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//! Tiny poll ffi
//!
//! A tiny wrapper around libc's poll system call.
use libc;
use super::error::*;
use std::io;
pub use libc::pollfd;
bitflags! {
#[repr(transparent)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Flags: ::libc::c_short {
const IN = ::libc::POLLIN;
const PRI = ::libc::POLLPRI;
const OUT = ::libc::POLLOUT;
const ERR = ::libc::POLLERR;
const HUP = ::libc::POLLHUP;
const NVAL = ::libc::POLLNVAL;
}
}
pub trait Descriptors {
fn count(&self) -> usize;
fn fill(&self, _: &mut [pollfd]) -> Result<usize>;
fn revents(&self, _: &[pollfd]) -> Result<Flags>;
/// Wrapper around count and fill - returns an array of pollfds
fn get(&self) -> Result<Vec<pollfd>> {
let mut v = vec![pollfd { fd: 0, events: 0, revents: 0 }; self.count()];
if self.fill(&mut v)? != v.len() { Err(Error::unsupported("did not fill the poll descriptors array")) }
else { Ok(v) }
}
}
impl Descriptors for pollfd {
fn count(&self) -> usize { 1 }
fn fill(&self, a: &mut [pollfd]) -> Result<usize> { a[0] = *self; Ok(1) }
fn revents(&self, a: &[pollfd]) -> Result<Flags> { Ok(Flags::from_bits_truncate(a[0].revents)) }
}
/// Wrapper around the libc poll call.
pub fn poll(fds: &mut[pollfd], timeout: i32) -> Result<usize> {
let r = unsafe { libc::poll(fds.as_mut_ptr(), fds.len() as libc::nfds_t, timeout as libc::c_int) };
if r >= 0 { Ok(r as usize) } else {
from_code("poll", -io::Error::last_os_error().raw_os_error().unwrap()).map(|_| unreachable!())
}
}
/// Builds a pollfd array, polls it, and returns the poll descriptors which have non-zero revents.
pub fn poll_all<'a>(desc: &[&'a dyn Descriptors], timeout: i32) -> Result<Vec<(&'a dyn Descriptors, Flags)>> {
let mut pollfds: Vec<pollfd> = vec!();
let mut indices = vec!();
for v2 in desc.iter().map(|q| q.get()) {
let v = v2?;
indices.push(pollfds.len() .. pollfds.len()+v.len());
pollfds.extend(v);
};
poll(&mut pollfds, timeout)?;
let mut res = vec!();
for (i, r) in indices.into_iter().enumerate() {
let z = desc[i].revents(&pollfds[r])?;
if !z.is_empty() { res.push((desc[i], z)); }
}
Ok(res)
}