Improve and deduplicate Rust code

src/main/rust/bridge.rs

@@ -3,23 +3,21 @@ use jni::{
     sys::jlong,
     JNIEnv,
 };
+use starship_battery::{Battery, Manager};
 
-use crate::{
-    create_manager, drop_battery, drop_manager, get_batteries, throw_io_exception, update_battery,
-};
+use crate::{create_manager, get_batteries, update_battery, util::drop_box};
 
 #[no_mangle]
 pub extern "system" fn Java_net_lostluma_battery_impl_ManagerImpl_create<'a>(
     mut env: JNIEnv<'a>,
     _class: JClass<'a>,
 ) -> jlong {
     match create_manager() {
-        Ok(value) => value,
-        Err(error) => {
-            throw_io_exception(&mut env, error);
-            jlong::default()
-        }
+        Ok(ptr) => return ptr,
+        Err(error) => error.throw(&mut env),
     }
+
+    jlong::default()
 }
 
 #[no_mangle]
@@ -28,12 +26,11 @@ pub extern "system" fn Java_net_lostluma_battery_impl_ManagerImpl_batteries0<'a>
     this: JObject<'a>,
 ) -> JObjectArray<'a> {
     match get_batteries(&mut env, &this) {
-        Ok(value) => value,
-        Err(error) => {
-            throw_io_exception(&mut env, error);
-            JObjectArray::default()
-        }
+        Ok(batteries) => return batteries,
+        Err(error) => error.throw(&mut env),
     }
+
+    JObjectArray::default()
 }
 
 #[no_mangle]
@@ -42,7 +39,7 @@ pub extern "system" fn Java_net_lostluma_battery_impl_ManagerImpl_drop<'a>(
     _this: JObject<'a>,
     ptr: jlong,
 ) {
-    drop_manager(ptr);
+    drop_box::<Manager>(ptr);
 }
 
 #[no_mangle]
@@ -51,7 +48,7 @@ pub extern "system" fn Java_net_lostluma_battery_impl_BatteryImpl_update0<'a>(
     this: JObject<'a>,
 ) {
     if let Err(error) = update_battery(&mut env, &this) {
-        throw_io_exception(&mut env, error);
+        error.throw(&mut env);
     }
 }
 
@@ -61,5 +58,5 @@ pub extern "system" fn Java_net_lostluma_battery_impl_ManagerImpl_dropBattery<'a
     _this: JObject<'a>,
     ptr: jlong,
 ) {
-    drop_battery(ptr)
+    drop_box::<Battery>(ptr);
 }

src/main/rust/lib.rs

@@ -12,7 +12,7 @@ use starship_battery::{
     },
     Battery, Manager,
 };
-use util::{as_descriptor, get_enum_member, get_ptr, ToJString};
+use util::{as_descriptor, get_enum_member, into_box, pull_box, ToJString};
 
 const STRING_CLASS: &str = "java/lang/String";
 const IO_EXCEPTION_CLASS: &str = "java/io/IOException";
@@ -30,6 +30,13 @@ struct Error {
     message: String, // Used as IOError message
 }
 
+impl Error {
+    fn throw(self, env: &mut JNIEnv) {
+        env.throw_new(IO_EXCEPTION_CLASS, self.message)
+            .expect("throw exception");
+    }
+}
+
 impl From<jni::errors::Error> for Error {
     fn from(value: jni::errors::Error) -> Self {
         Error {
@@ -50,12 +57,11 @@ type Result<T> = result::Result<T, Error>;
 
 fn create_manager() -> Result<i64> {
     let manager = Manager::new()?;
-    Ok(Box::into_raw(Box::from(manager)) as jlong)
+    Ok(into_box(manager) as jlong)
 }
 
 fn get_batteries<'a>(env: &mut JNIEnv<'a>, this: &JObject<'a>) -> Result<JObjectArray<'a>> {
-    let ptr = get_ptr(env, this)?;
-    let manager = unsafe { &mut *(ptr as *mut Manager) };
+    let manager = pull_box::<Manager>(env, this)?;
 
     let mut count = 0;
     let mut batteries: Vec<Battery> = Vec::new();
@@ -78,11 +84,6 @@ fn get_batteries<'a>(env: &mut JNIEnv<'a>, this: &JObject<'a>) -> Result<JObject
     Ok(array)
 }
 
-fn drop_manager<'a>(ptr: jlong) {
-    #[allow(unused_variables)]
-    let manager = unsafe { Box::from_raw(ptr as *mut Manager) };
-}
-
 fn create_battery<'a>(
     env: &mut JNIEnv<'a>,
     parent: &JObject<'a>,
@@ -94,8 +95,7 @@ fn create_battery<'a>(
     let model = battery.model().to_jstring(env)?;
     let serial_number = battery.serial_number().to_jstring(env)?;
 
-    let ptr = Box::into_raw(Box::from(battery)) as jlong;
-
+    let ptr = into_box(battery);
     let class = env.find_class(BATTERY_CLASS)?;
 
     let object = env.new_object(
@@ -112,8 +112,8 @@ fn update_battery<'a>(env: &mut JNIEnv<'a>, this: &JObject<'a>) -> Result<()> {
         .get_field(this, "manager", as_descriptor(MANAGER_CLASS))?
         .l()?;
 
-    let battery = unsafe { &mut *(get_ptr(env, this)? as *mut Battery) };
-    let manager = unsafe { &mut *(get_ptr(env, &parent)? as *mut Manager) };
+    let battery = pull_box::<Battery>(env, this)?;
+    let manager = pull_box::<Manager>(env, &parent)?;
 
     manager.refresh(battery)?;
 
@@ -166,13 +166,3 @@ fn update_battery<'a>(env: &mut JNIEnv<'a>, this: &JObject<'a>) -> Result<()> {
 
     Ok(())
 }
-
-fn drop_battery<'a>(ptr: jlong) {
-    #[allow(unused_variables)]
-    let battery = unsafe { Box::from_raw(ptr as *mut Battery) };
-}
-
-fn throw_io_exception<'a>(env: &mut JNIEnv<'a>, error: Error) {
-    env.throw_new(IO_EXCEPTION_CLASS, error.message)
-        .expect("throw exception");
-}

src/main/rust/util.rs

@@ -10,8 +10,22 @@ pub fn as_descriptor(class: &str) -> String {
     format!("L{class};")
 }
 
-pub fn get_ptr<'a>(env: &mut JNIEnv<'a>, this: &JObject<'a>) -> Result<jlong> {
-    Ok(env.get_field(this, "ptr", "J")?.try_into()?)
+pub fn into_box<T>(t: T) -> jlong {
+    Box::into_raw(Box::from(t)) as jlong
+}
+
+pub fn drop_box<T>(ptr: jlong) {
+    #[allow(unused_variables)]
+    let value = unsafe { Box::from_raw(ptr as *mut T) };
+}
+
+fn get_pointer(env: &mut JNIEnv, object: &JObject) -> Result<jlong> {
+    Ok(env.get_field(object, "ptr", "J")?.j()?)
+}
+
+pub fn pull_box<'r, T>(env: &mut JNIEnv, object: &JObject) -> Result<&'r mut T> {
+    let pointer = get_pointer(env, object)?;
+    Ok(unsafe { &mut *(pointer as *mut T) })
 }
 
 pub fn get_enum_member<'a>(