Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 676 insertions, 0 deletions

diff --git a/gfx/wr/peek-poke/src/euclid.rs b/gfx/wr/peek-poke/src/euclid.rs
new file mode 100644
index 0000000000..dc4dd7774b
--- /dev/null
+++ b/gfx/wr/peek-poke/src/euclid.rs
@@ -0,0 +1,191 @@
+// Copyright 2019 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use crate::{Peek, Poke};
+use euclid::{Point2D, Rect, Box2D, SideOffsets2D, Size2D, Transform3D, Vector2D};
+
+unsafe impl<T: Poke, U> Poke for Point2D<T, U> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        2 * T::max_size()
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        let bytes = self.x.poke_into(bytes);
+        let bytes = self.y.poke_into(bytes);
+        bytes
+    }
+}
+impl<T: Peek, U> Peek for Point2D<T, U> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let bytes = T::peek_from(bytes, &mut (*output).x);
+        let bytes = T::peek_from(bytes, &mut (*output).y);
+        bytes
+    }
+}
+
+unsafe impl<T: Poke, U> Poke for Rect<T, U> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        Point2D::<T, U>::max_size() + Size2D::<T, U>::max_size()
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        let bytes = self.origin.poke_into(bytes);
+        let bytes = self.size.poke_into(bytes);
+        bytes
+    }
+}
+impl<T: Peek, U> Peek for Rect<T, U> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let bytes = Point2D::<T, U>::peek_from(bytes, &mut (*output).origin);
+        let bytes = Size2D::<T, U>::peek_from(bytes, &mut (*output).size);
+        bytes
+    }
+}
+
+unsafe impl<T: Poke, U> Poke for Box2D<T, U> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        Point2D::<T, U>::max_size() * 2
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        let bytes = self.min.poke_into(bytes);
+        let bytes = self.max.poke_into(bytes);
+        bytes
+    }
+}
+impl<T: Peek, U> Peek for Box2D<T, U> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let bytes = Point2D::<T, U>::peek_from(bytes, &mut (*output).min);
+        let bytes = Point2D::<T, U>::peek_from(bytes, &mut (*output).max);
+        bytes
+    }
+}
+
+unsafe impl<T: Poke, U> Poke for SideOffsets2D<T, U> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        4 * T::max_size()
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        let bytes = self.top.poke_into(bytes);
+        let bytes = self.right.poke_into(bytes);
+        let bytes = self.bottom.poke_into(bytes);
+        let bytes = self.left.poke_into(bytes);
+        bytes
+    }
+}
+impl<T: Peek, U> Peek for SideOffsets2D<T, U> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let bytes = T::peek_from(bytes, &mut (*output).top);
+        let bytes = T::peek_from(bytes, &mut (*output).right);
+        let bytes = T::peek_from(bytes, &mut (*output).bottom);
+        let bytes = T::peek_from(bytes, &mut (*output).left);
+        bytes
+    }
+}
+
+unsafe impl<T: Poke, U> Poke for Size2D<T, U> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        2 * T::max_size()
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        let bytes = self.width.poke_into(bytes);
+        let bytes = self.height.poke_into(bytes);
+        bytes
+    }
+}
+impl<T: Peek, U> Peek for Size2D<T, U> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let bytes = T::peek_from(bytes, &mut (*output).width);
+        let bytes = T::peek_from(bytes, &mut (*output).height);
+        bytes
+    }
+}
+
+unsafe impl<T: Poke, S, D> Poke for Transform3D<T, S, D> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        16 * T::max_size()
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        let bytes = self.m11.poke_into(bytes);
+        let bytes = self.m12.poke_into(bytes);
+        let bytes = self.m13.poke_into(bytes);
+        let bytes = self.m14.poke_into(bytes);
+        let bytes = self.m21.poke_into(bytes);
+        let bytes = self.m22.poke_into(bytes);
+        let bytes = self.m23.poke_into(bytes);
+        let bytes = self.m24.poke_into(bytes);
+        let bytes = self.m31.poke_into(bytes);
+        let bytes = self.m32.poke_into(bytes);
