Update Message and lowlevel Message API with GstMessagePtr.

Add GstMessagePtr and direct access to source obj and type without instantiation.
Add parse methods in GstMessageAPI using typed pointers.
Update Message with Handle subclass and use of new API for Message construction.
Add method to return a default value (or null) from NativeEnum conversion rather than throw exception.

Author: neilcsmith-net

src/org/freedesktop/gstreamer/glib/NativeEnum.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019 Neil C Smith
+ * Copyright (c) 2020 Neil C Smith
  *
  * This file is part of gstreamer-java.
  *
@@ -15,26 +15,57 @@
  * You should have received a copy of the GNU Lesser General Public License
  * version 3 along with this work.  If not, see <http://www.gnu.org/licenses/>.
  */
-
 package org.freedesktop.gstreamer.glib;
 
 /**
  * Interface for enums that wrap a native int-based enum.
+ *
  * @param <T> Java enum type
  */
 public interface NativeEnum<T extends Enum<T>> {
 
     public int intValue();
 
+    /**
+     * Convert a native int value to the specified NativeEnum type.
+     *
+     * @param <T> enum type
+     * @param type enum class
+     * @param intValue native int value
+     * @return enum value
+     * @throws IllegalArgumentException if no enum value matches the specified
+     * native int value
+     */
     public static <T extends Enum<T> & NativeEnum<T>> T fromInt(Class<T> type, int intValue) {
         for (T value : type.getEnumConstants()) {
             if (value.intValue() == intValue) {
                 return value;
             }
         }
 
-        throw new IllegalArgumentException("Value " + intValue + " is unacceptable for " +
-                type.getSimpleName() + " enum");
+        throw new IllegalArgumentException("Value " + intValue + " is unacceptable for "
+                + type.getSimpleName() + " enum");
+    }
+
+    /**
+     * Convert a native int value to the specified NativeEnum type, allowing for
+     * a default value (or null) to be returned instead of throwing an exception
+     * on invalid values.
+     *
+     * @param <T> enum type
+     * @param type enum class
+     * @param defValue default value to return if no match (may be null)
+     * @param intValue native int value
+     * @return enum value
+     */
+    public static <T extends Enum<T> & NativeEnum<T>> T fromInt(Class<T> type, T defValue, int intValue) {
+        for (T value : type.getEnumConstants()) {
+            if (value.intValue() == intValue) {
+                return value;
+            }
+        }
+
+        return defValue;
     }
 
 }

src/org/freedesktop/gstreamer/lowlevel/GstMessageAPI.java

@@ -1,4 +1,5 @@
 /* 
+ * Copyright (c) 2020 Neil C Smith
  * Copyright (c) 2014 Tom Greenwood <[email protected]>
  * Copyright (c) 2009 Levente Farkas
  * Copyright (c) 2007, 2008 Wayne Meissner
@@ -35,21 +36,24 @@
 import org.freedesktop.gstreamer.lowlevel.annotations.Invalidate;
 
 import com.sun.jna.Pointer;
+import com.sun.jna.Structure.FieldOrder;
+import com.sun.jna.ptr.IntByReference;
+import com.sun.jna.ptr.LongByReference;
 import com.sun.jna.ptr.PointerByReference;
-import java.util.Arrays;
-import java.util.List;
 
 /*
  * GstMessage functions
  */
 public interface GstMessageAPI extends com.sun.jna.Library {
     GstMessageAPI GSTMESSAGE_API = GstNative.load(GstMessageAPI.class);
 
+    @FieldOrder({"mini_object", "type", "timestamp", "src",
+        "seqnum", "lock", "cond"})
     public static final class MessageStruct extends com.sun.jna.Structure {
     	public volatile MiniObjectStruct mini_object;
-        public volatile MessageType type;
+        public volatile int type;
         public volatile long timestamp;
-        public volatile GstObject src;
+        public volatile GstObjectPtr src;
         public volatile int seqnum;
 
         public volatile Pointer lock;
@@ -63,39 +67,48 @@ public MessageStruct() {
         public MessageStruct(Pointer ptr) {
             useMemory(ptr);
         }
-
-        @Override
-        protected List<String> getFieldOrder() {
-            return Arrays.asList(new String[]{
-                "mini_object", 
-                "type", "timestamp", "src",
-                "seqnum",
-                "lock", "cond"
-            });
+        
+        int typeOffset() {
+            return fieldOffset("type");
+        }
+        
+        int srcOffset() {
+            return fieldOffset("src");
         }
     }
 
