Retrieve attributes with 16bit uuid if 128bit fails.

When retrieving attribute handles using the 128bit base version of a 16 bit UUID some devices will
report "not found". This will attempt to convert the UUID to the 16bit version and try again.

* Adds `to16()` method to NimBLEUUID.

Author: h2zero

src/NimBLEClient.cpp

@@ -587,14 +587,23 @@ NimBLERemoteService* NimBLEClient::getService(const NimBLEUUID &uuid) {
             return m_servicesVector.back();
         }
 
-        // If the request was successful but 16/32 bit service not found
+        // If the request was successful but 16/32 bit uuid not found
         // try again with the 128 bit uuid.
         if(uuid.bitSize() == BLE_UUID_TYPE_16 ||
            uuid.bitSize() == BLE_UUID_TYPE_32)
         {
             NimBLEUUID uuid128(uuid);
             uuid128.to128();
             return getService(uuid128);
+        } else {
+            // If the request was successful but the 128 bit uuid not found
+            // try again with the 16 bit uuid.
+            NimBLEUUID uuid16(uuid);
+            uuid16.to16();
+            // if the uuid was 128 bit but not of the BLE base type this check will fail
+            if (uuid16.bitSize() == BLE_UUID_TYPE_16) {
+                return getService(uuid16);
+            }
         }
     }
 

src/NimBLERemoteCharacteristic.cpp

@@ -319,14 +319,23 @@ NimBLERemoteDescriptor* NimBLERemoteCharacteristic::getDescriptor(const NimBLEUU
             return m_descriptorVector.back();
         }
 
-        // If the request was successful but 16/32 bit descriptor not found
+        // If the request was successful but 16/32 bit uuid not found
         // try again with the 128 bit uuid.
         if(uuid.bitSize() == BLE_UUID_TYPE_16 ||
            uuid.bitSize() == BLE_UUID_TYPE_32)
         {
             NimBLEUUID uuid128(uuid);
             uuid128.to128();
             return getDescriptor(uuid128);
+        } else {
+            // If the request was successful but the 128 bit uuid not found
+            // try again with the 16 bit uuid.
+            NimBLEUUID uuid16(uuid);
+            uuid16.to16();
+            // if the uuid was 128 bit but not of the BLE base type this check will fail
+            if (uuid16.bitSize() == BLE_UUID_TYPE_16) {
+                return getDescriptor(uuid16);
+            }
         }
     }
 

src/NimBLERemoteService.cpp

@@ -109,14 +109,23 @@ NimBLERemoteCharacteristic* NimBLERemoteService::getCharacteristic(const NimBLEU
             return m_characteristicVector.back();
         }
 
-        // If the request was successful but 16/32 bit characteristic not found
+        // If the request was successful but 16/32 bit uuid not found
         // try again with the 128 bit uuid.
         if(uuid.bitSize() == BLE_UUID_TYPE_16 ||
            uuid.bitSize() == BLE_UUID_TYPE_32)
         {
             NimBLEUUID uuid128(uuid);
             uuid128.to128();
             return getCharacteristic(uuid128);
+        } else {
+            // If the request was successful but the 128 bit uuid not found
+            // try again with the 16 bit uuid.
+            NimBLEUUID uuid16(uuid);
+            uuid16.to16();
+            // if the uuid was 128 bit but not of the BLE base type this check will fail
+            if (uuid16.bitSize() == BLE_UUID_TYPE_16) {
+                return getCharacteristic(uuid16);
+            }
         }
     }
 

src/NimBLEUUID.cpp

@@ -234,8 +234,8 @@ const ble_uuid_any_t* NimBLEUUID::getNative() const {
 
 /**
  * @brief Convert a UUID to its 128 bit representation.
- * @details A UUID can be internally represented as 16bit, 32bit or the full 128bit.  This method
- * will convert 16 or 32 bit representations to the full 128bit.
+ * @details A UUID can be internally represented as 16bit, 32bit or the full 128bit.
+ * This method will convert 16 or 32bit representations to the full 128bit.
  * @return The NimBLEUUID converted to 128bit.
  */
 const NimBLEUUID &NimBLEUUID::to128() {
@@ -256,6 +256,29 @@ const NimBLEUUID &NimBLEUUID::to128() {
 } // to128
 
 
+/**
+ * @brief Convert 128 bit UUID to its 16 bit representation.
+ * @details A UUID can be internally represented as 16bit, 32bit or the full 128bit.
+ * This method will convert a 128bit uuid to 16bit if it contains the ble base uuid.
+ * @return The NimBLEUUID converted to 16bit if successful, otherwise the original uuid.
+ */
+const NimBLEUUID& NimBLEUUID::to16() {
+    if (!m_valueSet || m_uuid.u.type == BLE_UUID_TYPE_16) {
+        return *this;
+    }
+
+    if (m_uuid.u.type == BLE_UUID_TYPE_128) {
+        uint8_t base128[] = {0xfb, 0x34, 0x9b, 0x5f, 0x80, 0x00,
+                             0x00, 0x80, 0x00, 0x10, 0x00, 0x00};
+        if (memcmp(m_uuid.u128.value, base128, sizeof(base128)) == 0 ) {
+            *this = NimBLEUUID(*(uint16_t*)(m_uuid.u128.value + 12));
+        }
+    }
+
+    return *this;
+}
+
+
 /**
  * @brief Get a string representation of the UUID.
  * @details

src/NimBLEUUID.h

@@ -42,6 +42,7 @@ class NimBLEUUID {
     bool                  equals(const NimBLEUUID &uuid) const;
     const ble_uuid_any_t* getNative() const;
     const NimBLEUUID &    to128();
+    const NimBLEUUID&     to16();
     std::string           toString() const;
     static NimBLEUUID     fromString(const std::string &uuid);