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|
use std::{
fmt::Debug,
future::Future,
marker::PhantomData,
ops::Deref,
pin::Pin,
task::{self, ready, Poll},
};
use tokio::io::{self, AsyncRead, ReadBuf};
/// Trailer represents up to 7 bytes of data read as part of the trailer block(s)
#[derive(Debug)]
pub(crate) struct Trailer {
data_len: u8,
buf: [u8; 7],
}
impl Deref for Trailer {
type Target = [u8];
fn deref(&self) -> &Self::Target {
&self.buf[..self.data_len as usize]
}
}
/// Tag defines a "trailer tag": specific, fixed bytes that must follow wire data.
pub(crate) trait Tag {
/// The expected suffix
///
/// The first 7 bytes may be ignored, and it must be an 8-byte aligned size.
const PATTERN: &'static [u8];
/// Suitably sized buffer for reading [Self::PATTERN]
///
/// HACK: This is a workaround for const generics limitations.
type Buf: AsRef<[u8]> + AsMut<[u8]> + Debug + Unpin;
/// Make an instance of [Self::Buf]
fn make_buf() -> Self::Buf;
}
#[derive(Debug)]
pub enum Pad {}
impl Tag for Pad {
const PATTERN: &'static [u8] = &[0; 8];
type Buf = [u8; 8];
fn make_buf() -> Self::Buf {
[0; 8]
}
}
#[derive(Debug)]
pub(crate) struct ReadTrailer<R, T: Tag> {
reader: R,
data_len: u8,
filled: u8,
buf: T::Buf,
_phantom: PhantomData<fn(T) -> T>,
}
/// read_trailer returns a [Future] that reads a trailer with a given [Tag] from `reader`
pub(crate) fn read_trailer<R: AsyncRead + Unpin, T: Tag>(
reader: R,
data_len: u8,
) -> ReadTrailer<R, T> {
assert!(data_len < 8, "payload in trailer must be less than 8 bytes");
let buf = T::make_buf();
assert_eq!(buf.as_ref().len(), T::PATTERN.len());
assert_eq!(T::PATTERN.len() % 8, 0);
ReadTrailer {
reader,
data_len,
filled: if data_len != 0 { 0 } else { 8 },
buf,
_phantom: PhantomData,
}
}
impl<R, T: Tag> ReadTrailer<R, T> {
pub fn len(&self) -> u8 {
self.data_len
}
}
impl<R: AsyncRead + Unpin, T: Tag> Future for ReadTrailer<R, T> {
type Output = io::Result<Trailer>;
fn poll(mut self: Pin<&mut Self>, cx: &mut task::Context) -> Poll<Self::Output> {
let this = &mut *self;
loop {
if this.filled >= this.data_len {
let check_range = || this.data_len as usize..this.filled as usize;
if this.buf.as_ref()[check_range()] != T::PATTERN[check_range()] {
return Err(io::Error::new(
io::ErrorKind::InvalidData,
"invalid trailer",
))
.into();
}
}
if this.filled as usize == T::PATTERN.len() {
let mut buf = [0; 7];
buf.copy_from_slice(&this.buf.as_ref()[..7]);
return Ok(Trailer {
data_len: this.data_len,
buf,
})
.into();
}
let mut buf = ReadBuf::new(this.buf.as_mut());
buf.advance(this.filled as usize);
ready!(Pin::new(&mut this.reader).poll_read(cx, &mut buf))?;
this.filled = {
let prev_filled = this.filled;
let filled = buf.filled().len() as u8;
if filled == prev_filled {
return Err(io::ErrorKind::UnexpectedEof.into()).into();
}
filled
};
}
}
}
#[cfg(test)]
mod tests {
use std::time::Duration;
use super::*;
#[tokio::test]
async fn unexpected_eof() {
let reader = tokio_test::io::Builder::new()
.read(&[0xed])
.wait(Duration::ZERO)
.read(&[0xef, 0x00])
.build();
assert_eq!(
read_trailer::<_, Pad>(reader, 2).await.unwrap_err().kind(),
io::ErrorKind::UnexpectedEof
);
}
#[tokio::test]
async fn invalid_padding() {
let reader = tokio_test::io::Builder::new()
.read(&[0xed])
.wait(Duration::ZERO)
.read(&[0xef, 0x01, 0x00])
.wait(Duration::ZERO)
.build();
assert_eq!(
read_trailer::<_, Pad>(reader, 2).await.unwrap_err().kind(),
io::ErrorKind::InvalidData
);
}
#[tokio::test]
async fn success() {
let reader = tokio_test::io::Builder::new()
.read(&[0xed])
.wait(Duration::ZERO)
.read(&[0xef, 0x00])
.wait(Duration::ZERO)
.read(&[0x00, 0x00, 0x00, 0x00, 0x00])
.build();
assert_eq!(
&*read_trailer::<_, Pad>(reader, 2).await.unwrap(),
&[0xed, 0xef]
);
}
#[tokio::test]
async fn no_padding() {
assert!(read_trailer::<_, Pad>(io::empty(), 0)
.await
.unwrap()
.is_empty());
}
}
|