     GType gst_message_get_type();
     String gst_message_type_get_name(MessageType type);
     void gst_message_parse_state_changed(Message msg, State[] old, State[] current, State[] pending);
+    void gst_message_parse_state_changed(GstMessagePtr msg, IntByReference old, IntByReference current, IntByReference pending);
     void gst_message_parse_tag(Message msg, PointerByReference tagList);
+    void gst_message_parse_tag(GstMessagePtr msg, PointerByReference tagList);
     void gst_message_parse_clock_provide(Message msg, PointerByReference clock, int[] reader);
     void gst_message_parse_new_clock(Message msg, PointerByReference clock);
     void gst_message_parse_error(Message msg, PointerByReference err, PointerByReference debug);
+    void gst_message_parse_error(GstMessagePtr msg, PointerByReference err, PointerByReference debug);
     void gst_message_parse_error(Message msg, GErrorStruct[] err, Pointer[] debug);
     void gst_message_parse_warning(Message msg, PointerByReference err, PointerByReference debug);
+    void gst_message_parse_warning(GstMessagePtr msg, PointerByReference err, PointerByReference debug);
     void gst_message_parse_warning(Message msg, GErrorStruct[] err, Pointer[] debug);
     void gst_message_parse_info(Message msg, PointerByReference err, PointerByReference debug);
+    void gst_message_parse_info(GstMessagePtr msg, PointerByReference err, PointerByReference debug);
     void gst_message_parse_info(Message msg, GErrorStruct[] err, Pointer[] debug);
     void gst_message_parse_buffering(Message msg, int[] percent);
+    void gst_message_parse_buffering(GstMessagePtr msg, IntByReference percent);
     void gst_message_parse_segment_start(Message message, Format[] format, long[] position); 
+    void gst_message_parse_segment_start(GstMessagePtr msg, IntByReference format, LongByReference position); 
     void gst_message_parse_segment_done(Message message, Format[] format, long[] position);
+    void gst_message_parse_segment_done(GstMessagePtr msg, IntByReference format, LongByReference position); 
     void gst_message_parse_duration(Message message, Format[] format, long[] position);
+    void gst_message_parse_duration(GstMessagePtr msg, IntByReference format, LongByReference position);
     void gst_message_parse_async_start(Message message, boolean[] new_base_time);
-    
     boolean gst_message_parse_context_type(Message message, String[] context_type);
+    boolean gst_message_parse_context_type(GstMessagePtr msg, PointerByReference /*String*/ context_type);
+    
     @CallerOwnsReturn Message gst_message_new_eos(GstObject src);
     Pointer ptr_gst_message_new_eos(GstObject src);
+    @CallerOwnsReturn GstMessagePtr gst_message_new_eos(GstObjectPtr src);
     @CallerOwnsReturn Message gst_message_new_error(GstObject src, GErrorStruct error, String debug);
     @CallerOwnsReturn Message gst_message_new_warning(GstObject src, GErrorStruct error, String debug);
     @CallerOwnsReturn Message gst_message_new_info(GstObject src, GErrorStruct error, String debug);

src/org/freedesktop/gstreamer/lowlevel/GstMessagePtr.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2020 Neil C Smith
+ * 
+ * This file is part of gstreamer-java.
+ *
+ * This code is free software: you can redistribute it and/or modify it under the terms of the GNU
+ * Lesser General Public License version 3 only, as published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
+ * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License version 3 for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License version 3 along with
+ * this work. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.freedesktop.gstreamer.lowlevel;
+
+import com.sun.jna.Pointer;
+
+/**
+ * GstMessage pointer.
+ */
+public class GstMessagePtr extends GstMiniObjectPtr {
+
+    private static final int TYPE_OFFSET;
+    private static final int SRC_OFFSET;
+    
+    static {
+        GstMessageAPI.MessageStruct struct = new GstMessageAPI.MessageStruct();
+        TYPE_OFFSET = struct.typeOffset();
+        SRC_OFFSET = struct.srcOffset();
+    }
+    
+    
+    public GstMessagePtr() {
+    }
+
+    public GstMessagePtr(Pointer ptr) {
+        super(ptr);
+    }
+    
+    public int getMessageType() {
+        return getPointer().getInt(TYPE_OFFSET);
+    }
+
+    public GstObjectPtr getSource() {
+        Pointer raw = getPointer().getPointer(SRC_OFFSET);
+        return raw == null ? null : new GstObjectPtr(raw);
+    }
+    
+    
+}

