Update //third_party/protobuf to version 3.

third_party/protobuf/src/google/protobuf/arena.h

+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_ARENA_H__
+#define GOOGLE_PROTOBUF_ARENA_H__
+
+#include <limits>
+#ifdef max
+#undef max  // Visual Studio defines this macro
+#endif
+#if __cplusplus >= 201103L
+#include <google/protobuf/stubs/type_traits.h>
+#endif
+#if defined(_MSC_VER) && !_HAS_EXCEPTIONS
+// Work around bugs in MSVC <typeinfo> header when _HAS_EXCEPTIONS=0.
+#include <exception>
+#include <typeinfo>
+namespace std {
+using type_info = ::type_info;
+}
+#else
+#include <typeinfo>
+#endif
+
+#include <google/protobuf/stubs/atomic_sequence_num.h>
+#include <google/protobuf/stubs/atomicops.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/mutex.h>
+#include <google/protobuf/stubs/type_traits.h>
+
+namespace google {
+namespace protobuf {
+
+class Arena;       // defined below
+class Message;     // message.h
+
+namespace internal {
+class ArenaString; // arenastring.h
+class LazyField;   // lazy_field.h
+
+template<typename Type>
+class GenericTypeHandler; // repeated_field.h
+
+// Templated cleanup methods.
+template<typename T> void arena_destruct_object(void* object) {
+  reinterpret_cast<T*>(object)->~T();
+}
+template<typename T> void arena_delete_object(void* object) {
+  delete reinterpret_cast<T*>(object);
+}
+inline void arena_free(void* object, size_t size) {
+  free(object);
+}
+
+}  // namespace internal
+
+// ArenaOptions provides optional additional parameters to arena construction
+// that control its block-allocation behavior.
+struct ArenaOptions {
+  // This defines the size of the first block requested from the system malloc.
+  // Subsequent block sizes will increase in a geometric series up to a maximum.
+  size_t start_block_size;
+
+  // This defines the maximum block size requested from system malloc (unless an
+  // individual arena allocation request occurs with a size larger than this
+  // maximum). Requested block sizes increase up to this value, then remain
+  // here.
+  size_t max_block_size;
+
+  // An initial block of memory for the arena to use, or NULL for none. If
+  // provided, the block must live at least as long as the arena itself. The
+  // creator of the Arena retains ownership of the block after the Arena is
+  // destroyed.
+  char* initial_block;
+
+  // The size of the initial block, if provided.
+  size_t initial_block_size;
+
+  // A function pointer to an alloc method that returns memory blocks of size
+  // requested. By default, it contains a ptr to the malloc function.
+  //
+  // NOTE: block_alloc and dealloc functions are expected to behave like
+  // malloc and free, including Asan poisoning.
+  void* (*block_alloc)(size_t);
+  // A function pointer to a dealloc method that takes ownership of the blocks
+  // from the arena. By default, it contains a ptr to a wrapper function that
+  // calls free.
+  void (*block_dealloc)(void*, size_t);
+
+  // Hooks for adding external functionality such as user-specific metrics
+  // collection, specific debugging abilities, etc.
+  // Init hook may return a pointer to a cookie to be stored in the arena.
+  // reset and destruction hooks will then be called with the same cookie
+  // pointer. This allows us to save an external object per arena instance and
+  // use it on the other hooks (Note: It is just as legal for init to return
+  // NULL and not use the cookie feature).
+  // on_arena_reset and on_arena_destruction also receive the space used in
+  // the arena just before the reset.
+  void* (*on_arena_init)(Arena* arena);
+  void (*on_arena_reset)(Arena* arena, void* cookie, uint64 space_used);
+  void (*on_arena_destruction)(Arena* arena, void* cookie, uint64 space_used);
+
+  // type_info is promised to be static - its lifetime extends to
+  // match program's lifetime (It is given by typeid operator).
