alsa/
poll.rs

1//! Tiny poll ffi
2//!
3//! A tiny wrapper around libc's poll system call.
4
5use libc;
6use super::error::*;
7pub use libc::pollfd;
8use ::alloc::vec;
9use ::alloc::vec::Vec;
10
11bitflags! {
12    #[repr(transparent)]
13    #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
14    pub struct Flags: ::libc::c_short {
15        const IN  = ::libc::POLLIN;
16        const PRI = ::libc::POLLPRI;
17        const OUT = ::libc::POLLOUT;
18        const ERR = ::libc::POLLERR;
19        const HUP = ::libc::POLLHUP;
20        const NVAL = ::libc::POLLNVAL;
21    }
22}
23
24pub trait Descriptors {
25    fn count(&self) -> usize;
26    fn fill(&self, _: &mut [pollfd]) -> Result<usize>;
27    fn revents(&self, _: &[pollfd]) -> Result<Flags>;
28
29    /// Wrapper around count and fill - returns an array of pollfds
30    fn get(&self) -> Result<Vec<pollfd>> {
31        let mut v = vec![pollfd { fd: 0, events: 0, revents: 0 }; self.count()];
32        if self.fill(&mut v)? != v.len() { Err(Error::unsupported("did not fill the poll descriptors array")) }
33        else { Ok(v) }
34    }
35}
36
37impl Descriptors for pollfd {
38    fn count(&self) -> usize { 1 }
39    fn fill(&self, a: &mut [pollfd]) -> Result<usize> { a[0] = *self; Ok(1) }
40    fn revents(&self, a: &[pollfd]) -> Result<Flags> { Ok(Flags::from_bits_truncate(a[0].revents)) }
41}
42
43/// Wrapper around the libc poll call.
44pub fn poll(fds: &mut[pollfd], timeout: i32) -> Result<usize> {
45    let r = unsafe { libc::poll(fds.as_mut_ptr(), fds.len() as libc::nfds_t, timeout as libc::c_int) };
46    if r >= 0 { Ok(r as usize) } else {
47        #[cfg(feature = "std")]
48        { from_code(
49            "poll",
50            -std::io::Error::last_os_error().raw_os_error().unwrap_or_default()).map(|_| unreachable!())
51        }
52        #[cfg(not(feature = "std"))]
53        { from_code("poll", -unsafe {super::error::errno}).map(|_| unreachable!()) }
54        
55    }
56}
57
58/// Builds a pollfd array, polls it, and returns the poll descriptors which have non-zero revents.
59pub fn poll_all<'a>(desc: &[&'a dyn Descriptors], timeout: i32) -> Result<Vec<(&'a dyn Descriptors, Flags)>> {
60
61    let mut pollfds: Vec<pollfd> = vec!();
62    let mut indices = vec!();
63    for v2 in desc.iter().map(|q| q.get()) {
64        let v = v2?;
65        indices.push(pollfds.len() .. pollfds.len()+v.len());
66        pollfds.extend(v);
67    };
68
69    poll(&mut pollfds, timeout)?;
70
71    let mut res = vec!();
72    for (i, r) in indices.into_iter().enumerate() {
73        let z = desc[i].revents(&pollfds[r])?;
74        if !z.is_empty() { res.push((desc[i], z)); }
75    }
76    Ok(res)
77}
alsa/poll.rs

alsa/
poll.rs
