FM / protobuf

/usr/include/google/protobuf

Name	Size	Mode	Actions
io/	-	0755	rm
stubs/	-	0755	rm
util/	-	0755	rm
any.h	6181	0644	edit dl rm
any.pb.h	17726	0644	edit dl rm
any.proto	5878	0644	edit dl rm
api.pb.h	64196	0644	edit dl rm
api.proto	7734	0644	edit dl rm
arena.h	31329	0644	edit dl rm
arenastring.h	14674	0644	edit dl rm
arena_impl.h	14316	0644	edit dl rm
descriptor.h	96357	0644	edit dl rm
descriptor.pb.h	587894	0644	edit dl rm
descriptor.proto	37986	0644	edit dl rm
descriptor_database.h	19379	0644	edit dl rm
duration.pb.h	9865	0644	edit dl rm
duration.proto	4888	0644	edit dl rm
dynamic_message.h	9986	0644	edit dl rm
empty.pb.h	7683	0644	edit dl rm
empty.proto	2422	0644	edit dl rm
extension_set.h	78461	0644	edit dl rm
extension_set_inl.h	12756	0644	edit dl rm
field_mask.pb.h	11825	0644	edit dl rm
field_mask.proto	8192	0644	edit dl rm
generated_enum_reflection.h	3954	0644	edit dl rm
generated_enum_util.h	3266	0644	edit dl rm
generated_message_reflection.h	12880	0644	edit dl rm
generated_message_table_driven.h	12610	0644	edit dl rm
generated_message_util.h	9560	0644	edit dl rm
has_bits.h	3528	0644	edit dl rm
implicit_weak_message.h	7014	0644	edit dl rm
inlined_string_field.h	9332	0644	edit dl rm
map.h	46287	0644	edit dl rm
map_entry.h	7276	0644	edit dl rm
map_entry_lite.h	26016	0644	edit dl rm
map_field.h	31208	0644	edit dl rm
map_field_inl.h	14512	0644	edit dl rm
map_field_lite.h	7559	0644	edit dl rm
map_type_handler.h	39082	0644	edit dl rm
message.h	61613	0644	edit dl rm
message_lite.h	25964	0644	edit dl rm
metadata.h	1857	0644	edit dl rm
metadata_lite.h	8260	0644	edit dl rm
parse_context.h	29812	0644	edit dl rm
port.h	2050	0644	edit dl rm
port_def.inc	17039	0644	edit dl rm
port_undef.inc	3498	0644	edit dl rm
reflection.h	22717	0644	edit dl rm
reflection_ops.h	3686	0644	edit dl rm
repeated_field.h	101032	0644	edit dl rm
service.h	13159	0644	edit dl rm
source_context.pb.h	12740	0644	edit dl rm
source_context.proto	2352	0644	edit dl rm
struct.pb.h	43629	0644	edit dl rm
struct.proto	3780	0644	edit dl rm
text_format.h	28948	0644	edit dl rm
timestamp.pb.h	9928	0644	edit dl rm
timestamp.proto	6200	0644	edit dl rm
type.pb.h	105722	0644	edit dl rm
type.proto	6129	0644	edit dl rm
unknown_field_set.h	14401	0644	edit dl rm
wire_format.h	17660	0644	edit dl rm
wire_format_lite.h	84033	0644	edit dl rm
wrappers.pb.h	61421	0644	edit dl rm
wrappers.proto	4035	0644	edit dl rm

Edit: /usr/include/google/protobuf/arena.h (31329B)

// 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.

// This file defines an Arena allocator for better allocation performance.

#ifndef GOOGLE_PROTOBUF_ARENA_H__
#define GOOGLE_PROTOBUF_ARENA_H__

#include <limits>
#include <type_traits>
#include <utility>
#ifdef max
#undef max  // Visual Studio defines this macro
#endif
#if defined(_MSC_VER) && !defined(_LIBCPP_STD_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 <type_traits>
#include <google/protobuf/arena_impl.h>
#include <google/protobuf/port.h>

#include <google/protobuf/port_def.inc>

#ifdef SWIG
#error "You cannot SWIG proto headers"
#endif

namespace google {
namespace protobuf {

struct ArenaOptions;  // defined below

}  // namespace protobuf
}  // namespace google

namespace google {
namespace protobuf {

class Arena;    // defined below
class Message;  // defined in message.h
class MessageLite;
template <typename Key, typename T>
class Map;

namespace arena_metrics {

void EnableArenaMetrics(ArenaOptions* options);

