C++: Utilize 'currentScanType' for start/stop discovery same as for Java code; use atomic<ScanType> avoiding race conditions

C++/Java: Only update the discovering state for false in DISCOVERING listener if keepAlive == false.

C++ like Java pendant, only perform start/stop discovery in appropriate discovery state

C++ expose discovery state 'currentScanType'

3 files changed, 32 insertions, 3 deletions

diff --git a/api/direct_bt/DBTAdapter.hpp b/api/direct_bt/DBTAdapter.hpp
index 48585a81..17bb9e43 100644
--- a/api/direct_bt/DBTAdapter.hpp
+++ b/api/direct_bt/DBTAdapter.hpp
@@ -155,7 +155,8 @@ namespace direct_bt {
             DBTManager& mgmt;
             std::shared_ptr<AdapterInfo> adapterInfo;
             NameAndShortName localName;
-            ScanType currentScanType = ScanType::SCAN_TYPE_NONE;
+            std::atomic<ScanType> currentScanType; // = ScanType::SCAN_TYPE_NONE
+            std::atomic<bool> keepDiscoveringAlive; //  = false;
 
             std::shared_ptr<HCIHandler> hci;
             std::vector<std::shared_ptr<DBTDevice>> connectedDevices;
@@ -167,7 +168,6 @@ namespace direct_bt {
             std::recursive_mutex mtx_discoveredDevices;
             std::recursive_mutex mtx_sharedDevices;
             std::recursive_mutex mtx_statusListenerList;
-            std::atomic<bool> keepDiscoveringAlive; //  = false;
 
             bool validateDevInfo();
 
@@ -417,6 +417,20 @@ namespace direct_bt {
             void stopDiscovery();
 
             /**
+             * Returns the discovering state the adapter. It can be modified through startDiscovery(..) and stopDiscovery().
+             */
+            ScanType getDiscoveringScanType() const {
+                return currentScanType;
+            }
+
+            /**
+             * Returns the discovering state the adapter. It can be modified through startDiscovery(..) and stopDiscovery().
+             */
+            bool getDiscovering() const {
+                return ScanType::SCAN_TYPE_NONE != currentScanType;
+            }
+
+            /**
              * Returns discovered devices from the last discovery.
              * <p>
              * Note that this list will be cleared when a new discovery is started over via startDiscovery().
diff --git a/java/direct_bt/tinyb/DBTAdapter.java b/java/direct_bt/tinyb/DBTAdapter.java
index 4f0d1025..4cbc071f 100644
--- a/java/direct_bt/tinyb/DBTAdapter.java
+++ b/java/direct_bt/tinyb/DBTAdapter.java
@@ -429,6 +429,10 @@ public class DBTAdapter extends DBTObject implements BluetoothAdapter
             if( DEBUG ) {
                 System.err.println("Adapter.StatusListener.DISCOVERING: enabled "+enabled+", keepAlive "+keepAlive+" on "+adapter);
             }
+            if( !enabled && keepAlive ) {
+                // Don't update isDiscovering:=false and don't notify user IF keepAlive!
+                return;
+            }
             if( isDiscovering.compareAndSet(!enabled, enabled) ) {
                 synchronized(userCallbackLock) {
                     if( null != userDiscoveringNotificationCB ) {
diff --git a/src/direct_bt/DBTAdapter.cpp b/src/direct_bt/DBTAdapter.cpp
index 293937d8..5b2a7643 100644
--- a/src/direct_bt/DBTAdapter.cpp
+++ b/src/direct_bt/DBTAdapter.cpp
@@ -106,6 +106,7 @@ std::shared_ptr<DBTDevice> DBTAdapter::findConnectedDevice (EUI48 const & mac) c
 // *************************************************
 
 bool DBTAdapter::validateDevInfo() {
+    currentScanType = ScanType::SCAN_TYPE_NONE;
     keepDiscoveringAlive = false;
 
     if( !mgmt.isOpen() || 0 > dev_id ) {
@@ -302,6 +303,9 @@ int DBTAdapter::removeAllStatusListener() {
 bool DBTAdapter::startDiscovery(const bool keepAlive, const HCIAddressType own_mac_type,
                                 const uint16_t le_scan_interval, const uint16_t le_scan_window)
 {
+    if( ScanType::SCAN_TYPE_NONE != currentScanType ) {
+        return true;
+    }
     (void)own_mac_type;
     (void)le_scan_interval;
     (void)le_scan_window;
@@ -318,8 +322,11 @@ void DBTAdapter::startDiscoveryBackground() {
 }
 
 void DBTAdapter::stopDiscovery() {
-    DBG_PRINT("DBTAdapter::stopDiscovery: ...");
     keepDiscoveringAlive = false;
+    if( ScanType::SCAN_TYPE_NONE == currentScanType ) {
+        return;
+    }
+    DBG_PRINT("DBTAdapter::stopDiscovery: ...");
     if( mgmt.stopDiscovery(dev_id, currentScanType) ) {
         currentScanType = ScanType::SCAN_TYPE_NONE;
     }
@@ -441,6 +448,10 @@ bool DBTAdapter::mgmtEvDeviceDiscoveringCB(std::shared_ptr<MgmtEvent> e) {
         dev_id, keepDiscoveringAlive.load(), e->toString().c_str());
     const MgmtEvtDiscovering &event = *static_cast<const MgmtEvtDiscovering *>(e.get());
     const bool enabled = event.getEnabled();
+    if( !enabled && !keepDiscoveringAlive ) {
+        // Only update currentScanType:=false IF keepAlive==false!
+        currentScanType = ScanType::SCAN_TYPE_NONE;
+    }
     int i=0;
     for_each_idx_mtx(mtx_statusListenerList, statusListenerList, [&](std::shared_ptr<AdapterStatusListener> &l) {
         try {