src/org/freedesktop/gstreamer/message/Message.java

@@ -1,5 +1,5 @@
 /* 
- * Copyright (c) 2019 Neil C Smith
+ * Copyright (c) 2020 Neil C Smith
  * Copyright (c) 2007, 2008 Wayne Meissner
  * Copyright (C) 2004 Wim Taymans <[email protected]>
  * 
@@ -26,8 +26,9 @@
 import org.freedesktop.gstreamer.GstObject;
 import org.freedesktop.gstreamer.MiniObject;
 import org.freedesktop.gstreamer.Structure;
+import org.freedesktop.gstreamer.glib.NativeEnum;
 import org.freedesktop.gstreamer.glib.Natives;
-import org.freedesktop.gstreamer.lowlevel.GstMessageAPI;
+import org.freedesktop.gstreamer.lowlevel.GstMessagePtr;
 import org.freedesktop.gstreamer.lowlevel.ReferenceManager;
 import org.freedesktop.gstreamer.lowlevel.annotations.HasSubtype;
 
@@ -82,16 +83,20 @@ public class Message extends MiniObject {
         TYPE_MAP.put(MessageType.NEED_CONTEXT, NeedContextMessage::new);
     }
 
-    private final GstMessageAPI.MessageStruct messageStruct;
+    private final Handle handle;
 
     /**
      * Creates a new instance of Message.
      *
      * @param init internal initialization data.
      */
     Message(Initializer init) {
-        super(init);
-        messageStruct = new GstMessageAPI.MessageStruct(init.ptr.getPointer());
+        this(new Handle(init.ptr.as(GstMessagePtr.class, GstMessagePtr::new), init.ownsHandle), init.needRef);
+    }
+
+    Message(Handle handle, boolean needRef) {
+        super(handle, needRef);
+        this.handle = handle;
     }
 
     /**
@@ -100,7 +105,7 @@ public class Message extends MiniObject {
      * @return the element that posted the message.
      */
     public GstObject getSource() {
-        return (GstObject) messageStruct.readField("src");
+        return Natives.objectFor(handle.getPointer().getSource(), GstObject.class, true, true);
     }
 
     /**
@@ -118,16 +123,18 @@ public Structure getStructure() {
      * @return the message type.
      */
     public MessageType getType() {
-        MessageType type = (MessageType) messageStruct.readField("type");
-        return type;
+        return NativeEnum.fromInt(MessageType.class, MessageType.UNKNOWN,
+                handle.getPointer().getMessageType());
     }
 
     private static Message create(Initializer init) {
-        GstMessageAPI.MessageStruct struct = new GstMessageAPI.MessageStruct(init.ptr.getPointer());
-        MessageType type = (MessageType) struct.readField("type");
+        MessageType type = NativeEnum.fromInt(MessageType.class,
+                MessageType.UNKNOWN,
+                init.ptr.as(GstMessagePtr.class, GstMessagePtr::new).getMessageType()
+        );
         return TYPE_MAP.getOrDefault(type, Message::new).apply(init);
     }
-    
+
     public static class Types implements TypeProvider {
 
         @Override
@@ -136,7 +143,20 @@ public Stream<TypeRegistration<?>> types() {
                     Natives.registration(Message.class, GTYPE_NAME, Message::create)
             );
         }
-        
+
+    }
+
+    static class Handle extends MiniObject.Handle {
+
+        Handle(GstMessagePtr ptr, boolean ownsHandle) {
+            super(ptr, ownsHandle);
+        }
+
+        @Override
+        protected GstMessagePtr getPointer() {
+            return (GstMessagePtr) super.getPointer();
+        }
+
     }
 
 }