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|
use std::{future::Future, sync::Arc, sync::Mutex};
use async_task::FallibleTask;
use super::{executor::global_executor, select, CondWait, Either, Executor};
/// TaskGroup is a group of spawned tasks.
///
/// # Example
///
/// ```
///
/// use std::sync::Arc;
///
/// use karyon_core::async_util::TaskGroup;
///
/// async {
///
/// let ex = Arc::new(smol::Executor::new());
/// let group = TaskGroup::new(ex);
///
/// group.spawn(smol::Timer::never(), |_| async {});
///
/// group.cancel().await;
///
/// };
///
/// ```
///
pub struct TaskGroup<'a> {
tasks: Mutex<Vec<TaskHandler>>,
stop_signal: Arc<CondWait>,
executor: Executor<'a>,
}
impl TaskGroup<'static> {
/// Creates a new task group without providing an executor
///
/// This will Spawn a task onto a global executor (single-threaded by default).
pub fn new_without_executor() -> Self {
Self {
tasks: Mutex::new(Vec::new()),
stop_signal: Arc::new(CondWait::new()),
executor: global_executor(),
}
}
}
impl<'a> TaskGroup<'a> {
/// Creates a new task group
pub fn new(executor: Executor<'a>) -> Self {
Self {
tasks: Mutex::new(Vec::new()),
stop_signal: Arc::new(CondWait::new()),
executor,
}
}
/// Spawns a new task and calls the callback after it has completed
/// or been canceled. The callback will have the `TaskResult` as a
/// parameter, indicating whether the task completed or was canceled.
pub fn spawn<T, Fut, CallbackF, CallbackFut>(&self, fut: Fut, callback: CallbackF)
where
T: Send + Sync + 'a,
Fut: Future<Output = T> + Send + 'a,
CallbackF: FnOnce(TaskResult<T>) -> CallbackFut + Send + 'a,
CallbackFut: Future<Output = ()> + Send + 'a,
{
let task = TaskHandler::new(
self.executor.clone(),
fut,
callback,
self.stop_signal.clone(),
);
self.tasks.lock().unwrap().push(task);
}
/// Checks if the task group is empty.
pub fn is_empty(&self) -> bool {
self.tasks.lock().unwrap().is_empty()
}
/// Get the number of the tasks in the group.
pub fn len(&self) -> usize {
self.tasks.lock().unwrap().len()
}
/// Cancels all tasks in the group.
pub async fn cancel(&self) {
self.stop_signal.broadcast().await;
loop {
let task = self.tasks.lock().unwrap().pop();
if let Some(t) = task {
t.cancel().await
} else {
break;
}
}
}
}
/// The result of a spawned task.
#[derive(Debug)]
pub enum TaskResult<T> {
Completed(T),
Cancelled,
}
impl<T: std::fmt::Debug> std::fmt::Display for TaskResult<T> {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
match self {
TaskResult::Cancelled => write!(f, "Task cancelled"),
TaskResult::Completed(res) => write!(f, "Task completed: {:?}", res),
}
}
}
/// TaskHandler
pub struct TaskHandler {
task: FallibleTask<()>,
cancel_flag: Arc<CondWait>,
}
impl<'a> TaskHandler {
/// Creates a new task handle
fn new<T, Fut, CallbackF, CallbackFut>(
ex: Executor<'a>,
fut: Fut,
callback: CallbackF,
stop_signal: Arc<CondWait>,
) -> TaskHandler
where
T: Send + Sync + 'a,
Fut: Future<Output = T> + Send + 'a,
CallbackF: FnOnce(TaskResult<T>) -> CallbackFut + Send + 'a,
CallbackFut: Future<Output = ()> + Send + 'a,
{
let cancel_flag = Arc::new(CondWait::new());
let cancel_flag_c = cancel_flag.clone();
let task = ex
.spawn(async move {
//start_signal.signal().await;
// Waits for either the stop signal or the task to complete.
let result = select(stop_signal.wait(), fut).await;
let result = match result {
Either::Left(_) => TaskResult::Cancelled,
Either::Right(res) => TaskResult::Completed(res),
};
// Call the callback with the result.
callback(result).await;
cancel_flag_c.signal().await;
})
.fallible();
TaskHandler { task, cancel_flag }
}
/// Cancels the task.
async fn cancel(self) {
self.cancel_flag.wait().await;
self.task.cancel().await;
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::{future, sync::Arc};
#[test]
fn test_task_group() {
let ex = Arc::new(smol::Executor::new());
smol::block_on(ex.clone().run(async move {
let group = Arc::new(TaskGroup::new(ex));
group.spawn(future::ready(0), |res| async move {
assert!(matches!(res, TaskResult::Completed(0)));
});
group.spawn(future::pending::<()>(), |res| async move {
assert!(matches!(res, TaskResult::Cancelled));
});
let groupc = group.clone();
group.spawn(
async move {
groupc.spawn(future::pending::<()>(), |res| async move {
assert!(matches!(res, TaskResult::Cancelled));
});
},
|res| async move {
assert!(matches!(res, TaskResult::Completed(_)));
},
);
// Do something
smol::Timer::after(std::time::Duration::from_millis(50)).await;
group.cancel().await;
}));
}
#[test]
fn test_task_group_without_executor() {
smol::block_on(async {
let group = Arc::new(TaskGroup::new_without_executor());
group.spawn(future::ready(0), |res| async move {
assert!(matches!(res, TaskResult::Completed(0)));
});
group.spawn(future::pending::<()>(), |res| async move {
assert!(matches!(res, TaskResult::Cancelled));
});
let groupc = group.clone();
group.spawn(
async move {
groupc.spawn(future::pending::<()>(), |res| async move {
assert!(matches!(res, TaskResult::Cancelled));
});
},
|res| async move {
assert!(matches!(res, TaskResult::Completed(_)));
},
);
// Do something
smol::Timer::after(std::time::Duration::from_millis(50)).await;
group.cancel().await;
});
}
}
|
