1 files changed, 26 insertions, 0 deletions
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);
+    }
+}