+        let bytes = self.m33.poke_into(bytes);
+        let bytes = self.m34.poke_into(bytes);
+        let bytes = self.m41.poke_into(bytes);
+        let bytes = self.m42.poke_into(bytes);
+        let bytes = self.m43.poke_into(bytes);
+        let bytes = self.m44.poke_into(bytes);
+        bytes
+    }
+}
+impl<T: Peek, S, D> Peek for Transform3D<T, S, D> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let bytes = T::peek_from(bytes, &mut (*output).m11);
+        let bytes = T::peek_from(bytes, &mut (*output).m12);
+        let bytes = T::peek_from(bytes, &mut (*output).m13);
+        let bytes = T::peek_from(bytes, &mut (*output).m14);
+        let bytes = T::peek_from(bytes, &mut (*output).m21);
+        let bytes = T::peek_from(bytes, &mut (*output).m22);
+        let bytes = T::peek_from(bytes, &mut (*output).m23);
+        let bytes = T::peek_from(bytes, &mut (*output).m24);
+        let bytes = T::peek_from(bytes, &mut (*output).m31);
+        let bytes = T::peek_from(bytes, &mut (*output).m32);
+        let bytes = T::peek_from(bytes, &mut (*output).m33);
+        let bytes = T::peek_from(bytes, &mut (*output).m34);
+        let bytes = T::peek_from(bytes, &mut (*output).m41);
+        let bytes = T::peek_from(bytes, &mut (*output).m42);
+        let bytes = T::peek_from(bytes, &mut (*output).m43);
+        let bytes = T::peek_from(bytes, &mut (*output).m44);
+        bytes
+    }
+}
+
+unsafe impl<T: Poke, U> Poke for Vector2D<T, U> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        2 * T::max_size()
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        let bytes = self.x.poke_into(bytes);
+        let bytes = self.y.poke_into(bytes);
+        bytes
+    }
+}
+impl<T: Peek, U> Peek for Vector2D<T, U> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let bytes = T::peek_from(bytes, &mut (*output).x);
+        let bytes = T::peek_from(bytes, &mut (*output).y);
+        bytes
+    }
+}
diff --git a/gfx/wr/peek-poke/src/lib.rs b/gfx/wr/peek-poke/src/lib.rs
new file mode 100644
index 0000000000..18f6a9acd8
--- /dev/null
+++ b/gfx/wr/peek-poke/src/lib.rs
@@ -0,0 +1,440 @@
+// Copyright 2019 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Fast binary serialization and deserialization for types with a known maximum size.
+//!
+//! ## Binary Encoding Scheme
+//!
+//! ## Usage
+//!
+//! ## Comparison to bincode
+
+#[cfg(feature = "derive")]
+pub use peek_poke_derive::*;
+
+use core::{marker::PhantomData, mem::size_of, slice};
+use crate::{slice_ext::*, vec_ext::*};
+
+mod slice_ext;
+mod vec_ext;
+
+union MaybeUninitShim<T: Copy> {
+    uninit: (),
+    init: T,
+}
+
+/// Peek helper for constructing a `T` by `Copy`ing into an uninitialized stack
+/// allocation.
+pub unsafe fn peek_from_uninit<T: Copy + Peek>(bytes: *const u8) -> (T, *const u8) {
+    let mut val = MaybeUninitShim { uninit: () };
+    let bytes = <T>::peek_from(bytes, &mut val.init);
+    (val.init, bytes)
+}
+
+/// Peek helper for constructing a `T` by `Default` initialized stack
+/// allocation.
+pub unsafe fn peek_from_default<T: Default + Peek>(bytes: *const u8) -> (T, *const u8) {
+    let mut val = T::default();
+    let bytes = <T>::peek_from(bytes, &mut val);
+    (val, bytes)
+}
+
+/// Peek inplace a `T` from a slice of bytes, returning a slice of the remaining
+/// bytes. `src` must contain at least `T::max_size()` bytes.
+///
+/// [`ensure_red_zone`] can be used to add required padding.
+pub fn peek_from_slice<'a, T: Peek>(src: &'a [u8], dst: &mut T) -> &'a [u8] {
+    unsafe {
+        // If src.len() == T::max_size() then src is at the start of the red-zone.
+        assert!(T::max_size() < src.len(), "WRDL: unexpected end of display list");
+        let end_ptr = T::peek_from(src.as_ptr(), dst);
+        let len = end_ptr as usize - src.as_ptr() as usize;
+        // Did someone break the T::peek_from() can't read more than T::max_size()
+        // bytes contract?
+        assert!(len <= src.len(), "WRDL: Peek::max_size was wrong");
+        slice::from_raw_parts(end_ptr, src.len() - len)
+    }
+}
+
+/// Poke helper to insert a serialized version of `src` at the beginning for `dst`.
