Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 244 insertions, 0 deletions

diff --git a/mfbt/CompactPair.h b/mfbt/CompactPair.h
new file mode 100644
index 0000000000..fa810dc0af
--- /dev/null
+++ b/mfbt/CompactPair.h
@@ -0,0 +1,244 @@
+/* -*- 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_CompactPair_h
+#define mozilla_CompactPair_h
+
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+#include "mozilla/Attributes.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 CompactPairHelper
+// 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 =
+              std::is_empty_v<A> ? detail::AsBase : detail::AsMember,
+          detail::StorageType = std::is_empty_v<B> &&
+                                        !std::is_base_of<A, B>::value &&
+                                        !std::is_base_of<B, A>::value
+                                    ? detail::AsBase
+                                    : detail::AsMember>
+struct CompactPairHelper;
+
+template <typename A, typename B>
+struct CompactPairHelper<A, B, AsMember, AsMember> {
+ protected:
+  template <typename... AArgs, std::size_t... AIndexes, typename... BArgs,
+            std::size_t... BIndexes>
+  constexpr CompactPairHelper(std::tuple<AArgs...>& aATuple,
+                              std::tuple<BArgs...>& aBTuple,
+                              std::index_sequence<AIndexes...>,
+                              std::index_sequence<BIndexes...>)
+      : mFirstA(std::forward<AArgs>(std::get<AIndexes>(aATuple))...),
+        mSecondB(std::forward<BArgs>(std::get<BIndexes>(aBTuple))...) {}
+
+ public:
+  template <typename AArg, typename BArg>
+  constexpr CompactPairHelper(AArg&& aA, BArg&& aB)
+      : mFirstA(std::forward<AArg>(aA)), mSecondB(std::forward<BArg>(aB)) {}
+
+  constexpr A& first() { return mFirstA; }
+  constexpr const A& first() const { return mFirstA; }
+  constexpr B& second() { return mSecondB; }
+  constexpr const B& second() const { return mSecondB; }
+
+  void swap(CompactPairHelper& aOther) {
+    std::swap(mFirstA, aOther.mFirstA);
+    std::swap(mSecondB, aOther.mSecondB);
+  }
+
+ private:
+  A mFirstA;
+  B mSecondB;
+};
+
+template <typename A, typename B>
+struct CompactPairHelper<A, B, AsMember, AsBase> : private B {
+ protected:
+  template <typename... AArgs, std::size_t... AIndexes, typename... BArgs,
+            std::size_t... BIndexes>
+  constexpr CompactPairHelper(std::tuple<AArgs...>& aATuple,
+                              std::tuple<BArgs...>& aBTuple,
+                              std::index_sequence<AIndexes...>,
+                              std::index_sequence<BIndexes...>)
+      : B(std::forward<BArgs>(std::get<BIndexes>(aBTuple))...),
+        mFirstA(std::forward<AArgs>(std::get<AIndexes>(aATuple))...) {}
+
+ public:
+  template <typename AArg, typename BArg>
+  constexpr CompactPairHelper(AArg&& aA, BArg&& aB)
+      : B(std::forward<BArg>(aB)), mFirstA(std::forward<AArg>(aA)) {}
+
+  constexpr A& first() { return mFirstA; }
+  constexpr const A& first() const { return mFirstA; }
+  constexpr B& second() { return *this; }
+  constexpr const B& second() const { return *this; }
+
+  void swap(CompactPairHelper& aOther) {
+    std::swap(mFirstA, aOther.mFirstA);
+    std::swap(static_cast<B&>(*this), static_cast<B&>(aOther));
+  }
+
+ private:
+  A mFirstA;
+};
+
+template <typename A, typename B>
+struct CompactPairHelper<A, B, AsBase, AsMember> : private A {
+ protected:
+  template <typename... AArgs, std::size_t... AIndexes, typename... BArgs,
+            std::size_t... BIndexes>
+  constexpr CompactPairHelper(std::tuple<AArgs...>& aATuple,
+                              std::tuple<BArgs...>& aBTuple,
+                              std::index_sequence<AIndexes...>,
+                              std::index_sequence<BIndexes...>)
+      : A(std::forward<AArgs>(std::get<AIndexes>(aATuple))...),
+        mSecondB(std::forward<BArgs>(std::get<BIndexes>(aBTuple))...) {}
+
+ public:
+  template <typename AArg, typename BArg>
+  constexpr CompactPairHelper(AArg&& aA, BArg&& aB)
