Add a sample implementation of a double ended stream

src/stream/double_ended_stream.rs

@@ -22,3 +22,31 @@ pub trait DoubleEndedStream: Stream {
     /// [trait-level]: trait.DoubleEndedStream.html
     fn poll_next_back(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>>;
 }
+
+pub struct Sample<T> {
+    inner: Vec<T>,
+}
+
+impl<T> From<Vec<T>> for Sample<T> {
+    fn from(data: Vec<T>) -> Self {
+        Sample { inner: data }
+    }
+}
+
+impl<T> Unpin for Sample<T> {}
+
+impl<T> Stream for Sample<T> {
+    type Item = T;
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        if self.inner.len() > 0 {
+            return Poll::Ready(Some(self.inner.remove(0)));
+        }
+        return Poll::Ready(None);
+    }
+}
+
+impl<T> DoubleEndedStream for Sample<T> {
+    fn poll_next_back(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        Poll::Ready(self.inner.pop())
+    }
+}