}  // namespace arena_metrics

namespace internal {

struct ArenaStringPtr;  // defined in arenastring.h
class LazyField;        // defined in lazy_field.h
class EpsCopyInputStream;  // defined in parse_context.h

template <typename Type>
class GenericTypeHandler;  // defined in 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) {
#if defined(__GXX_DELETE_WITH_SIZE__) || defined(__cpp_sized_deallocation)
  ::operator delete(object, size);
#else
  (void)size;
  ::operator delete(object);
#endif
}

}  // 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);

ArenaOptions()
      : start_block_size(kDefaultStartBlockSize),
        max_block_size(kDefaultMaxBlockSize),
        initial_block(NULL),
        initial_block_size(0),
        block_alloc(&::operator new),
        block_dealloc(&internal::arena_free),
        on_arena_init(NULL),
        on_arena_reset(NULL),
        on_arena_destruction(NULL),
        on_arena_allocation(NULL) {}

private:
  // Hooks for adding external functionality such as user-specific metrics
  // collection, specific debugging abilities, etc.
  // Init hook (if set) will always be called at Arena init time. 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: If init hook returns NULL, the other hooks will NOT be
  // called on this arena instance).
  // 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);

// 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;

friend void arena_metrics::EnableArenaMetrics(ArenaOptions*);
  friend class Arena;
  friend class ArenaOptionsTestFriend;
};

// Support for non-RTTI environments. (The metrics hooks API uses type
// information.)
#if PROTOBUF_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>(Arena* arena, Args&&... args), is as follows:
//
// - The type T must have (at least) two constructors: a constructor callable
//   with `args` (without `arena`), called when a T is allocated on the heap;
//   and a constructor callable with `Arena* arena, Args&&... args`, 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
//   (`args`-only) 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.
//
// This protocol is implemented by all arena-enabled proto2 message classes as
// well as protobuf container types like RepeatedPtrField and Map. The protocol
// is internal to protobuf and is not guaranteed to be stable. Non-proto types
// should not rely on this protocol.
class PROTOBUF_EXPORT PROTOBUF_ALIGNAS(8) Arena final {
 public:
  // Arena constructor taking custom options. See ArenaOptions below for
  // descriptions of the options available.
  explicit Arena(const ArenaOptions& options) : impl_(options) {
    Init(options);
  }

// Block overhead.  Use this as a guide for how much to over-allocate the
  // initial block if you want an allocation of size N to fit inside it.
  //
  // WARNING: if you allocate multiple objects, it is difficult to guarantee
  // that a series of allocations will fit in the initial block, especially if
  // Arena changes its alignment guarantees in the future!
  static const size_t kBlockOverhead = internal::ArenaImpl::kBlockHeaderSize +
                                       internal::ArenaImpl::kSerialArenaSize;

// Default constructor with sensible default options, tuned for average
  // use-cases.
  Arena() : impl_(ArenaOptions()) { Init(ArenaOptions()); }

~Arena() {
    if (hooks_cookie_) {
      CallDestructorHooks();
    }
  }

void Init(const ArenaOptions& options) {
    on_arena_allocation_ = options.on_arena_allocation;
    on_arena_reset_ = options.on_arena_reset;
    on_arena_destruction_ = options.on_arena_destruction;
    // Call the initialization hook
    if (options.on_arena_init != NULL) {
      hooks_cookie_ = options.on_arena_init(this);
    } else {
      hooks_cookie_ = NULL;
    }
  }

// 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, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* CreateMessage(Arena* arena, Args&&... args) {
    static_assert(
        InternalHelper<T>::is_arena_constructable::value,
        "CreateMessage can only construct types that are ArenaConstructable");
    // We must delegate to CreateMaybeMessage() and NOT CreateMessageInternal()
    // because protobuf generated classes specialize CreateMaybeMessage() and we
    // need to use that specialization for code size reasons.
    return Arena::CreateMaybeMessage<T>(arena, std::forward<Args>(args)...);
  }

// 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, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* Create(Arena* arena, Args&&... args) {
    return CreateNoMessage<T>(arena, is_arena_constructable<T>(),
                              std::forward<Args>(args)...);
  }