+  // Note: typeid(void) will be passed as allocated_type every time we
+  // intentionally want to avoid monitoring an allocation. (i.e. internal
+  // allocations for managing the arena)
+  void (*on_arena_allocation)(const std::type_info* allocated_type,
+      uint64 alloc_size, void* cookie);
+
+  ArenaOptions()
+      : start_block_size(kDefaultStartBlockSize),
+        max_block_size(kDefaultMaxBlockSize),
+        initial_block(NULL),
+        initial_block_size(0),
+        block_alloc(&malloc),
+        block_dealloc(&internal::arena_free),
+        on_arena_init(NULL),
+        on_arena_reset(NULL),
+        on_arena_destruction(NULL),
+        on_arena_allocation(NULL) {}
+
+ private:
+  // Constants define default starting block size and max block size for
+  // arena allocator behavior -- see descriptions above.
+  static const size_t kDefaultStartBlockSize = 256;
+  static const size_t kDefaultMaxBlockSize   = 8192;
+};
+
+// Support for non-RTTI environments. (The metrics hooks API uses type
+// information.)
+#ifndef GOOGLE_PROTOBUF_NO_RTTI
+#define RTTI_TYPE_ID(type) (&typeid(type))
+#else
+#define RTTI_TYPE_ID(type) (NULL)
+#endif
+
+// Arena allocator. Arena allocation replaces ordinary (heap-based) allocation
+// with new/delete, and improves performance by aggregating allocations into
+// larger blocks and freeing allocations all at once. Protocol messages are
+// allocated on an arena by using Arena::CreateMessage<T>(Arena*), below, and
+// are automatically freed when the arena is destroyed.
+//
+// This is a thread-safe implementation: multiple threads may allocate from the
+// arena concurrently. Destruction is not thread-safe and the destructing
+// thread must synchronize with users of the arena first.
+//
+// An arena provides two allocation interfaces: CreateMessage<T>, which works
+// for arena-enabled proto2 message types as well as other types that satisfy
+// the appropriate protocol (described below), and Create<T>, which works for
+// any arbitrary type T. CreateMessage<T> is better when the type T supports it,
+// because this interface (i) passes the arena pointer to the created object so
+// that its sub-objects and internal allocations can use the arena too, and (ii)
+// elides the object's destructor call when possible. Create<T> does not place
+// any special requirements on the type T, and will invoke the object's
+// destructor when the arena is destroyed.
+//
+// The arena message allocation protocol, required by CreateMessage<T>, is as
+// follows:
+//
+// - The type T must have (at least) two constructors: a constructor with no
+//   arguments, called when a T is allocated on the heap; and a constructor with
+//   a google::protobuf::Arena* argument, called when a T is allocated on an arena. If the
+//   second constructor is called with a NULL arena pointer, it must be
+//   equivalent to invoking the first (no-argument) constructor.
+//
+// - The type T must have a particular type trait: a nested type
+//   |InternalArenaConstructable_|. This is usually a typedef to |void|. If no
+//   such type trait exists, then the instantiation CreateMessage<T> will fail
+//   to compile.
+//
+// - The type T *may* have the type trait |DestructorSkippable_|. If this type
+//   trait is present in the type, then its destructor will not be called if and
+//   only if it was passed a non-NULL arena pointer. If this type trait is not
+//   present on the type, then its destructor is always called when the
+//   containing arena is destroyed.
+//
+// - One- and two-user-argument forms of CreateMessage<T>() also exist that
+//   forward these constructor arguments to T's constructor: for example,
+//   CreateMessage<T>(Arena*, arg1, arg2) forwards to a constructor T(Arena*,
+//   arg1, arg2).
+//
+// This protocol is implemented by all arena-enabled proto2 message classes as
+// well as RepeatedPtrField.
+class LIBPROTOBUF_EXPORT Arena {
+ public:
+  // Arena constructor taking custom options. See ArenaOptions below for
+  // descriptions of the options available.
+  explicit Arena(const ArenaOptions& options) : options_(options) {
+    Init();
+  }
+
+  // Default constructor with sensible default options, tuned for average
+  // use-cases.
+  Arena() {
+    Init();
+  }
+
+  // Destructor deletes all owned heap allocated objects, and destructs objects
+  // that have non-trivial destructors, except for proto2 message objects whose
+  // destructors can be skipped. Also, frees all blocks except the initial block
+  // if it was passed in.
