Added a way to obtain an indication of the current task state

.clippy.toml

@@ -1 +1 @@
-msrv = "1.39"
+msrv = "1.40"

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
       matrix:
         # When updating this, the reminder to update the minimum supported
         # Rust version in Cargo.toml and .clippy.toml.
-        rust: ['1.39']
+        rust: ['1.40']
     steps:
       - uses: actions/checkout@v2
       - name: Install Rust

Cargo.toml

@@ -6,7 +6,7 @@ name = "async-task"
 version = "4.1.0"
 authors = ["Stjepan Glavina <[email protected]>"]
 edition = "2018"
-rust-version = "1.39"
+rust-version = "1.40"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-task"
 description = "Task abstraction for building executors"

src/task.rs

@@ -395,6 +395,23 @@ impl<T> Task<T> {
         let header = ptr as *const Header;
         unsafe { &*header }
     }
+
+    /// Get the current state of the task.
+    ///
+    /// Note that in a multithreaded environment, this state can change immediately after calling this function.
+    pub fn state(&self) -> TaskState {
+        let ptr = self.ptr.as_ptr();
+        let header = ptr as *const Header;
+
+        unsafe {
+            let state = (*header).state.load(Ordering::Acquire);
+            if state & (CLOSED | COMPLETED) != 0 {
+                TaskState::Completed
+            } else {
+                TaskState::Running
+            }
+        }
+    }
 }
 
 impl<T> Drop for Task<T> {
@@ -515,3 +532,14 @@ impl<T> fmt::Debug for FallibleTask<T> {
             .finish()
     }
 }
+
+/// The state of a task.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum TaskState {
+    /// The task is still running.
+    Running,
+
+    /// The task has completed.
+    Completed,
+}