From 570329b17648727a2800b3ecb1bf21dfd13bb320 Mon Sep 17 00:00:00 2001
From: Fedor Sakharov <fedor.sakharov@gmail.com>
Date: Sat, 21 Sep 2019 14:40:25 +0300
Subject: [PATCH 1/3] adds stream::skip combinator

---
 src/stream/stream/mod.rs  | 27 ++++++++++++++++++++++++++
 src/stream/stream/skip.rs | 41 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 src/stream/stream/skip.rs

diff --git a/src/stream/stream/mod.rs b/src/stream/stream/mod.rs
index 8ddab2126..5f4010ca6 100644
--- a/src/stream/stream/mod.rs
+++ b/src/stream/stream/mod.rs
@@ -33,6 +33,7 @@ mod min_by;
 mod next;
 mod nth;
 mod scan;
+mod skip;
 mod take;
 mod zip;
 
@@ -51,6 +52,7 @@ use fold::FoldFuture;
 use min_by::MinByFuture;
 use next::NextFuture;
 use nth::NthFuture;
+use skip::Skip;
 
 use std::cmp::Ordering;
 use std::marker::PhantomData;
@@ -661,6 +663,31 @@ pub trait Stream {
         Scan::new(self, initial_state, f)
     }
 
+    /// Creates a combinator that skips the first `n` elements.
+    ///
+    /// ## Examples
+    ///
+    /// ```
+    /// # fn main() { async_std::task::block_on(async {
+    /// #
+    /// use std::collections::VecDeque;
+    /// use async_std::stream::Stream;
+    ///
+    /// let s: VecDeque<usize> = vec![1, 2, 3].into_iter().collect();
+    /// let mut skipped = s.skip(2);
+    ///
+    /// assert_eq!(skipped.next().await, Some(3));
+    /// assert_eq!(skipped.next().await, None);
+    /// #
+    /// # }) }
+    /// ```
+    fn skip(self, n: usize) -> Skip<Self>
+    where
+        Self: Sized,
+    {
+        Skip::new(self, n)
+    }
+
     /// 'Zips up' two streams into a single stream of pairs.
     ///
     /// `zip()` returns a new stream that will iterate over two other streams, returning a tuple
diff --git a/src/stream/stream/skip.rs b/src/stream/stream/skip.rs
new file mode 100644
index 000000000..09f5cab8f
--- /dev/null
+++ b/src/stream/stream/skip.rs
@@ -0,0 +1,41 @@
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use crate::stream::Stream;
+
+#[doc(hidden)]
+#[allow(missing_debug_implementations)]
+pub struct Skip<S> {
+    stream: S,
+    n: usize,
+}
+
+impl<S> Skip<S> {
+    pin_utils::unsafe_pinned!(stream: S);
+    pin_utils::unsafe_unpinned!(n: usize);
+
+    pub(crate) fn new(stream: S, n: usize) -> Self {
+        Skip { stream, n }
+    }
+}
+
+impl<S> Stream for Skip<S>
+where
+    S: Stream,
+{
+    type Item = S::Item;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        loop {
+            let next = futures_core::ready!(self.as_mut().stream().poll_next(cx));
+
+            match next {
+                Some(v) => match self.n {
+                    0 => return Poll::Ready(Some(v)),
+                    _ => *self.as_mut().n() -= 1,
+                },
+                None => return Poll::Ready(None),
+            }
+        }
+    }
+}

From 75da138696b495b65775aab356ad8146f1c2b8e8 Mon Sep 17 00:00:00 2001
From: Fedor Sakharov <fedor.sakharov@gmail.com>
Date: Sat, 21 Sep 2019 16:37:30 +0300
Subject: [PATCH 2/3] export Skip type

---
 src/stream/stream/mod.rs  | 2 +-
 src/stream/stream/skip.rs | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/stream/stream/mod.rs b/src/stream/stream/mod.rs
index 5f4010ca6..6444651ab 100644
--- a/src/stream/stream/mod.rs
+++ b/src/stream/stream/mod.rs
@@ -39,6 +39,7 @@ mod zip;
 
 pub use fuse::Fuse;
 pub use scan::Scan;
+use skip::Skip;
 pub use take::Take;
 pub use zip::Zip;
 
@@ -52,7 +53,6 @@ use fold::FoldFuture;
 use min_by::MinByFuture;
 use next::NextFuture;
 use nth::NthFuture;
-use skip::Skip;
 
 use std::cmp::Ordering;
 use std::marker::PhantomData;
diff --git a/src/stream/stream/skip.rs b/src/stream/stream/skip.rs
index 09f5cab8f..8a2d966d8 100644
--- a/src/stream/stream/skip.rs
+++ b/src/stream/stream/skip.rs
@@ -3,8 +3,8 @@ use std::task::{Context, Poll};
 
 use crate::stream::Stream;
 
-#[doc(hidden)]
-#[allow(missing_debug_implementations)]
+/// A stream to skip first n elements of another stream.
+#[derive(Debug)]
 pub struct Skip<S> {
     stream: S,
     n: usize,

From fdd81e1b2a04d174fb8f4a0f1f7e170dcffa501d Mon Sep 17 00:00:00 2001
From: Fedor Sakharov <fedor.sakharov@gmail.com>
Date: Sat, 21 Sep 2019 16:40:58 +0300
Subject: [PATCH 3/3] Actually export Skip

---
 src/stream/stream/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/stream/stream/mod.rs b/src/stream/stream/mod.rs
index 6444651ab..6284062d2 100644
--- a/src/stream/stream/mod.rs
+++ b/src/stream/stream/mod.rs
@@ -39,7 +39,7 @@ mod zip;
 
 pub use fuse::Fuse;
 pub use scan::Scan;
-use skip::Skip;
+pub use skip::Skip;
 pub use take::Take;
 pub use zip::Zip;