+  ~Arena();
+
+  // API to create proto2 message objects on the arena. If the arena passed in
+  // is NULL, then a heap allocated object is returned. Type T must be a message
+  // defined in a .proto file with cc_enable_arenas set to true, otherwise a
+  // compilation error will occur.
+  //
+  // RepeatedField and RepeatedPtrField may also be instantiated directly on an
+  // arena with this method.
+  //
+  // This function also accepts any type T that satisfies the arena message
+  // allocation protocol, documented above.
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateMessage(::google::protobuf::Arena* arena) {
+    if (arena == NULL) {
+      return new T;
+    } else {
+      return arena->CreateMessageInternal<T>(static_cast<T*>(0));
+    }
+  }
+
+  // One-argument form of CreateMessage. This is useful for constructing objects
+  // that implement the arena message construction protocol described above but
+  // take additional constructor arguments.
+  template <typename T, typename Arg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateMessage(::google::protobuf::Arena* arena, const Arg& arg) {
+    if (arena == NULL) {
+      return new T(NULL, arg);
+    } else {
+      return arena->CreateMessageInternal<T>(static_cast<T*>(0),
+                                             arg);
+    }
+  }
+
+  // Two-argument form of CreateMessage. This is useful for constructing objects
+  // that implement the arena message construction protocol described above but
+  // take additional constructor arguments.
+  template <typename T, typename Arg1, typename Arg2> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateMessage(::google::protobuf::Arena* arena,
+                          const Arg1& arg1,
+                          const Arg2& arg2) {
+    if (arena == NULL) {
+      return new T(NULL, arg1, arg2);
+    } else {
+      return arena->CreateMessageInternal<T>(static_cast<T*>(0),
+                                             arg1, arg2);
+    }
+  }
+
+  // API to create any objects on the arena. Note that only the object will
+  // be created on the arena; the underlying ptrs (in case of a proto2 message)
+  // will be still heap allocated. Proto messages should usually be allocated
+  // with CreateMessage<T>() instead.
+  //
+  // Note that even if T satisfies the arena message construction protocol
+  // (InternalArenaConstructable_ trait and optional DestructorSkippable_
+  // trait), as described above, this function does not follow the protocol;
+  // instead, it treats T as a black-box type, just as if it did not have these
+  // traits. Specifically, T's constructor arguments will always be only those
+  // passed to Create<T>() -- no additional arena pointer is implicitly added.
+  // Furthermore, the destructor will always be called at arena destruction time
+  // (unless the destructor is trivial). Hence, from T's point of view, it is as
+  // if the object were allocated on the heap (except that the underlying memory
+  // is obtained from the arena).
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* Create(::google::protobuf::Arena* arena) {
+    if (arena == NULL) {
+      return new T();
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value);
+    }
+  }
+
+  // Version of the above with one constructor argument for the created object.
+  template <typename T, typename Arg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* Create(::google::protobuf::Arena* arena, const Arg& arg) {
+    if (arena == NULL) {
+      return new T(arg);
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value,
+                                      arg);
+    }
+  }
+
+  // Version of the above with two constructor arguments for the created object.
+  template <typename T, typename Arg1, typename Arg2> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* Create(::google::protobuf::Arena* arena, const Arg1& arg1, const Arg2& arg2) {
+    if (arena == NULL) {
+      return new T(arg1, arg2);
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value,
+                                      arg1, arg2);
+    }
+  }
+
+  // Version of the above with three constructor arguments for the created
+  // object.
+  template <typename T, typename Arg1, typename Arg2, typename Arg3>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE static T* Create(::google::protobuf::Arena* arena,
+                                           const Arg1& arg1, const Arg2& arg2,
+                                           const Arg3& arg3) {
+    if (arena == NULL) {
+      return new T(arg1, arg2, arg3);
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value,
+                                      arg1, arg2, arg3);
+    }
+  }
+
+  // Version of the above with four constructor arguments for the created
+  // object.
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE static T* Create(::google::protobuf::Arena* arena,
+                                           const Arg1& arg1, const Arg2& arg2,
+                                           const Arg3& arg3, const Arg4& arg4) {
+    if (arena == NULL) {
+      return new T(arg1, arg2, arg3, arg4);
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value,
+                                      arg1, arg2, arg3, arg4);
+    }
+  }
+
+  // Version of the above with five constructor arguments for the created
+  // object.
