Introduce Submit trait and add Link struct for linked operations

Cargo.toml

@@ -24,6 +24,7 @@ io-uring = "0.6.0"
 socket2 = { version = "0.4.4", features = ["all"] }
 bytes = { version = "1.0", optional = true }
 futures-util = { version = "0.3.26", default-features = false, features = ["std"] }
+pin-project-lite = "0.2.13"
 
 [dev-dependencies]
 tempfile = "3.2.0"

examples/cat.rs

@@ -3,7 +3,7 @@ use std::{
     {env, io},
 };
 
-use tokio_uring::fs::File;
+use tokio_uring::{fs::File, Submit};
 
 fn main() {
     // The file to `cat` is passed as a CLI argument

examples/mix.rs

@@ -4,7 +4,7 @@
 
 use std::env;
 
-use tokio_uring::{fs::File, net::TcpListener};
+use tokio_uring::{fs::File, net::TcpListener, Submit};
 
 fn main() {
     // The file to serve over TCP is passed as a CLI argument

examples/tcp_stream.rs

@@ -1,6 +1,6 @@
 use std::{env, net::SocketAddr};
 
-use tokio_uring::net::TcpStream;
+use tokio_uring::{net::TcpStream, Submit};
 
 fn main() {
     let args: Vec<_> = env::args().collect();

examples/unix_listener.rs

@@ -1,6 +1,6 @@
 use std::env;
 
-use tokio_uring::net::UnixListener;
+use tokio_uring::{net::UnixListener, Submit};
 
 fn main() {
     let args: Vec<_> = env::args().collect();

examples/unix_stream.rs

@@ -1,6 +1,6 @@
 use std::env;
 
-use tokio_uring::net::UnixStream;
+use tokio_uring::{net::UnixStream, Submit};
 
 fn main() {
     let args: Vec<_> = env::args().collect();

examples/wrk-bench.rs

@@ -1,6 +1,7 @@
 use std::io;
 use std::rc::Rc;
 use tokio::task::JoinHandle;
+use tokio_uring::Submit;
 
 pub const RESPONSE: &'static [u8] =
     b"HTTP/1.1 200 OK\nContent-Type: text/plain\nContent-Length: 12\n\nHello world!";

src/fs/file.rs

@@ -3,7 +3,7 @@ use crate::buf::{BoundedBuf, BoundedBufMut, IoBuf, IoBufMut, Slice};
 use crate::fs::OpenOptions;
 use crate::io::SharedFd;
 
-use crate::runtime::driver::op::Op;
+use crate::runtime::driver::op::{Op, Submit};
 use crate::{UnsubmittedOneshot, UnsubmittedRead, UnsubmittedWrite};
 use std::fmt;
 use std::io;
@@ -32,6 +32,7 @@ use std::path::Path;
 ///
 /// ```no_run
 /// use tokio_uring::fs::File;
+/// use tokio_uring::Submit;
 ///
 /// fn main() -> Result<(), Box<dyn std::error::Error>> {
 ///     tokio_uring::start(async {
@@ -158,6 +159,7 @@ impl File {
     ///
     /// ```no_run
     /// use tokio_uring::fs::File;
+    /// use tokio_uring::Submit;
     ///
     /// fn main() -> Result<(), Box<dyn std::error::Error>> {
     ///     tokio_uring::start(async {
@@ -518,6 +520,7 @@ impl File {
     ///
     /// ```no_run
     /// use tokio_uring::fs::File;
+    /// use tokio_uring::Submit;
     ///
     /// fn main() -> Result<(), Box<dyn std::error::Error>> {
     ///     tokio_uring::start(async {
@@ -767,6 +770,7 @@ impl File {
     ///
     /// ```no_run
     /// use tokio_uring::fs::File;
+    /// use tokio_uring::Submit;
     ///
     /// fn main() -> Result<(), Box<dyn std::error::Error>> {
     ///     tokio_uring::start(async {
@@ -804,6 +808,7 @@ impl File {
     ///
     /// ```no_run
     /// use tokio_uring::fs::File;
+    /// use tokio_uring::Submit;
     ///
     /// fn main() -> Result<(), Box<dyn std::error::Error>> {
     ///     tokio_uring::start(async {

src/io/socket.rs

@@ -1,5 +1,5 @@
 use crate::io::write::UnsubmittedWrite;
-use crate::runtime::driver::op::Op;
+use crate::runtime::driver::op::{Op, Submit};
 use crate::{
     buf::fixed::FixedBuf,
     buf::{BoundedBuf, BoundedBufMut, IoBuf, Slice},

