How to wrap Method handle behind a class?

[tison]

The related methods and calls are like:

// java
nativeMethod.invoke(21) // not work
nativeMethod.handle.invoke(21) // OK
// rust
#[no_mangle]
pub unsafe extern "C" fn hello_world(n: c_int) -> c_int {
    42 + n
}

Best,
tison.


tison <wander4096 at gmail.com> 于2023年9月27日周三 17:13写道：

> I'm using OpenJDK 21 and prototyping FFM APIs.
>
> Instead of passing the MethodHandle returned by linker.downcallHandle here
> and there, I'm trying to wrap it into a NativeMethod class:
>
> public final class NativeMethod {
>     private final String name;
>     private final FunctionDescriptor descriptor;
>     private final MethodHandle handle;
>     public Object invoke(Object... args) throws Throwable {
>         return this.handle.invoke(args);
>     }
> }
>
> But it seems the varargs pass through is not quit fluent:
>
> java.lang.invoke.WrongMethodTypeException: cannot convert
> MethodHandle(int)int to (Object[])Object
>
> at
> java.base/java.lang.invoke.MethodHandle.asTypeUncached(MethodHandle.java:903)
> at java.base/java.lang.invoke.MethodHandle.asType(MethodHandle.java:870)
> at java.base/java.lang.invoke.Invokers.checkGenericType(Invokers.java:541)
> at io.montumi.datafusion.core.NativeMethod.invoke(NativeMethod.java:22)
>
> While if I public the handle and call invoke from the handle directly, all
> the behavior is expected.
>
> Best,
> tison.
>
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