From c2d50838e17b8870f835ae8c218ec8abb4bf1580 Mon Sep 17 00:00:00 2001
From: Nick Fitzgerald <fitzgen@gmail.com>
Date: Fri, 6 Mar 2015 15:37:00 -0500
Subject: [PATCH] Bug 1139993 - Add VectorBase::ConstRange that gives out
 |const T&| entries. r=Waldo

---
 mfbt/Vector.h             | 22 +++++++++++++++++++++-
 mfbt/tests/TestVector.cpp | 24 ++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/mfbt/Vector.h b/mfbt/Vector.h
index 989841df897..874e56f712c 100644
--- a/mfbt/Vector.h
+++ b/mfbt/Vector.h
@@ -473,7 +473,6 @@ public:
     }
 
   public:
-    Range() {}
     bool empty() const { return mCur == mEnd; }
     size_t remain() const { return PointerRangeSize(mCur, mEnd); }
     T& front() const { MOZ_ASSERT(!empty()); return *mCur; }
@@ -481,7 +480,28 @@ public:
     T popCopyFront() { MOZ_ASSERT(!empty()); return *mCur++; }
   };
 
+  class ConstRange
+  {
+    friend class VectorBase;
+    const T* mCur;
+    const T* mEnd;
+    ConstRange(const T* aCur, const T* aEnd)
+      : mCur(aCur)
+      , mEnd(aEnd)
+    {
+      MOZ_ASSERT(aCur <= aEnd);
+    }
+
+  public:
+    bool empty() const { return mCur == mEnd; }
+    size_t remain() const { return PointerRangeSize(mCur, mEnd); }
+    const T& front() const { MOZ_ASSERT(!empty()); return *mCur; }
+    void popFront() { MOZ_ASSERT(!empty()); ++mCur; }
+    T popCopyFront() { MOZ_ASSERT(!empty()); return *mCur++; }
+  };
+
   Range all() { return Range(begin(), end()); }
+  ConstRange all() const { return ConstRange(begin(), end()); }
 
   /* mutators */
 
diff --git a/mfbt/tests/TestVector.cpp b/mfbt/tests/TestVector.cpp
index dff589e3f16..794c3f08fdf 100644
--- a/mfbt/tests/TestVector.cpp
+++ b/mfbt/tests/TestVector.cpp
@@ -14,6 +14,7 @@ using mozilla::Vector;
 struct mozilla::detail::VectorTesting
 {
   static void testReserved();
+  static void testConstRange();
 };
 
 void
@@ -75,8 +76,31 @@ mozilla::detail::VectorTesting::testReserved()
 #endif
 }
 
+void
+mozilla::detail::VectorTesting::testConstRange()
+{
+#ifdef DEBUG
+  Vector<int> vec;
+
+  for (int i = 0; i < 10; i++) {
+    MOZ_RELEASE_ASSERT(vec.append(i));
+  }
+
+  const auto &vecRef = vec;
+
+  Vector<int>::ConstRange range = vecRef.all();
+  for (int i = 0; i < 10; i++) {
+    MOZ_RELEASE_ASSERT(!range.empty());
+    MOZ_RELEASE_ASSERT(range.front() == i);
+    range.popFront();
+  }
+#endif
+}
+
+
 int
 main()
 {
   VectorTesting::testReserved();
+  VectorTesting::testConstRange();
 }