use std::{
future::Future,
io,
num::NonZeroU64,
ops::RangeBounds,
pin::Pin,
task::{self, ready, Poll},
};
use tokio::io::{AsyncBufRead, AsyncRead, AsyncReadExt, ReadBuf};
use trailer::{read_trailer, ReadTrailer, Trailer};
#[doc(hidden)]
pub use self::trailer::Pad;
pub(crate) use self::trailer::Tag;
mod trailer;
/// Reads a "bytes wire packet" from the underlying reader.
/// The format is the same as in [crate::wire::bytes::read_bytes],
/// however this structure provides a [AsyncRead] interface,
/// allowing to not having to pass around the entire payload in memory.
///
/// It is constructed by reading a size with [BytesReader::new],
/// and yields payload data until the end of the packet is reached.
///
/// It will not return the final bytes before all padding has been successfully
/// consumed as well, but the full length of the reader must be consumed.
///
/// If the data is not read all the way to the end, or an error is encountered,
/// the underlying reader is no longer usable and might return garbage.
#[derive(Debug)]
#[allow(private_bounds)]
pub struct BytesReader<R, T: Tag = Pad> {
state: State<R, T>,
}
/// Split the `user_len` into `body_len` and `tail_len`, which are respectively
/// the non-terminal 8-byte blocks, and the ≤8 bytes of user data contained in
/// the trailer block.
#[inline(always)]
fn split_user_len(user_len: NonZeroU64) -> (u64, u8) {
let n = user_len.get() - 1;
let body_len = n & !7;
let tail_len = (n & 7) as u8 + 1;
(body_len, tail_len)
}
#[derive(Debug)]
enum State<R, T: Tag> {
/// Full 8-byte blocks are being read and released to the caller.
/// NOTE: The final 8-byte block is *always* part of the trailer.
Body {
reader: Option<R>,
consumed: u64,
/// The total length of all user data contained in both the body and trailer.
user_len: NonZeroU64,
},
/// The trailer is in the process of being read.
ReadTrailer(ReadTrailer<R, T>),
/// The trailer has been fully read and validated,
/// and data can now be released to the caller.
ReleaseTrailer { consumed: u8, data: Trailer },
}
impl<R> BytesReader<R>
where
R: AsyncRead + Unpin,
{
/// Constructs a new BytesReader, using the underlying passed reader.
pub async fn new<S: RangeBounds<u64>>(reader: R, allowed_size: S) -> io::Result<Self> {
BytesReader::new_internal(reader, allowed_size).await
}
}
#[allow(private_bounds)]
impl<R, T: Tag> BytesReader<R, T>
where
R: AsyncRead + Unpin,
{
/// Constructs a new BytesReader, using the underlying passed reader.
pub(crate) async fn new_internal<S: RangeBounds<u64>>(
mut reader: R,
allowed_size: S,
) -> io::Result<Self> {
let size = reader.read_u64_le().await?;
if !allowed_size.contains(&size) {
return Err(io::Error::new(io::ErrorKind::InvalidData, "invalid size"));
}
Ok(Self {
state: match NonZeroU64::new(size) {
Some(size) => State::Body {
reader: Some(reader),
consumed: 0,
user_len: size,
},
None => State::ReleaseTrailer {
consumed: 0,
data: read_trailer::<R, T>(reader, 0).await?,
},
},
})
}
/// Returns whether there is any remaining data to be read.
pub fn is_empty(&self) -> bool {
self.len() == 0
}
/// Remaining data length, ie not including data already read.
pub fn len(&self) -> u64 {
match self.state {
State::Body {
consumed, user_len, ..
