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use std::future::Future;
use std::marker::PhantomData;
use std::mem;
use std::pin::Pin;
use std::process::abort;
use std::sync::atomic::AtomicBool;
use std::sync::atomic::Ordering;
use std::sync::Arc;
use std::task::Context;
use std::task::Poll;
use std::task::RawWaker;
use std::task::RawWakerVTable;
use std::task::Waker;
use std::thread;
use std::thread::Thread;
pub fn abort_on_panic<R>(f: impl FnOnce() -> R) -> R {
struct Bomb;
impl Drop for Bomb {
fn drop(&mut self) {
abort();
}
}
let bomb = Bomb;
let r = f();
mem::forget(bomb);
r
}
#[derive(Debug)]
pub struct Yields(pub usize);
impl Future for Yields {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<()> {
if self.0 == 0 {
Poll::Ready(())
} else {
self.0 -= 1;
cx.waker().wake_by_ref();
Poll::Pending
}
}
}
pub fn block_on<F: Future>(f: F) -> F::Output {
static VTABLE: RawWakerVTable = RawWakerVTable::new(
|clone_me| {
let clone_me = unsafe { Arc::from_raw(clone_me as *const Unparker) };
mem::forget(clone_me.clone());
RawWaker::new(Arc::into_raw(clone_me) as *const (), &VTABLE)
},
|wake_me| unsafe { Arc::from_raw(wake_me as *const Unparker) }.unpark(),
|wake_me_by_ref| unsafe { &*(wake_me_by_ref as *const Unparker) }.unpark(),
|drop_me| drop(unsafe { Arc::from_raw(drop_me as *const Unparker) }),
);
let parker = Parker::new();
let waker = {
let raw = RawWaker::new(Arc::into_raw(parker.unparker()) as *const (), &VTABLE);
unsafe { Waker::from_raw(raw) }
};
let mut f = f;
let mut cx = Context::from_waker(&waker);
loop {
match unsafe { Pin::new_unchecked(&mut f) }.poll(&mut cx) {
Poll::Pending => parker.park(),
Poll::Ready(val) => return val,
}
}
}
struct ParkerInner {
parked: AtomicBool,
thread: Thread,
_marker: PhantomData<*mut ()>,
}
impl ParkerInner {
fn new() -> ParkerInner {
ParkerInner {
parked: AtomicBool::new(false),
thread: thread::current(),
_marker: PhantomData,
}
}
fn park(&self) {
while !self.parked.load(Ordering::Relaxed) {
thread::park();
}
self.parked.store(false, Ordering::Relaxed);
}
fn unpark(&self) {
self.parked.store(true, Ordering::Relaxed);
self.thread.unpark();
}
}
pub struct Parker(Arc<ParkerInner>);
impl Parker {
pub fn new() -> Parker {
Parker(Arc::new(ParkerInner::new()))
}
pub fn park(&self) {
self.0.park();
}
pub fn unparker(&self) -> Arc<Unparker> {
let cloned = self.0.clone();
unsafe { mem::transmute(cloned) }
}
}
pub struct Unparker(ParkerInner);
impl Unparker {
pub fn unpark(&self) {
self.0.unpark();
}
}
unsafe impl Send for Unparker {}
unsafe impl Sync for Unparker {}