// 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>
  PROTOBUF_ALWAYS_INLINE static T* CreateArray(Arena* arena,
                                               size_t num_elements) {
    static_assert(std::is_pod<T>::value,
                  "CreateArray requires a trivially constructible type");
    static_assert(std::is_trivially_destructible<T>::value,
                  "CreateArray requires a trivially destructible type");
    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 allocated by the arena, which is the sum of the
  // sizes of the underlying blocks. This method is relatively fast; a counter
  // is kept as blocks are allocated.
  uint64 SpaceAllocated() const { return impl_.SpaceAllocated(); }
  // Returns the total space used by the arena. Similar to SpaceAllocated but
  // does not include free space and block overhead. The total space returned
  // may not include space used by other threads executing concurrently with
  // the call to this method.
  uint64 SpaceUsed() const { return impl_.SpaceUsed(); }

// 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.
  PROTOBUF_NOINLINE uint64 Reset() {
    // Call the reset hook
    if (on_arena_reset_ != NULL) {
      on_arena_reset_(this, hooks_cookie_, impl_.SpaceAllocated());
    }
    return impl_.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>
  PROTOBUF_NOINLINE void Own(T* object) {
    OwnInternal(object, std::is_convertible<T*, 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>
  PROTOBUF_NOINLINE void OwnDestructor(T* object) {
    if (object != NULL) {
      impl_.AddCleanup(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.
  PROTOBUF_NOINLINE void OwnCustomDestructor(void* object,
                                             void (*destruct)(void*)) {
    impl_.AddCleanup(object, destruct);
  }

// Retrieves the arena associated with |value| if |value| is an arena-capable
  // message, or NULL otherwise. If possible, the call resolves at compile time.
  // Note that we can often devirtualize calls to `value->GetArena()` so usually
  // calling this method is unnecessary.
  template <typename T>
  PROTOBUF_ALWAYS_INLINE static Arena* GetArena(const T* value) {
    return GetArenaInternal(value);
  }

template <typename T>
  class InternalHelper {
    template <typename U>
    static char DestructorSkippable(const typename U::DestructorSkippable_*);
    template <typename U>
    static double DestructorSkippable(...);

typedef std::integral_constant<
        bool, sizeof(DestructorSkippable<T>(static_cast<const T*>(0))) ==
                      sizeof(char) ||
                  std::is_trivially_destructible<T>::value>
        is_destructor_skippable;

template <typename U>
    static char ArenaConstructable(
        const typename U::InternalArenaConstructable_*);
    template <typename U>
    static double ArenaConstructable(...);

typedef std::integral_constant<bool, sizeof(ArenaConstructable<T>(
                                             static_cast<const T*>(0))) ==
                                             sizeof(char)>
        is_arena_constructable;

template <typename U,
              typename std::enable_if<
                  std::is_same<Arena*, decltype(std::declval<const U>()
                                                    .GetArena())>::value,
                  int>::type = 0>
    static char HasGetArena(decltype(&U::GetArena));
    template <typename U>
    static double HasGetArena(...);

typedef std::integral_constant<bool, sizeof(HasGetArena<T>(nullptr)) ==
                                             sizeof(char)>
        has_get_arena;

template <typename... Args>
    static T* Construct(void* ptr, Args&&... args) {
      return new (ptr) T(std::forward<Args>(args)...);
    }

static Arena* GetArena(const T* p) { return p->GetArena(); }

friend class Arena;
  };

// Helper typetraits 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.
  //
  // is_destructor_skippable<T>::value is true if the message type T has told
  // the arena that it is safe to skip the destructor, 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 : InternalHelper<T>::is_arena_constructable {};
  template <typename T>
  struct is_destructor_skippable : InternalHelper<T>::is_destructor_skippable {
  };

private:
  template <typename T>
  struct has_get_arena : InternalHelper<T>::has_get_arena {};

template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* CreateMessageInternal(Arena* arena,
                                                         Args&&... args) {
    static_assert(
        InternalHelper<T>::is_arena_constructable::value,
        "CreateMessage can only construct types that are ArenaConstructable");
    if (arena == NULL) {
      return new T(nullptr, std::forward<Args>(args)...);
    } else {
      return arena->DoCreateMessage<T>(std::forward<Args>(args)...);
    }
  }

