Current File : //usr/local/include/google/protobuf/arena.h
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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// 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,
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// 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 TestUtil {
class ReflectionTester; // defined in test_util.h
} // namespace TestUtil
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
inline PROTOBUF_ALWAYS_INLINE
void* AlignTo(void* ptr, size_t align) {
return reinterpret_cast<void*>(
(reinterpret_cast<uintptr_t>(ptr) + align - 1) & (~align + 1));
}
// Templated cleanup methods.
template <typename T>
void arena_destruct_object(void* object) {
reinterpret_cast<T*>(object)->~T();
}
template <bool destructor_skippable, typename T>
struct ObjectDestructor {
constexpr static void (*destructor)(void*) = &arena_destruct_object<T>;
};
template <typename T>
struct ObjectDestructor<true, T> {
constexpr static void (*destructor)(void*) = nullptr;
};
template <typename T>
void arena_delete_object(void* object) {
delete reinterpret_cast<T*>(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);
ArenaOptions()
: start_block_size(internal::AllocationPolicy::kDefaultStartBlockSize),
max_block_size(internal::AllocationPolicy::kDefaultMaxBlockSize),
initial_block(NULL),
initial_block_size(0),
block_alloc(nullptr),
block_dealloc(nullptr),
make_metrics_collector(nullptr) {}
private:
// If make_metrics_collector is not nullptr, it will be called at Arena init
// time. It may return a pointer to a collector instance that will be notified
// of interesting events related to the arena.
internal::ArenaMetricsCollector* (*make_metrics_collector)();
internal::ArenaMetricsCollector* MetricsCollector() const {
return make_metrics_collector ? (*make_metrics_collector)() : nullptr;
}
internal::AllocationPolicy AllocationPolicy() const {
internal::AllocationPolicy res;
res.start_block_size = start_block_size;
res.max_block_size = max_block_size;
res.block_alloc = block_alloc;
res.block_dealloc = block_dealloc;
res.metrics_collector = MetricsCollector();
return res;
}
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:
// Default constructor with sensible default options, tuned for average
// use-cases.
inline Arena() : impl_() {}
// Construct an arena with default options, except for the supplied
// initial block. It is more efficient to use this constructor
// instead of passing ArenaOptions if the only configuration needed
// by the caller is supplying an initial block.
inline Arena(char* initial_block, size_t initial_block_size)
: impl_(initial_block, initial_block_size) {}
// Arena constructor taking custom options. See ArenaOptions above for
// descriptions of the options available.
explicit Arena(const ArenaOptions& options)
: impl_(options.initial_block, options.initial_block_size,
options.AllocationPolicy()) {}
// 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::ThreadSafeArena::kBlockHeaderSize +
internal::ThreadSafeArena::kSerialArenaSize;
inline ~Arena() {}
// TODO(protobuf-team): Fix callers to use constructor and delete this method.
void Init(const ArenaOptions&) {}
// 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_NDEBUG_INLINE static T* Create(Arena* arena, Args&&... args) {
return CreateInternal<T>(arena, std::is_convertible<T*, MessageLite*>(),
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_NDEBUG_INLINE static T* CreateArray(Arena* arena,
size_t num_elements) {
static_assert(std::is_trivial<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);
}
}
// The following are routines are for monitoring. They will approximate the
// total sum allocated and used memory, but the exact value is an
// implementation deal. For instance allocated space depends on growth
// policies. Do not use these in unit tests.
// Returns the total space allocated by the arena, which is the sum of the
// sizes of the underlying blocks.
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.
uint64 Reset() { 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_ALWAYS_INLINE void Own(T* object) {
OwnInternal(object, std::is_convertible<T*, MessageLite*>());
}
// 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_ALWAYS_INLINE 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_ALWAYS_INLINE 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 {
public:
// Provides access to protected GetOwningArena to generated messages.
static Arena* GetOwningArena(const T* p) { return p->GetOwningArena(); }
// Provides access to protected GetArenaForAllocation to generated messages.
static Arena* GetArenaForAllocation(const T* p) {
return GetArenaForAllocationInternal(
p, std::is_convertible<T*, MessageLite*>());
}
private:
static Arena* GetArenaForAllocationInternal(
const T* p, std::true_type /*is_derived_from<MessageLite>*/) {
return p->GetArenaForAllocation();
}
static Arena* GetArenaForAllocationInternal(
const T* p, std::false_type /*is_derived_from<MessageLite>*/) {
return GetArenaForAllocationForNonMessage(
p, typename is_arena_constructable::type());
}
static Arena* GetArenaForAllocationForNonMessage(
const T* p, std::true_type /*is_arena_constructible*/) {
return p->GetArena();
}
static Arena* GetArenaForAllocationForNonMessage(
const T* p, std::false_type /*is_arena_constructible*/) {
return GetArenaForAllocationForNonMessageNonArenaConstructible(
p, typename has_get_arena::type());
}
static Arena* GetArenaForAllocationForNonMessageNonArenaConstructible(
const T* p, std::true_type /*has_get_arena*/) {
return p->GetArena();
}
static Arena* GetArenaForAllocationForNonMessageNonArenaConstructible(
const T* p, std::false_type /*has_get_arena*/) {
return nullptr;
}
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 T* New() {
return new T(nullptr);
}
static Arena* GetArena(const T* p) { return p->GetArena(); }
friend class Arena;
friend class TestUtil::ReflectionTester;
};
// 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:
internal::ThreadSafeArena impl_;
template <typename T>
struct has_get_arena : InternalHelper<T>::has_get_arena {};
template <typename T, typename... Args>
PROTOBUF_NDEBUG_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_NDEBUG_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) {
// Generated arena constructor T(Arena*) is protected. Call via
// InternalHelper.
return InternalHelper<T>::New();
} else {
return arena->DoCreateMessage<T>();
}
}
// Allocate and also optionally call collector with the allocated type info
// when allocation recording is enabled.
