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use crate::rate_limit::{Bucket, SharedBucket};
use diem_infallible::Mutex;
use futures::{
io::AsyncRead,
ready,
task::{Context, Poll},
AsyncWrite, Future,
};
use pin_project::pin_project;
use std::{io, pin::Pin, sync::Arc};
use tokio::time::{sleep_until, Sleep};
struct PollRateLimiter {
bucket: SharedBucket,
delay: Option<Pin<Box<Sleep>>>,
}
impl PollRateLimiter {
fn new(bucket: Option<SharedBucket>) -> Self {
let bucket =
bucket.unwrap_or_else(|| Arc::new(Mutex::new(Bucket::open(String::from("None")))));
PollRateLimiter {
bucket,
delay: None,
}
}
fn poll_acquire(&mut self, cx: &mut Context<'_>, requested: usize) -> Poll<usize> {
loop {
if let Some(ref mut delay) = self.delay {
ready!(Pin::new(delay).poll(cx));
self.delay = None;
}
match self.bucket.lock().acquire_tokens(requested) {
Ok(allowed) => return Poll::Ready(allowed),
Err(wait_time) => {
self.delay = Some(Box::pin(sleep_until(tokio::time::Instant::from_std(
wait_time,
))));
}
}
}
}
pub fn poll_limited<
T,
Action: FnOnce(Pin<&mut T>, &mut Context<'_>, usize) -> Poll<io::Result<usize>>,
>(
&mut self,
resource: Pin<&mut T>,
cx: &mut Context<'_>,
requested: usize,
poll_resource: Action,
) -> Poll<io::Result<usize>> {
let allowed = ready!(self.poll_acquire(cx, requested));
let result = poll_resource(resource, cx, allowed);
let tokens_to_return = match &result {
Poll::Ready(Ok(actual)) => allowed.saturating_sub(*actual),
_ => allowed,
};
self.bucket.lock().return_tokens(tokens_to_return);
result
}
}
#[pin_project]
pub struct AsyncRateLimiter<T> {
#[pin]
inner: T,
rate_limiter: PollRateLimiter,
}
impl<T> AsyncRateLimiter<T> {
pub fn new(inner: T, bucket: Option<SharedBucket>) -> Self {
Self {
inner,
rate_limiter: PollRateLimiter::new(bucket),
}
}
}
impl<T: AsyncRead> AsyncRead for AsyncRateLimiter<T> {
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
let this = self.project();
this.rate_limiter
.poll_limited(this.inner, cx, buf.len(), |resource, cx, allowed| {
resource.poll_read(cx, &mut buf[..allowed])
})
}
}
impl<T: AsyncWrite> AsyncWrite for AsyncRateLimiter<T> {
fn poll_write(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<io::Result<usize>> {
let this = self.project();
this.rate_limiter
.poll_limited(this.inner, cx, buf.len(), |resource, cx, allowed| {
resource.poll_write(cx, &buf[..allowed])
})
}
fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
self.project().inner.poll_flush(cx)
}
fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
self.project().inner.poll_close(cx)
}
}
#[cfg(test)]
mod tests {
use super::*;
use futures::io::AsyncReadExt;
#[tokio::test]
async fn test_async_read() {
let source: &[u8] = b"12345678901234567890123456";
let rate_limiter = Arc::new(Mutex::new(Bucket::new(
"test".to_string(),
"test".to_string(),
"test".to_string(),
15,
15,
5,
None,
)));
let mut reader = AsyncRateLimiter::new(source, Some(rate_limiter));
let mut buf: [u8; 30] = [0; 30];
assert_eq!(15, reader.read(&mut buf).await.expect("Successful read"));
assert_eq!(
5,
reader.read(&mut buf[15..]).await.expect("Successful read")
);
assert_eq!(
5,
reader.read(&mut buf[20..]).await.expect("Successful read")
);
assert_eq!(
1,
reader.read(&mut buf[25..]).await.expect("Successful read")
);
assert_eq!(
0,
reader.read(&mut buf[26..]).await.expect("Successful read")
);
assert_eq!(&buf[..26], source);
}
}