1 files changed, 110 insertions, 0 deletions
diff --git a/mfbt/Array.h b/mfbt/Array.h
new file mode 100644
index 0000000000..55b724a288
--- /dev/null
+++ b/mfbt/Array.h
@@ -0,0 +1,110 @@
+/* -*- 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/. */
+
+/* A compile-time constant-length array with bounds-checking assertions. */
+
+#ifndef mozilla_Array_h
+#define mozilla_Array_h
+
+#include <stddef.h>
+
+#include <iterator>
+#include <ostream>
+#include <utility>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Likely.h"
+
+namespace mozilla {
+
+template <typename T, size_t _Length>
+class Array {
+  T mArr[_Length];
+
+ public:
+  using ElementType = T;
+  static constexpr size_t Length = _Length;
+
+  constexpr Array() = default;
+
+  template <typename... Args>
+  MOZ_IMPLICIT constexpr Array(Args&&... aArgs)
+      : mArr{std::forward<Args>(aArgs)...} {
+    static_assert(sizeof...(aArgs) == Length,
+                  "The number of arguments should be equal to the template "
+                  "parameter Length");
+  }
+
+  T& operator[](size_t aIndex) {
+    if (MOZ_UNLIKELY(aIndex >= Length)) {
+      detail::InvalidArrayIndex_CRASH(aIndex, Length);
+    }
+    return mArr[aIndex];
+  }
+
+  const T& operator[](size_t aIndex) const {
+    if (MOZ_UNLIKELY(aIndex >= Length)) {
+      detail::InvalidArrayIndex_CRASH(aIndex, Length);
+    }
+    return mArr[aIndex];
+  }
+
+  bool operator==(const Array<T, Length>& aOther) const {
+    for (size_t i = 0; i < Length; i++) {
+      if (mArr[i] != aOther[i]) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  typedef T* iterator;
+  typedef const T* const_iterator;
+  typedef std::reverse_iterator<T*> reverse_iterator;
+  typedef std::reverse_iterator<const T*> const_reverse_iterator;
+
+  // Methods for range-based for loops.
+  iterator begin() { return mArr; }
+  constexpr const_iterator begin() const { return mArr; }
+  constexpr const_iterator cbegin() const { return begin(); }
+  iterator end() { return mArr + Length; }
+  constexpr const_iterator end() const { return mArr + Length; }
+  constexpr const_iterator cend() const { return end(); }
+
+  // Methods for reverse iterating.
+  reverse_iterator rbegin() { return reverse_iterator(end()); }
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+  const_reverse_iterator crbegin() const { return rbegin(); }
+  reverse_iterator rend() { return reverse_iterator(begin()); }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+  const_reverse_iterator crend() const { return rend(); }
+};
+
+template <typename T>
+class Array<T, 0> {
+ public:
+  T& operator[](size_t aIndex) { MOZ_CRASH("indexing into zero-length array"); }
+
+  const T& operator[](size_t aIndex) const {
+    MOZ_CRASH("indexing into zero-length array");
+  }
+};
+
+// MOZ_DBG support
+
+template <typename T, size_t Length>
+std::ostream& operator<<(std::ostream& aOut, const Array<T, Length>& aArray) {
+  return aOut << Span(aArray);
+}
+
+} /* namespace mozilla */
+
+#endif /* mozilla_Array_h */