diff -r 000000000000 -r 6474c204b198 mfbt/Range.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mfbt/Range.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,51 @@
+/* -*- 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_Range_h
+#define mozilla_Range_h
+
+#include "mozilla/NullPtr.h"
+#include "mozilla/RangedPtr.h"
+
+#include <stddef.h>
+
+namespace mozilla {
+
+// Range<T> is a tuple containing a pointer and a length.
+template <typename T>
+class Range
+{
+    RangedPtr<T> mStart;
+    RangedPtr<T> mEnd;
+
+    typedef void (Range::* ConvertibleToBool)();
+    void nonNull() {}
+
+  public:
+    Range() : mStart(nullptr, 0), mEnd(nullptr, 0) {}
+    Range(T* p, size_t len)
+      : mStart(p, p, p + len),
+        mEnd(p + len, p, p + len)
+    {}
+
+    RangedPtr<T> start() const { return mStart; }
+    RangedPtr<T> end() const { return mEnd; }
+    size_t length() const { return mEnd - mStart; }
+
+    T& operator[](size_t offset) {
+      return mStart[offset];
+    }
+
+    const T& operator[](size_t offset) const {
+      return mStart[offset];
+    }
+
+    operator ConvertibleToBool() const { return mStart ? &Range::nonNull : 0; }
+};
+
+} // namespace mozilla
+
+#endif /* mozilla_Range_h */