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE static T* Create(::google::protobuf::Arena* arena,
+                                           const Arg1& arg1, const Arg2& arg2,
+                                           const Arg3& arg3, const Arg4& arg4,
+                                           const Arg5& arg5) {
+    if (arena == NULL) {
+      return new T(arg1, arg2, arg3, arg4, arg5);
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value,
+                                      arg1, arg2, arg3, arg4, arg5);
+    }
+  }
+
+  // Version of the above with six constructor arguments for the created
+  // object.
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5, typename Arg6>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE static T* Create(::google::protobuf::Arena* arena,
+                                           const Arg1& arg1, const Arg2& arg2,
+                                           const Arg3& arg3, const Arg4& arg4,
+                                           const Arg5& arg5, const Arg6& arg6) {
+    if (arena == NULL) {
+      return new T(arg1, arg2, arg3, arg4, arg5, arg6);
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value,
+                                      arg1, arg2, arg3, arg4, arg5, arg6);
+    }
+  }
+
+  // Version of the above with seven constructor arguments for the created
+  // object.
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5, typename Arg6, typename Arg7>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE static T* Create(::google::protobuf::Arena* arena,
+                                           const Arg1& arg1, const Arg2& arg2,
+                                           const Arg3& arg3, const Arg4& arg4,
+                                           const Arg5& arg5, const Arg6& arg6,
+                                           const Arg7& arg7) {
+    if (arena == NULL) {
+      return new T(arg1, arg2, arg3, arg4, arg5, arg6, arg7);
+    } else {
+      return arena->CreateInternal<T>(google::protobuf::internal::has_trivial_destructor<T>::value,
+                                      arg1, arg2, arg3, arg4, arg5, arg6, arg7);
+    }
+  }
+
+  // Version of the above with eight constructor arguments for the created
+  // object.
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5, typename Arg6, typename Arg7,
+            typename Arg8>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE static T* Create(::google::protobuf::Arena* arena,
+                                           const Arg1& arg1, const Arg2& arg2,
+                                           const Arg3& arg3, const Arg4& arg4,
+                                           const Arg5& arg5, const Arg6& arg6,
+                                           const Arg7& arg7, const Arg8& arg8) {
+    if (arena == NULL) {
+      return new T(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8);
+    } else {
+      return arena->CreateInternal<T>(
+          google::protobuf::internal::has_trivial_destructor<T>::value,
+          arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8);
+    }
+  }
+
+  // Create an array of object type T on the arena *without* invoking the
+  // constructor of T. If `arena` is null, then the return value should be freed
+  // with `delete[] x;` (or `::operator delete[](x);`).
+  // To ensure safe uses, this function checks at compile time
+  // (when compiled as C++11) that T is trivially default-constructible and
+  // trivially destructible.
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateArray(::google::protobuf::Arena* arena, size_t num_elements) {
+    GOOGLE_CHECK_LE(num_elements,
+             std::numeric_limits<size_t>::max() / sizeof(T))
+        << "Requested size is too large to fit into size_t.";
+    if (arena == NULL) {
+      return static_cast<T*>(::operator new[](num_elements * sizeof(T)));
+    } else {
+      return arena->CreateInternalRawArray<T>(num_elements);
+    }
+  }
+
+  // Returns the total space used by the arena, which is the sums of the sizes
+  // of the underlying blocks. The total space used may not include the new
+  // blocks that are allocated by this arena from other threads concurrently
+  // with the call to this method.
+  GOOGLE_ATTRIBUTE_NOINLINE uint64 SpaceAllocated() const;
+  // As above, but does not include any free space in underlying blocks.
+  GOOGLE_ATTRIBUTE_NOINLINE uint64 SpaceUsed() const;
+
+  // Frees all storage allocated by this arena after calling destructors
+  // registered with OwnDestructor() and freeing objects registered with Own().
+  // Any objects allocated on this arena are unusable after this call. It also
+  // returns the total space used by the arena which is the sums of the sizes
+  // of the allocated blocks. This method is not thread-safe.
