(rc != 0 && retryCount--);
 
     NIMBLE_LOGD(LOG_TAG, "<< readValue(): length: %d", m_value.length());
-    return m_value;
+
+    m_semaphoreReadCharEvt.take("returnValue");
+    std::string value = m_value;
+    if(timestamp != nullptr) {
+        *timestamp = m_timestamp;
+    }
+    m_semaphoreReadCharEvt.give();
+
+    return value;
 } // readValue
 
 
@@ -451,6 +459,7 @@ std::string NimBLERemoteCharacteristic::getValue(time_t *timestamp) {
     if(timestamp != nullptr) {
         *timestamp = m_timestamp;
     }
+
     m_semaphoreReadCharEvt.give();
     return value;
 }

src/NimBLERemoteCharacteristic.h

@@ -53,11 +53,29 @@ public:
     uint16_t                                       getHandle();
     uint16_t                                       getDefHandle();
     NimBLEUUID                                     getUUID();
-    std::string                                    readValue();
-    uint8_t                                        readUInt8();
-    uint16_t                                       readUInt16();
-    uint32_t                                       readUInt32();
+    std::string                                    readValue(time_t *timestamp = nullptr);
+
+    template<typename T>
+    T                                              readValue(time_t *timestamp = nullptr, bool skipSizeCheck = false) {
+        std::string value = readValue(timestamp);
+        if(!skipSizeCheck && value.size() < sizeof(T)) return T();
+        const char *pData = value.data();
+        return *((T *)pData);
+    }
+
+    uint8_t                                        readUInt8()  __attribute__ ((deprecated));
+    uint16_t                                       readUInt16() __attribute__ ((deprecated));
+    uint32_t                                       readUInt32() __attribute__ ((deprecated));
     std::string                                    getValue(time_t *timestamp = nullptr);
+
+    template<typename T>
+    T                                              getValue(time_t *timestamp = nullptr, bool skipSizeCheck = false) {
+        std::string value = getValue(timestamp);
+        if(!skipSizeCheck && value.size() < sizeof(T)) return T();
+        const char *pData = value.data();
+        return *((T *)pData);
+    }
+
     bool                                           registerForNotify(notify_callback _callback,
                                                                      bool notifications = true,
                                                                      bool response = true);