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use std::fmt;
use std::mem::MaybeUninit;
use std::ops::DerefMut;
use std::pin::Pin;
use std::task::{Context, Poll};
// New IO traits? What?! Why, are you bonkers?
//
// I mean, yes, probably. But, here's the goals:
//
// 1. Supports poll-based IO operations.
// 2. Opt-in vectored IO.
// 3. Can use an optional buffer pool.
// 4. Able to add completion-based (uring) IO eventually.
//
// Frankly, the last point is the entire reason we're doing this. We want to
// have forwards-compatibility with an eventually stable io-uring runtime. We
// don't need that to work right away. But it must be possible to add in here
// without breaking hyper 1.0.
//
// While in here, if there's small tweaks to poll_read or poll_write that would
// allow even the "slow" path to be faster, such as if someone didn't remember
// to forward along an `is_completion` call.
/// Reads bytes from a source.
///
/// This trait is similar to `std::io::Read`, but supports asynchronous reads.
pub trait Read {
/// Attempts to read bytes into the `buf`.
///
/// On success, returns `Poll::Ready(Ok(()))` and places data in the
/// unfilled portion of `buf`. If no data was read (`buf.remaining()` is
/// unchanged), it implies that EOF has been reached.
///
/// If no data is available for reading, the method returns `Poll::Pending`
/// and arranges for the current task (via `cx.waker()`) to receive a
/// notification when the object becomes readable or is closed.
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: ReadBufCursor<'_>,
) -> Poll<Result<(), std::io::Error>>;
}
/// Write bytes asynchronously.
///
/// This trait is similar to `std::io::Write`, but for asynchronous writes.
pub trait Write {
/// Attempt to write bytes from `buf` into the destination.
///
/// On success, returns `Poll::Ready(Ok(num_bytes_written)))`. If
/// successful, it must be guaranteed that `n <= buf.len()`. A return value
/// of `0` means that the underlying object is no longer able to accept
/// bytes, or that the provided buffer is empty.
///
/// If the object is not ready for writing, the method returns
/// `Poll::Pending` and arranges for the current task (via `cx.waker()`) to
/// receive a notification when the object becomes writable or is closed.
fn poll_write(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<Result<usize, std::io::Error>>;
/// Attempts to flush the object.
///
/// On success, returns `Poll::Ready(Ok(()))`.
///
/// If flushing cannot immediately complete, this method returns
/// `Poll::Pending` and arranges for the current task (via `cx.waker()`) to
/// receive a notification when the object can make progress.
fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), std::io::Error>>;
/// Attempts to shut down this writer.
fn poll_shutdown(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), std::io::Error>>;
/// Returns whether this writer has an efficient `poll_write_vectored`
/// implementation.
///
/// The default implementation returns `false`.
fn is_write_vectored(&self) -> bool {
false
}
/// Like `poll_write`, except that it writes from a slice of buffers.
fn poll_write_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &[std::io::IoSlice<'_>],
) -> Poll<Result<usize, std::io::Error>> {
let buf = bufs
.iter()
.find(|b| !b.is_empty())
.map_or(&[][..], |b| &**b);
self.poll_write(cx, buf)
}
}
/// A wrapper around a byte buffer that is incrementally filled and initialized.
///
/// This type is a sort of "double cursor". It tracks three regions in the
/// buffer: a region at the beginning of the buffer that has been logically
/// filled with data, a region that has been initialized at some point but not
/// yet logically filled, and a region at the end that may be uninitialized.
/// The filled region is guaranteed to be a subset of the initialized region.
///
/// In summary, the contents of the buffer can be visualized as:
///
/// ```not_rust
/// [ capacity ]
/// [ filled | unfilled ]
/// [ initialized | uninitialized ]
/// ```
///
/// It is undefined behavior to de-initialize any bytes from the uninitialized
/// region, since it is merely unknown whether this region is uninitialized or
/// not, and if part of it turns out to be initialized, it must stay initialized.
pub struct ReadBuf<'a> {
raw: &'a mut [MaybeUninit<u8>],
filled: usize,
init: usize,
}
/// The cursor part of a [`ReadBuf`].
///
/// This is created by calling `ReadBuf::unfilled()`.
#[derive(Debug)]
pub struct ReadBufCursor<'a> {
buf: &'a mut ReadBuf<'a>,
}
impl<'data> ReadBuf<'data> {
/// Create a new `ReadBuf` with a slice of initialized bytes.
#[inline]
pub fn new(raw: &'data mut [u8]) -> Self {
let len = raw.len();
Self {
// SAFETY: We never de-init the bytes ourselves.
raw: unsafe { &mut *(raw as *mut [u8] as *mut [MaybeUninit<u8>]) },
filled: 0,
init: len,
}
}
/// Create a new `ReadBuf` with a slice of uninitialized bytes.
#[inline]
pub fn uninit(raw: &'data mut [MaybeUninit<u8>]) -> Self {
Self {
raw,
filled: 0,
init: 0,
}
}
/// Get a slice of the buffer that has been filled in with bytes.
#[inline]
pub fn filled(&self) -> &[u8] {
// SAFETY: We only slice the filled part of the buffer, which is always valid
unsafe { &*(&self.raw[0..self.filled] as *const [MaybeUninit<u8>] as *const [u8]) }
}
/// Get a cursor to the unfilled portion of the buffer.