+  GOOGLE_ATTRIBUTE_NOINLINE uint64 Reset();
+
+  // Adds |object| to a list of heap-allocated objects to be freed with |delete|
+  // when the arena is destroyed or reset.
+  template <typename T> GOOGLE_ATTRIBUTE_NOINLINE
+  void Own(T* object) {
+    OwnInternal(object, google::protobuf::internal::is_convertible<T*, ::google::protobuf::Message*>());
+  }
+
+  // Adds |object| to a list of objects whose destructors will be manually
+  // called when the arena is destroyed or reset. This differs from Own() in
+  // that it does not free the underlying memory with |delete|; hence, it is
+  // normally only used for objects that are placement-newed into
+  // arena-allocated memory.
+  template <typename T> GOOGLE_ATTRIBUTE_NOINLINE
+  void OwnDestructor(T* object) {
+    if (object != NULL) {
+      AddListNode(object, &internal::arena_destruct_object<T>);
+    }
+  }
+
+  // Adds a custom member function on an object to the list of destructors that
+  // will be manually called when the arena is destroyed or reset. This differs
+  // from OwnDestructor() in that any member function may be specified, not only
+  // the class destructor.
+  GOOGLE_ATTRIBUTE_NOINLINE void OwnCustomDestructor(void* object,
+                                              void (*destruct)(void*)) {
+    AddListNode(object, destruct);
+  }
+
+  // Retrieves the arena associated with |value| if |value| is an arena-capable
+  // message, or NULL otherwise. This differs from value->GetArena() in that the
+  // latter is a virtual call, while this method is a templated call that
+  // resolves at compile-time.
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static ::google::protobuf::Arena* GetArena(const T* value) {
+    return GetArenaInternal(value, static_cast<T*>(0));
+  }
+
+ private:
+  struct InternalIsArenaConstructableHelper {
+    template<typename U>
+    static char ArenaConstructable(
+        const typename U::InternalArenaConstructable_*);
+    template<typename U>
+    static double ArenaConstructable(...);
+  };
+
+ public:
+  // Helper typetrait that indicates support for arenas in a type T at compile
+  // time. This is public only to allow construction of higher-level templated
+  // utilities. is_arena_constructable<T>::value is true if the message type T
+  // has arena support enabled, and false otherwise.
+  //
+  // This is inside Arena because only Arena has the friend relationships
+  // necessary to see the underlying generated code traits.
+  template<typename T>
+  struct is_arena_constructable :
+      public google::protobuf::internal::integral_constant<bool,
+          sizeof(InternalIsArenaConstructableHelper::ArenaConstructable<
+                 const T>(static_cast<const T*>(0))) == sizeof(char)> {
+  };
+
+ private:
+  // Blocks are variable length malloc-ed objects.  The following structure
+  // describes the common header for all blocks.
+  struct Block {
+    void* owner;   // &ThreadCache of thread that owns this block, or
+                   // &this->owner if not yet owned by a thread.
+    Block* next;   // Next block in arena (may have different owner)
+    // ((char*) &block) + pos is next available byte. It is always
+    // aligned at a multiple of 8 bytes.
+    size_t pos;
+    size_t size;  // total size of the block.
+    GOOGLE_ATTRIBUTE_ALWAYS_INLINE size_t avail() const { return size - pos; }
+    // data follows
+  };
+
+  template<typename Type> friend class ::google::protobuf::internal::GenericTypeHandler;
+  friend class MockArena;              // For unit-testing.
+  friend class internal::ArenaString;  // For AllocateAligned.
+  friend class internal::LazyField;    // For CreateMaybeMessage.
+
+  struct ThreadCache {
+    // The ThreadCache is considered valid as long as this matches the
+    // lifecycle_id of the arena being used.
+    int64 last_lifecycle_id_seen;
+    Block* last_block_used_;
+  };
+
+  static const size_t kHeaderSize = sizeof(Block);
+  static google::protobuf::internal::SequenceNumber lifecycle_id_generator_;
+#if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL)
+  // Android ndk does not support GOOGLE_THREAD_LOCAL keyword so we use a custom thread
+  // local storage class we implemented.
