FdSet: allow conversion from iterable of AsFd

changelog/2383.added.md

@@ -0,0 +1 @@
+Added implementations of `FromIterator` and `From` for `FdSet`, allowing them to be constructed from iterables of types that implement `AsFd`.

src/sys/select.rs

@@ -7,7 +7,7 @@ use std::convert::TryFrom;
 use std::iter::FusedIterator;
 use std::mem;
 use std::ops::Range;
-use std::os::unix::io::{AsRawFd, BorrowedFd, RawFd};
+use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, RawFd};
 use std::ptr::{null, null_mut};
 
 pub use libc::FD_SETSIZE;
@@ -163,6 +163,24 @@ impl<'a, 'fd> DoubleEndedIterator for Fds<'a, 'fd> {
 
 impl<'a, 'fd> FusedIterator for Fds<'a, 'fd> {}
 
+impl<'fd, F> FromIterator<F> for FdSet<'fd> where F: 'fd + AsFd {
+    fn from_iter<T>(iter: T) -> Self where T: IntoIterator<Item = F> {
+        let mut result = FdSet::new();
+        for fd in iter.into_iter() {
+            let fd = fd.as_fd();
+            assert_fd_valid(fd.as_raw_fd());
+            unsafe { libc::FD_SET(fd.as_raw_fd(), &mut result.set) };
+        }
+        result
+    }
+}
+
+impl<'fd, T, F> From<T> for FdSet<'fd> where T: IntoIterator<Item = F>, F: 'fd + AsFd {
+    fn from(value: T) -> Self {
+        value.into_iter().collect()
+    }
+}
+
 /// Monitors file descriptors for readiness
 ///
 /// Returns the total number of ready file descriptors in all sets. The sets are changed so that all

test/sys/test_select.rs

@@ -291,3 +291,30 @@ fn test_select_nfds2() {
     assert!(fd_set.contains(r1.as_fd()));
     assert!(!fd_set.contains(r2.as_fd()));
 }
+
+#[test]
+fn test_fdset_from_iterable() {
+    let (r1, w1) = pipe().unwrap();
+    let (r2, w2) = pipe().unwrap();
+    let reads = [r1, r2]
+        .into_iter()
+        .map(|fd| (fd.as_raw_fd(), fd))
+        .collect::<std::collections::HashMap<_, _>>();
+    let writes = [w1, w2];
+    let reads_fdset: FdSet = reads.values().into();
+    let writes_fdset: FdSet = writes.iter().into();
+    assert_eq!(
+        reads_fdset
+            .fds(None)
+            .map(|fd| fd.as_raw_fd())
+            .collect::<std::collections::HashSet<_>>(),
+        reads.values().map(|fd| fd.as_raw_fd()).collect()
+    );
+    assert_eq!(
+        writes_fdset
+            .fds(None)
+            .map(|fd| fd.as_raw_fd())
+            .collect::<std::collections::HashSet<_>>(),
+        writes.iter().map(|fd| fd.as_raw_fd()).collect()
+    );
+}