PROTOBUF_NDEBUG_INLINE void* AllocateInternal(size_t size, size_t align,
void (*destructor)(void*),
const std::type_info* type) {
// Monitor allocation if needed.
if (destructor == nullptr) {
return AllocateAlignedWithHook(size, align, type);
} else {
if (align <= 8) {
auto res = AllocateAlignedWithCleanup(internal::AlignUpTo8(size), type);
res.second->elem = res.first;
res.second->cleanup = destructor;
return res.first;
} else {
auto res = AllocateAlignedWithCleanup(size + align - 8, type);
auto ptr = internal::AlignTo(res.first, align);
res.second->elem = ptr;
res.second->cleanup = destructor;
return ptr;
}
}
}
// 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 Create<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)...);
}
// Just allocate the required size for the given type assuming the
// type has a trivial constructor.
template <typename T>
PROTOBUF_NDEBUG_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.";
// We count on compiler to realize that if sizeof(T) is a multiple of
// 8 AlignUpTo can be elided.
const size_t n = sizeof(T) * num_elements;
return static_cast<T*>(
AllocateAlignedWithHook(n, alignof(T), RTTI_TYPE_ID(T)));
}
template <typename T, typename... Args>
PROTOBUF_NDEBUG_INLINE T* DoCreateMessage(Args&&... args) {
return InternalHelper<T>::Construct(
AllocateInternal(sizeof(T), alignof(T),
internal::ObjectDestructor<
InternalHelper<T>::is_destructor_skippable::value,
T>::destructor,
RTTI_TYPE_ID(T)),
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 Create(). The second parameter has type 'true_type' if T is
// a subtype of Message and 'false_type' otherwise.
template <typename T, typename... Args>
PROTOBUF_ALWAYS_INLINE static T* CreateInternal(Arena* arena, std::true_type,
Args&&... args) {
if (arena == nullptr) {
return new T(std::forward<Args>(args)...);
} else {
auto destructor =
internal::ObjectDestructor<std::is_trivially_destructible<T>::value,
T>::destructor;
T* result =
new (arena->AllocateInternal(sizeof(T), alignof(T), destructor,
RTTI_TYPE_ID(T)))
T(std::forward<Args>(args)...);
return result;
}
}
template <typename T, typename... Args>
PROTOBUF_ALWAYS_INLINE static T* CreateInternal(Arena* arena, std::false_type,
Args&&... args) {
if (arena == nullptr) {
return new T(std::forward<Args>(args)...);
} else {
auto destructor =
internal::ObjectDestructor<std::is_trivially_destructible<T>::value,
T>::destructor;
return new (arena->AllocateInternal(sizeof(T), alignof(T), destructor,
RTTI_TYPE_ID(T)))
T(std::forward<Args>(args)...);
}
}
// 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<MessageLite>);
}
}
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;
}
template <typename T>
PROTOBUF_ALWAYS_INLINE static Arena* GetOwningArena(const T* value) {
return GetOwningArenaInternal(
value, std::is_convertible<T*, MessageLite*>());
}
// Implementation for GetOwningArena(). All and only message objects have
// GetOwningArena() method.
template <typename T>
PROTOBUF_ALWAYS_INLINE static Arena* GetOwningArenaInternal(
const T* value, std::true_type) {
return InternalHelper<T>::GetOwningArena(value);
}
template <typename T>
PROTOBUF_ALWAYS_INLINE static Arena* GetOwningArenaInternal(
const T* /* value */, std::false_type) {
return nullptr;
}
// For friends of arena.
void* AllocateAligned(size_t n, size_t align = 8) {
if (align <= 8) {
return AllocateAlignedNoHook(internal::AlignUpTo8(n));
} else {
// We are wasting space by over allocating align - 8 bytes. Compared
// to a dedicated function that takes current alignment in consideration.
// Such a scheme would only waste (align - 8)/2 bytes on average, but
// requires a dedicated function in the outline arena allocation
// functions. Possibly re-evaluate tradeoffs later.
return internal::AlignTo(AllocateAlignedNoHook(n + align - 8), align);
}
}
void* AllocateAlignedWithHook(size_t n, size_t align,
const std::type_info* type) {
if (align <= 8) {
return AllocateAlignedWithHook(internal::AlignUpTo8(n), type);
} else {
// We are wasting space by over allocating align - 8 bytes. Compared
// to a dedicated function that takes current alignment in consideration.
// Such a schemee would only waste (align - 8)/2 bytes on average, but
// requires a dedicated function in the outline arena allocation
// functions. Possibly re-evaluate tradeoffs later.
return internal::AlignTo(AllocateAlignedWithHook(n + align - 8, type),
align);
}
}
void* AllocateAlignedNoHook(size_t n);
void* AllocateAlignedWithHook(size_t n, const std::type_info* type);
std::pair<void*, internal::SerialArena::CleanupNode*>
AllocateAlignedWithCleanup(size_t n, const std::type_info* type);
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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