feat(java): xxh3 hash checking

dist/java/src/mp/code/BufferController.java

@@ -13,12 +13,12 @@ public class BufferController {
 		this.ptr = ptr;
 	}
 
-	public static native String get_name(long self);
+	private static native String get_name(long self);
 	public String getName() {
 		return get_name(this.ptr);
 	}
 
-	public static native String get_content(long self) throws CodeMPException;
+	private static native String get_content(long self) throws CodeMPException;
 	public String getContent() throws CodeMPException {
 		return get_content(this.ptr);
 	}
@@ -40,7 +40,6 @@ public class BufferController {
 
 	private static native void free(long self);
 	@Override
-	@SuppressWarnings("removal")
 	protected void finalize() {
 		free(this.ptr);
 	}

dist/java/src/mp/code/Client.java

@@ -36,7 +36,6 @@ public class Client {
 	
 	private static native void free(long self);
 	@Override
-	@SuppressWarnings("removal") // muh java 8
 	protected void finalize() {
 		free(this.ptr);
 	}

dist/java/src/mp/code/CursorController.java

@@ -29,7 +29,6 @@ public class CursorController {
 
 	private static native void free(long self);
 	@Override
-	@SuppressWarnings("removal")
 	protected void finalize() {
 		free(this.ptr);
 	}

dist/java/src/mp/code/Workspace.java

@@ -79,7 +79,6 @@ public class Workspace {
 
 	private static native void free(long self);
 	@Override
-	@SuppressWarnings("removal")
 	protected void finalize() {
 		free(this.ptr);
 	}

dist/java/src/mp/code/data/TextChange.java

@@ -4,10 +4,18 @@ public class TextChange {
 	public final long start;
 	public final long end;
 	public final String content;
+	private final long hash; // xxh3 hash
 
-	public TextChange(long start, long end, String content) {
+	public TextChange(long start, long end, String content, long hash) {
 		this.start = start;
 		this.end = end;
 		this.content = content;
+		this.hash = hash;
+	}
+
+	private static native long hash(String content);
+	public boolean hashMatches(String content) {
+		// 0 is Rust default value and a very unlikely hash
+		return hash == 0L || this.hash == hash(content);
 	}
 }

src/ffi/java/buffer.rs

@@ -1,4 +1,5 @@
-use jni::{objects::{JClass, JObject, JValueGen}, sys::{jlong, jobject, jstring}, JNIEnv};
+use jni::{objects::{JClass, JObject, JString, JValueGen}, sys::{jlong, jobject, jstring}, JNIEnv};
+use xxhash_rust::xxh3::xxh3_64;
 
 use crate::api::Controller;
 
@@ -67,11 +68,12 @@ fn recv_jni(env: &mut JNIEnv, change: Option<crate::api::TextChange>) -> jobject
 				.and_then(|class| {
 					env.new_object(
 						class,
-						"(JJLjava/lang/String;)V",
+						"(JJLjava/lang/String;J)V",
 						&[
 							JValueGen::Long(jlong::from(event.start)),
 							JValueGen::Long(jlong::from(event.end)),
 							JValueGen::Object(&content),
+							JValueGen::Long(event.hash.unwrap_or_default())
 						]
 					)
 				}).jexcept(env)
@@ -116,3 +118,18 @@ pub extern "system" fn Java_mp_code_BufferController_free(
 	let _ = unsafe { Box::from_raw(self_ptr as *mut crate::cursor::Controller) };
 }
 
+
+/// Calculates the XXH3 hash for a given String.
+#[no_mangle]
+pub extern "system" fn Java_mp_code_data_TextChange_hash<'local>(
+	mut env: JNIEnv,
+	_class: JClass<'local>,
+	content: JString<'local>,
+) -> jlong {
+	let content: String = env.get_string(&content)
+		.map(|s| s.into())
+		.jexcept(&mut env);
+
+	let hash = xxh3_64(content.as_bytes());
+	i64::from_ne_bytes(hash.to_ne_bytes())
+}