// This specialization for no arguments is necessary, because its behavior is
  // slightly different.  When the arena pointer is nullptr, it calls T()
  // instead of T(nullptr).
  template <typename T>
  PROTOBUF_ALWAYS_INLINE static T* CreateMessageInternal(Arena* arena) {
    static_assert(
        InternalHelper<T>::is_arena_constructable::value,
        "CreateMessage can only construct types that are ArenaConstructable");
    if (arena == NULL) {
      return new T();
    } else {
      return arena->DoCreateMessage<T>();
    }
  }

template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* CreateInternal(Arena* arena,
                                                  Args&&... args) {
    if (arena == NULL) {
      return new T(std::forward<Args>(args)...);
    } else {
      return arena->DoCreate<T>(std::is_trivially_destructible<T>::value,
                                std::forward<Args>(args)...);
    }
  }

void CallDestructorHooks();
  void OnArenaAllocation(const std::type_info* allocated_type, size_t n) const;
  inline void AllocHook(const std::type_info* allocated_type, size_t n) const {
    if (PROTOBUF_PREDICT_FALSE(hooks_cookie_ != NULL)) {
      OnArenaAllocation(allocated_type, n);
    }
  }

// 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.
  template <typename T>
  PROTOBUF_ALWAYS_INLINE void* AllocateInternal(bool skip_explicit_ownership) {
    static_assert(alignof(T) <= 8, "T is overaligned, see b/151247138");
    const size_t n = internal::AlignUpTo8(sizeof(T));
    AllocHook(RTTI_TYPE_ID(T), n);
    // Monitor allocation if needed.
    if (skip_explicit_ownership) {
      return AllocateAlignedNoHook(n);
    } else {
      return impl_.AllocateAlignedAndAddCleanup(
          n, &internal::arena_destruct_object<T>);
    }
  }

// 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, typename... Args>
  PROTOBUF_ALWAYS_INLINE static Msg* DoCreateMaybeMessage(Arena* arena,
                                                          std::true_type,
                                                          Args&&... args) {
    return CreateMessageInternal<Msg>(arena, std::forward<Args>(args)...);
  }

template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* DoCreateMaybeMessage(Arena* arena,
                                                        std::false_type,
                                                        Args&&... args) {
    return CreateInternal<T>(arena, std::forward<Args>(args)...);
  }

template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* CreateMaybeMessage(Arena* arena,
                                                      Args&&... args) {
    return DoCreateMaybeMessage<T>(arena, is_arena_constructable<T>(),
                                   std::forward<Args>(args)...);
  }

template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* CreateNoMessage(Arena* arena, std::true_type,
                                                   Args&&... args) {
    // User is constructing with Create() despite the fact that T supports arena
    // construction.  In this case we have to delegate to CreateInternal(), and
    // we can't use any CreateMaybeMessage() specialization that may be defined.
    return CreateInternal<T>(arena, std::forward<Args>(args)...);
  }

template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE static T* CreateNoMessage(Arena* arena,
                                                   std::false_type,
                                                   Args&&... args) {
    // User is constructing with Create() and the type does not support arena
    // construction.  In this case we can delegate to CreateMaybeMessage() and
    // use any specialization that may be available for that.
    return CreateMaybeMessage<T>(arena, std::forward<Args>(args)...);
  }

// Just allocate the required size for the given type assuming the
  // type has a trivial constructor.
  template <typename T>
  PROTOBUF_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.";
    const size_t n = internal::AlignUpTo8(sizeof(T) * num_elements);
    // Monitor allocation if needed.
    AllocHook(RTTI_TYPE_ID(T), n);
    return static_cast<T*>(AllocateAlignedNoHook(n));
  }

template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE T* DoCreate(bool skip_explicit_ownership,
                                     Args&&... args) {
    return new (AllocateInternal<T>(skip_explicit_ownership))
        T(std::forward<Args>(args)...);
  }
  template <typename T, typename... Args>
  PROTOBUF_ALWAYS_INLINE T* DoCreateMessage(Args&&... args) {
    return InternalHelper<T>::Construct(
        AllocateInternal<T>(InternalHelper<T>::is_destructor_skippable::value),
        this, std::forward<Args>(args)...);
  }

