1 files changed, 81 insertions, 0 deletions
diff --git a/third_party/rust/futures-0.1.31/src/future/select_ok.rs b/third_party/rust/futures-0.1.31/src/future/select_ok.rs
new file mode 100644
index 0000000000..f122a0ea30
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+++ b/third_party/rust/futures-0.1.31/src/future/select_ok.rs
@@ -0,0 +1,81 @@
+//! Definition of the `SelectOk` combinator, finding the first successful future
+//! in a list.
+
+use std::mem;
+use std::prelude::v1::*;
+
+use {Future, IntoFuture, Poll, Async};
+
+/// Future for the `select_ok` combinator, waiting for one of any of a list of
+/// futures to successfully complete. Unlike `select_all`, this future ignores all
+/// but the last error, if there are any.
+///
+/// This is created by the `select_ok` function.
+#[derive(Debug)]
+#[must_use = "futures do nothing unless polled"]
+pub struct SelectOk<A> where A: Future {
+    inner: Vec<A>,
+}
+
+/// Creates a new future which will select the first successful future over a list of futures.
+///
+/// The returned future will wait for any future within `iter` to be ready and Ok. Unlike
+/// `select_all`, this will only return the first successful completion, or the last
+/// failure. This is useful in contexts where any success is desired and failures
+/// are ignored, unless all the futures fail.
+///
+/// # Panics
+///
+/// This function will panic if the iterator specified contains no items.
+pub fn select_ok<I>(iter: I) -> SelectOk<<I::Item as IntoFuture>::Future>
+    where I: IntoIterator,
+          I::Item: IntoFuture,
+{
+    let ret = SelectOk {
+        inner: iter.into_iter()
+                   .map(|a| a.into_future())
+                   .collect(),
+    };
+    assert!(ret.inner.len() > 0);
+    ret
+}
+
+impl<A> Future for SelectOk<A> where A: Future {
+    type Item = (A::Item, Vec<A>);
+    type Error = A::Error;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        // loop until we've either exhausted all errors, a success was hit, or nothing is ready
+        loop {
+            let item = self.inner.iter_mut().enumerate().filter_map(|(i, f)| {
+                match f.poll() {
+                    Ok(Async::NotReady) => None,
+                    Ok(Async::Ready(e)) => Some((i, Ok(e))),
+                    Err(e) => Some((i, Err(e))),
+                }
+            }).next();
+
+            match item {
+                Some((idx, res)) => {
+                    // always remove Ok or Err, if it's not the last Err continue looping
+                    drop(self.inner.remove(idx));
+                    match res {
+                        Ok(e) => {
+                            let rest = mem::replace(&mut self.inner, Vec::new());
+                            return Ok(Async::Ready((e, rest)))
+                        },
+                        Err(e) => {
+                            if self.inner.is_empty() {
+                                return Err(e)
+                            }
+                        },
+                    }
+                }
+                None => {
+                    // based on the filter above, nothing is ready, return
+                    return Ok(Async::NotReady)
+                },
+            }
+        }
+    }
+}