1 files changed, 76 insertions, 0 deletions
diff --git a/xpcom/ds/ArenaAllocatorExtensions.h b/xpcom/ds/ArenaAllocatorExtensions.h
new file mode 100644
index 0000000000..60819381d5
--- /dev/null
+++ b/xpcom/ds/ArenaAllocatorExtensions.h
@@ -0,0 +1,76 @@
+/* -*- 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 mozilla_ArenaAllocatorExtensions_h
+#define mozilla_ArenaAllocatorExtensions_h
+
+#include "mozilla/ArenaAllocator.h"
+#include "mozilla/CheckedInt.h"
+#include "nsAString.h"
+
+/**
+ * Extensions to the ArenaAllocator class.
+ */
+namespace mozilla {
+
+namespace detail {
+
+template <typename T, size_t ArenaSize, size_t Alignment>
+T* DuplicateString(const T* aSrc, const CheckedInt<size_t>& aLen,
+                   ArenaAllocator<ArenaSize, Alignment>& aArena);
+
+}  // namespace detail
+
+/**
+ * Makes an arena allocated null-terminated copy of the source string. The
+ * source string must be null-terminated.
+ *
+ * @param aSrc String to copy.
+ * @param aArena The arena to allocate the string copy out of.
+ * @return An arena allocated null-terminated string.
+ */
+template <typename T, size_t ArenaSize, size_t Alignment>
+T* ArenaStrdup(const T* aStr, ArenaAllocator<ArenaSize, Alignment>& aArena) {
+  return detail::DuplicateString(aStr, nsCharTraits<T>::length(aStr), aArena);
+}
+
+/**
+ * Makes an arena allocated null-terminated copy of the source string.
+ *
+ * @param aSrc String to copy.
+ * @param aArena The arena to allocate the string copy out of.
+ * @return An arena allocated null-terminated string.
+ */
+template <typename T, size_t ArenaSize, size_t Alignment>
+T* ArenaStrdup(const detail::nsTStringRepr<T>& aStr,
+               ArenaAllocator<ArenaSize, Alignment>& aArena) {
+  return detail::DuplicateString(aStr.BeginReading(), aStr.Length(), aArena);
+}
+
+/**
+ * Copies the source string and adds a null terminator. Source string does not
+ * have to be null terminated.
+ */
+template <typename T, size_t ArenaSize, size_t Alignment>
+T* detail::DuplicateString(const T* aSrc, const CheckedInt<size_t>& aLen,
+                           ArenaAllocator<ArenaSize, Alignment>& aArena) {
+  const auto byteLen = (aLen + 1) * sizeof(T);
+  if (!byteLen.isValid()) {
+    return nullptr;
+  }
+
+  T* p = static_cast<T*>(aArena.Allocate(byteLen.value(), mozilla::fallible));
+  if (p) {
+    memcpy(p, aSrc, byteLen.value() - sizeof(T));
+    p[aLen.value()] = T(0);
+  }
+
+  return p;
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_ArenaAllocatorExtensions_h