Add get world and free string

java/patchbukkit/src/main/java/org/patchbukkit/bridge/NativePatchBukkit.java

@@ -16,6 +16,8 @@ public class NativePatchBukkit {
     private static MethodHandle getAbilitiesNative;
     private static MethodHandle setAbilitiesNative;
     private static MethodHandle getLocationNative;
+    private static MethodHandle getWorldNative;
+    private static MethodHandle freeStringNative;
 
     // Struct layout matching Rust's #[repr(C)] AbilitiesFFI
     private static final StructLayout ABILITIES_LAYOUT =
@@ -223,6 +225,19 @@ public class NativePatchBukkit {
                 ValueLayout.ADDRESS // out pointer to Vec3FFI
             )
         );
+
+        // const char* rust_get_world(const char* uuid)
+        getWorldNative = LINKER.downcallHandle(
+            MemorySegment.ofAddress(getWorldAddr),
+            FunctionDescriptor.of(ValueLayout.ADDRESS, ValueLayout.ADDRESS)
+        );
+
+        // void rust_free_string(const char* str)
+        freeStringNative = LINKER.downcallHandle(
+            MemorySegment.ofAddress(freeStringAddr),
+            FunctionDescriptor.ofVoid(ValueLayout.ADDRESS)
+        );
+
     }
 
     /**
@@ -348,4 +363,40 @@ public class NativePatchBukkit {
             throw new RuntimeException("Failed to call native getLocation", t);
         }
     }
+
+    /**
+     * Free a string allocated by the Rust side.
+     */
+    private static void freeRustString(MemorySegment ptr) {
+        try {
+            freeStringNative.invokeExact(ptr);
+        } catch (Throwable t) {
+            throw new RuntimeException("Failed to free Rust string", t);
+        }
+    }
+
+    /**
+     * Get the world UUID for an entity.
+     */
+    public static String getWorld(UUID entityUuid) {
+        try (Arena arena = Arena.ofConfined()) {
+            MemorySegment uuidStr = arena.allocateFrom(entityUuid.toString());
+            MemorySegment resultPtr = (MemorySegment) getWorldNative.invokeExact(uuidStr);
+
+            if (resultPtr.equals(MemorySegment.NULL)) {
+                return null;
+            }
+
+            // Read the string, then free the Rust-allocated memory
+            try {
+                String result = resultPtr.reinterpret(Long.MAX_VALUE).getString(0);
+                return result;
+            } finally {
+                freeRustString(resultPtr);
+            }
+        } catch (Throwable t) {
+            throw new RuntimeException("Failed to call native getWorld", t);
+        }
+    }
+
 }

rust/src/java/native_callbacks/memory.rs

@@ -0,0 +1,9 @@
+use std::ffi::{CString, c_char};
+
+pub extern "C" fn rust_free_string(ptr: *mut c_char) {
+    if !ptr.is_null() {
+        unsafe {
+            drop(CString::from_raw(ptr));
+        }
+    }
+}

rust/src/java/native_callbacks/mod.rs

@@ -7,6 +7,7 @@ use pumpkin::plugin::Context;
 pub mod abilities;
 pub mod events;
 pub mod location;
+pub mod memory;
 pub mod message;
 pub mod utils;
 pub mod world;
@@ -39,6 +40,8 @@ pub fn initialize_callbacks(jvm: &Jvm) -> Result<()> {
     let get_abilities_addr = abilities::rust_get_abilities as *const () as i64;
     let set_abilities_addr = abilities::rust_set_abilities as *const () as i64;
     let get_location_addr = location::rust_get_location as *const () as i64;
+    let free_string_addr = memory::rust_free_string as *const () as i64;
+    let get_world_addr = world::rust_get_world as *const () as i64;
 
     jvm.invoke_static(
         "org.patchbukkit.bridge.NativePatchBukkit",
@@ -49,6 +52,8 @@ pub fn initialize_callbacks(jvm: &Jvm) -> Result<()> {
             InvocationArg::try_from(get_abilities_addr)?.into_primitive()?,
             InvocationArg::try_from(set_abilities_addr)?.into_primitive()?,
             InvocationArg::try_from(get_location_addr)?.into_primitive()?,
+            InvocationArg::try_from(free_string_addr)?.into_primitive()?,
+            InvocationArg::try_from(get_world_addr)?.into_primitive()?,
         ],
     )?;
 

rust/src/java/native_callbacks/world.rs

@@ -4,24 +4,36 @@ use pumpkin::command::args::entities::{EntitySelectorType, TargetSelector};
 
 use crate::java::native_callbacks::{CALLBACK_CONTEXT, utils::get_string};
 
-pub extern "C" fn rust_get_world(uuid_ptr: *const c_char) -> *const c_char {
-    let uuid_str = get_string(uuid_ptr);
-    if let Some(ctx) = CALLBACK_CONTEXT.get() {
-        let uuid = uuid::Uuid::parse_str(&uuid_str).unwrap();
-        let entity = ctx
-            .plugin_context
-            .server
-            .select_entities(&TargetSelector::new(EntitySelectorType::Uuid(uuid)), None);
-        if entity.len() == 1 {
-            let entity = entity.first().unwrap().get_entity();
-            let world = entity.world.load();
-
-            let cstring = match CString::new(world.dimension.minecraft_name) {
-                Ok(s) => s,
-                Err(_) => return std::ptr::null(),
-            };
-        }
+pub extern "C" fn rust_get_world(entity_uuid_ptr: *const c_char) -> *mut c_char {
+    if entity_uuid_ptr.is_null() {
+        return std::ptr::null_mut();
     }
 
-    std::ptr::null()
+    let entity_uuid = get_string(entity_uuid_ptr);
+
+    let Some(ctx) = CALLBACK_CONTEXT.get() else {
+        return std::ptr::null_mut();
+    };
+
+    let Ok(uuid) = uuid::Uuid::parse_str(&entity_uuid) else {
+        return std::ptr::null_mut();
+    };
+
+    let entities = ctx
+        .plugin_context
+        .server
+        .select_entities(&TargetSelector::new(EntitySelectorType::Uuid(uuid)), None);
+
+    if entities.len() != 1 {
+        return std::ptr::null_mut();
+    }
+
+    let entity = entities.first().unwrap().get_entity();
+    let world = entity.world.load();
+    let world_uuid = world.uuid.to_string();
+
+    match CString::new(world_uuid) {
+        Ok(cstring) => cstring.into_raw(), // Transfers ownership to caller
+        Err(_) => std::ptr::null_mut(),
+    }
 }