From 54e908530db0fbd7f1b4aec5bd50b19d5632ddcf Mon Sep 17 00:00:00 2001
From: TudbuT <forge-public@mail.tudbut.de>
Date: Sun, 14 Jul 2024 01:56:36 +0000
Subject: [PATCH] Initial commit

---
 .gitignore        |  1 +
 Cargo.lock        | 16 ++++++++++++
 Cargo.toml        |  7 +++++
 examples/basic.rs | 13 ++++++++++
 src/lib.rs        | 27 +++++++++++++++++++
 src/rt/mod.rs     | 66 +++++++++++++++++++++++++++++++++++++++++++++++
 src/rt/waker.rs   | 37 ++++++++++++++++++++++++++
 7 files changed, 167 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 examples/basic.rs
 create mode 100644 src/lib.rs
 create mode 100644 src/rt/mod.rs
 create mode 100644 src/rt/waker.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..71cbd31
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,16 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "microasync"
+version = "0.1.0"
+dependencies = [
+ "microlock",
+]
+
+[[package]]
+name = "microlock"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "849d9daa132b37b3082c2ef186343573aedf6ebc7e1b57343e9278e81a2b5b20"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..48b8f75
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "microasync"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+microlock = "0.2.0"
diff --git a/examples/basic.rs b/examples/basic.rs
new file mode 100644
index 0000000..6da307f
--- /dev/null
+++ b/examples/basic.rs
@@ -0,0 +1,13 @@
+use std::time::Duration;
+
+use microasync::rt::{MiniAsync, TimerDuration};
+
+fn main() {
+    let rt = MiniAsync::new(TimerDuration::Real(Duration::from_millis(20)));
+    rt.add_task(async_main());
+    rt.run_until_empty();
+}
+
+async fn async_main() {
+    println!("Hello from async!")
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..f9bfa08
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,27 @@
+pub mod rt;
+
+use std::{cell::RefCell, ptr};
+
+use rt::MiniAsync;
+thread_local! {
+    static RUNTIME: RefCell<*const MiniAsync> = const { RefCell::new(ptr::null()) };
+}
+
+pub(crate) fn current_runtime(rt: &MiniAsync) {
+    RUNTIME.with_borrow_mut(|x| *x = rt as *const _);
+}
+
+pub(crate) fn exiting_runtime() {
+    RUNTIME.with_borrow_mut(|x| *x = ptr::null());
+}
+
+/// # Safety
+/// The lifetime given out by this function is static but the underlying
+/// struct is not, leading to use after free if this is not paid attention to.
+pub unsafe fn get_runtime() -> &'static MiniAsync {
+    unsafe { &*RUNTIME.with_borrow(|x| *x) }
+}
+
+pub fn runtime(f: impl FnOnce(&MiniAsync)) {
+    f(unsafe { get_runtime() })
+}
diff --git a/src/rt/mod.rs b/src/rt/mod.rs
new file mode 100644
index 0000000..504b074
--- /dev/null
+++ b/src/rt/mod.rs
@@ -0,0 +1,66 @@
+mod waker;
+
+use std::{
+    future::Future,
+    pin::Pin,
+    sync::Mutex,
+    task::{Context, Poll},
+    vec::Vec,
+};
+
+pub use microlock::timer::TimerDuration;
+use microlock::Lock;
+
+use crate::{current_runtime, exiting_runtime};
+
+use self::waker::MicroWaker;
+
+pub type Task<T> = Pin<Box<dyn Future<Output = T>>>;
+
+pub struct MiniAsync {
+    tasks: Vec<Task<()>>,
+    tasks_to_add: Mutex<Vec<Task<()>>>,
+    waker: MicroWaker,
+    wake_attempt_delay: TimerDuration,
+}
+
+impl MiniAsync {
+    pub fn new(wake_attempt_delay: TimerDuration) -> Self {
+        Self {
+            tasks: Vec::new(),
+            tasks_to_add: Mutex::new(Vec::new()),
+            waker: MicroWaker::new(),
+            wake_attempt_delay,
+        }
+    }
+
+    pub fn add_boxed_task(&self, future: Pin<Box<impl Future<Output = ()> + 'static>>) {
+        self.tasks_to_add.lock().unwrap().push(future);
+        self.waker.lock.unlock();
+    }
+
+    pub fn add_task(&self, future: impl Future<Output = ()> + 'static) {
+        self.tasks_to_add.lock().unwrap().push(Box::pin(future));
+        self.waker.lock.unlock();
+    }
+
+    pub fn run_until_empty(mut self) {
+        current_runtime(&self);
+        let waker = self.waker.rust_waker();
+        let mut cx = Context::from_waker(&waker);
+        while !self.tasks.is_empty() {
+            let mut next_tasks = Vec::with_capacity(self.tasks.len());
+            for mut task in self.tasks {
+                match Future::poll(task.as_mut(), &mut cx) {
+                    Poll::Ready(_) => drop(task),
+                    Poll::Pending => next_tasks.push(task),
+                };
+            }
+            next_tasks.append(&mut self.tasks_to_add.lock().unwrap());
+            self.tasks = next_tasks;
+            self.waker.lock.wait_here_for(self.wake_attempt_delay);
+            self.waker.lock.try_lock();
+        }
+        exiting_runtime();
+    }
+}
diff --git a/src/rt/waker.rs b/src/rt/waker.rs
new file mode 100644
index 0000000..ddd17ff
--- /dev/null
+++ b/src/rt/waker.rs
@@ -0,0 +1,37 @@
+use std::task::{RawWaker, RawWakerVTable, Waker};
+
+use microlock::{Lock, TimedLock};
+
+pub struct MicroWaker {
+    pub(crate) lock: TimedLock,
+}
+impl MicroWaker {
+    pub fn new() -> MicroWaker {
+        Self {
+            lock: TimedLock::locked(),
+        }
+    }
+
+    pub fn rust_waker(&self) -> Waker {
+        unsafe { Waker::from_raw(Self::clone(self as *const _ as _)) }
+    }
+
+    fn clone(me: *const ()) -> RawWaker {
+        RawWaker::new(
+            me,
+            &RawWakerVTable::new(Self::clone, Self::wake, Self::wake_by_ref, Self::drop),
+        )
+    }
+
+    unsafe fn wake(me: *const ()) {
+        let me = &*(me as *const Self);
+        me.lock.unlock();
+    }
+
+    unsafe fn wake_by_ref(me: *const ()) {
+        let me = &*(me as *const Self);
+        me.lock.unlock();
+    }
+
+    unsafe fn drop(_me: *const ()) {}
+}