+pub fn poke_inplace_slice<T: Poke>(src: &T, dst: &mut [u8]) {
+    assert!(T::max_size() <= dst.len(),  "WRDL: buffer too small to write into");
+    unsafe {
+        src.poke_into(dst.as_mut_ptr());
+    }
+}
+
+/// Poke helper to append a serialized version of `src` to the end of `dst`.
+pub fn poke_into_vec<T: Poke>(src: &T, dst: &mut Vec<u8>) {
+    dst.reserve(T::max_size());
+    unsafe {
+        let ptr = dst.as_end_mut_ptr();
+        let end_ptr = src.poke_into(ptr);
+        dst.set_end_ptr(end_ptr);
+    }
+}
+
+// TODO: Is returning the len of the iterator of any practical use?
+pub fn poke_extend_vec<I>(src: I, dst: &mut Vec<u8>) -> usize
+where
+    I: ExactSizeIterator,
+    I::Item: Poke,
+{
+    let len = src.len();
+    let max_size = len * I::Item::max_size();
+    dst.reserve(max_size);
+    unsafe {
+        let ptr = dst.as_end_mut_ptr();
+        // Guard against the possibility of a misbehaved implementation of
+        // ExactSizeIterator by writing at most `len` items.
+        let end_ptr = src.take(len).fold(ptr, |ptr, item| item.poke_into(ptr));
+        dst.set_end_ptr(end_ptr);
+    }
+
+    len
+}
+
+/// Add `T::max_size()` "red zone" (padding of zeroes) to the end of the vec of
+/// `bytes`. This allows deserialization to assert that at least `T::max_size()`
+/// bytes exist at all times.
+pub fn ensure_red_zone<T: Poke>(bytes: &mut Vec<u8>) {
+    bytes.reserve(T::max_size());
+    unsafe {
+        let end_ptr = bytes.as_end_mut_ptr();
+        end_ptr.write_bytes(0, T::max_size());
+        bytes.set_end_ptr(end_ptr.add(T::max_size()));
+    }
+}
+
+/// Remove the "red zone" (padding of zeroes) from the end of the vec of `bytes`.
+/// This is effectively the inverse of `ensure_red_zone`, with the caveat that
+/// space reserved for the red zone is not un-reserved. Callers are repsonsible
+/// for making sure the vec actually has a red zone, otherwise data bytes can
+/// get stripped instead.
+pub fn strip_red_zone<T: Poke>(bytes: &mut Vec<u8>) {
+    assert!(bytes.len() >= T::max_size());
+    unsafe {
+        let end_ptr = bytes.as_end_mut_ptr();
+        bytes.set_end_ptr(end_ptr.sub(T::max_size()));
+    }
+}
+
+#[inline]
+unsafe fn read_verbatim<T>(src: *const u8, dst: *mut T) -> *const u8 {
+    *dst = (src as *const T).read_unaligned();
+    src.add(size_of::<T>())
+}
+
+#[inline]
+unsafe fn write_verbatim<T>(src: T, dst: *mut u8) -> *mut u8 {
+    (dst as *mut T).write_unaligned(src);
+    dst.add(size_of::<T>())
+}
+
+#[cfg(feature = "extras")]
+mod euclid;
+
+/// A trait for values that provide serialization into buffers of bytes.
+///
+/// # Example
+///
+/// ```no_run
+/// use peek_poke::Poke;
+///
+/// struct Bar {
+///     a: u32,
+///     b: u8,
+///     c: i16,
+/// }
+///
+/// unsafe impl Poke for Bar {
+///     fn max_size() -> usize {
+///         <u32>::max_size() + <u8>::max_size() + <i16>::max_size()
+///     }
+///     unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+///         let bytes = self.a.poke_into(bytes);
+///         let bytes = self.b.poke_into(bytes);
+///         self.c.poke_into(bytes)
+///     }
+/// }
+/// ```
+///
+/// # Safety
+///
+/// The `Poke` trait is an `unsafe` trait for the reasons, and implementors must
+/// ensure that they adhere to these contracts:
+///
+/// * `max_size()` query and calculations in general must be correct.  Callers
+///    of this trait are expected to rely on the contract defined on each
+///    method, and implementors must ensure such contracts remain true.
+pub unsafe trait Poke {
+    /// Return the maximum number of bytes that the serialized version of `Self`
+    /// will occupy.
