1 files changed, 81 insertions, 0 deletions
diff --git a/layout/style/nsStyleAutoArray.h b/layout/style/nsStyleAutoArray.h
new file mode 100644
index 0000000000..368b7c6a7b
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+++ b/layout/style/nsStyleAutoArray.h
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsStyleAutoArray_h_
+#define nsStyleAutoArray_h_
+
+#include "nsTArray.h"
+#include "mozilla/Assertions.h"
+
+/**
+ * An array of objects, similar to AutoTArray<T,1> but which is memmovable. It
+ * always has length >= 1.
+ */
+template <typename T>
+class nsStyleAutoArray {
+ public:
+  // This constructor places a single element in mFirstElement.
+  enum WithSingleInitialElement { WITH_SINGLE_INITIAL_ELEMENT };
+  explicit nsStyleAutoArray(WithSingleInitialElement) {}
+
+  nsStyleAutoArray(const nsStyleAutoArray&) = delete;
+  nsStyleAutoArray& operator=(const nsStyleAutoArray&) = delete;
+
+  nsStyleAutoArray(nsStyleAutoArray&&) = default;
+  nsStyleAutoArray& operator=(nsStyleAutoArray&&) = default;
+
+  bool Assign(const nsStyleAutoArray& aOther, mozilla::fallible_t) {
+    mFirstElement = aOther.mFirstElement;
+    return mOtherElements.Assign(aOther.mOtherElements, mozilla::fallible);
+  }
+
+  nsStyleAutoArray Clone() const {
+    nsStyleAutoArray res(WITH_SINGLE_INITIAL_ELEMENT);
+    res.mFirstElement = mFirstElement;
+    res.mOtherElements = mOtherElements.Clone();
+    return res;
+  }
+
+  bool operator==(const nsStyleAutoArray& aOther) const {
+    return Length() == aOther.Length() &&
+           mFirstElement == aOther.mFirstElement &&
+           mOtherElements == aOther.mOtherElements;
+  }
+  bool operator!=(const nsStyleAutoArray& aOther) const {
+    return !(*this == aOther);
+  }
+
+  size_t Length() const { return mOtherElements.Length() + 1; }
+  const T& operator[](size_t aIndex) const {
+    return aIndex == 0 ? mFirstElement : mOtherElements[aIndex - 1];
+  }
+  T& operator[](size_t aIndex) {
+    return aIndex == 0 ? mFirstElement : mOtherElements[aIndex - 1];
+  }
+
+  void EnsureLengthAtLeast(size_t aMinLen) {
+    if (aMinLen > 0) {
+      mOtherElements.EnsureLengthAtLeast(aMinLen - 1);
+    }
+  }
+
+  void SetLengthNonZero(size_t aNewLen) {
+    MOZ_ASSERT(aNewLen > 0);
+    mOtherElements.SetLength(aNewLen - 1);
+  }
+
+  void TruncateLengthNonZero(size_t aNewLen) {
+    MOZ_ASSERT(aNewLen > 0);
+    MOZ_ASSERT(aNewLen <= Length());
+    mOtherElements.TruncateLength(aNewLen - 1);
+  }
+
+ private:
+  T mFirstElement;
+  nsTArray<T> mOtherElements;
+};
+
+#endif /* nsStyleAutoArray_h_ */