jna: typed "reference placeholders"

gistfile.java

package com.sun.jna.platform.mac;

import com.sun.jna.Pointer;
import com.sun.jna.ptr.PointerByReference;

import java.util.function.Function;

class ByReference<T extends CoreFoundation.CFTypeRef> extends PointerByReference {
    private final Function<Pointer, T> typedValueFactory;

    public ByReference(Function<Pointer, T> typedValueFactory) {
        this(typedValueFactory, null);
    }

    public ByReference(Function<Pointer, T> typedValueFactory, T initialValue) {
        super(initialValue == null ? null : initialValue.getPointer());
        this.typedValueFactory = typedValueFactory;
    }

    @Override
    public void setValue(Pointer value) {
        // type check
        typedValueFactory.apply(value);

        super.setValue(value);
    }

    public T getRefValue() {
        Pointer value = super.getValue();
        if (value == null) {
            return null;
        }
        return typedValueFactory.apply(value);
    }
}

class CFDictionaryRefPlaceholder extends ByReference<CoreFoundation.CFDictionaryRef> {
    public CFDictionaryRefPlaceholder() {
        this(null);
    }

    public CFDictionaryRefPlaceholder(CoreFoundation.CFDictionaryRef initialValue) {
        super(CoreFoundation.CFDictionaryRef::new, initialValue);
    }
}