Support nullable timeout in ppoll

Author: MikailBag

CHANGELOG.md

@@ -36,10 +36,11 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Changed `fallocate` return type from `c_int` to `()` (#[1201](https://github.com/nix-rust/nix/pull/1201))
 - Enabled `sys::ptrace::setregs` and `sys::ptrace::getregs` on x86_64-unknown-linux-musl target
   (#[1198](https://github.com/nix-rust/nix/pull/1198))
-- On Linux, `ptrace::write` is now an `unsafe` function.  Caveat programmer.
+- On Linux, `ptrace::write` is now an `unsafe` function. Caveat programmer.
   (#[1245](https://github.com/nix-rust/nix/pull/1245))
 - `execv`, `execve`, `execvp` and `execveat` in `::nix::unistd` and `reboot` in
   `::nix::sys::reboot` now return `Result<Infallible>` instead of `Result<Void>` (#[1239](https://github.com/nix-rust/nix/pull/1239))
+- `nix::poll::ppoll`: `timeout` parameter is now optional, None is equivalent for infinite timeout.
 
 ### Fixed
 

src/poll.rs

@@ -130,16 +130,20 @@ pub fn poll(fds: &mut [PollFd], timeout: libc::c_int) -> Result<libc::c_int> {
 /// ([`poll(2)`](http://man7.org/linux/man-pages/man2/poll.2.html))
 ///
 /// `ppoll` behaves like `poll`, but let you specify what signals may interrupt it
-/// with the `sigmask` argument.
+/// with the `sigmask` argument. If you want `ppoll` to block indefinitely,
+/// specify `None` as `timeout` (it is like `timeout = -1` for `poll`).
 ///
 #[cfg(any(target_os = "android", target_os = "dragonfly", target_os = "freebsd", target_os = "linux"))]
-pub fn ppoll(fds: &mut [PollFd], timeout: TimeSpec, sigmask: SigSet) -> Result<libc::c_int> {
-
+pub fn ppoll(fds: &mut [PollFd], timeout: Option<TimeSpec>, sigmask: SigSet) -> Result<libc::c_int> {
+    let timeout = match timeout {
+        Some(t) => t.as_ref(),
+        None => core::ptr::null()
+    };
 
     let res = unsafe {
         libc::ppoll(fds.as_mut_ptr() as *mut libc::pollfd,
                     fds.len() as libc::nfds_t,
-                    timeout.as_ref(),
+                    timeout,
                     sigmask.as_ref())
     };
     Errno::result(res)

test/test_poll.rs

@@ -37,14 +37,14 @@ fn test_ppoll() {
     let mut fds = [PollFd::new(r, PollFlags::POLLIN)];
 
     // Poll an idle pipe.  Should timeout
-    let nfds = ppoll(&mut fds, timeout, SigSet::empty()).unwrap();
+    let nfds = ppoll(&mut fds, Some(timeout), SigSet::empty()).unwrap();
     assert_eq!(nfds, 0);
     assert!(!fds[0].revents().unwrap().contains(PollFlags::POLLIN));
 
     write(w, b".").unwrap();
 
     // Poll a readable pipe.  Should return an event.
-    let nfds = ppoll(&mut fds, timeout, SigSet::empty()).unwrap();
+    let nfds = ppoll(&mut fds, Some(timeout), SigSet::empty()).unwrap();
     assert_eq!(nfds, 1);
     assert!(fds[0].revents().unwrap().contains(PollFlags::POLLIN));
 }