} => user_len.get() - consumed,
State::ReadTrailer(ref fut) => fut.len() as u64,
State::ReleaseTrailer { consumed, ref data } => data.len() as u64 - consumed as u64,
}
}
}
#[allow(private_bounds)]
impl<R: AsyncRead + Unpin, T: Tag> AsyncRead for BytesReader<R, T> {
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut task::Context,
buf: &mut ReadBuf,
) -> Poll<io::Result<()>> {
let this = &mut self.state;
loop {
match this {
State::Body {
reader,
consumed,
user_len,
} => {
let (body_len, tail_len) = split_user_len(*user_len);
let remaining = body_len - *consumed;
let reader = if remaining == 0 {
let reader = reader.take().unwrap();
*this = State::ReadTrailer(read_trailer(reader, tail_len));
continue;
} else {
Pin::new(reader.as_mut().unwrap())
};
let mut bytes_read = 0;
ready!(with_limited(buf, remaining, |buf| {
let ret = reader.poll_read(cx, buf);
bytes_read = buf.filled().len();
ret
}))?;
*consumed += bytes_read as u64;
return if bytes_read != 0 {
Ok(())
} else {
Err(io::ErrorKind::UnexpectedEof.into())
}
.into();
}
State::ReadTrailer(fut) => {
*this = State::ReleaseTrailer {
consumed: 0,
data: ready!(Pin::new(fut).poll(cx))?,
};
}
State::ReleaseTrailer { consumed, data } => {
let data = &data[*consumed as usize..];
let data = &data[..usize::min(data.len(), buf.remaining())];
buf.put_slice(data);
*consumed += data.len() as u8;
return Ok(()).into();
}
}
}
}
}
#[allow(private_bounds)]
impl<R: AsyncBufRead + Unpin, T: Tag> AsyncBufRead for BytesReader<R, T> {
fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut task::Context) -> Poll<io::Result<&[u8]>> {
let this = &mut self.get_mut().state;
loop {
match this {
// This state comes *after* the following case,
// but we can't keep it in logical order because
// that would lengthen the borrow lifetime.
State::Body {
reader,
consumed,
user_len,
} if {
let (body_len, _) = split_user_len(*user_len);
let remaining = body_len - *consumed;
remaining == 0
} =>
{
let reader = reader.take().unwrap();
let (_, tail_len) = split_user_len(*user_len);
*this = State::ReadTrailer(read_trailer(reader, tail_len));
}
State::Body {
reader,
consumed,
user_len,
} => {
let (body_len, _) = split_user_len(*user_len);
let remaining = body_len - *consumed;
let reader = Pin::new(reader.as_mut().unwrap());
match ready!(reader.poll_fill_buf(cx))? {
&[] => {
return Err(io::ErrorKind::UnexpectedEof.into()).into();
}
mut buf => {
if buf.len() as u64 > remaining {
buf = &buf[..remaining as usize];
}
return Ok(buf).into();
}
}
}
State::ReadTrailer(fut) => {
*this = State::ReleaseTrailer {
consumed: 0,
data: ready!(Pin::new(fut).poll(cx))?,
};
}
State::ReleaseTrailer { consumed, data } => {
return Ok(&data[*consumed as usize..]).into();
}
}
}
}
fn consume(mut self: Pin<&mut Self>, amt: usize) {
match &mut self.state {
State::Body {
reader,
consumed,
user_len,
} => {
let reader = Pin::new(reader.as_mut().unwrap());
let (body_len, _) = split_user_len(*user_len);
*consumed = consumed
.checked_add(amt as u64)
.filter(|&consumed| consumed <= body_len)
.expect("consumed out of bounds");
reader.consume(amt);
}
State::ReadTrailer(_) => unreachable!(),
State::ReleaseTrailer { consumed, data } => {
*consumed = amt
.checked_add(*consumed as usize)
.filter(|&consumed| consumed <= data.len())
.expect("consumed out of bounds") as u8;
}
}
}
}
/// Make a limited version of `buf`, consisting only of up to `n` bytes of the unfilled section, and call `f` with it.
/// After `f` returns, we propagate the filled cursor advancement back to `buf`.
fn with_limited<R>(buf: &mut ReadBuf, n: u64, f: impl FnOnce(&mut ReadBuf) -> R) -> R {
let mut nbuf = buf.take(n.try_into().unwrap_or(usize::MAX));
let ptr = nbuf.initialized().as_ptr();
let ret = f(&mut nbuf);
// SAFETY: `ReadBuf::take` only returns the *unfilled* section of `buf`,
// so anything filled is new, initialized data.