+  // iOS also does not support the GOOGLE_THREAD_LOCAL keyword.
+  static ThreadCache& thread_cache();
+#elif defined(PROTOBUF_USE_DLLS)
+  // Thread local variables cannot be exposed through DLL interface but we can
+  // wrap them in static functions.
+  static ThreadCache& thread_cache();
+#else
+  static GOOGLE_THREAD_LOCAL ThreadCache thread_cache_;
+  static ThreadCache& thread_cache() { return thread_cache_; }
+#endif
+
+  // SFINAE for skipping addition to delete list for a message type when created
+  // with CreateMessage. This is mainly to skip proto2/proto1 message objects
+  // with cc_enable_arenas=true from being part of the delete list. Also, note,
+  // compiler will optimize out the branch in CreateInternal<T>.
+  template<typename T>
+  static inline bool SkipDeleteList(typename T::DestructorSkippable_*) {
+    return true;
+  }
+
+  // For message objects that don't have the DestructorSkippable_ trait, we
+  // always add to the delete list.
+  template<typename T>
+  static inline bool SkipDeleteList(...) {
+    return google::protobuf::internal::has_trivial_destructor<T>::value;
+  }
+
+ private:
+  struct InternalIsDestructorSkippableHelper {
+    template<typename U>
+    static char DestructorSkippable(
+        const typename U::DestructorSkippable_*);
+    template<typename U>
+    static double DestructorSkippable(...);
+  };
+
+ public:
+  // Helper typetrait that indicates whether the desctructor of type T should be
+  // called when arena is destroyed at compile time. This is only to allow
+  // construction of higher-level templated utilities.
+  // is_destructor_skippable<T>::value is true if the destructor of the message
+  // type T should not be called when arena is destroyed or false otherwise.
+  // This is inside Arena because only Arena has the friend relationships
+  // necessary to see the underlying generated code traits.
+  template<typename T>
+  struct is_destructor_skippable
+      : public google::protobuf::internal::integral_constant<
+            bool,
+            sizeof(InternalIsDestructorSkippableHelper::DestructorSkippable<
+                   const T>(static_cast<const T*>(0))) == sizeof(char) ||
+                google::protobuf::internal::has_trivial_destructor<T>::value> {};
+
+  // CreateMessage<T> requires that T supports arenas, but this private method
+  // works whether or not T supports arenas. These are not exposed to user code
+  // as it can cause confusing API usages, and end up having double free in
+  // user code. These are used only internally from LazyField and Repeated
+  // fields, since they are designed to work in all mode combinations.
+  template<typename Msg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static Msg* CreateMaybeMessage(
+      Arena* arena, typename Msg::InternalArenaConstructable_*) {
+    return CreateMessage<Msg>(arena);
+  }
+
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateMaybeMessage(Arena* arena, ...) {
+    return Create<T>(arena);
+  }
+
+  // Just allocate the required size for the given type assuming the
+  // type has a trivial constructor.
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  T* CreateInternalRawArray(size_t num_elements) {
+    GOOGLE_CHECK_LE(num_elements,
+             std::numeric_limits<size_t>::max() / sizeof(T))
+        << "Requested size is too large to fit into size_t.";
+    return static_cast<T*>(
+        AllocateAligned(RTTI_TYPE_ID(T), sizeof(T) * num_elements));
+  }
+
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  T* CreateInternal(bool skip_explicit_ownership) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T))) T();
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  T* CreateInternal(bool skip_explicit_ownership, const Arg& arg) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T))) T(arg);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  T* CreateInternal(
+      bool skip_explicit_ownership, const Arg1& arg1, const Arg2& arg2) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T))) T(arg1, arg2);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2, typename Arg3>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE T* CreateInternal(bool skip_explicit_ownership,
+                                            const Arg1& arg1,
+                                            const Arg2& arg2,
+                                            const Arg3& arg3) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T)))
+        T(arg1, arg2, arg3);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE T* CreateInternal(bool skip_explicit_ownership,
+                                            const Arg1& arg1,
+                                            const Arg2& arg2,
+                                            const Arg3& arg3,
+                                            const Arg4& arg4) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T)))
+        T(arg1, arg2, arg3, arg4);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE T* CreateInternal(bool skip_explicit_ownership,
+                                            const Arg1& arg1,
+                                            const Arg2& arg2,
