From 4894e500cf8c60c2971d186d6a21b994bf36e7d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= <biwanczuk@gmail.com>
Date: Sat, 4 Mar 2023 20:10:31 -0400
Subject: refactor: move TaskQueue from deno_runtime to deno_core (#18016)

This utility is useful in several contexts so it seems reasonable to
have it in `deno_core`.
---
 runtime/ops/utils.rs | 147 ---------------------------------------------------
 1 file changed, 147 deletions(-)

(limited to 'runtime/ops/utils.rs')

diff --git a/runtime/ops/utils.rs b/runtime/ops/utils.rs
index bdbe7f6d0..e7bf02c10 100644
--- a/runtime/ops/utils.rs
+++ b/runtime/ops/utils.rs
@@ -2,13 +2,6 @@
 
 use deno_core::error::custom_error;
 use deno_core::error::AnyError;
-use deno_core::futures::task::AtomicWaker;
-use deno_core::futures::Future;
-use deno_core::parking_lot::Mutex;
-use std::collections::LinkedList;
-use std::sync::atomic::AtomicBool;
-use std::sync::atomic::Ordering;
-use std::sync::Arc;
 
 /// A utility function to map OsStrings to Strings
 pub fn into_string(s: std::ffi::OsString) -> Result<String, AnyError> {
@@ -17,143 +10,3 @@ pub fn into_string(s: std::ffi::OsString) -> Result<String, AnyError> {
     custom_error("InvalidData", message)
   })
 }
-
-#[derive(Default)]
-struct TaskQueueTaskWaker {
-  is_ready: AtomicBool,
-  waker: AtomicWaker,
-}
-
-#[derive(Default)]
-struct TaskQueueTasks {
-  is_running: bool,
-  wakers: LinkedList<Arc<TaskQueueTaskWaker>>,
-}
-
-/// A queue that executes tasks sequentially one after the other
-/// ensuring order and that no task runs at the same time as another.
-///
-/// Note that tokio's semaphore doesn't seem to maintain order
-/// and so we can't use that in the code that uses this or use
-/// that here.
-#[derive(Clone, Default)]
-pub struct TaskQueue {
-  tasks: Arc<Mutex<TaskQueueTasks>>,
-}
-
-impl TaskQueue {
-  /// Alternate API that acquires a permit internally
-  /// for the duration of the future.
-  #[cfg(test)]
-  pub async fn queue<R>(&self, future: impl Future<Output = R>) -> R {
-    let _permit = self.acquire().await;
-    future.await
-  }
-
-  /// Acquires a permit where the tasks are executed one at a time
-  /// and in the order that they were acquired.
-  pub async fn acquire(&self) -> TaskQueuePermit {
-    let acquire = TaskQueuePermitAcquire::new(self.tasks.clone());
-    acquire.await;
-    TaskQueuePermit {
-      tasks: self.tasks.clone(),
-    }
-  }
-}
-
-/// A permit that when dropped will allow another task to proceed.
-pub struct TaskQueuePermit {
-  tasks: Arc<Mutex<TaskQueueTasks>>,
-}
-
-impl Drop for TaskQueuePermit {
-  fn drop(&mut self) {
-    let next_item = {
-      let mut tasks = self.tasks.lock();
-      let next_item = tasks.wakers.pop_front();
-      tasks.is_running = next_item.is_some();
-      next_item
-    };
-    if let Some(next_item) = next_item {
-      next_item.is_ready.store(true, Ordering::SeqCst);
-      next_item.waker.wake();
-    }
-  }
-}
-
-struct TaskQueuePermitAcquire {
-  tasks: Arc<Mutex<TaskQueueTasks>>,
-  initialized: AtomicBool,
-  waker: Arc<TaskQueueTaskWaker>,
-}
-
-impl TaskQueuePermitAcquire {
-  pub fn new(tasks: Arc<Mutex<TaskQueueTasks>>) -> Self {
-    Self {
-      tasks,
-      initialized: Default::default(),
-      waker: Default::default(),
-    }
-  }
-}
-
-impl Future for TaskQueuePermitAcquire {
-  type Output = ();
-
-  fn poll(
-    self: std::pin::Pin<&mut Self>,
-    cx: &mut std::task::Context<'_>,
-  ) -> std::task::Poll<Self::Output> {
-    // update with the latest waker
-    self.waker.waker.register(cx.waker());
-
-    // ensure this is initialized
-    if !self.initialized.swap(true, Ordering::SeqCst) {
-      let mut tasks = self.tasks.lock();
-      if !tasks.is_running {
-        tasks.is_running = true;
-        return std::task::Poll::Ready(());
-      }
-      tasks.wakers.push_back(self.waker.clone());
-      return std::task::Poll::Pending;
-    }
-
-    // check if we're ready to run
-    if self.waker.is_ready.load(Ordering::SeqCst) {
-      std::task::Poll::Ready(())
-    } else {
-      std::task::Poll::Pending
-    }
-  }
-}
-
-#[cfg(test)]
-mod tests {
-  use deno_core::futures;
-  use deno_core::parking_lot::Mutex;
-  use std::sync::Arc;
-
-  use super::TaskQueue;
-
-  #[tokio::test]
-  async fn task_queue_runs_one_after_other() {
-    let task_queue = TaskQueue::default();
-    let mut tasks = Vec::new();
-    let data = Arc::new(Mutex::new(0));
-    for i in 0..100 {
-      let data = data.clone();
-      tasks.push(task_queue.queue(async move {
-        tokio::task::spawn_blocking(move || {
-          let mut data = data.lock();
-          if *data != i {
-            panic!("Value was not equal.");
-          }
-          *data = i + 1;
-        })
-        .await
-        .unwrap();
-      }));
-    }
-    futures::future::join_all(tasks).await;
-  }
-}
-- 
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