+    ///
+    /// # Safety
+    ///
+    /// Implementors of `Poke` guarantee to not write more than the result of
+    /// calling `max_size()` into the buffer pointed to by `bytes` when
+    /// `poke_into()` is called.
+    fn max_size() -> usize;
+    /// Serialize into the buffer pointed to by `bytes`.
+    ///
+    /// Returns a pointer to the next byte after the serialized representation of `Self`.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe because undefined behavior can result if the
+    /// caller does not ensure all of the following:
+    ///
+    /// * `bytes` must denote a valid pointer to a block of memory.
+    ///
+    /// * `bytes` must pointer to at least the number of bytes returned by
+    ///   `max_size()`.
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8;
+}
+
+/// A trait for values that provide deserialization from buffers of bytes.
+///
+/// # Example
+///
+/// ```ignore
+/// use peek_poke::Peek;
+///
+/// struct Bar {
+///     a: u32,
+///     b: u8,
+///     c: i16,
+/// }
+///
+/// ...
+///
+/// impl Peek for Bar {
+///     unsafe fn peek_from(&mut self, bytes: *const u8) -> *const u8 {
+///         let bytes = self.a.peek_from(bytes);
+///         let bytes = self.b.peek_from(bytes);
+///         self.c.peek_from(bytes)
+///     }
+/// }
+/// ```
+///
+/// # Safety
+///
+/// The `Peek` trait contains unsafe methods for the following reasons, and
+/// implementors must ensure that they adhere to these contracts:
+///
+/// * Callers of this trait are expected to rely on the contract defined on each
+///   method, and implementors must ensure that `peek_from()` doesn't read more
+///   bytes from `bytes` than is returned by `Peek::max_size()`.
+pub trait Peek: Poke {
+    /// Deserialize from the buffer pointed to by `bytes`.
+    ///
+    /// Returns a pointer to the next byte after the unconsumed bytes not used
+    /// to deserialize the representation of `Self`.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe because undefined behavior can result if the
+    /// caller does not ensure all of the following:
+    ///
+    /// * `bytes` must denote a valid pointer to a block of memory.
+    ///
+    /// * `bytes` must pointer to at least the number of bytes returned by
+    ///   `Poke::max_size()`.
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8;
+}
+
+macro_rules! impl_poke_for_deref {
+    (<$($desc:tt)+) => {
+        unsafe impl <$($desc)+ {
+            #[inline(always)]
+            fn max_size() -> usize {
+                <T>::max_size()
+            }
+            unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+                (**self).poke_into(bytes)
+            }
+        }
+    }
+}
+
+impl_poke_for_deref!(<'a, T: Poke> Poke for &'a T);
+impl_poke_for_deref!(<'a, T: Poke> Poke for &'a mut T);
+
+macro_rules! impl_for_primitive {
+    ($($ty:ty)+) => {
+        $(unsafe impl Poke for $ty {
+            #[inline(always)]
+            fn max_size() -> usize {
+                size_of::<Self>()
+            }
+            #[inline(always)]
+            unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+                write_verbatim(*self, bytes)
+            }
+        }
+        impl Peek for $ty {
+            #[inline(always)]
+            unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+                read_verbatim(bytes, output)
+            }
+        })+
+    };
+}
+
+impl_for_primitive! {
+    i8 i16 i32 i64 isize
+    u8 u16 u32 u64 usize
+    f32 f64
+}
+
+unsafe impl Poke for bool {
+    #[inline(always)]
+    fn max_size() -> usize {
+        u8::max_size()
+    }
+    #[inline]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        (*self as u8).poke_into(bytes)
+    }
+}
+
+impl Peek for bool {
+    #[inline]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let mut int_bool = 0u8;
+        let ptr = <u8>::peek_from(bytes, &mut int_bool);
+        *output = int_bool != 0;
+        ptr
+    }
+}
+
+unsafe impl<T> Poke for PhantomData<T> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        0
+    }
+    #[inline(always)]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        bytes
+    }
+}
+
+impl<T> Peek for PhantomData<T> {