+                                            const Arg3& arg3,
+                                            const Arg4& arg4,
+                                            const Arg5& arg5) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T)))
+        T(arg1, arg2, arg3, arg4, arg5);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5, typename Arg6>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE T* CreateInternal(bool skip_explicit_ownership,
+                                            const Arg1& arg1,
+                                            const Arg2& arg2,
+                                            const Arg3& arg3,
+                                            const Arg4& arg4,
+                                            const Arg5& arg5,
+                                            const Arg6& arg6) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T)))
+        T(arg1, arg2, arg3, arg4, arg5, arg6);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5, typename Arg6, typename Arg7>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE T* CreateInternal(bool skip_explicit_ownership,
+                                            const Arg1& arg1,
+                                            const Arg2& arg2,
+                                            const Arg3& arg3,
+                                            const Arg4& arg4,
+                                            const Arg5& arg5,
+                                            const Arg6& arg6,
+                                            const Arg7& arg7) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T)))
+        T(arg1, arg2, arg3, arg4, arg5, arg6, arg7);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2, typename Arg3,
+            typename Arg4, typename Arg5, typename Arg6, typename Arg7,
+            typename Arg8>
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE T* CreateInternal(bool skip_explicit_ownership,
+                                            const Arg1& arg1,
+                                            const Arg2& arg2,
+                                            const Arg3& arg3,
+                                            const Arg4& arg4,
+                                            const Arg5& arg5,
+                                            const Arg6& arg6,
+                                            const Arg7& arg7,
+                                            const Arg8& arg8) {
+    T* t = new (AllocateAligned(RTTI_TYPE_ID(T), sizeof(T)))
+        T(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  T* CreateMessageInternal(typename T::InternalArenaConstructable_*) {
+    return CreateInternal<T, Arena*>(SkipDeleteList<T>(static_cast<T*>(0)),
+                                     this);
+  }
+
+  template <typename T, typename Arg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  T* CreateMessageInternal(typename T::InternalArenaConstructable_*,
+                           const Arg& arg) {
+    return CreateInternal<T, Arena*>(SkipDeleteList<T>(static_cast<T*>(0)),
+                                     this, arg);
+  }
+
+  template <typename T, typename Arg1, typename Arg2> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  T* CreateMessageInternal(typename T::InternalArenaConstructable_*,
+                           const Arg1& arg1, const Arg2& arg2) {
+    return CreateInternal<T, Arena*>(SkipDeleteList<T>(static_cast<T*>(0)),
+                                     this, arg1, arg2);
+  }
+
+  // CreateInArenaStorage is used to implement map field. Without it,
+  // google::protobuf::Map need to call generated message's protected arena constructor,
+  // which needs to declare google::protobuf::Map as friend of generated message.
+  template <typename T>
+  static void CreateInArenaStorage(T* ptr, Arena* arena) {
+    CreateInArenaStorageInternal(ptr, arena,
+                                 typename is_arena_constructable<T>::type());
+    RegisterDestructorInternal(ptr, arena,
+                               typename is_destructor_skippable<T>::type());
+  }
+
+  template <typename T>
+  static void CreateInArenaStorageInternal(
+      T* ptr, Arena* arena, google::protobuf::internal::true_type) {
+    new (ptr) T(arena);
+  }
+  template <typename T>
+  static void CreateInArenaStorageInternal(
+      T* ptr, Arena* arena, google::protobuf::internal::false_type) {
+    new (ptr) T;
+  }
+
+  template <typename T>
+  static void RegisterDestructorInternal(
+      T* ptr, Arena* arena, google::protobuf::internal::true_type) {}
+  template <typename T>
+  static void RegisterDestructorInternal(
+      T* ptr, Arena* arena, google::protobuf::internal::false_type) {
+    arena->OwnDestructor(ptr);
+  }
+
+  // These implement Own(), which registers an object for deletion (destructor
+  // call and operator delete()). The second parameter has type 'true_type' if T
+  // is a subtype of ::google::protobuf::Message and 'false_type' otherwise. Collapsing
+  // all template instantiations to one for generic Message reduces code size,
+  // using the virtual destructor instead.