// CreateInArenaStorage is used to implement map field. Without it,
  // Map need to call generated message's protected arena constructor,
  // which needs to declare Map as friend of generated message.
  template <typename T, typename... Args>
  static void CreateInArenaStorage(T* ptr, Arena* arena, Args&&... args) {
    CreateInArenaStorageInternal(ptr, arena,
                                 typename is_arena_constructable<T>::type(),
                                 std::forward<Args>(args)...);
    RegisterDestructorInternal(
        ptr, arena,
        typename InternalHelper<T>::is_destructor_skippable::type());
  }

template <typename T, typename... Args>
  static void CreateInArenaStorageInternal(T* ptr, Arena* arena,
                                           std::true_type, Args&&... args) {
    InternalHelper<T>::Construct(ptr, arena, std::forward<Args>(args)...);
  }
  template <typename T, typename... Args>
  static void CreateInArenaStorageInternal(T* ptr, Arena* /* arena */,
                                           std::false_type, Args&&... args) {
    new (ptr) T(std::forward<Args>(args)...);
  }

template <typename T>
  static void RegisterDestructorInternal(T* /* ptr */, Arena* /* arena */,
                                         std::true_type) {}
  template <typename T>
  static void RegisterDestructorInternal(T* ptr, Arena* arena,
                                         std::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 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>
  PROTOBUF_ALWAYS_INLINE void OwnInternal(T* object, std::true_type) {
    if (object != NULL) {
      impl_.AddCleanup(object, &internal::arena_delete_object<Message>);
    }
  }
  template <typename T>
  PROTOBUF_ALWAYS_INLINE void OwnInternal(T* object, std::false_type) {
    if (object != NULL) {
      impl_.AddCleanup(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 GetArena() method.
  template <typename T, typename std::enable_if<
                            is_arena_constructable<T>::value, int>::type = 0>
  PROTOBUF_ALWAYS_INLINE static Arena* GetArenaInternal(const T* value) {
    return InternalHelper<T>::GetArena(value);
  }
  template <typename T,
            typename std::enable_if<!is_arena_constructable<T>::value &&
                                        has_get_arena<T>::value,
                                    int>::type = 0>
  PROTOBUF_ALWAYS_INLINE static Arena* GetArenaInternal(const T* value) {
    return value->GetArena();
  }
  template <typename T,
            typename std::enable_if<!is_arena_constructable<T>::value &&
                                        !has_get_arena<T>::value,
                                    int>::type = 0>
  PROTOBUF_ALWAYS_INLINE static Arena* GetArenaInternal(const T* value) {
    (void)value;
    return nullptr;
  }

// For friends of arena.
  void* AllocateAligned(size_t n) {
    AllocHook(NULL, n);
    return AllocateAlignedNoHook(internal::AlignUpTo8(n));
  }
  template<size_t Align>
  void* AllocateAlignedTo(size_t n) {
    static_assert(Align > 0, "Alignment must be greater than 0");
    static_assert((Align & (Align - 1)) == 0, "Alignment must be power of two");
    if (Align <= 8) return AllocateAligned(n);
    // TODO(b/151247138): if the pointer would have been aligned already,
    // this is wasting space. We should pass the alignment down.
    uintptr_t ptr = reinterpret_cast<uintptr_t>(AllocateAligned(n + Align - 8));
    ptr = (ptr + Align - 1) & -Align;
    return reinterpret_cast<void*>(ptr);
  }

void* AllocateAlignedNoHook(size_t n);

internal::ArenaImpl impl_;

void (*on_arena_allocation_)(const std::type_info* allocated_type,
                               uint64 alloc_size, void* cookie);
  void (*on_arena_reset_)(Arena* arena, void* cookie, uint64 space_used);
  void (*on_arena_destruction_)(Arena* arena, void* cookie, uint64 space_used);

// 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_;

template <typename Type>
  friend class internal::GenericTypeHandler;
  friend struct internal::ArenaStringPtr;  // For AllocateAligned.
  friend class internal::LazyField;        // For CreateMaybeMessage.
  friend class internal::EpsCopyInputStream;  // For parser performance
  friend class MessageLite;
  template <typename Key, typename T>
  friend class Map;
};

// Defined above for supporting environments without RTTI.
#undef RTTI_TYPE_ID

}  // namespace protobuf
}  // namespace google

#include <google/protobuf/port_undef.inc>

#endif  // GOOGLE_PROTOBUF_ARENA_H__

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