Add support Java bindings

This add support for Java bindings in the bindings/java directory.

bindings/java/rs_src/connection.rs

@@ -0,0 +1,84 @@
+use crate::cursor::Cursor;
+use jni::objects::JClass;
+use jni::sys::jlong;
+use jni::JNIEnv;
+use std::rc::Rc;
+use std::sync::{Arc, Mutex};
+
+#[derive(Clone)]
+pub struct Connection {
+    pub(crate) conn: Arc<Mutex<Rc<limbo_core::Connection>>>,
+    pub(crate) io: Arc<limbo_core::PlatformIO>,
+}
+
+/// Returns a pointer to a `Cursor` object.
+///
+/// The Java application will pass this pointer to native functions,
+/// which will use it to reference the `Cursor` object.
+///
+/// # Arguments
+///
+/// * `_env` - The JNI environment pointer.
+/// * `_class` - The Java class calling this function.
+/// * `connection_ptr` - A pointer to the `Connection` object.
+///
+/// # Returns
+///
+/// A `jlong` representing the pointer to the newly created `Cursor` object.
+#[no_mangle]
+pub extern "system" fn Java_org_github_tursodatabase_limbo_Connection_cursor<'local>(
+    _env: JNIEnv<'local>,
+    _class: JClass<'local>,
+    connection_ptr: jlong,
+) -> jlong {
+    let connection = to_connection(connection_ptr);
+    let cursor = Cursor {
+        array_size: 1,
+        conn: connection.clone(),
+        description: None,
+        rowcount: -1,
+        smt: None,
+    };
+    Box::into_raw(Box::new(cursor)) as jlong
+}
+
+/// Closes the connection and releases the associated resources.
+///
+/// This function is called from the Java side to close the connection
+/// and free the memory allocated for the `Connection` object.
+///
+/// # Arguments
+///
+/// * `_env` - The JNI environment pointer.
+/// * `_class` - The Java class calling this function.
+/// * `connection_ptr` - A pointer to the `Connection` object to be closed.
+#[no_mangle]
+pub unsafe extern "system" fn Java_org_github_tursodatabase_limbo_Connection_close<'local>(
+    _env: JNIEnv<'local>,
+    _class: JClass<'local>,
+    connection_ptr: jlong,
+) {
+    let _boxed_connection = Box::from_raw(connection_ptr as *mut Connection);
+}
+
+#[no_mangle]
+pub extern "system" fn Java_org_github_tursodatabase_limbo_Connection_commit<'local>(
+    _env: &mut JNIEnv<'local>,
+    _class: JClass<'local>,
+    _connection_id: jlong,
+) {
+    unimplemented!()
+}
+
+#[no_mangle]
+pub extern "system" fn Java_org_github_tursodatabase_limbo_Connection_rollback<'local>(
+    _env: &mut JNIEnv<'local>,
+    _class: JClass<'local>,
+    _connection_id: jlong,
+) {
+    unimplemented!()
+}
+
+fn to_connection(connection_ptr: jlong) -> &'static mut Connection {
+    unsafe { &mut *(connection_ptr as *mut Connection) }
+}