[WIP] impl uring cmd feature

src/fs/file.rs

@@ -1,6 +1,7 @@
 use crate::buf::fixed::FixedBuf;
 use crate::buf::{BoundedBuf, BoundedBufMut, IoBuf, IoBufMut, Slice};
 use crate::fs::OpenOptions;
+use crate::io::cmd::UnsubmittedCmd;
 use crate::io::SharedFd;
 
 use crate::runtime::driver::op::{Op, Submit};
@@ -879,6 +880,11 @@ impl File {
     pub async fn close(mut self) -> io::Result<()> {
         self.fd.close().await
     }
+
+    #[allow(missing_docs)]
+    pub fn cmd<T>(&self, op: u32, cmd: [u8; 16], data: T) -> UnsubmittedCmd<T> {
+        UnsubmittedCmd::cmd(&self.fd, op, cmd, data)
+    }
 }
 
 impl FromRawFd for File {

src/io/cmd.rs

@@ -0,0 +1,54 @@
+use std::marker::PhantomData;
+
+use io_uring::cqueue::Entry;
+use io_uring::{opcode, types};
+
+use crate::buf::BoundedBuf;
+use crate::io::SharedFd;
+
+use crate::{OneshotOutputTransform, UnsubmittedOneshot};
+
+/// An unsubmitted read operation.
+pub type UnsubmittedCmd<T> = UnsubmittedOneshot<CmdData<T>, CmdTransform<T>>;
+
+impl<T> UnsubmittedCmd<T> {
+    pub(crate) fn cmd(fd: &SharedFd, op: u32, cmd: [u8; 16], data: T) -> Self {
+        Self::new(
+            CmdData { data },
+            CmdTransform {
+                _phantom: PhantomData,
+            },
+            opcode::UringCmd16::new(types::Fd(fd.raw_fd()), op)
+                .cmd(cmd)
+                .build(),
+        )
+    }
+}
+
+#[allow(missing_docs)]
+pub struct CmdData<T> {
+    data: T,
+}
+
+#[allow(missing_docs)]
+pub struct CmdTransform<B> {
+    _phantom: PhantomData<B>,
+}
+
+impl<T> OneshotOutputTransform for CmdTransform<T> {
+    type Output = (i32, T);
+    type StoredData = CmdData<T>;
+
+    fn transform_oneshot_output(self, mut data: Self::StoredData, cqe: Entry) -> Self::Output {
+        // let result = cqe.result();
+        // let res = if n >= 0 {
+        //     // Safety: the kernel wrote `n` bytes to the buffer.
+        //     unsafe { data.buf.set_init(n as usize) };
+        //     Ok(n as usize)
+        // } else {
+        //     Err(io::Error::from_raw_os_error(-n))
+        // };
+
+        (cqe.result(), data.data)
+    }
+}

src/io/mod.rs

@@ -56,3 +56,5 @@ pub(crate) mod writev;
 
 mod writev_all;
 pub(crate) use writev_all::writev_at_all;
+
+pub(crate) mod cmd;

src/lib.rs

@@ -79,6 +79,7 @@ pub mod buf;
 pub mod fs;
 pub mod net;
 
+pub use io::cmd::*;
 pub use io::read::*;
 pub use io::readv::*;
 pub use io::write::*;