refactor(ble): Avoid unnecessary String copies

Pass String by const reference to many `setValue()` functions
to avoid copying it.

Even there are not so much data inside these strings, it just
looks too odd to copy them every time.

Also this change decreases binary size (~200 bytes in my case).

Author: Kolcha

libraries/BLE/src/BLE2901.cpp

@@ -47,7 +47,7 @@ BLE2901::BLE2901() : BLEDescriptor(BLEUUID((uint16_t)BLE2901_UUID)) {}
 /**
  * @brief Set the Characteristic User Description
  */
-void BLE2901::setDescription(String userDesc) {
+void BLE2901::setDescription(const String &userDesc) {
   if (userDesc.length() > ESP_GATT_MAX_ATTR_LEN) {
     log_e("Size %d too large, must be no bigger than %d", userDesc.length(), ESP_GATT_MAX_ATTR_LEN);
     return;

libraries/BLE/src/BLE2901.h

@@ -40,7 +40,7 @@ class BLE2901 : public BLEDescriptor {
    ***************************************************************************/
 
   BLE2901();
-  void setDescription(String desc);
+  void setDescription(const String &desc);
 };  // BLE2901
 
 #endif /* CONFIG_BLUEDROID_ENABLED || CONFIG_NIMBLE_ENABLED */

libraries/BLE/src/BLECharacteristic.cpp

@@ -371,8 +371,8 @@ void BLECharacteristic::setValue(const uint8_t *data, size_t length) {
  * @param [in] Set the value of the characteristic.
  * @return N/A.
  */
-void BLECharacteristic::setValue(String value) {
-  setValue((uint8_t *)(value.c_str()), value.length());
+void BLECharacteristic::setValue(const String &value) {
+  setValue(reinterpret_cast<const uint8_t *>(value.c_str()), value.length());
 }  // setValue
 
 void BLECharacteristic::setValue(uint16_t data16) {

libraries/BLE/src/BLECharacteristic.h

@@ -185,7 +185,7 @@ class BLECharacteristic {
   void notify(bool is_notification = true);
   void setCallbacks(BLECharacteristicCallbacks *pCallbacks);
   void setValue(const uint8_t *data, size_t size);
-  void setValue(String value);
+  void setValue(const String &value);
   void setValue(uint16_t data16);
   void setValue(uint32_t data32);
   void setValue(int data32);

libraries/BLE/src/BLEDescriptor.cpp

@@ -203,7 +203,7 @@ void BLEDescriptor::setValue(const uint8_t *data, size_t length) {
  * @brief Set the value of the descriptor.
  * @param [in] value The value of the descriptor in string form.
  */
-void BLEDescriptor::setValue(String value) {
+void BLEDescriptor::setValue(const String &value) {
   setValue((uint8_t *)value.c_str(), value.length());
 }  // setValue
 

libraries/BLE/src/BLEDescriptor.h

@@ -95,7 +95,7 @@ class BLEDescriptor {
   void setAccessPermissions(uint8_t perm);                // Set the permissions of the descriptor.
   void setCallbacks(BLEDescriptorCallbacks *pCallbacks);  // Set callbacks to be invoked for the descriptor.
   void setValue(const uint8_t *data, size_t size);        // Set the value of the descriptor as a pointer to data.
-  void setValue(String value);                            // Set the value of the descriptor as a data buffer.
+  void setValue(const String &value);                     // Set the value of the descriptor as a data buffer.
 
   String toString();  // Convert the descriptor to a string representation.
 

libraries/BLE/src/BLEValue.cpp

@@ -37,7 +37,7 @@ BLEValue::BLEValue() {
  * The accumulation is a growing set of data that is added to until a commit or cancel.
  * @param [in] part A message part being added.
  */
-void BLEValue::addPart(String part) {
+void BLEValue::addPart(const String &part) {
   log_v(">> addPart: length=%d", part.length());
   m_accumulation += part;
 }  // addPart
@@ -121,7 +121,7 @@ void BLEValue::setReadOffset(uint16_t readOffset) {
 /**
  * @brief Set the current value.
  */
-void BLEValue::setValue(String value) {
+void BLEValue::setValue(const String &value) {
   m_value = value;
 }  // setValue
 

libraries/BLE/src/BLEValue.h

@@ -34,7 +34,7 @@ class BLEValue {
    ***************************************************************************/
 
   BLEValue();
-  void addPart(String part);
+  void addPart(const String &part);
   void addPart(const uint8_t *pData, size_t length);
   void cancel();
   void commit();
@@ -43,7 +43,7 @@ class BLEValue {
   uint16_t getReadOffset();
   String getValue();
   void setReadOffset(uint16_t readOffset);
-  void setValue(String value);
+  void setValue(const String &value);
   void setValue(const uint8_t *pData, size_t length);
 
 private: