Limit the use of "get_native_id()" to only current thread.

This is a part of #30

We can't get another thread's ID if we didn't store it when it was
created. As we don't have control over that, we can't properly
implement the `ThreadExt::get_native_id()` for any thread which isn't
current.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "thread-priority"
-version = "0.14.0"
+version = "0.15.0"
 authors = ["Victor Polevoy <[email protected]>"]
 description = "Library for managing threads priority and schedule policies"
 repository = "https://github.com/vityafx/thread-priority"

src/unix.rs

@@ -741,14 +741,20 @@ pub trait ThreadExt {
     /// ```rust
     /// use thread_priority::*;
     ///
-    /// assert!(std::thread::current().get_native_id() > 0);
-    fn get_native_id(&self) -> ThreadId {
-        thread_native_id()
-    }
+    /// assert!(std::thread::current().get_native_id().unwrap() > 0);
+    fn get_native_id(&self) -> Result<ThreadId, Error>;
 }
 
 /// Auto-implementation of this trait for the [`std::thread::Thread`].
-impl ThreadExt for std::thread::Thread {}
+impl ThreadExt for std::thread::Thread {
+    fn get_native_id(&self) -> Result<ThreadId, Error> {
+        if self.id() == std::thread::current().id() {
+            Ok(thread_native_id())
+        } else {
+            Err(Error::Priority("The `ThreadExt::get_native_id()` is currently limited to be called on the current thread."))
+        }
+    }
+}
 
 /// Returns current thread id, which is the current OS's native handle.
 /// It may or may not be equal or even related to rust's thread id,

src/windows.rs

@@ -405,9 +405,8 @@ pub trait ThreadExt {
     ///
     /// assert!(!std::thread::current().get_native_id().is_null());
     /// ```
-    fn get_native_id(&self) -> ThreadId {
-        thread_native_id()
-    }
+    fn get_native_id(&self) -> Result<ThreadId, Error>;
+
     /// Sets current thread's ideal processor.
     /// For more info see [`set_current_thread_ideal_processor`].
     ///
@@ -437,4 +436,12 @@ pub trait ThreadExt {
 }
 
 /// Auto-implementation of this trait for the [`std::thread::Thread`].
-impl ThreadExt for std::thread::Thread {}
+impl ThreadExt for std::thread::Thread {
+    fn get_native_id(&self) -> Result<ThreadId, Error> {
+        if self.id() == std::thread::current().id() {
+            Ok(thread_native_id())
+        } else {
+            Err(Error::Priority("The `ThreadExt::get_native_id()` is currently limited to be called on the current thread."))
+        }
+    }
+}

tests/common.rs

@@ -6,3 +6,34 @@ fn should_be_possible_to_reset_the_same_priority() {
     let set_result = thread_priority::set_current_thread_priority(current);
     assert_eq!(set_result, Ok(()));
 }
+
+#[rstest]
+fn should_be_possible_to_get_current_thread_native_id_via_threadext() {
+    use thread_priority::ThreadExt;
+
+    let current = std::thread::current();
+    #[cfg(unix)]
+    assert_eq!(
+        current.get_native_id(),
+        Ok(thread_priority::unix::thread_native_id())
+    );
+    #[cfg(windows)]
+    assert_eq!(
+        current.get_native_id(),
+        Ok(thread_priority::windows::thread_native_id())
+    );
+}
+
+#[rstest]
+fn should_be_impossible_to_get_other_thread_native_id_via_threadext() {
+    use thread_priority::ThreadExt;
+
+    let current = std::thread::current();
+    let another_thread = std::thread::spawn(move || {
+        #[cfg(unix)]
+        assert!(current.get_native_id().is_err());
+        #[cfg(windows)]
+        assert!(current.get_native_id().is_err());
+    });
+    another_thread.join().unwrap();
+}