close sejda-pdf#7: Prevent garbage collection of Encoder/Decoder obje…

…cts during native encode/decode calls

src/main/java/com/luciad/imageio/webp/WebP.java

@@ -54,7 +54,13 @@ public static int[] decode(WebPDecoderOptions aOptions, byte[] aData, int aOffse
       throw new IllegalArgumentException("Offset/length exceeds array size");
     }
 
-    int[] pixels = decode(aOptions.fPointer, aData, aOffset, aLength, aOut, ByteOrder.nativeOrder().equals(ByteOrder.BIG_ENDIAN));
+    int[] pixels;
+    try {
+        pixels = decode(aOptions.fPointer, aData, aOffset, aLength, aOut, ByteOrder.nativeOrder().equals(ByteOrder.BIG_ENDIAN));
+    } finally {
+        aOptions.objectCanBeFinalized();
+    }
+
     VP8StatusCode status = VP8StatusCode.getStatusCode(aOut[0]);
     switch (status) {
       case VP8_STATUS_OK:
@@ -83,13 +89,21 @@ public static int[] getInfo(byte[] aData, int aOffset, int aLength) throws IOExc
   private static native int getInfo(byte[] aData, int aOffset, int aLength, int[] aOut);
 
   public static byte[] encodeRGBA(WebPEncoderOptions aOptions, byte[] aRgbaData, int aWidth, int aHeight, int aStride) {
-    return encodeRGBA(aOptions.fPointer, aRgbaData, aWidth, aHeight, aStride);
+      try {
+          return encodeRGBA(aOptions.fPointer, aRgbaData, aWidth, aHeight, aStride);
+      } finally {
+          aOptions.objectCanBeFinalized();
+      }
   }
 
   private static native byte[] encodeRGBA(long aConfig, byte[] aRgbaData, int aWidth, int aHeight, int aStride);
 
   public static byte[] encodeRGB(WebPEncoderOptions aOptions, byte[] aRgbaData, int aWidth, int aHeight, int aStride) {
-    return encodeRGB(aOptions.fPointer, aRgbaData, aWidth, aHeight, aStride);
+    try {
+        return encodeRGB(aOptions.fPointer, aRgbaData, aWidth, aHeight, aStride);
+    } finally {
+        aOptions.objectCanBeFinalized();
+    }
   }
 
   private static native byte[] encodeRGB(long aConfig, byte[] aRgbaData, int aWidth, int aHeight, int aStride);

src/main/java/com/luciad/imageio/webp/WebPDecoderOptions.java

@@ -36,6 +36,20 @@ protected void finalize() throws Throwable {
     fPointer = 0L;
   }
 
+  /**
+   * Method to tell the Java Garbage collector that the object can now be released (and the native method
+   * is done working with the object).
+   *
+   * There is a finalizer in this object which clears the native assigned memory used by the WebP library
+   * during garbage collection. Without this method being properly called, garbage collection might happen
+   * before the native procedure has finished executing since the object is only forwarded via JNI by the
+   * fPointer and the underlying WebP library directly uses the complete object.
+   *
+   * This issue only manifests under high load because the time window between the native memory being used
+   * and the finalizer being called is very small.
+   */
+  public void objectCanBeFinalized() {};
+
   public int getCropHeight() {
     return getCropHeight( fPointer );
   }

src/main/java/com/luciad/imageio/webp/WebPEncoderOptions.java

@@ -36,6 +36,20 @@ protected void finalize() throws Throwable {
     fPointer = 0L;
   }
 
+  /**
+   * Method to tell the Java Garbage collector that the object can now be released (and the native method
+   * is done working with the object).
+   *
+   * There is a finalizer in this object which clears the native assigned memory used by the WebP library
+   * during garbage collection. Without this method being properly called, garbage collection might happen
+   * before the native procedure has finished executing since the object is only forwarded via JNI by the
+   * fPointer and the underlying WebP library directly uses the complete object.
+   *
+   * This issue only manifests under high load because the time window between the native memory being used
+   * and the finalizer being called is very small.
+   */
+  public void objectCanBeFinalized() {};
+
   private static native long createConfig();
 
   private static native void deleteConfig( long aPointer );