Implement task IDs

Author: Stjepan Glavina

Cargo.toml

@@ -19,6 +19,7 @@ async-spawn = { path = "async-spawn" }
 crossbeam = "0.7.1"
 futures-preview = "0.3.0-alpha.16"
 lazy_static = "1.3.0"
+libc = "0.2.58"
 num_cpus = "1.10.0"
 pin-utils = "0.1.0-alpha.4"
 

src/task.rs

@@ -143,6 +143,7 @@ impl Builder {
         }
 
         let task = Task(Arc::new(Inner {
+            id: TaskId::new(),
             name: self.name.take(),
             locals: RefCell::new(HashMap::default()),
         }));
@@ -176,9 +177,10 @@ impl Builder {
 ///
 /// # Panics
 ///
-/// This function will panic if not called within the context of a task spawned by [`spawn`] or
-/// [`Builder::spawn`].
+/// This function will panic if not called within the context of a task created by [`block_on`],
+/// [`spawn`], or [`Builder::spawn`].
 ///
+/// [`block_on`]: fn.block_on.html
 /// [`spawn`]: fn.spawn.html
 /// [`Builder::spawn`]: struct.Builder.html#method.spawn
 ///
@@ -195,7 +197,7 @@ pub fn current() -> Task {
     TASK.with(|task| {
         let raw = task
             .get()
-            .expect("`task::current()` called outside the context of a spawned task");
+            .expect("`task::current()` called outside the context of a task");
         unsafe { Task::clone(&*raw) }
     })
 }
@@ -211,6 +213,7 @@ thread_local! {
 pub struct Task(Arc<Inner>);
 
 struct Inner {
+    id: TaskId,
     name: Option<String>,
     locals: LocalMap,
 }
@@ -219,6 +222,11 @@ unsafe impl Send for Inner {}
 unsafe impl Sync for Inner {}
 
 impl Task {
+    /// Gets the task's unique identifier.
+    pub fn id(&self) -> TaskId {
+        self.0.id
+    }
+
     /// Returns the name of this task.
     ///
     /// The name is configured by [`Builder::name`] before spawning.
@@ -235,6 +243,40 @@ impl fmt::Debug for Task {
     }
 }
 
+/// A unique identifier for a task.
+///
+/// # Examples
+///
+/// ```
+/// # #![feature(async_await)]
+/// use async_std::task;
+///
+/// # async_std::task::block_on(async {
+/// task::block_on(async {
+///     println!("id = {:?}", task::current().id());
+/// })
+/// # });
+/// ```
+#[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
+pub struct TaskId(u64);
+
+impl TaskId {
+    fn new() -> TaskId {
+        use std::i64;
+        use std::sync::atomic::{AtomicU64, Ordering};
+
+        static COUNTER: AtomicU64 = AtomicU64::new(1);
+
+        let id = COUNTER.fetch_add(1, Ordering::Relaxed);
+        if id > i64::MAX as u64 {
+            unsafe {
+                libc::abort();
+            }
+        }
+        TaskId(id)
+    }
+}
+
 /// Declares task-local values.
 ///
 /// The macro wraps any number of static declarations and makes them task-local. Attributes and
@@ -306,9 +348,10 @@ impl<T: Send + 'static> LocalKey<T> {
     ///
     /// # Panics
     ///
-    /// This method will panic if not called within the context of a task spawned by [`spawn`] or
-    /// [`Builder::spawn`].
+    /// This function will panic if not called within the context of a task created by
+    /// [`block_on`], [`spawn`], or [`Builder::spawn`].
     ///
+    /// [`block_on`]: fn.block_on.html
     /// [`spawn`]: fn.spawn.html
     /// [`Builder::spawn`]: struct.Builder.html#method.spawn
     ///