1 files changed, 81 insertions, 0 deletions
diff --git a/servo/components/style_traits/owned_str.rs b/servo/components/style_traits/owned_str.rs
new file mode 100644
index 0000000000..ebfdcd5e06
--- /dev/null
+++ b/servo/components/style_traits/owned_str.rs
@@ -0,0 +1,81 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#![allow(unsafe_code)]
+
+//! A replacement for `Box<str>` that has a defined layout for FFI.
+
+use crate::owned_slice::OwnedSlice;
+use std::fmt;
+use std::ops::{Deref, DerefMut};
+
+/// A struct that basically replaces a Box<str>, but with a defined layout,
+/// suitable for FFI.
+#[repr(C)]
+#[derive(Clone, Default, Eq, MallocSizeOf, PartialEq, ToShmem)]
+pub struct OwnedStr(OwnedSlice<u8>);
+
+impl fmt::Debug for OwnedStr {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        self.deref().fmt(formatter)
+    }
+}
+
+impl Deref for OwnedStr {
+    type Target = str;
+
+    #[inline(always)]
+    fn deref(&self) -> &Self::Target {
+        unsafe { std::str::from_utf8_unchecked(&*self.0) }
+    }
+}
+
+impl DerefMut for OwnedStr {
+    #[inline(always)]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { std::str::from_utf8_unchecked_mut(&mut *self.0) }
+    }
+}
+
+impl OwnedStr {
+    /// Convert the OwnedStr into a boxed str.
+    #[inline]
+    pub fn into_box(self) -> Box<str> {
+        self.into_string().into_boxed_str()
+    }
+
+    /// Convert the OwnedStr into a `String`.
+    #[inline]
+    pub fn into_string(self) -> String {
+        unsafe { String::from_utf8_unchecked(self.0.into_vec()) }
+    }
+}
+
+impl From<OwnedStr> for String {
+    #[inline]
+    fn from(b: OwnedStr) -> Self {
+        b.into_string()
+    }
+}
+
+impl From<OwnedStr> for Box<str> {
+    #[inline]
+    fn from(b: OwnedStr) -> Self {
+        b.into_box()
+    }
+}
+
+impl From<Box<str>> for OwnedStr {
+    #[inline]
+    fn from(b: Box<str>) -> Self {
+        Self::from(b.into_string())
+    }
+}
+
+impl From<String> for OwnedStr {
+    #[inline]
+    fn from(s: String) -> Self {
+        OwnedStr(s.into_bytes().into())
+    }
+}