remove WindowsDirectory

[rmuir]

Description

Having native code complicates the gradle build and causes bugs.

The Direct-IO directory no longer needs native code, it uses JDK APIs. So the only thing left is WindowsDirectory.

I'm not sure this thing is really faster than the JDK. If i remember, the synchronization that causes the issues was in windows. Honestly, users should use MmapDirectory on windows IMO.

So maybe net/net it is better for our windows support to remove this thing?

[dweiss]

I've no idea who uses this thing but I'm open to removing this - it does complicate things a bit.

[uschindler]

+1

[rmuir]

I kinda feel that going forwards, we would not do things this way with C code, but instead look to use the new FFI interfaces being added to openjdk if we really need to call native stuff...

[dweiss]

If there are no objections, I'll handle the removal - there are some gradle scripts involved there that will also benefit from the cleanup.

[uschindler]

Project Panama is the way to go, no need for FFI or anything like that. You can create a MethodHandle that downcalls into libc/kernel.dll.

I have an example in some talk.

[uschindler]

This is how to call getpid() with Java 19 (you need to enable preview APIs and also enable access to native code (disabled for security by default):

var cLinker = Linker.nativeLinker();
// Using a MethodHandle
MethodHandle getpidMH = cLinker.downcallHandle(cLinker.defaultLookup().lookup("getpid").get(),
                    FunctionDescriptor.of(JAVA_INT));
int pid    = (int) getpidMH.invokeExact();
System.out.printf("MethodHandle calling getpid() (%d)\n", pid);

[rmuir]

yeah, sorry when i said FFI i meant panama (its an FFI to me).

[dweiss]

That's pretty neat.

[dweiss]

We should apply this to main, but I think there's no harm to backport to 9.x, right? It's not a stable API and there is a safe replacement.

[rmuir]

+1

[uschindler]

Let's remove it. Actually the whole code is not tested at all. The removed Testcase extends LuceneTestCase and not BaseDirectoryTestcase. The only thing it does is to instantiate a Directory and an IndexOutput (!!) that is not even triggering custom code, because the native code is an IndexInput.

[dweiss]

Applied on 9x and main.