+      : A(std::forward<AArg>(aA)), mSecondB(std::forward<BArg>(aB)) {}
+
+  constexpr A& first() { return *this; }
+  constexpr const A& first() const { return *this; }
+  constexpr B& second() { return mSecondB; }
+  constexpr const B& second() const { return mSecondB; }
+
+  void swap(CompactPairHelper& aOther) {
+    std::swap(static_cast<A&>(*this), static_cast<A&>(aOther));
+    std::swap(mSecondB, aOther.mSecondB);
+  }
+
+ private:
+  B mSecondB;
+};
+
+template <typename A, typename B>
+struct CompactPairHelper<A, B, AsBase, AsBase> : private A, private B {
+ protected:
+  template <typename... AArgs, std::size_t... AIndexes, typename... BArgs,
+            std::size_t... BIndexes>
+  constexpr CompactPairHelper(std::tuple<AArgs...>& aATuple,
+                              std::tuple<BArgs...>& aBTuple,
+                              std::index_sequence<AIndexes...>,
+                              std::index_sequence<BIndexes...>)
+      : A(std::forward<AArgs>(std::get<AIndexes>(aATuple))...),
+        B(std::forward<BArgs>(std::get<BIndexes>(aBTuple))...) {}
+
+ public:
+  template <typename AArg, typename BArg>
+  constexpr CompactPairHelper(AArg&& aA, BArg&& aB)
+      : A(std::forward<AArg>(aA)), B(std::forward<BArg>(aB)) {}
+
+  constexpr A& first() { return static_cast<A&>(*this); }
+  constexpr const A& first() const { return static_cast<A&>(*this); }
+  constexpr B& second() { return static_cast<B&>(*this); }
+  constexpr const B& second() const { return static_cast<B&>(*this); }
+
+  void swap(CompactPairHelper& aOther) {
+    std::swap(static_cast<A&>(*this), static_cast<A&>(aOther));
+    std::swap(static_cast<B&>(*this), static_cast<B&>(aOther));
+  }
+};
+
+}  // namespace detail
+
+/**
+ * CompactPair 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.
+ *
+ * In general if space conservation is not critical is preferred to use
+ * std::pair.
+ *
+ * It's typically clearer to have individual A and B member fields.  Except if
+ * you want the space-conserving qualities of CompactPair, 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 CompactPair : private detail::CompactPairHelper<A, B> {
+  typedef typename detail::CompactPairHelper<A, B> Base;
+
+  using Base::Base;
+
+  template <typename... AArgs, typename... BArgs>
+  constexpr CompactPair(std::piecewise_construct_t, std::tuple<AArgs...> aFirst,
+                        std::tuple<BArgs...> aSecond)
+      : Base(aFirst, aSecond, std::index_sequence_for<AArgs...>(),
+             std::index_sequence_for<BArgs...>()) {}
+
+  CompactPair(CompactPair&& aOther) = default;
+  CompactPair(const CompactPair& aOther) = default;
+
+  CompactPair& operator=(CompactPair&& aOther) = default;
+  CompactPair& operator=(const CompactPair& aOther) = default;
+
+  /** The A instance. */
+  using Base::first;
+  /** The B instance. */
+  using Base::second;
+
+  /** Swap this pair with another pair. */
+  void swap(CompactPair& aOther) { Base::swap(aOther); }
+};
+
+/**
+ * MakeCompactPair allows you to construct a CompactPair instance using type
+ * inference. A call like this:
+ *
+ *   MakeCompactPair(Foo(), Bar())
+ *
+ * will return a CompactPair<Foo, Bar>.
+ */
+template <typename A, typename B>
+CompactPair<std::remove_cv_t<std::remove_reference_t<A>>,
+            std::remove_cv_t<std::remove_reference_t<B>>>
+MakeCompactPair(A&& aA, B&& aB) {
+  return CompactPair<std::remove_cv_t<std::remove_reference_t<A>>,
+                     std::remove_cv_t<std::remove_reference_t<B>>>(
+      std::forward<A>(aA), std::forward<B>(aB));
+}
+
+/**
+ * CompactPair equality comparison
+ */
+template <typename A, typename B>
+bool operator==(const CompactPair<A, B>& aLhs, const CompactPair<A, B>& aRhs) {
+  return aLhs.first() == aRhs.first() && aLhs.second() == aRhs.second();
+}
+
+}  // namespace mozilla
+
+namespace std {
+
+template <typename A, class B>
+void swap(mozilla::CompactPair<A, B>& aX, mozilla::CompactPair<A, B>& aY) {
+  aX.swap(aY);
+}
+
+}  // namespace std
+
+#endif /* mozilla_CompactPair_h */