Implement Debug trait for PollFd

This is useful when using printf-style debugging to observe the variables of
the program.

Also includes a test.

Fixes #885.

1 files changed, 19 insertions, 1 deletions

diff --git a/test/test_poll.rs b/test/test_poll.rs
index c28c8fd8..a9831ed4 100644
--- a/test/test_poll.rs
+++ b/test/test_poll.rs
@@ -1,7 +1,7 @@
 use nix::poll::{EventFlags, poll, PollFd};
 use nix::sys::signal::SigSet;
 use nix::sys::time::{TimeSpec, TimeValLike};
-use nix::unistd::{write, pipe};
+use nix::unistd::{write, pipe, close};
 
 #[test]
 fn test_poll() {
@@ -21,6 +21,24 @@ fn test_poll() {
     assert!(fds[0].revents().unwrap().contains(EventFlags::POLLIN));
 }
 
+#[test]
+fn test_poll_debug() {
+    assert_eq!(format!("{:?}", PollFd::new(0, EventFlags::empty())),
+               "PollFd { fd: 0, events: (empty), revents: (empty) }");
+    assert_eq!(format!("{:?}", PollFd::new(1, EventFlags::POLLIN)),
+               "PollFd { fd: 1, events: POLLIN, revents: (empty) }");
+
+    // Testing revents requires doing some I/O
+    let (r, w) = pipe().unwrap();
+    let mut fds = [PollFd::new(r, EventFlags::POLLIN)];
+    write(w, b" ").unwrap();
+    close(w).unwrap();
+    poll(&mut fds, -1).unwrap();
+    assert_eq!(format!("{:?}", fds[0]),
+               format!("PollFd {{ fd: {}, events: POLLIN, revents: POLLIN | POLLHUP }}", r));
+    close(r).unwrap();
+}
+
 // ppoll(2) is the same as poll except for how it handles timeouts and signals.
 // Repeating the test for poll(2) should be sufficient to check that our
 // bindings are correct.