+    #[inline(always)]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        *output = PhantomData;
+        bytes
+    }
+}
+
+unsafe impl<T: Poke> Poke for Option<T> {
+    #[inline(always)]
+    fn max_size() -> usize {
+        u8::max_size() + T::max_size()
+    }
+
+    #[inline]
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        match self {
+            None => 0u8.poke_into(bytes),
+            Some(ref v) => {
+                let bytes = 1u8.poke_into(bytes);
+                let bytes = v.poke_into(bytes);
+                bytes
+            }
+        }
+    }
+}
+
+impl<T: Default + Peek> Peek for Option<T> {
+    #[inline]
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        let (variant, bytes) = peek_from_default::<u8>(bytes);
+        match variant {
+            0 => {
+                *output = None;
+                bytes
+            }
+            1 => {
+                let (val, bytes) = peek_from_default(bytes);
+                *output = Some(val);
+                bytes
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
+macro_rules! impl_for_arrays {
+    ($($len:tt)+) => {
+        $(unsafe impl<T: Poke> Poke for [T; $len] {
+            fn max_size() -> usize {
+                $len * T::max_size()
+            }
+            unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+                self.iter().fold(bytes, |bytes, e| e.poke_into(bytes))
+            }
+        }
+        impl<T: Peek> Peek for [T; $len] {
+            unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+                (&mut *output).iter_mut().fold(bytes, |bytes, e| <T>::peek_from(bytes, e))
+            }
+        })+
+    }
+}
+
+impl_for_arrays! {
+    01 02 03 04 05 06 07 08 09 10
+    11 12 13 14 15 16 17 18 19 20
+    21 22 23 24 25 26 27 28 29 30
+    31 32
+}
+
+unsafe impl Poke for () {
+    fn max_size() -> usize {
+        0
+    }
+    unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+        bytes
+    }
+}
+impl Peek for () {
+    unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+        *output = ();
+        bytes
+    }
+}
+
+macro_rules! impl_for_tuple {
+    ($($n:tt: $ty:ident),+) => {
+        unsafe impl<$($ty: Poke),+> Poke for ($($ty,)+) {
+            #[inline(always)]
+            fn max_size() -> usize {
+                0 $(+ <$ty>::max_size())+
+            }
+            unsafe fn poke_into(&self, bytes: *mut u8) -> *mut u8 {
+                $(let bytes = self.$n.poke_into(bytes);)+
+                bytes
+            }
+        }
+        impl<$($ty: Peek),+> Peek for ($($ty,)+) {
+            unsafe fn peek_from(bytes: *const u8, output: *mut Self) -> *const u8 {
+                $(let bytes = $ty::peek_from(bytes, &mut (*output).$n);)+
+                bytes
+            }
+        }
+    }
+}
+
+impl_for_tuple!(0: A);
+impl_for_tuple!(0: A, 1: B);
+impl_for_tuple!(0: A, 1: B, 2: C);
+impl_for_tuple!(0: A, 1: B, 2: C, 3: D);
+impl_for_tuple!(0: A, 1: B, 2: C, 3: D, 4: E);
diff --git a/gfx/wr/peek-poke/src/slice_ext.rs b/gfx/wr/peek-poke/src/slice_ext.rs
new file mode 100644
index 0000000000..f309d2f741
--- /dev/null
+++ b/gfx/wr/peek-poke/src/slice_ext.rs
@@ -0,0 +1,19 @@
+// Copyright 2019 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub trait AsEndMutPtr<T> {
+    fn as_end_mut_ptr(self) -> *mut T;
+}
+
+impl<'a> AsEndMutPtr<u8> for &'a mut [u8] {
+    fn as_end_mut_ptr(self) -> *mut u8 {
+        unsafe { self.as_mut_ptr().add(self.len()) }
+    }
+}
diff --git a/gfx/wr/peek-poke/src/vec_ext.rs b/gfx/wr/peek-poke/src/vec_ext.rs
new file mode 100644
index 0000000000..42e26032e5
--- /dev/null
+++ b/gfx/wr/peek-poke/src/vec_ext.rs
@@ -0,0 +1,26 @@
+// Copyright 2019 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::vec::Vec;
+
+pub trait VecExt  {
+    type Item;
+    unsafe fn set_end_ptr(&mut self, end: *const Self::Item);
+}
+
+impl<T> VecExt for Vec<T> {
+    type Item = T;
+    unsafe fn set_end_ptr(&mut self, end: *const T) {
+        assert!(end as usize >= self.as_ptr() as usize);
+        let new_len = end as usize - self.as_ptr() as usize;
+        assert!(new_len <= self.capacity());
+        self.set_len(new_len);
+    }
+}