NimBLEClient/ Add getCharacteristic() by handle.

* Add getCharacteristic() by handle.

Add a convenience method for getting a characteristic by the 16-bit
handle.

src/NimBLEClient.cpp

@@ -641,6 +641,31 @@ bool NimBLEClient::setValue(const NimBLEUUID &serviceUUID, const NimBLEUUID &cha
 } // setValue
 
 
+/**
+ * @brief Get the remote characteristic with the specified handle.
+ * @param [in] handle The handle of the desired characteristic.
+ * @returns The matching remote characteristic, nullptr otherwise.
+ */
+NimBLERemoteCharacteristic* NimBLEClient::getCharacteristic(const uint16_t handle)
+{
+    NimBLERemoteService *pService = nullptr;
+    for(auto it = m_servicesVector.begin(); it != m_servicesVector.end(); ++it) {
+      if ((*it)->getStartHandle() <= handle && handle <= (*it)->getEndHandle()) {
+          pService = *it;
+          break;
+      }
+    }
+
+    if (pService != nullptr) {
+        for (auto it = pService->begin(); it != pService->end(); ++it) {
+            if ((*it)->getHandle() == handle) {
+                return *it;
+            }
+        }
+    }
+
+    return nullptr;
+}
 
 /**
  * @brief Get the current mtu of this connection.

src/NimBLEClient.h

@@ -30,6 +30,7 @@
 #include <string>
 
 class NimBLERemoteService;
+class NimBLERemoteCharacteristic;
 class NimBLEClientCallbacks;
 class NimBLEAdvertisedDevice;
 
@@ -55,6 +56,7 @@ public:
     std::string                                 getValue(const NimBLEUUID &serviceUUID, const NimBLEUUID &characteristicUUID);
     bool                                        setValue(const NimBLEUUID &serviceUUID, const NimBLEUUID &characteristicUUID,
                                                          const std::string &value);
+    NimBLERemoteCharacteristic*                 getCharacteristic(const uint16_t handle);
     bool                                        isConnected();
     void                                        setClientCallbacks(NimBLEClientCallbacks *pClientCallbacks,
                                                                    bool deleteCallbacks = true);