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use std::fmt;
use std::future::Future;
use std::pin::Pin;
use std::sync::{Arc, Mutex, MutexGuard};
use std::task::{Context, Poll, Waker};
use super::error::{ClientError, NotLeaderError};
use super::serde::{NodeID, ReadRes, WriteRes};
struct RastFutureState<T> {
finished: bool,
result: Option<Result<T, ClientError>>,
waker: Option<Waker>,
}
impl<T: fmt::Debug> fmt::Debug for RastFutureState<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{:?}", self.result)
}
}
#[derive(Debug, Clone)]
struct RastFuture<T> {
state: Arc<Mutex<RastFutureState<T>>>,
}
impl<T> RastFuture<T> {
fn new() -> RastFuture<T> {
RastFuture {
state: Arc::new(Mutex::new(RastFutureState { finished: false, result: None, waker: None })),
}
}
fn fill(&mut self, result: Result<T, ClientError>) {
if let Ok(mut state) = self.state.lock() {
debug_assert_eq!(state.finished, false);
state.finished = true;
state.result = Some(result);
state.waker.iter_mut().for_each(|waker| waker.wake_by_ref());
}
}
fn poll(&self, cx: &mut Context) -> Poll<Result<T, ClientError>> {
let mut state: MutexGuard<RastFutureState<T>> = match self.state.lock() {
Ok(guard) => guard,
Err(_) => {
return Poll::Ready(Err(ClientError::NotLeaderError(NotLeaderError::new(Some(NodeID(0))))));
}
};
if let Some(result) = state.result.take() {
Poll::Ready(result)
} else {
state.waker = Some(cx.waker().clone());
Poll::Pending
}
}
}
#[derive(Debug, Clone)]
pub struct WriteFuture {
f: RastFuture<WriteRes>,
}
impl WriteFuture {
pub fn new() -> WriteFuture {
WriteFuture { f: RastFuture::new() }
}
pub(crate) fn fill(&mut self, result: Result<WriteRes, ClientError>) {
self.f.fill(result)
}
}
impl Future for WriteFuture {
type Output = Result<WriteRes, ClientError>;
fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
self.f.poll(cx)
}
}
#[derive(Debug, Clone)]
pub struct ReadFuture {
f: RastFuture<ReadRes>,
}
impl ReadFuture {
pub fn new() -> ReadFuture {
ReadFuture { f: RastFuture::new() }
}
pub(crate) fn fill(&mut self, result: Result<ReadRes, ClientError>) {
self.f.fill(result)
}
}
impl Future for ReadFuture {
type Output = Result<ReadRes, ClientError>;
fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
self.f.poll(cx)
}
}