Add alternative characteristic read/write callbacks

Added alternative characteristic read/write callbacks that carry the connection description information.
Fixes h2zero/NimBLE-Arduino#83

Author: lknop <lknop@users.noreply.github.com>

docs/Improvements_and_updates.md

@@ -45,12 +45,16 @@ A new method `NimBLEServer::advertiseOnDisconnect(bool)` has been implemented to
 
 `NimBLEServer::removeService` takes an additional parameter `bool deleteSvc` that if true will delete the service  
 and all characteristics / descriptors belonging to it and invalidating any pointers to them.  
-
 If false the service is only removed from visibility by clients. The pointers to the service and  
 it's characteristics / descriptors will remain valid and the service can be re-added in the future  
 using `NimBLEServer::addService`.  
 <br/>
 
+New characteristic read/write callbacks added to NimBLECharacteristicCallbacks that receive a pointer to the connection  
+description of the client reading/writing.  
+This is useful when connected to multiple clients to discern which client is performing the operation.
+<br/>
+
 # Client  
 
 NimBLERemoteCharacteristic::readValue(time_t\*, bool)  

src/NimBLECharacteristic.cpp

@@ -207,6 +207,7 @@ int NimBLECharacteristic::handleGapEvent(uint16_t conn_handle, uint16_t attr_han
 {
     const ble_uuid_t *uuid;
     int rc;
+    struct ble_gap_conn_desc desc;
     NimBLECharacteristic* pCharacteristic = (NimBLECharacteristic*)arg;
 
     NIMBLE_LOGD(LOG_TAG, "Characteristic %s %s event", pCharacteristic->getUUID().toString().c_str(),
@@ -219,7 +220,10 @@ int NimBLECharacteristic::handleGapEvent(uint16_t conn_handle, uint16_t attr_han
                 // If the packet header is only 8 bytes this is a follow up of a long read
                 // so we don't want to call the onRead() callback again.
                 if(ctxt->om->om_pkthdr_len > 8) {
+                    rc = ble_gap_conn_find(conn_handle, &desc);
+                    assert(rc == 0);
                     pCharacteristic->m_pCallbacks->onRead(pCharacteristic);
+                    pCharacteristic->m_pCallbacks->onRead(pCharacteristic, &desc);
                 }
 
                 portENTER_CRITICAL(&pCharacteristic->m_valMux);
@@ -249,10 +253,11 @@ int NimBLECharacteristic::handleGapEvent(uint16_t conn_handle, uint16_t attr_han
                     len += next->om_len;
                     next = SLIST_NEXT(next, om_next);
                 }
-
+                rc = ble_gap_conn_find(conn_handle, &desc);
+                assert(rc == 0);
                 pCharacteristic->setValue(buf, len);
                 pCharacteristic->m_pCallbacks->onWrite(pCharacteristic);
-
+                pCharacteristic->m_pCallbacks->onWrite(pCharacteristic, &desc);
                 return 0;
             }
             default:
@@ -524,6 +529,14 @@ void NimBLECharacteristicCallbacks::onRead(NimBLECharacteristic* pCharacteristic
     NIMBLE_LOGD("NimBLECharacteristicCallbacks", "onRead: default");
 } // onRead
 
+/**
+ * @brief Callback function to support a read request.
+ * @param [in] pCharacteristic The characteristic that is the source of the event.
+ * @param [in] desc The connection description struct that is associated with the peer that performed the read.
+ */
+void NimBLECharacteristicCallbacks::onRead(NimBLECharacteristic* pCharacteristic, ble_gap_conn_desc* desc) {
+    NIMBLE_LOGD("NimBLECharacteristicCallbacks", "onRead: default");
+} // onRead
 
 /**
  * @brief Callback function to support a write request.
@@ -533,6 +546,14 @@ void NimBLECharacteristicCallbacks::onWrite(NimBLECharacteristic* pCharacteristi
     NIMBLE_LOGD("NimBLECharacteristicCallbacks", "onWrite: default");
 } // onWrite
 
+/**
+ * @brief Callback function to support a write request.
+ * @param [in] pCharacteristic The characteristic that is the source of the event.
+ * @param [in] desc The connection description struct that is associated with the peer that performed the write.
+ */
+void NimBLECharacteristicCallbacks::onWrite(NimBLECharacteristic* pCharacteristic, ble_gap_conn_desc* desc) {
+    NIMBLE_LOGD("NimBLECharacteristicCallbacks", "onWrite: default");
+} // onWrite
 
 /**
  * @brief Callback function to support a Notify request.

src/NimBLECharacteristic.h

@@ -176,7 +176,9 @@ public:
 
     virtual ~NimBLECharacteristicCallbacks();
     virtual void onRead(NimBLECharacteristic* pCharacteristic);
+    virtual void onRead(NimBLECharacteristic* pCharacteristic, ble_gap_conn_desc* desc);
     virtual void onWrite(NimBLECharacteristic* pCharacteristic);
+    virtual void onWrite(NimBLECharacteristic* pCharacteristic, ble_gap_conn_desc* desc);
     virtual void onNotify(NimBLECharacteristic* pCharacteristic);
     virtual void onStatus(NimBLECharacteristic* pCharacteristic, Status s, int code);
 };