device: Use OwnedFd type and bump MSRV to 1.66

The first new commit 22a2365 on `next` switches to the `RawFd` type from
the `std::os::fd` module which is only available since Rust 1.66.  This
module also provides an `OwnedFd` type which already has a `close()`
call in the `Drop` implementation, and implements the desired `AsRawFd`
(and `AsFd` and `IntoRawFd`) traits.

Note that these types were already stabilized in Rust 1.63 under
`std::os::unix::io`, which is now merely a reexport of `std::os::fd`.

This also replaces the forgotten `.fd()` calls with `.as_raw_fd()` from
from commit 17c2871.

Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 license = "MIT"
 readme = "README.md"
 repository= "https://github.com/raymanfx/libv4l-rs"
+rust-version = "1.66"
 
 [dependencies]
 bitflags = "1.2.1"

src/device.rs

@@ -1,8 +1,8 @@
-use std::convert::TryFrom;
-use std::path::Path;
 use std::{
+    convert::TryFrom,
     io, mem,
-    os::fd::{AsRawFd, RawFd},
+    os::fd::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd},
+    path::Path,
     sync::Arc,
 };
 
@@ -361,14 +361,14 @@ impl io::Write for Device {
 /// Device handle for low-level access.
 ///
 /// Acquiring a handle facilitates (possibly mutating) interactions with the device.
-#[derive(Debug, Clone)]
-pub struct Handle(RawFd);
+#[derive(Debug)]
+pub struct Handle(OwnedFd);
 
 impl Handle {
     /// Wraps an existing file descriptor
     ///
     /// The caller must ensure that `fd` is a valid, open file descriptor for a V4L device.
-    pub unsafe fn new(fd: RawFd) -> Self {
+    pub unsafe fn new(fd: OwnedFd) -> Self {
         Self(fd)
     }
 
@@ -385,7 +385,7 @@ impl Handle {
             return Err(io::Error::last_os_error());
         }
 
-        Ok(Handle(fd))
+        Ok(Handle(unsafe { OwnedFd::from_raw_fd(fd) }))
     }
 
     /// Polls the file descriptor for I/O events
@@ -400,35 +400,38 @@ impl Handle {
     pub fn poll(&self, events: i16, timeout: i32) -> io::Result<i32> {
         match unsafe {
             libc::poll(
-                [libc::pollfd {
-                    fd: self.0,
+                &mut libc::pollfd {
+                    fd: self.as_raw_fd(),
                     events,
                     revents: 0,
-                }]
-                .as_mut_ptr(),
+                },
                 1,
                 timeout,
             )
         } {
             -1 => Err(io::Error::last_os_error()),
-            ret => {
-                // A return value of zero means that we timed out. A positive value signifies the
-                // number of fds with non-zero revents fields (aka I/O activity).
-                assert!(ret == 0 || ret == 1);
-                Ok(ret)
-            }
+            // A return value of zero means that we timed out. A positive value signifies the
+            // number of fds with non-zero revents fields (aka I/O activity).
+            ret @ 0..=1 => Ok(ret),
+            ret => panic!("Invalid return value {}", ret),
         }
     }
 }
 
-impl Drop for Handle {
-    fn drop(&mut self) {
-        let _ = v4l2::close(self.0);
+impl AsFd for Handle {
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        self.0.as_fd()
     }
 }
 
 impl AsRawFd for Handle {
     fn as_raw_fd(&self) -> RawFd {
-        self.0
+        self.0.as_raw_fd()
+    }
+}
+
+impl IntoRawFd for Handle {
+    fn into_raw_fd(self) -> RawFd {
+        self.0.into_raw_fd()
     }
 }

src/io/mod.rs

@@ -3,6 +3,7 @@ use std::{
     marker::PhantomData,
     mem,
     ops::{Index, IndexMut},
+    os::fd::AsRawFd,
     ptr, slice,
     sync::Arc,
 };
@@ -65,7 +66,7 @@ impl<B, S> Queue<B, S> {
 
         unsafe {
             v4l2::ioctl(
-                self.handle.fd(),
+                self.handle.as_raw_fd(),
                 v4l2::vidioc::VIDIOC_REQBUFS,
                 &mut v4l2_reqbufs as *mut _ as *mut std::os::raw::c_void,
             )?;
@@ -88,7 +89,7 @@ impl<B, S> Queue<B, S> {
 
         unsafe {
             v4l2::ioctl(
-                self.handle.fd(),
+                self.handle.as_raw_fd(),
                 v4l2::vidioc::VIDIOC_QUERYBUF,
                 &mut buf as *mut _ as *mut std::os::raw::c_void,
             )?;
@@ -101,7 +102,7 @@ impl<B, S> Queue<B, S> {
     fn streamon(&mut self) -> io::Result<()> {
         unsafe {
             v4l2::ioctl(
-                self.handle.fd(),
+                self.handle.as_raw_fd(),
                 v4l2::vidioc::VIDIOC_STREAMON,
                 &mut self.buf_type as *mut _ as *mut std::os::raw::c_void,
             )
@@ -112,7 +113,7 @@ impl<B, S> Queue<B, S> {
     fn streamoff(&mut self) -> io::Result<()> {
         unsafe {
             v4l2::ioctl(
-                self.handle.fd(),
+                self.handle.as_raw_fd(),
                 v4l2::vidioc::VIDIOC_STREAMOFF,
                 &mut self.buf_type as *mut _ as *mut std::os::raw::c_void,
             )
@@ -125,7 +126,7 @@ impl<B, S> Queue<B, S> {
 
         unsafe {
             v4l2::ioctl(
-                self.handle.fd(),
+                self.handle.as_raw_fd(),
                 v4l2::vidioc::VIDIOC_QBUF,
                 buf as *mut _ as *mut std::os::raw::c_void,
             )
@@ -138,7 +139,7 @@ impl<B, S> Queue<B, S> {
 
         unsafe {
             v4l2::ioctl(
-                self.handle.fd(),
+                self.handle.as_raw_fd(),
                 v4l2::vidioc::VIDIOC_DQBUF,
                 buf as *mut _ as *mut std::os::raw::c_void,
             )
@@ -244,7 +245,7 @@ impl Queue<Mmap<'_>, queue::Idle> {
 
             let mapping = unsafe {
                 v4l2::ioctl(
-                    queue.handle.fd(),
+                    queue.handle.as_raw_fd(),
                     v4l2::vidioc::VIDIOC_QUERYBUF,
                     &mut v4l2_buf as *mut _ as *mut std::os::raw::c_void,
                 )?;
@@ -254,7 +255,7 @@ impl Queue<Mmap<'_>, queue::Idle> {
                     v4l2_buf.length as usize,
                     libc::PROT_READ | libc::PROT_WRITE,
                     libc::MAP_SHARED,
-                    queue.handle.fd(),
+                    queue.handle.as_raw_fd(),
                     v4l2_buf.m.offset as libc::off_t,
                 )?;
 
@@ -322,7 +323,7 @@ impl Queue<UserPtr, queue::Idle> {
         };
         unsafe {
             v4l2::ioctl(
-                queue.handle.fd(),
+                queue.handle.as_raw_fd(),
                 v4l2::vidioc::VIDIOC_G_FMT,
                 &mut v4l2_fmt as *mut _ as *mut std::os::raw::c_void,
             )?;