1 files changed, 111 insertions, 0 deletions
diff --git a/servo/components/style/gecko_bindings/sugar/ns_style_auto_array.rs b/servo/components/style/gecko_bindings/sugar/ns_style_auto_array.rs
new file mode 100644
index 0000000000..b5772a6c77
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/ns_style_auto_array.rs
@@ -0,0 +1,111 @@
+/* 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/. */
+
+//! Rust helpers for Gecko's `nsStyleAutoArray`.
+
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleAnimationArrayLength;
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleScrollTimelineArrayLength;
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleTransitionArrayLength;
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleViewTimelineArrayLength;
+use crate::gecko_bindings::structs::nsStyleAutoArray;
+use crate::gecko_bindings::structs::{StyleAnimation, StyleTransition};
+use crate::gecko_bindings::structs::{StyleScrollTimeline, StyleViewTimeline};
+use std::iter::{once, Chain, IntoIterator, Once};
+use std::ops::{Index, IndexMut};
+use std::slice::{Iter, IterMut};
+
+impl<T> Index<usize> for nsStyleAutoArray<T> {
+    type Output = T;
+    fn index(&self, index: usize) -> &T {
+        match index {
+            0 => &self.mFirstElement,
+            _ => &self.mOtherElements[index - 1],
+        }
+    }
+}
+
+impl<T> IndexMut<usize> for nsStyleAutoArray<T> {
+    fn index_mut(&mut self, index: usize) -> &mut T {
+        match index {
+            0 => &mut self.mFirstElement,
+            _ => &mut self.mOtherElements[index - 1],
+        }
+    }
+}
+
+impl<T> nsStyleAutoArray<T> {
+    /// Mutably iterate over the array elements.
+    pub fn iter_mut(&mut self) -> Chain<Once<&mut T>, IterMut<T>> {
+        once(&mut self.mFirstElement).chain(self.mOtherElements.iter_mut())
+    }
+
+    /// Iterate over the array elements.
+    pub fn iter(&self) -> Chain<Once<&T>, Iter<T>> {
+        once(&self.mFirstElement).chain(self.mOtherElements.iter())
+    }
+
+    /// Returns the length of the array.
+    ///
+    /// Note that often structs containing autoarrays will have additional
+    /// member fields that contain the length, which must be kept in sync.
+    pub fn len(&self) -> usize {
+        1 + self.mOtherElements.len()
+    }
+}
+
+impl nsStyleAutoArray<StyleAnimation> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleAnimationArrayLength(
+                self as *mut nsStyleAutoArray<StyleAnimation> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl nsStyleAutoArray<StyleTransition> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleTransitionArrayLength(
+                self as *mut nsStyleAutoArray<StyleTransition> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl nsStyleAutoArray<StyleViewTimeline> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleViewTimelineArrayLength(
+                self as *mut nsStyleAutoArray<StyleViewTimeline> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl nsStyleAutoArray<StyleScrollTimeline> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleScrollTimelineArrayLength(
+                self as *mut nsStyleAutoArray<StyleScrollTimeline> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl<'a, T> IntoIterator for &'a mut nsStyleAutoArray<T> {
+    type Item = &'a mut T;
+    type IntoIter = Chain<Once<&'a mut T>, IterMut<'a, T>>;
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter_mut()
+    }
+}