android: use ByteBuffer to send or store pointers in JNI bindings

Using direct ByteBuffer is much nicer option to store or send
pointers between C(++) code and Java via JNI as it handles endiness
and pointer size for us. Using "long" type can have unexpected
results in 32-bit architectures (mostly Android). This was causing
grief especially when Android introduced support for 64-bit
architectures starting with SDK 19.

Change-Id: Ie92d0f913b668e1724e846d70d1820445d9cb086

android/Bootstrap/src/org/libreoffice/kit/Document.java

@@ -24,9 +24,9 @@ public class Document {
     public static final int DOCTYPE_DRAWING = 3;
     public static final int DOCTYPE_OTHER = 4;
 
-    private final long handle;
+    private final ByteBuffer handle;
 
-    public Document(long handle) {
+    public Document(ByteBuffer handle) {
         this.handle = handle;
     }
 

android/Bootstrap/src/org/libreoffice/kit/LibreOfficeKit.java

@@ -14,6 +14,7 @@ import android.content.pm.ApplicationInfo;
 import android.util.Log;
 
 import java.io.InputStream;
+import java.nio.ByteBuffer;
 
 // Native methods in this class are all implemented in
 // sal/android/lo-bootstrap.c as the lo-bootstrap library is loaded with
@@ -34,7 +35,7 @@ public final class LibreOfficeKit
     // Trigger initialization on the JNI - LOKit side.
     private static native boolean initializeNative(String dataDir, String cacheDir, String apkFile);
 
-    public static native long getLibreOfficeKitHandle();
+    public static native ByteBuffer getLibreOfficeKitHandle();
 
     // Wrapper for putenv()
     public static native void putenv(String string);

android/Bootstrap/src/org/libreoffice/kit/Office.java

@@ -9,22 +9,24 @@
 
 package org.libreoffice.kit;
 
+import java.nio.ByteBuffer;
+
 public class Office {
 
-    private long handle;
+    private ByteBuffer handle;
 
-    public Office(long handle) {
+    public Office(ByteBuffer handle) {
         this.handle = handle;
     }
 
     public native String getError();
 
-    private native long documentLoadNative(String url);
+    private native ByteBuffer documentLoadNative(String url);
 
     public Document documentLoad(String url) {
-        long documentHandle = documentLoadNative(url);
+        ByteBuffer documentHandle = documentLoadNative(url);
         Document document = null;
-        if (documentHandle > 0) {
+        if (documentHandle != null) {
             document = new Document(documentHandle);
         }
         return document;

desktop/source/lib/lokandroid.cxx

@@ -25,21 +25,14 @@
 jfieldID getHandleField(JNIEnv* pEnv, jobject aObject)
 {
     jclass clazz = pEnv->GetObjectClass(aObject);
-    return pEnv->GetFieldID(clazz, "handle", "J");
+    return pEnv->GetFieldID(clazz, "handle", "Ljava/nio/ByteBuffer;");
 }
 
 template <typename T>
 T* getHandle(JNIEnv* pEnv, jobject aObject)
 {
-    jlong aHandle = pEnv->GetLongField(aObject, getHandleField(pEnv, aObject));
-    return reinterpret_cast<T*>(aHandle);
-}
-
-template <typename T>
-void setHandle(JNIEnv* pEnv, jobject aObject, T* aType)
-{
-    jlong aHandle = reinterpret_cast<jlong>(aType);
-    pEnv->SetLongField(aObject, getHandleField(pEnv, aObject), aHandle);
+    jobject aHandle = pEnv->GetObjectField(aObject, getHandleField(pEnv, aObject));
+    return reinterpret_cast<T*>(pEnv->GetDirectBufferAddress(aHandle));
 }
 
 const char* copyJavaString(JNIEnv* pEnv, jstring aJavaString)
@@ -60,11 +53,6 @@ extern "C" SAL_JNI_EXPORT jstring JNICALL Java_org_libreoffice_kit_Office_getErr
     return pEnv->NewStringUTF(pError);
 }
 
-extern "C" SAL_JNI_EXPORT void JNICALL Java_org_libreoffice_kit_Office_initialize(JNIEnv* pEnv, jobject aObject, jlong aLokHandle)
-{
-    pEnv->SetLongField(aObject, getHandleField(pEnv, aObject), aLokHandle);
-}
-
 extern "C" SAL_JNI_EXPORT void JNICALL Java_org_libreoffice_kit_Office_destroy(JNIEnv* pEnv, jobject aObject)
 {
     LibreOfficeKit* pLibreOfficeKit = getHandle<LibreOfficeKit>(pEnv, aObject);
@@ -80,13 +68,15 @@ extern "C" SAL_JNI_EXPORT void JNICALL Java_org_libreoffice_kit_Office_destroyAn
     _exit(0);
 }
 
-extern "C" SAL_JNI_EXPORT jlong JNICALL Java_org_libreoffice_kit_Office_documentLoadNative(JNIEnv* pEnv, jobject aObject, jstring documentPath)
+extern "C" SAL_JNI_EXPORT jobject JNICALL Java_org_libreoffice_kit_Office_documentLoadNative(JNIEnv* pEnv, jobject aObject, jstring documentPath)
 {
     const char* aCloneDocumentPath = copyJavaString(pEnv, documentPath);
     LibreOfficeKit* pLibreOfficeKit = getHandle<LibreOfficeKit>(pEnv, aObject);
 
     LibreOfficeKitDocument* pDocument = pLibreOfficeKit->pClass->documentLoad(pLibreOfficeKit, aCloneDocumentPath);
-    return (jlong) pDocument;
+    jobject aHandle = pEnv->NewDirectByteBuffer((void*) pDocument, sizeof(LibreOfficeKitDocument));
+
+    return aHandle;
 }
 
 /* Document */

sal/android/libreofficekit-jni.c

@@ -147,13 +147,17 @@ jboolean Java_org_libreoffice_kit_LibreOfficeKit_initializeNative
 }
 
 __attribute__ ((visibility("default")))
-jlong Java_org_libreoffice_kit_LibreOfficeKit_getLibreOfficeKitHandle
+jobject Java_org_libreoffice_kit_LibreOfficeKit_getLibreOfficeKitHandle
     (JNIEnv* env, jobject clazz)
 {
+    LibreOfficeKit* aOffice;
+
     (void) env;
     (void) clazz;
 
-    return (jlong) (intptr_t) libreofficekit_hook(full_program_dir);
+    aOffice = libreofficekit_hook(full_program_dir);
+
+    return (*env)->NewDirectByteBuffer(env, (void*) aOffice, sizeof(LibreOfficeKit));
 }
 
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