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use bincode::config;
use byteorder::{ByteOrder, NetworkEndian};
use bytes::buf::Buf;
use bytes::BytesMut;
use futures_core::ready;
use serde::Deserialize;
use std::io;
use std::marker::PhantomData;
use std::pin::Pin;
use std::task::{Context, Poll};
macro_rules! make_reader {
($read_trait:path, $internal_poll_reader:path) => {
/// A wrapper around an asynchronous reader that produces an asynchronous stream of
/// bincode-decoded values.
///
/// To use, provide a reader that implements
#[doc=concat!("[`", stringify!($read_trait), "`],")]
/// and then use [`futures_core::Stream`] to access the deserialized values.
///
/// Note that the sender *must* prefix each serialized item with its size as reported by
/// [`bincode::serialized_size`] encoded as a four-byte network-endian encoded. Use the
/// marker trait [`AsyncDestination`] to add it automatically when using
/// [`AsyncBincodeWriter`].
#[derive(Debug)]
pub struct AsyncBincodeReader<R, T>(crate::reader::AsyncBincodeReader<R, T>);
impl<R, T> Unpin for AsyncBincodeReader<R, T> where R: Unpin {}
impl<R, T> Default for AsyncBincodeReader<R, T>
where
R: Default,
{
fn default() -> Self {
Self::from(R::default())
}
}
impl<R, T> From<R> for AsyncBincodeReader<R, T> {
fn from(reader: R) -> Self {
Self(crate::reader::AsyncBincodeReader {
buffer: ::bytes::BytesMut::with_capacity(8192),
reader,
into: ::std::marker::PhantomData,
})
}
}
impl<R, T> AsyncBincodeReader<R, T> {
/// Gets a reference to the underlying reader.
///
/// It is inadvisable to directly read from the underlying reader.
pub fn get_ref(&self) -> &R {
&self.0.reader
}
/// Gets a mutable reference to the underlying reader.
///
/// It is inadvisable to directly read from the underlying reader.
pub fn get_mut(&mut self) -> &mut R {
&mut self.0.reader
}
/// Returns a reference to the internally buffered data.
///
/// This will not attempt to fill the buffer if it is empty.
pub fn buffer(&self) -> &[u8] {
&self.0.buffer[..]
}
/// Unwraps this `AsyncBincodeReader`, returning the underlying reader.
///
/// Note that any leftover data in the internal buffer is lost.
pub fn into_inner(self) -> R {
self.0.reader
}
}
impl<R, T> ::futures_core::Stream for AsyncBincodeReader<R, T>
where
for<'a> T: ::serde::Deserialize<'a>,
R: $read_trait + Unpin,
{
type Item = Result<T, bincode::error::DecodeError>;
fn poll_next(
mut self: std::pin::Pin<&mut Self>,
cx: &mut std::task::Context,
) -> std::task::Poll<Option<Self::Item>> {
std::pin::Pin::new(&mut self.0).internal_poll_next(cx, $internal_poll_reader)
}
}
};
}
#[derive(Debug)]
pub(crate) struct AsyncBincodeReader<R, T> {
pub(crate) reader: R,
pub(crate) buffer: BytesMut,
pub(crate) into: PhantomData<T>,
}
impl<R, T> Unpin for AsyncBincodeReader<R, T> where R: Unpin {}
enum FillResult {
Filled,
Eof,
}
impl<R: Unpin, T> AsyncBincodeReader<R, T>
where
for<'a> T: Deserialize<'a>,
{
pub(crate) fn internal_poll_next<F>(
mut self: Pin<&mut Self>,
cx: &mut Context,
poll_reader: F,
) -> Poll<Option<Result<T, bincode::error::DecodeError>>>
where
F: Fn(Pin<&mut R>, &mut Context, &mut [u8]) -> Poll<Result<usize, io::Error>> + Copy,
{
if let FillResult::Eof = ready!(self.as_mut().fill(cx, 5, poll_reader).map_err(|inner| {
bincode::error::DecodeError::Io {
inner,
additional: 4,
}
}))? {
return Poll::Ready(None);
}
let message_size: u32 = NetworkEndian::read_u32(&self.buffer[..4]);
let target_buffer_size = message_size as usize;
// since self.buffer.len() >= 4, we know that we can't get an clean EOF here
ready!(self
.as_mut()
.fill(cx, target_buffer_size + 4, poll_reader)
.map_err(|inner| {
bincode::error::DecodeError::Io {
inner,
additional: target_buffer_size,
}
}))?;
self.buffer.advance(4);
let (message, decoded) = bincode::serde::decode_from_slice(
&self.buffer[..target_buffer_size],
config::standard().with_limit::<{ u32::MAX as usize }>(),
)?;
if decoded != target_buffer_size {
return Poll::Ready(Some(Err(bincode::error::DecodeError::OtherString(
format!("only decoded {decoded} out of {target_buffer_size}-length message"),
))));
}
self.buffer.advance(target_buffer_size);
Poll::Ready(Some(Ok(message)))
}
fn fill<F>(
mut self: Pin<&mut Self>,
cx: &mut Context,
target_size: usize,
poll_reader: F,
) -> Poll<Result<FillResult, io::Error>>
where
F: Fn(Pin<&mut R>, &mut Context, &mut [u8]) -> Poll<Result<usize, io::Error>>,
{
if self.buffer.len() >= target_size {
// we already have the bytes we need!
return Poll::Ready(Ok(FillResult::Filled));
}
// make sure we can fit all the data we're about to read
// and then some, so we don't do a gazillion syscalls
if self.buffer.capacity() < target_size {
let missing = target_size - self.buffer.capacity();
self.buffer.reserve(missing);
}
let had = self.buffer.len();
// this is the bit we'll be reading into
let mut rest = self.buffer.split_off(had);
// this is safe because we're not extending beyond the reserved capacity
// and we're never reading unwritten bytes
let max = rest.capacity();
unsafe { rest.set_len(max) };
while self.buffer.len() < target_size {
match poll_reader(Pin::new(&mut self.reader), cx, &mut rest[..]) {
Poll::Ready(result) => {
match result {
Ok(n) => {
if n == 0 {
if self.buffer.is_empty() {
return Poll::Ready(Ok(FillResult::Eof));
} else {
return Poll::Ready(Err(io::Error::from(
io::ErrorKind::BrokenPipe,
)));
}
}
// adopt the new bytes
let read = rest.split_to(n);
self.buffer.unsplit(read);
}
Err(err) => {
// reading failed, put the buffer back
rest.truncate(0);
self.buffer.unsplit(rest);
return Poll::Ready(Err(err));
}
}
}
Poll::Pending => {
// reading in progress, put the buffer back
rest.truncate(0);
self.buffer.unsplit(rest);
return Poll::Pending;
}
}
}
Poll::Ready(Ok(FillResult::Filled))
}
}