#[inline]
pub fn unfilled<'cursor>(&'cursor mut self) -> ReadBufCursor<'cursor> {
ReadBufCursor {
// SAFETY: self.buf is never re-assigned, so its safe to narrow
// the lifetime.
buf: unsafe {
std::mem::transmute::<&'cursor mut ReadBuf<'data>, &'cursor mut ReadBuf<'cursor>>(
self,
)
},
}
}
#[inline]
#[cfg(all(any(feature = "client", feature = "server"), feature = "http2"))]
pub(crate) unsafe fn set_init(&mut self, n: usize) {
self.init = self.init.max(n);
}
#[inline]
#[cfg(all(any(feature = "client", feature = "server"), feature = "http2"))]
pub(crate) unsafe fn set_filled(&mut self, n: usize) {
self.filled = self.filled.max(n);
}
#[inline]
#[cfg(all(any(feature = "client", feature = "server"), feature = "http2"))]
pub(crate) fn len(&self) -> usize {
self.filled
}
#[inline]
#[cfg(all(any(feature = "client", feature = "server"), feature = "http2"))]
pub(crate) fn init_len(&self) -> usize {
self.init
}
#[inline]
fn remaining(&self) -> usize {
self.capacity() - self.filled
}
#[inline]
fn capacity(&self) -> usize {
self.raw.len()
}
}
impl<'data> fmt::Debug for ReadBuf<'data> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ReadBuf")
.field("filled", &self.filled)
.field("init", &self.init)
.field("capacity", &self.capacity())
.finish()
}
}
impl<'data> ReadBufCursor<'data> {
/// Access the unfilled part of the buffer.
///
/// # Safety
///
/// The caller must not uninitialize any bytes that may have been
/// initialized before.
#[inline]
pub unsafe fn as_mut(&mut self) -> &mut [MaybeUninit<u8>] {
&mut self.buf.raw[self.buf.filled..]
}
/// Advance the `filled` cursor by `n` bytes.
///
/// # Safety
///
/// The caller must take care that `n` more bytes have been initialized.
#[inline]
pub unsafe fn advance(&mut self, n: usize) {
self.buf.filled = self.buf.filled.checked_add(n).expect("overflow");
self.buf.init = self.buf.filled.max(self.buf.init);
}
/// Returns the number of bytes that can be written from the current
/// position until the end of the buffer is reached.
///
/// This value is equal to the length of the slice returned by `as_mut()``.
#[inline]
pub fn remaining(&self) -> usize {
self.buf.remaining()
}
/// Transfer bytes into `self`` from `src` and advance the cursor
/// by the number of bytes written.
///
/// # Panics
///
/// `self` must have enough remaining capacity to contain all of `src`.
#[inline]
pub fn put_slice(&mut self, src: &[u8]) {
assert!(
self.buf.remaining() >= src.len(),
"src.len() must fit in remaining()"
);
let amt = src.len();
// Cannot overflow, asserted above
let end = self.buf.filled + amt;
// Safety: the length is asserted above
unsafe {
self.buf.raw[self.buf.filled..end]
.as_mut_ptr()
.cast::<u8>()
.copy_from_nonoverlapping(src.as_ptr(), amt);
}
if self.buf.init < end {
self.buf.init = end;
}
self.buf.filled = end;
}
}
macro_rules! deref_async_read {
() => {
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: ReadBufCursor<'_>,
) -> Poll<std::io::Result<()>> {
Pin::new(&mut **self).poll_read(cx, buf)
}
};
}
impl<T: ?Sized + Read + Unpin> Read for Box<T> {
deref_async_read!();
}
impl<T: ?Sized + Read + Unpin> Read for &mut T {
deref_async_read!();
}
impl<P> Read for Pin<P>
where
P: DerefMut,
P::Target: Read,
{
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: ReadBufCursor<'_>,
) -> Poll<std::io::Result<()>> {
pin_as_deref_mut(self).poll_read(cx, buf)
}
}
macro_rules! deref_async_write {
() => {
fn poll_write(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<std::io::Result<usize>> {
Pin::new(&mut **self).poll_write(cx, buf)
}
fn poll_write_vectored(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &[std::io::IoSlice<'_>],
) -> Poll<std::io::Result<usize>> {
Pin::new(&mut **self).poll_write_vectored(cx, bufs)
}
fn is_write_vectored(&self) -> bool {
(**self).is_write_vectored()
}
fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<std::io::Result<()>> {
Pin::new(&mut **self).poll_flush(cx)
}
fn poll_shutdown(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<std::io::Result<()>> {
Pin::new(&mut **self).poll_shutdown(cx)
}
};
}
impl<T: ?Sized + Write + Unpin> Write for Box<T> {
deref_async_write!();
}
impl<T: ?Sized + Write + Unpin> Write for &mut T {
deref_async_write!();
}
impl<P> Write for Pin<P>
where
P: DerefMut,
P::Target: Write,
{
fn poll_write(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<std::io::Result<usize>> {
pin_as_deref_mut(self).poll_write(cx, buf)
}
fn poll_write_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &[std::io::IoSlice<'_>],
) -> Poll<std::io::Result<usize>> {
pin_as_deref_mut(self).poll_write_vectored(cx, bufs)
}
fn is_write_vectored(&self) -> bool {
(**self).is_write_vectored()
}
fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<std::io::Result<()>> {
pin_as_deref_mut(self).poll_flush(cx)
}
fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<std::io::Result<()>> {
pin_as_deref_mut(self).poll_shutdown(cx)
}
}
/// Polyfill for Pin::as_deref_mut()
/// TODO: use Pin::as_deref_mut() instead once stabilized
fn pin_as_deref_mut<P: DerefMut>(pin: Pin<&mut Pin<P>>) -> Pin<&mut P::Target> {
// SAFETY: we go directly from Pin<&mut Pin<P>> to Pin<&mut P::Target>, without moving or
// giving out the &mut Pin<P> in the process. See Pin::as_deref_mut() for more detail.
unsafe { pin.get_unchecked_mut() }.as_mut()
}