//
// We verify that `nbuf` still points to the same buffer,
// so we're sure it hasn't been swapped out.
unsafe {
// ensure our buffer hasn't been swapped out
assert_eq!(nbuf.initialized().as_ptr(), ptr);
let n = nbuf.filled().len();
buf.assume_init(n);
buf.advance(n);
}
ret
}
#[cfg(test)]
mod tests {
use std::sync::LazyLock;
use std::time::Duration;
use crate::wire::bytes::{padding_len, write_bytes};
use hex_literal::hex;
use rstest::rstest;
use tokio::io::{AsyncReadExt, BufReader};
use tokio_test::io::Builder;
use super::*;
/// The maximum length of bytes packets we're willing to accept in the test
/// cases.
const MAX_LEN: u64 = 1024;
pub static LARGE_PAYLOAD: LazyLock<Vec<u8>> =
LazyLock::new(|| (0..255).collect::<Vec<u8>>().repeat(4 * 1024));
/// Helper function, calling the (simpler) write_bytes with the payload.
/// We use this to create data we want to read from the wire.
async fn produce_packet_bytes(payload: &[u8]) -> Vec<u8> {
let mut exp = vec![];
write_bytes(&mut exp, payload).await.unwrap();
exp
}
/// Read bytes packets of various length, and ensure read_to_end returns the
/// expected payload.
#[rstest]
#[case::empty(&[])] // empty bytes packet
#[case::size_1b(&[0xff])] // 1 bytes payload
#[case::size_8b(&hex!("0001020304050607"))] // 8 bytes payload (no padding)
#[case::size_9b(&hex!("000102030405060708"))] // 9 bytes payload (7 bytes padding)
#[case::size_1m(LARGE_PAYLOAD.as_slice())] // larger bytes packet
#[tokio::test]
async fn read_payload_correct(#[case] payload: &[u8]) {
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await)
.build();
let mut r = BytesReader::new(&mut mock, ..=LARGE_PAYLOAD.len() as u64)
.await
.unwrap();
let mut buf = Vec::new();
r.read_to_end(&mut buf).await.expect("must succeed");
assert_eq!(payload, &buf[..]);
}
/// Read bytes packets of various length, and ensure copy_buf reads the
/// expected payload.
#[rstest]
#[case::empty(&[])] // empty bytes packet
#[case::size_1b(&[0xff])] // 1 bytes payload
#[case::size_8b(&hex!("0001020304050607"))] // 8 bytes payload (no padding)
#[case::size_9b(&hex!("000102030405060708"))] // 9 bytes payload (7 bytes padding)
#[case::size_1m(LARGE_PAYLOAD.as_slice())] // larger bytes packet
#[tokio::test]
async fn read_payload_correct_readbuf(#[case] payload: &[u8]) {
let mut mock = BufReader::new(
Builder::new()
.read(&produce_packet_bytes(payload).await)
.build(),
);
let mut r = BytesReader::new(&mut mock, ..=LARGE_PAYLOAD.len() as u64)
.await
.unwrap();
let mut buf = Vec::new();
tokio::io::copy_buf(&mut r, &mut buf)
.await
.expect("copy_buf must succeed");
assert_eq!(payload, &buf[..]);
}
/// Fail if the bytes packet is larger than allowed
#[tokio::test]
async fn read_bigger_than_allowed_fail() {
let payload = LARGE_PAYLOAD.as_slice();
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await[0..8]) // We stop reading after the size packet
.build();
assert_eq!(
BytesReader::new(&mut mock, ..2048)
.await
.unwrap_err()
.kind(),
io::ErrorKind::InvalidData
);
}
/// Fail if the bytes packet is smaller than allowed
#[tokio::test]
async fn read_smaller_than_allowed_fail() {
let payload = &[0x00, 0x01, 0x02];
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await[0..8]) // We stop reading after the size packet
.build();
assert_eq!(
BytesReader::new(&mut mock, 1024..2048)
.await
.unwrap_err()
.kind(),
io::ErrorKind::InvalidData
);
}
/// Read the trailer immediately if there is no payload.
