1 files changed, 117 insertions, 0 deletions
diff --git a/third_party/rust/tokio-io/src/window.rs b/third_party/rust/tokio-io/src/window.rs
new file mode 100644
index 0000000000..4ded9ad403
--- /dev/null
+++ b/third_party/rust/tokio-io/src/window.rs
@@ -0,0 +1,117 @@
+use std::ops;
+
+/// A owned window around an underlying buffer.
+///
+/// Normally slices work great for considering sub-portions of a buffer, but
+/// unfortunately a slice is a *borrowed* type in Rust which has an associated
+/// lifetime. When working with future and async I/O these lifetimes are not
+/// always appropriate, and are sometimes difficult to store in tasks. This
+/// type strives to fill this gap by providing an "owned slice" around an
+/// underlying buffer of bytes.
+///
+/// A `Window<T>` wraps an underlying buffer, `T`, and has configurable
+/// start/end indexes to alter the behavior of the `AsRef<[u8]>` implementation
+/// that this type carries.
+///
+/// This type can be particularly useful when working with the `write_all`
+/// combinator in this crate. Data can be sliced via `Window`, consumed by
+/// `write_all`, and then earned back once the write operation finishes through
+/// the `into_inner` method on this type.
+#[derive(Debug)]
+pub struct Window<T> {
+    inner: T,
+    range: ops::Range<usize>,
+}
+
+impl<T: AsRef<[u8]>> Window<T> {
+    /// Creates a new window around the buffer `t` defaulting to the entire
+    /// slice.
+    ///
+    /// Further methods can be called on the returned `Window<T>` to alter the
+    /// window into the data provided.
+    pub fn new(t: T) -> Window<T> {
+        Window {
+            range: 0..t.as_ref().len(),
+            inner: t,
+        }
+    }
+
+    /// Gets a shared reference to the underlying buffer inside of this
+    /// `Window`.
+    pub fn get_ref(&self) -> &T {
+        &self.inner
+    }
+
+    /// Gets a mutable reference to the underlying buffer inside of this
+    /// `Window`.
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut self.inner
+    }
+
+    /// Consumes this `Window`, returning the underlying buffer.
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+
+    /// Returns the starting index of this window into the underlying buffer
+    /// `T`.
+    pub fn start(&self) -> usize {
+        self.range.start
+    }
+
+    /// Returns the end index of this window into the underlying buffer
+    /// `T`.
+    pub fn end(&self) -> usize {
+        self.range.end
+    }
+
+    /// Changes the starting index of this window to the index specified.
+    ///
+    /// Returns the windows back to chain multiple calls to this method.
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if `start` is out of bounds for the underlying
+    /// slice or if it comes after the `end` configured in this window.
+    pub fn set_start(&mut self, start: usize) -> &mut Window<T> {
+        assert!(start <= self.inner.as_ref().len());
+        assert!(start <= self.range.end);
+        self.range.start = start;
+        self
+    }
+
+    /// Changes the end index of this window to the index specified.
+    ///
+    /// Returns the windows back to chain multiple calls to this method.
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if `end` is out of bounds for the underlying
+    /// slice or if it comes before the `start` configured in this window.
+    pub fn set_end(&mut self, end: usize) -> &mut Window<T> {
+        assert!(end <= self.inner.as_ref().len());
+        assert!(self.range.start <= end);
+        self.range.end = end;
+        self
+    }
+
+    // TODO: how about a generic set() method along the lines of:
+    //
+    //       buffer.set(..3)
+    //             .set(0..2)
+    //             .set(4..)
+    //
+    // etc.
+}
+
+impl<T: AsRef<[u8]>> AsRef<[u8]> for Window<T> {
+    fn as_ref(&self) -> &[u8] {
+        &self.inner.as_ref()[self.range.start..self.range.end]
+    }
+}
+
+impl<T: AsMut<[u8]>> AsMut<[u8]> for Window<T> {
+    fn as_mut(&mut self) -> &mut [u8] {
+        &mut self.inner.as_mut()[self.range.start..self.range.end]
+    }
+}