fix #480 and add simple test cases for that.

r? @fiveop

src/sys/epoll.rs

@@ -1,6 +1,7 @@
 use {Errno, Result};
 use libc::{self, c_int};
 use std::os::unix::io::RawFd;
+use std::ptr;
 
 bitflags!(
     #[repr(C)]
@@ -57,6 +58,16 @@ impl EpollEvent {
     }
 }
 
+impl<'a> Into<&'a mut EpollEvent> for Option<&'a mut EpollEvent> {
+    #[inline]
+    fn into(self) -> &'a mut EpollEvent {
+        match self {
+            Some(epoll_event) => epoll_event,
+            None => unsafe { &mut *ptr::null_mut::<EpollEvent>() }
+        }
+    }
+}
+
 #[inline]
 pub fn epoll_create() -> Result<RawFd> {
     let res = unsafe { libc::epoll_create(1024) };
@@ -72,9 +83,10 @@ pub fn epoll_create1(flags: EpollCreateFlags) -> Result<RawFd> {
 }
 
 #[inline]
-pub fn epoll_ctl(epfd: RawFd, op: EpollOp, fd: RawFd, event: &mut EpollEvent) -> Result<()> {
-    let res = unsafe { libc::epoll_ctl(epfd, op as c_int, fd, &mut event.event) };
-
+pub fn epoll_ctl<'a, T>(epfd: RawFd, op: EpollOp, fd: RawFd, event: T) -> Result<()>
+    where T: Into<&'a mut EpollEvent>
+{
+    let res = unsafe { libc::epoll_ctl(epfd, op as c_int, fd, &mut event.into().event) };
     Errno::result(res).map(drop)
 }
 

test/sys/mod.rs

@@ -6,3 +6,4 @@ mod test_ioctl;
 mod test_wait;
 mod test_select;
 mod test_uio;
+mod test_epoll;

test/sys/test_epoll.rs

@@ -0,0 +1,20 @@
+use nix::sys::epoll::{EpollCreateFlags, EpollFlags, EpollOp, EpollEvent};
+use nix::sys::epoll::{EPOLLIN, EPOLLERR};
+use nix::sys::epoll::{epoll_create1, epoll_ctl};
+use nix::{Error, Errno};
+
+#[test]
+pub fn test_epoll_errno() {
+    let efd = epoll_create1(EpollCreateFlags::empty()).unwrap();
+    let result = epoll_ctl(efd, EpollOp::EpollCtlDel, 1, None);
+    assert!(result.is_err());
+    assert_eq!(result.unwrap_err(), Error::Sys(Errno::ENOENT));
+}
+
+#[test]
+pub fn test_epoll_ctl() {
+    let efd = epoll_create1(EpollCreateFlags::empty()).unwrap();
+    let mut event = EpollEvent::new(EPOLLIN | EPOLLERR, 1);
+    epoll_ctl(efd, EpollOp::EpollCtlAdd, 1, &mut event).unwrap();
+    epoll_ctl(efd, EpollOp::EpollCtlDel, 1, None).unwrap();
+}