Add m-esr52 at 52.6.0

1 files changed, 219 insertions, 0 deletions

diff --git a/mfbt/Pair.h b/mfbt/Pair.h
new file mode 100644
index 000000000..ad7b86a29
--- /dev/null
+++ b/mfbt/Pair.h
@@ -0,0 +1,219 @@
+/* -*- 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 class holding a pair of objects that tries to conserve storage space. */
+
+#ifndef mozilla_Pair_h
+#define mozilla_Pair_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Move.h"
+#include "mozilla/TypeTraits.h"
+
+namespace mozilla {
+
+namespace detail {
+
+enum StorageType { AsBase, AsMember };
+
+// Optimize storage using the Empty Base Optimization -- that empty base classes
+// don't take up space -- to optimize size when one or the other class is
+// stateless and can be used as a base class.
+//
+// The extra conditions on storage for B are necessary so that PairHelper won't
+// ambiguously inherit from either A or B, such that one or the other base class
+// would be inaccessible.
+template<typename A, typename B,
+         detail::StorageType =
+           IsEmpty<A>::value ? detail::AsBase : detail::AsMember,
+         detail::StorageType =
+           IsEmpty<B>::value && !IsBaseOf<A, B>::value && !IsBaseOf<B, A>::value
+           ? detail::AsBase
+           : detail::AsMember>
+struct PairHelper;
+
+template<typename A, typename B>
+struct PairHelper<A, B, AsMember, AsMember>
+{
+protected:
+  template<typename AArg, typename BArg>
+  PairHelper(AArg&& aA, BArg&& aB)
+    : mFirstA(Forward<AArg>(aA)),
+      mSecondB(Forward<BArg>(aB))
+  {}
+
+  A& first() { return mFirstA; }
+  const A& first() const { return mFirstA; }
+  B& second() { return mSecondB; }
+  const B& second() const { return mSecondB; }
+
+  void swap(PairHelper& aOther)
+  {
+    Swap(mFirstA, aOther.mFirstA);
+    Swap(mSecondB, aOther.mSecondB);
+  }
+
+private:
+  A mFirstA;
+  B mSecondB;
+};
+
+template<typename A, typename B>
+struct PairHelper<A, B, AsMember, AsBase> : private B
+{
+protected:
+  template<typename AArg, typename BArg>
+  PairHelper(AArg&& aA, BArg&& aB)
+    : B(Forward<BArg>(aB)),
+      mFirstA(Forward<AArg>(aA))
+  {}
+
+  A& first() { return mFirstA; }
+  const A& first() const { return mFirstA; }
+  B& second() { return *this; }
+  const B& second() const { return *this; }
+
+  void swap(PairHelper& aOther)
+  {
+    Swap(mFirstA, aOther.mFirstA);
+    Swap(static_cast<B&>(*this), static_cast<B&>(aOther));
+  }
+
+private:
+  A mFirstA;
+};
+
+template<typename A, typename B>
+struct PairHelper<A, B, AsBase, AsMember> : private A
+{
+protected:
+  template<typename AArg, typename BArg>
+  PairHelper(AArg&& aA, BArg&& aB)
+    : A(Forward<AArg>(aA)),
+      mSecondB(Forward<BArg>(aB))
+  {}
+
+  A& first() { return *this; }
+  const A& first() const { return *this; }
+  B& second() { return mSecondB; }
+  const B& second() const { return mSecondB; }
+
+  void swap(PairHelper& aOther)
+  {
+    Swap(static_cast<A&>(*this), static_cast<A&>(aOther));
+    Swap(mSecondB, aOther.mSecondB);
+  }
+
+private:
+  B mSecondB;
+};
+
+template<typename A, typename B>
+struct PairHelper<A, B, AsBase, AsBase> : private A, private B
+{
+protected:
+  template<typename AArg, typename BArg>
+  PairHelper(AArg&& aA, BArg&& aB)
+    : A(Forward<AArg>(aA)),
+      B(Forward<BArg>(aB))
+  {}
+
+  A& first() { return static_cast<A&>(*this); }
+  const A& first() const { return static_cast<A&>(*this); }
+  B& second() { return static_cast<B&>(*this); }
+  const B& second() const { return static_cast<B&>(*this); }
+
+  void swap(PairHelper& aOther)
+  {
+    Swap(static_cast<A&>(*this), static_cast<A&>(aOther));
+    Swap(static_cast<B&>(*this), static_cast<B&>(aOther));
+  }
+};
+
+} // namespace detail
+
+/**
+ * Pair is the logical concatenation of an instance of A with an instance B.
+ * Space is conserved when possible.  Neither A nor B may be a final class.
+ *
+ * It's typically clearer to have individual A and B member fields.  Except if
+ * you want the space-conserving qualities of Pair, you're probably better off
+ * not using this!
+ *
+ * No guarantees are provided about the memory layout of A and B, the order of
+ * initialization or destruction of A and B, and so on.  (This is approximately
+ * required to optimize space usage.)  The first/second names are merely
+ * conceptual!
+ */
+template<typename A, typename B>
+struct Pair
+  : private detail::PairHelper<A, B>
+{
+  typedef typename detail::PairHelper<A, B> Base;
+
+public:
+  template<typename AArg, typename BArg>
+  Pair(AArg&& aA, BArg&& aB)
+    : Base(Forward<AArg>(aA), Forward<BArg>(aB))
+  {}
+
+  Pair(Pair&& aOther)
+    : Base(Move(aOther.first()), Move(aOther.second()))
+  { }
+
+  Pair(const Pair& aOther) = default;
+
+  Pair& operator=(Pair&& aOther)
+  {
+    MOZ_ASSERT(this != &aOther, "Self-moves are prohibited");
+
+    first() = Move(aOther.first());
+    second() = Move(aOther.second());
+
+    return *this;
+  }
+
+  Pair& operator=(const Pair& aOther) = default;
+
+  /** The A instance. */
+  using Base::first;
+  /** The B instance. */
+  using Base::second;
+
+  /** Swap this pair with another pair. */
+  void swap(Pair& aOther) { Base::swap(aOther); }
+};
+
+template<typename A, class B>
+void
+Swap(Pair<A, B>& aX, Pair<A, B>& aY)
+{
+  aX.swap(aY);
+}
+
+/**
+ * MakePair allows you to construct a Pair instance using type inference. A call
+ * like this:
+ *
+ *   MakePair(Foo(), Bar())
+ *
+ * will return a Pair<Foo, Bar>.
+ */
+template<typename A, typename B>
+Pair<typename RemoveCV<typename RemoveReference<A>::Type>::Type,
+     typename RemoveCV<typename RemoveReference<B>::Type>::Type>
+MakePair(A&& aA, B&& aB)
+{
+  return
+    Pair<typename RemoveCV<typename RemoveReference<A>::Type>::Type,
+         typename RemoveCV<typename RemoveReference<B>::Type>::Type>(
+             Forward<A>(aA),
+             Forward<B>(aB));
+}
+
+} // namespace mozilla
+
+#endif /* mozilla_Pair_h */