#[cfg(feature = "async")]
#[tokio::test]
async fn read_trailer_immediately() {
use crate::nar::wire::PadPar;
let mut mock = Builder::new()
.read(&[0; 8])
.read(&PadPar::PATTERN[8..])
.build();
BytesReader::<_, PadPar>::new_internal(&mut mock, ..)
.await
.unwrap();
// The mock reader will panic if dropped without reading all data.
}
/// Read the trailer even if we only read the exact payload size.
#[cfg(feature = "async")]
#[tokio::test]
async fn read_exact_trailer() {
use crate::nar::wire::PadPar;
let mut mock = Builder::new()
.read(&16u64.to_le_bytes())
.read(&[0x55; 16])
.read(&PadPar::PATTERN[8..])
.build();
let mut reader = BytesReader::<_, PadPar>::new_internal(&mut mock, ..)
.await
.unwrap();
let mut buf = [0; 16];
reader.read_exact(&mut buf).await.unwrap();
assert_eq!(buf, [0x55; 16]);
// The mock reader will panic if dropped without reading all data.
}
/// Fail if the padding is not all zeroes
#[tokio::test]
async fn read_fail_if_nonzero_padding() {
let payload = &[0x00, 0x01, 0x02];
let mut packet_bytes = produce_packet_bytes(payload).await;
// Flip some bits in the padding
packet_bytes[12] = 0xff;
let mut mock = Builder::new().read(&packet_bytes).build(); // We stop reading after the faulty bit
let mut r = BytesReader::new(&mut mock, ..MAX_LEN).await.unwrap();
let mut buf = Vec::new();
r.read_to_end(&mut buf).await.expect_err("must fail");
}
/// Start a 9 bytes payload packet, but have the underlying reader return
/// EOF in the middle of the size packet (after 4 bytes).
/// We should get an unexpected EOF error, already when trying to read the
/// first byte (of payload)
#[tokio::test]
async fn read_9b_eof_during_size() {
let payload = &hex!("FF0102030405060708");
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await[..4])
.build();
assert_eq!(
BytesReader::new(&mut mock, ..MAX_LEN)
.await
.expect_err("must fail")
.kind(),
io::ErrorKind::UnexpectedEof
);
}
/// Start a 9 bytes payload packet, but have the underlying reader return
/// EOF in the middle of the payload (4 bytes into the payload).
/// We should get an unexpected EOF error, after reading the first 4 bytes
/// (successfully).
#[tokio::test]
async fn read_9b_eof_during_payload() {
let payload = &hex!("FF0102030405060708");
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await[..8 + 4])
.build();
let mut r = BytesReader::new(&mut mock, ..MAX_LEN).await.unwrap();
let mut buf = [0; 9];
r.read_exact(&mut buf[..4]).await.expect("must succeed");
assert_eq!(
r.read_exact(&mut buf[4..=4])
.await
.expect_err("must fail")
.kind(),
std::io::ErrorKind::UnexpectedEof
);
}
/// Start a 9 bytes payload packet, but don't supply the necessary padding.
/// This is expected to always fail before returning the final data.
#[rstest]
#[case::before_padding(8 + 9)]
#[case::during_padding(8 + 9 + 2)]
#[case::after_padding(8 + 9 + padding_len(9) as usize - 1)]
#[tokio::test]
async fn read_9b_eof_after_payload(#[case] offset: usize) {
let payload = &hex!("FF0102030405060708");
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await[..offset])
.build();
let mut r = BytesReader::new(&mut mock, ..MAX_LEN).await.unwrap();
// read_exact of the payload *body* will succeed, but a subsequent read will
// return UnexpectedEof error.
assert_eq!(r.read_exact(&mut [0; 8]).await.unwrap(), 8);
assert_eq!(
r.read_exact(&mut [0]).await.unwrap_err().kind(),
std::io::ErrorKind::UnexpectedEof
);
}
/// Start a 9 bytes payload packet, but return an error after a certain position.
/// Ensure that error is propagated.
