Initial working Java binding for the direct_bt C++ module

Example ScannerTinyB01 demonstrates efficient scanning devices using the new BluetoothDeviceDiscoveryListener interface.

The C++ HCIObject extends JavaUplink, which handles the java object references
via 'std::shared_ptr<JavaAnonObj>', where JavaAnonObj relies on later polymorph specialization.

JavaAnonObj gets derived in the java/jni of direct_bt, where the JNI header + libraries are available.

+++

The java inplementing NativeDownlink implementations
store the nativeInstance to the C++ instances
as well as handle their java references within the native instances.

The C++ JavaUplink and Java NativeDownlink interfaces are complete
the cross referencing java <-> native.

+++

Native libraries are now split into pairs:
- tinyb + javatinyb
- direct_bt + javadirect_bt

TODO: BluetoothFactory must chose the proper bundle!

+++

The Java Adapter received a BluetoothDeviceDiscoveryListener hook,
matching C++ Adapter's HCIDeviceDiscoveryListener.

Since the Java Adapter implements its own discovery thread,
using the BluetoothDeviceDiscoveryListener is more efficient then polling
over a list of Devices fetched.

++++

TODO: Align Java and C++ class names, foremost in the C++ direct_bt space.

TODO: Bind the whole C++ GATT functionality

More testing.

1 files changed, 25 insertions, 3 deletions

diff --git a/java/jni/JNIMem.hpp b/java/jni/JNIMem.hpp
index 389a915..a133bd9 100644
--- a/java/jni/JNIMem.hpp
+++ b/java/jni/JNIMem.hpp
@@ -2,6 +2,10 @@
  * Author: Petre Eftime <[email protected]>
  * Copyright (c) 2016 Intel Corporation.
  *
+ * Author: Sven Gothel <[email protected]>
+ * Copyright (c) 2020 Gothel Software e.K.
+ * Copyright (c) 2020 ZAFENA AB
+ *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
  * "Software"), to deal in the Software without restriction, including
@@ -22,10 +26,14 @@
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
-#pragma once
+#ifndef JNIMEM__HPP_
+#define JNIMEM__HPP_
+
 #include <jni.h>
 #include <stdexcept>
 
+#include "BasicTypes.hpp"
+
 extern JavaVM* vm;
 
 
@@ -67,12 +75,26 @@ private:
     jobject object;
 
 public:
+    static inline void check(jobject object, const char* file, int line) {
+        if( nullptr == object ) {
+            throw direct_bt::RuntimeException("JNIGlobalRef::check: Null jobject", file, line);
+        }
+    }
+
     /* Creates a GlobalRef from an object passed to it */
     JNIGlobalRef(jobject object);
+
     /* Deletes the stored GlobalRef */
     ~JNIGlobalRef();
 
-    /* Provides access to the stored GlobalRef */
-    jobject operator*();
+    /* Provides access to the stored GlobalRef as an jobject. */
+    jobject operator*() { return object; }
+
+    /* Provides access to the stored GlobalRef as an jobject. */
+    jobject getObject() const { return object; }
+    /* Provides access to the stored GlobalRef as a jclass. */
+    jclass getClass() const { return (jclass)object; }
 };
 
+#endif /* JNIMEM__HPP_ */
+