FromNativeContext using java.lang.reflect.Type instead of java.lang.Class

[marco2357]

Dummy example:

class Pointer<T> implements NativeMapped {
    public Object fromNative(Object nativeValue, FromNativeContext context) {
       // context.getTargetType() -> Pointer.class
    }
}

Sometimes it would be useful to know the full generic information. E.g. whether a Pointer<Integer>, a Pointer<Double> or a Pointer<Pointer<Pointer<Short>>> needs to be created.

This would be easy to implement; in the Native class, just give method.getGenericReturnType() to registerMethod() instead of method.getReturnType(), adapt fromNative() to take a Type and change the C code.
Though this would change the API and requires Java 1.5. So maybe instead of changing the API an addition would be better.

[twall]

Where do you envision doing this extra transformation? do you have an example?

On Mar 24, 2014, at 9:14 AM, marco2357 notifications@github.com wrote:

Dummy example:

class Pointer implements NativeMapped {
public Object fromNative(Object nativeValue, FromNativeContext context) {
// context.getTargetType() -> Pointer.class
}
}

Sometimes it would be useful to know the full generic information. E.g. whether a Pointer, a Pointer or a Pointer<Pointer<Pointer>> needs to be created.

This would be easy to implement; in the Native class, just give method.getGenericReturnType() to registerMethod() instead of method.getReturnType(), adapt fromNative() to take a Type and change the C code.
Though this would change the API and requires Java 1.5. So maybe instead of changing the API an addition would be better.

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[marco2357]

Do you mean where/how I could make use of this extended information? If FromNativeContext.getTargetType() would return a Type instance (instead of Class), I could do something like:

class Pointer<T> implements NativeMapped {
    private Memory m;

    private Pointer(ParameterizedType type) {
        Type elementType = t.getActualTypeArguments()[0];
        if(elementType == Short.class) {
            m = new Memory(2);
        } else if(elementType == Integer.class) {
            m = new Memory(4);
        }
        // ...
    }

    public Object fromNative(Object nativeValue, FromNativeContext context) {
        return new Pointer((ParameterizedType)context.getTargetType());
    }
}

But I now decided to write little wrappers around native methods taking care of such conversions. This works right now, should execute faster and the JNA TODO file says anyway "eliminate type conversion contexts". So this seems the best thing to do.

Thanks!
Marco