///usr/bin/env jbang "$0" "$@" ; exit $?

//JAVA 25+

//JAVA_OPTIONS --enable-native-access=ALL-UNNAMED

import java.lang.foreign.*;

import java.lang.invoke.MethodHandle;

import java.util.Optional;

/// Proof: call-c-from-java

/// Source: content/language/call-c-from-java.yaml

void main() throws Throwable {

try (Arena arena = Arena.ofConfined()) {

// Use a system library to prove FFM compiles and links

SymbolLookup stdlib = Linker.nativeLinker().defaultLookup();

Optional<MemorySegment> segment = stdlib.find("strlen");

MemorySegment foreignFuncAddr = segment.get();

FunctionDescriptor strlen_sig =

FunctionDescriptor.of(ValueLayout.JAVA_LONG, ValueLayout.ADDRESS);

MethodHandle strlenMethod =

Linker.nativeLinker().downcallHandle(foreignFuncAddr, strlen_sig);

var ret = (long) strlenMethod.invokeExact(arena.allocateFrom("Bambi"));

System.out.println("Return value " + ret);

}

}