Bug 811060 - Implement mozilla::Range; r=Waldo

--HG--
extra : rebase_source : a303294de705fca72eb31f7b5c7db787d0bc7260

mfbt/Range.h

@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sw=4 et tw=78:
+ *
+ * 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];
+    }
+
+    operator ConvertibleToBool() const { return mStart ? &Range::nonNull : 0; }
+};
+
+} // namespace mozilla
+
+#endif // mozilla_Range_h_
+

mfbt/RangedPtr.h

@@ -46,6 +46,9 @@ class RangedPtr
     T* const rangeEnd;
 #endif
 
+    typedef void (RangedPtr::* ConvertibleToBool)();
+    void nonNull() {}
+
     void checkSanity() {
       MOZ_ASSERT(rangeStart <= ptr);
       MOZ_ASSERT(ptr <= rangeEnd);
@@ -110,6 +113,8 @@ class RangedPtr
       return ptr;
     }
 
+    operator ConvertibleToBool() const { return ptr ? &RangedPtr::nonNull : 0; }
+
     /*
      * You can only assign one RangedPtr into another if the two pointers have
      * the same valid range:
@@ -242,7 +247,6 @@ class RangedPtr
   private:
     RangedPtr() MOZ_DELETE;
     T* operator&() MOZ_DELETE;
-    operator T*() const MOZ_DELETE;
 };
 
 } /* namespace mozilla */

mfbt/exported_headers.mk

@@ -25,6 +25,7 @@ EXPORTS_mozilla += \
   MathAlgorithms.h \
   MSStdInt.h \
   NullPtr.h \
+  Range.h \
   RangedPtr.h \
   RefPtr.h \
   Scoped.h \