Merge branch 'master' into fs-stream-skip-while

src/fs/metadata.rs

@@ -70,7 +70,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata("a.txt").await?;
             /// println!("{:?}", metadata.file_type());
@@ -90,7 +90,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata(".").await?;
             /// println!("{:?}", metadata.is_dir());
@@ -110,7 +110,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata("a.txt").await?;
             /// println!("{:?}", metadata.is_file());
@@ -128,7 +128,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata("a.txt").await?;
             /// println!("{}", metadata.len());
@@ -146,7 +146,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata("a.txt").await?;
             /// println!("{:?}", metadata.permissions());
@@ -169,7 +169,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata("a.txt").await?;
             /// println!("{:?}", metadata.modified());
@@ -192,7 +192,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata("a.txt").await?;
             /// println!("{:?}", metadata.accessed());
@@ -215,7 +215,7 @@ cfg_if! {
             /// ```no_run
             /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
             /// #
-            /// use std::fs;
+            /// use async_std::fs;
             ///
             /// let metadata = fs::metadata("a.txt").await?;
             /// println!("{:?}", metadata.created());

src/stream/stream/filter.rs

@@ -0,0 +1,49 @@
+use std::marker::PhantomData;
+use std::pin::Pin;
+
+use crate::stream::Stream;
+use crate::task::{Context, Poll};
+
+/// A stream to filter elements of another stream with a predicate.
+#[derive(Debug)]
+pub struct Filter<S, P, T> {
+    stream: S,
+    predicate: P,
+    __t: PhantomData<T>,
+}
+
+impl<S, P, T> Filter<S, P, T> {
+    pin_utils::unsafe_pinned!(stream: S);
+    pin_utils::unsafe_unpinned!(predicate: P);
+
+    pub(super) fn new(stream: S, predicate: P) -> Self {
+        Filter {
+            stream,
+            predicate,
+            __t: PhantomData,
+        }
+    }
+}
+
+impl<S, P> futures_core::stream::Stream for Filter<S, P, S::Item>
+where
+    S: Stream,
+    P: FnMut(&S::Item) -> bool,
+{
+    type Item = S::Item;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let next = futures_core::ready!(self.as_mut().stream().poll_next(cx));
+
+        match next {
+            Some(v) => match (self.as_mut().predicate())(&v) {
+                true => Poll::Ready(Some(v)),
+                false => {
+                    cx.waker().wake_by_ref();
+                    Poll::Pending
+                }
+            },
+            None => Poll::Ready(None),
+        }
+    }
+}

src/stream/stream/mod.rs

@@ -24,6 +24,7 @@
 mod all;
 mod any;
 mod enumerate;
+mod filter;
 mod filter_map;
 mod find;
 mod find_map;
@@ -33,12 +34,15 @@ mod min_by;
 mod next;
 mod nth;
 mod scan;
+mod skip;
 mod skip_while;
 mod take;
 mod zip;
 
+pub use filter::Filter;
 pub use fuse::Fuse;
 pub use scan::Scan;
+pub use skip::Skip;
 pub use skip_while::SkipWhile;
 pub use take::Take;
 pub use zip::Zip;
@@ -284,6 +288,34 @@ pub trait Stream {
             done: false,
         }
     }
+    /// Creates a stream that uses a predicate to determine if an element
+    /// should be yeilded.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    ///```
+    /// # 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, 4].into_iter().collect();
+    /// let mut s = s.filter(|i| i % 2 == 0);
+    ///
+    /// assert_eq!(s.next().await, Some(2));
+    /// assert_eq!(s.next().await, Some(4));
+    /// assert_eq!(s.next().await, None);
+    /// #
+    /// # }) }
+    fn filter<P>(self, predicate: P) -> Filter<Self, P, Self::Item>
+    where
+        Self: Sized,
+        P: FnMut(&Self::Item) -> bool,
+    {
+        Filter::new(self, predicate)
+    }
 
     /// Both filters and maps a stream.
     ///
@@ -672,6 +704,7 @@ pub trait Stream {
     /// elements in the strem are yeilded.
     ///
     /// ## Examples
+    ///
     /// ```
     /// # fn main() { async_std::task::block_on(async {
     /// #
@@ -695,6 +728,25 @@ pub trait Stream {
         SkipWhile::new(self, predicate)
     }
 
+    /// Creates a combinator that skips the first `n` elements.
+    ///
+    /// ## Examples
+    ///
+    /// 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

src/stream/stream/skip.rs

@@ -0,0 +1,41 @@
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use crate::stream::Stream;
+
+/// A stream to skip first n elements of another stream.
+#[derive(Debug)]
+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),
+            }
+        }
+    }
+}