src/lib.rs

@@ -10,6 +10,7 @@
 //!
 //! ```no_run
 //! use tokio_uring::fs::File;
+//! use tokio_uring::Submit;
 //!
 //! fn main() -> Result<(), Box<dyn std::error::Error>> {
 //!     tokio_uring::start(async {
@@ -80,7 +81,9 @@ pub mod net;
 
 pub use io::read::*;
 pub use io::write::*;
-pub use runtime::driver::op::{InFlightOneshot, OneshotOutputTransform, UnsubmittedOneshot};
+pub use runtime::driver::op::{
+    InFlightOneshot, OneshotOutputTransform, Submit, UnsubmittedOneshot,
+};
 pub use runtime::spawn;
 pub use runtime::Runtime;
 
@@ -106,6 +109,7 @@ use std::future::Future;
 ///
 /// ```no_run
 /// use tokio_uring::fs::File;
+/// use tokio_uring::Submit;
 ///
 /// fn main() -> Result<(), Box<dyn std::error::Error>> {
 ///     tokio_uring::start(async {
@@ -245,6 +249,7 @@ impl Builder {
 ///
 /// ```no_run
 /// use tokio_uring::fs::File;
+/// use tokio_uring::Submit;
 ///
 /// fn main() -> Result<(), Box<dyn std::error::Error>> {
 ///     tokio_uring::start(async {

src/net/tcp/listener.rs

@@ -16,6 +16,7 @@ use std::{
 /// ```
 /// use tokio_uring::net::TcpListener;
 /// use tokio_uring::net::TcpStream;
+/// use tokio_uring::Submit;
 ///
 /// let listener = TcpListener::bind("127.0.0.1:2345".parse().unwrap()).unwrap();
 ///

src/net/tcp/stream.rs

@@ -20,6 +20,7 @@ use crate::{
 ///
 /// ```no_run
 /// use tokio_uring::net::TcpStream;
+/// use tokio_uring::Submit;
 /// use std::net::ToSocketAddrs;
 ///
 /// fn main() -> std::io::Result<()> {

src/net/udp.rs

@@ -26,6 +26,7 @@ use std::{
 ///
 /// ```
 /// use tokio_uring::net::UdpSocket;
+/// use tokio_uring::Submit;
 /// use std::net::SocketAddr;
 /// fn main() -> std::io::Result<()> {
 ///     tokio_uring::start(async {

src/net/unix/listener.rs

@@ -12,6 +12,7 @@ use std::{io, path::Path};
 /// ```
 /// use tokio_uring::net::UnixListener;
 /// use tokio_uring::net::UnixStream;
+/// use tokio_uring::Submit;
 ///
 /// let sock_file = "/tmp/tokio-uring-unix-test.sock";
 /// let listener = UnixListener::bind(&sock_file).unwrap();

src/net/unix/stream.rs

@@ -20,6 +20,7 @@ use std::{
 ///
 /// ```no_run
 /// use tokio_uring::net::UnixStream;
+/// use tokio_uring::Submit;
 /// use std::net::ToSocketAddrs;
 ///
 /// fn main() -> std::io::Result<()> {

src/runtime/driver/op/link.rs

@@ -0,0 +1,86 @@
+use pin_project_lite::pin_project;
+use std::{
+    future::Future,
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+use crate::{OneshotOutputTransform, Submit, UnsubmittedOneshot};
+
+pub struct Link<D, N> {
+    data: D,
+    next: N,
+}
+
+impl<D, N> Link<D, N> {
+    pub fn new(data: D, next: N) -> Self {
+        Self { data, next }
+    }
+}
+
+impl<D, N> Submit for Link<D, N>
+where
+    D: Submit,
+    N: Submit,
+{
+    type Output = LinkedInflightOneshot<D::Output, N::Output>;
+
+    fn submit(self) -> Self::Output {
+        LinkedInflightOneshot {
+            data: self.data.submit(),
+            next: Some(self.next.submit()),
+        }
+    }
+}
+
+impl<D1, T1: OneshotOutputTransform<StoredData = D1>, N> Link<UnsubmittedOneshot<D1, T1>, N> {
+    pub fn link<D2, T2: OneshotOutputTransform<StoredData = D2>>(
+        self,
+        other: UnsubmittedOneshot<D2, T2>,
+    ) -> Link<UnsubmittedOneshot<D1, T1>, Link<N, UnsubmittedOneshot<D2, T2>>> {
+        Link {
+            data: self.data.set_flags(io_uring::squeue::Flags::IO_LINK),
+            next: Link {
+                data: self.next,
+                next: other,
+            },
+        }
+    }
+
+    pub fn hard_link<D2, T2: OneshotOutputTransform<StoredData = D2>>(
+        self,
+        other: UnsubmittedOneshot<D2, T2>,
+    ) -> Link<UnsubmittedOneshot<D1, T1>, Link<N, UnsubmittedOneshot<D2, T2>>> {
+        Link {
+            data: self.data.set_flags(io_uring::squeue::Flags::IO_LINK),
+            next: Link {
+                data: self.next,
+                next: other,
+            },
+        }
+    }
+}
+
+pin_project! {
+    pub struct LinkedInflightOneshot<D, N> {
+        #[pin]
+        data: D,
+        next: Option<N>,
+    }
+}
+
+impl<D, N> Future for LinkedInflightOneshot<D, N>
+where
+    D: Future,
+{
+    type Output = (D::Output, N);
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let this = self.project();
+
+        let output = ready!(this.data.poll(cx));
+        let next = this.next.take().unwrap();
+
+        Poll::Ready((output, next))
+    }
+}