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  void OwnInternal(T* object, google::protobuf::internal::true_type) {
+    if (object != NULL) {
+      AddListNode(object, &internal::arena_delete_object< ::google::protobuf::Message >);
+    }
+  }
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  void OwnInternal(T* object, google::protobuf::internal::false_type) {
+    if (object != NULL) {
+      AddListNode(object, &internal::arena_delete_object<T>);
+    }
+  }
+
+  // Implementation for GetArena(). Only message objects with
+  // InternalArenaConstructable_ tags can be associated with an arena, and such
+  // objects must implement a GetArenaNoVirtual() method.
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static ::google::protobuf::Arena* GetArenaInternal(
+      const T* value, typename T::InternalArenaConstructable_*) {
+    return value->GetArenaNoVirtual();
+  }
+
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static ::google::protobuf::Arena* GetArenaInternal(const T* value, ...) {
+    return NULL;
+  }
+
+  // Allocate and also optionally call on_arena_allocation callback with the
+  // allocated type info when the hooks are in place in ArenaOptions and
+  // the cookie is not null.
+  void* AllocateAligned(const std::type_info* allocated, size_t n);
+
+  // Allocate an internal allocation, avoiding optional typed monitoring.
+  GOOGLE_ATTRIBUTE_ALWAYS_INLINE void* AllocateAligned(size_t n) {
+    return AllocateAligned(NULL, n);
+  }
+
+  void Init();
+
+  // Free all blocks and return the total space used which is the sums of sizes
+  // of the all the allocated blocks.
+  uint64 FreeBlocks();
+
+  // Add object pointer and cleanup function pointer to the list.
+  // TODO(rohananil, cfallin): We could pass in a sub-arena into this method
+  // to avoid polluting blocks of this arena with list nodes. This would help in
+  // mixed mode (where many protobufs have cc_enable_arenas=false), and is an
+  // alternative to a chunked linked-list, but with extra overhead of *next.
+  void AddListNode(void* elem, void (*cleanup)(void*));
+  // Delete or Destruct all objects owned by the arena.
+  void CleanupList();
+  uint64 ResetInternal();
+
+  inline void SetThreadCacheBlock(Block* block) {
+    thread_cache().last_block_used_ = block;
+    thread_cache().last_lifecycle_id_seen = lifecycle_id_;
+  }
+
+  int64 lifecycle_id_;  // Unique for each arena. Changes on Reset().
+
+  google::protobuf::internal::AtomicWord blocks_;  // Head of linked list of all allocated blocks
+  google::protobuf::internal::AtomicWord hint_;    // Fast thread-local block access
+
+  // Node contains the ptr of the object to be cleaned up and the associated
+  // cleanup function ptr.
+  struct Node {
+    void* elem;              // Pointer to the object to be cleaned up.
+    void (*cleanup)(void*);  // Function pointer to the destructor or deleter.
+    Node* next;              // Next node in the list.
+  };
+
+  google::protobuf::internal::AtomicWord cleanup_list_;  // Head of a linked list of nodes containing object
+                             // ptrs and cleanup methods.
+
+  bool owns_first_block_;    // Indicates that arena owns the first block
+  Mutex blocks_lock_;
+
+  void AddBlock(Block* b);
+  // Access must be synchronized, either by blocks_lock_ or by being called from
+  // Init()/Reset().
+  void AddBlockInternal(Block* b);
+  void* SlowAlloc(size_t n);
+  Block* FindBlock(void* me);
+  Block* NewBlock(void* me, Block* my_last_block, size_t n,
+                  size_t start_block_size, size_t max_block_size);
+  static void* AllocFromBlock(Block* b, size_t n);
+  template <typename Key, typename T>
+  friend class Map;
+
+  // The arena may save a cookie it receives from the external on_init hook
+  // and then use it when calling the on_reset and on_destruction hooks.
+  void* hooks_cookie_;
+
+  ArenaOptions options_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Arena);
+};
+
+// Defined above for supporting environments without RTTI.
+#undef RTTI_TYPE_ID
+
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_ARENA_H__