#[rstest]
#[case::during_size(4)]
#[case::before_payload(8)]
#[case::during_payload(8 + 4)]
#[case::before_padding(8 + 4)]
#[case::during_padding(8 + 9 + 2)]
#[tokio::test]
async fn propagate_error_from_reader(#[case] offset: usize) {
let payload = &hex!("FF0102030405060708");
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await[..offset])
.read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo"))
.build();
// Either length reading or data reading can fail, depending on which test case we're in.
let err: io::Error = async {
let mut r = BytesReader::new(&mut mock, ..MAX_LEN).await?;
let mut buf = Vec::new();
r.read_to_end(&mut buf).await?;
Ok(())
}
.await
.expect_err("must fail");
assert_eq!(
err.kind(),
std::io::ErrorKind::Other,
"error kind must match"
);
assert_eq!(
err.into_inner().unwrap().to_string(),
"foo",
"error payload must contain foo"
);
}
/// Start a 9 bytes payload packet, but return an error after a certain position.
/// Ensure that error is propagated (AsyncReadBuf case)
#[rstest]
#[case::during_size(4)]
#[case::before_payload(8)]
#[case::during_payload(8 + 4)]
#[case::before_padding(8 + 4)]
#[case::during_padding(8 + 9 + 2)]
#[tokio::test]
async fn propagate_error_from_reader_buffered(#[case] offset: usize) {
let payload = &hex!("FF0102030405060708");
let mock = Builder::new()
.read(&produce_packet_bytes(payload).await[..offset])
.read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo"))
.build();
let mut mock = BufReader::new(mock);
// Either length reading or data reading can fail, depending on which test case we're in.
let err: io::Error = async {
let mut r = BytesReader::new(&mut mock, ..MAX_LEN).await?;
let mut buf = Vec::new();
tokio::io::copy_buf(&mut r, &mut buf).await?;
Ok(())
}
.await
.expect_err("must fail");
assert_eq!(
err.kind(),
std::io::ErrorKind::Other,
"error kind must match"
);
assert_eq!(
err.into_inner().unwrap().to_string(),
"foo",
"error payload must contain foo"
);
}
/// If there's an error right after the padding, we don't propagate it, as
/// we're done reading. We just return EOF.
#[tokio::test]
async fn no_error_after_eof() {
let payload = &hex!("FF0102030405060708");
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await)
.read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo"))
.build();
let mut r = BytesReader::new(&mut mock, ..MAX_LEN).await.unwrap();
let mut buf = Vec::new();
r.read_to_end(&mut buf).await.expect("must succeed");
assert_eq!(buf.as_slice(), payload);
}
/// If there's an error right after the padding, we don't propagate it, as
/// we're done reading. We just return EOF.
#[tokio::test]
async fn no_error_after_eof_buffered() {
let payload = &hex!("FF0102030405060708");
let mock = Builder::new()
.read(&produce_packet_bytes(payload).await)
.read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo"))
.build();
let mut mock = BufReader::new(mock);
let mut r = BytesReader::new(&mut mock, ..MAX_LEN).await.unwrap();
let mut buf = Vec::new();
tokio::io::copy_buf(&mut r, &mut buf)
.await
.expect("must succeed");
assert_eq!(buf.as_slice(), payload);
}
/// Introduce various stalls in various places of the packet, to ensure we
/// handle these cases properly, too.
#[rstest]
#[case::beginning(0)]
#[case::before_payload(8)]
#[case::during_payload(8 + 4)]
#[case::before_padding(8 + 4)]
#[case::during_padding(8 + 9 + 2)]
#[tokio::test]
async fn read_payload_correct_pending(#[case] offset: usize) {
let payload = &hex!("FF0102030405060708");
let mut mock = Builder::new()
.read(&produce_packet_bytes(payload).await[..offset])
.wait(Duration::from_nanos(0))
.read(&produce_packet_bytes(payload).await[offset..])
.build();
let mut r = BytesReader::new(&mut mock, ..=LARGE_PAYLOAD.len() as u64)
.await
.unwrap();
let mut buf = Vec::new();
r.read_to_end(&mut buf).await.expect("must succeed");
assert_eq!(payload, &buf[..]);
}
}