src/runtime/driver/op/mod.rs

@@ -7,8 +7,10 @@ use std::task::{Context, Poll, Waker};
 use io_uring::squeue::Flags;
 use io_uring::{cqueue, squeue};
 
+mod link;
 mod slab_list;
 
+use link::Link;
 use slab::Slab;
 use slab_list::{SlabListEntry, SlabListIndices};
 
@@ -38,29 +40,43 @@ impl<D, T: OneshotOutputTransform<StoredData = D>> UnsubmittedOneshot<D, T> {
         }
     }
 
+    /// Link two UnsubmittedOneshots.
+    pub fn link<D2, T2: OneshotOutputTransform<StoredData = D2>>(
+        self,
+        other: UnsubmittedOneshot<D2, T2>,
+    ) -> Link<UnsubmittedOneshot<D, T>, UnsubmittedOneshot<D2, T2>> {
+        Link::new(self.set_flags(io_uring::squeue::Flags::IO_LINK), other)
+    }
+
+    /// Hard-link two UnsubmittedOneshots.
+    pub fn hard_link<D2, T2: OneshotOutputTransform<StoredData = D2>>(
+        self,
+        other: UnsubmittedOneshot<D2, T2>,
+    ) -> Link<UnsubmittedOneshot<D, T>, UnsubmittedOneshot<D2, T2>> {
+        Link::new(self.set_flags(io_uring::squeue::Flags::IO_HARDLINK), other)
+    }
+
     /// Set the SQE's flags.
-    pub fn set_flags(mut self, flags: Flags) -> Self {
+    pub(crate) fn set_flags(mut self, flags: Flags) -> Self {
         self.sqe = self.sqe.flags(flags);
         self
     }
+}
+
+impl<D, T: OneshotOutputTransform<StoredData = D>> Submit for UnsubmittedOneshot<D, T> {
+    type Output = InFlightOneshot<D, T>;
 
     /// Submit an operation to the driver for batched entry to the kernel.
-    pub fn submit(self) -> InFlightOneshot<D, T> {
+    fn submit(self) -> Self::Output {
         let handle = CONTEXT
             .with(|x| x.handle())
             .expect("Could not submit op; not in runtime context");
 
-        self.submit_with_driver(&handle)
-    }
-
-    fn submit_with_driver(self, driver: &driver::Handle) -> InFlightOneshot<D, T> {
-        let index = driver.submit_op_2(self.sqe);
-
-        let driver = driver.into();
+        let index = handle.submit_op_2(self.sqe);
 
         let inner = InFlightOneshotInner {
             index,
-            driver,
+            driver: (&handle).into(),
             stable_data: self.stable_data,
             post_op: self.post_op,
         };
@@ -121,6 +137,15 @@ impl<D: 'static, T: OneshotOutputTransform<StoredData = D>> Drop for InFlightOne
     }
 }
 
+/// Submit an operation or operations to the driver.
+pub trait Submit {
+    /// The submitted output with an in-flight operation or linked in-flight operations.
+    type Output;
+
+    /// Submit an operation or linked operations.
+    fn submit(self) -> Self::Output;
+}
+
 /// Transforms the output of a oneshot operation into a more user-friendly format.
 pub trait OneshotOutputTransform {
     /// The final output after the transformation.

tests/driver.rs

@@ -1,6 +1,6 @@
 use tempfile::NamedTempFile;
 
-use tokio_uring::{buf::IoBuf, fs::File};
+use tokio_uring::{buf::IoBuf, fs::File, Submit};
 
 #[path = "../src/future.rs"]
 #[allow(warnings)]