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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
//
// 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_IMPL_H__
#define GOOGLE_PROTOBUF_ARENA_IMPL_H__
#include <atomic>
#include <limits>
#include <typeinfo>
#include <google/protobuf/stubs/common.h>
#include <google/protobuf/stubs/logging.h>
#include <google/protobuf/stubs/port.h>
#ifdef ADDRESS_SANITIZER
#include <sanitizer/asan_interface.h>
#endif // ADDRESS_SANITIZER
#include <google/protobuf/arenaz_sampler.h>
// Must be included last.
#include <google/protobuf/port_def.inc>
namespace google {
namespace protobuf {
namespace internal {
// To prevent sharing cache lines between threads
#ifdef __cpp_aligned_new
enum { kCacheAlignment = 64 };
#else
enum { kCacheAlignment = alignof(max_align_t) }; // do the best we can
#endif
inline constexpr size_t AlignUpTo8(size_t n) {
// Align n to next multiple of 8 (from Hacker's Delight, Chapter 3.)
return (n + 7) & static_cast<size_t>(-8);
}
using LifecycleIdAtomic = uint64_t;
// MetricsCollector collects stats for a particular arena.
class PROTOBUF_EXPORT ArenaMetricsCollector {
public:
ArenaMetricsCollector(bool record_allocs) : record_allocs_(record_allocs) {}
// Invoked when the arena is about to be destroyed. This method will
// typically finalize any metric collection and delete the collector.
// space_allocated is the space used by the arena.
virtual void OnDestroy(uint64_t space_allocated) = 0;
// OnReset() is called when the associated arena is reset.
// space_allocated is the space used by the arena just before the reset.
virtual void OnReset(uint64_t space_allocated) = 0;
// OnAlloc is called when an allocation happens.
// 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)
virtual void OnAlloc(const std::type_info* allocated_type,
uint64_t alloc_size) = 0;
// Does OnAlloc() need to be called? If false, metric collection overhead
// will be reduced since we will not do extra work per allocation.
bool RecordAllocs() { return record_allocs_; }
protected:
// This class is destructed by the call to OnDestroy().
~ArenaMetricsCollector() = default;
const bool record_allocs_;
};
struct AllocationPolicy {
static constexpr size_t kDefaultStartBlockSize = 256;
static constexpr size_t kDefaultMaxBlockSize = 8192;
size_t start_block_size = kDefaultStartBlockSize;
size_t max_block_size = kDefaultMaxBlockSize;
void* (*block_alloc)(size_t) = nullptr;
void (*block_dealloc)(void*, size_t) = nullptr;
ArenaMetricsCollector* metrics_collector = nullptr;
bool IsDefault() const {
return start_block_size == kDefaultMaxBlockSize &&
max_block_size == kDefaultMaxBlockSize && block_alloc == nullptr &&
block_dealloc == nullptr && metrics_collector == nullptr;
}
};
// Tagged pointer to an AllocationPolicy.
class TaggedAllocationPolicyPtr {
public:
constexpr TaggedAllocationPolicyPtr() : policy_(0) {}
explicit TaggedAllocationPolicyPtr(AllocationPolicy* policy)
: policy_(reinterpret_cast<uintptr_t>(policy)) {}
void set_policy(AllocationPolicy* policy) {
auto bits = policy_ & kTagsMask;
policy_ = reinterpret_cast<uintptr_t>(policy) | bits;
}
AllocationPolicy* get() {
return reinterpret_cast<AllocationPolicy*>(policy_ & kPtrMask);
}
const AllocationPolicy* get() const {
return reinterpret_cast<const AllocationPolicy*>(policy_ & kPtrMask);
}
AllocationPolicy& operator*() { return *get(); }
const AllocationPolicy& operator*() const { return *get(); }
AllocationPolicy* operator->() { return get(); }
const AllocationPolicy* operator->() const { return get(); }
bool is_user_owned_initial_block() const {
return static_cast<bool>(get_mask<kUserOwnedInitialBlock>());
}
void set_is_user_owned_initial_block(bool v) {
set_mask<kUserOwnedInitialBlock>(v);
}
bool should_record_allocs() const {
return static_cast<bool>(get_mask<kRecordAllocs>());
}
void set_should_record_allocs(bool v) { set_mask<kRecordAllocs>(v); }
uintptr_t get_raw() const { return policy_; }
inline void RecordAlloc(const std::type_info* allocated_type,
size_t n) const {
get()->metrics_collector->OnAlloc(allocated_type, n);
}
private:
enum : uintptr_t {
kUserOwnedInitialBlock = 1,
kRecordAllocs = 2,
};
static constexpr uintptr_t kTagsMask = 7;
static constexpr uintptr_t kPtrMask = ~kTagsMask;
template <uintptr_t kMask>
uintptr_t get_mask() const {
return policy_ & kMask;
}
template <uintptr_t kMask>
void set_mask(bool v) {
if (v) {
policy_ |= kMask;
} else {
policy_ &= ~kMask;
}
}
uintptr_t policy_;
};
enum class AllocationClient { kDefault, kArray };
// A simple arena allocator. Calls to allocate functions must be properly
// serialized by the caller, hence this class cannot be used as a general
// purpose allocator in a multi-threaded program. It serves as a building block
// for ThreadSafeArena, which provides a thread-safe arena allocator.
//
// This class manages
// 1) Arena bump allocation + owning memory blocks.
// 2) Maintaining a cleanup list.
// It delagetes the actual memory allocation back to ThreadSafeArena, which
// contains the information on block growth policy and backing memory allocation
// used.
class PROTOBUF_EXPORT SerialArena {
public:
struct Memory {
void* ptr;
size_t size;
};
// Node contains the ptr of the object to be cleaned up and the associated
// cleanup function ptr.
struct CleanupNode {
void* elem; // Pointer to the object to be cleaned up.
void (*cleanup)(void*); // Function pointer to the destructor or deleter.
};
void CleanupList();
uint64_t SpaceAllocated() const {
return space_allocated_.load(std::memory_order_relaxed);
}
uint64_t SpaceUsed() const;
bool HasSpace(size_t n) const {
return n <= static_cast<size_t>(limit_ - ptr_);
}
// See comments on `cached_blocks_` member for details.
PROTOBUF_ALWAYS_INLINE void* TryAllocateFromCachedBlock(size_t size) {
if (PROTOBUF_PREDICT_FALSE(size < 16)) return nullptr;
// We round up to the next larger block in case the memory doesn't match
// the pattern we are looking for.
const size_t index = Bits::Log2FloorNonZero64(size - 1) - 3;
if (index >= cached_block_length_) return nullptr;
auto& cached_head = cached_blocks_[index];
if (cached_head == nullptr) return nullptr;
void* ret = cached_head;
#ifdef ADDRESS_SANITIZER
ASAN_UNPOISON_MEMORY_REGION(ret, size);
#endif // ADDRESS_SANITIZER
cached_head = cached_head->next;
return ret;
}
// In kArray mode we look through cached blocks.
// We do not do this by default because most non-array allocations will not
// have the right size and will fail to find an appropriate cached block.
//
// TODO(sbenza): Evaluate if we should use cached blocks for message types of
// the right size. We can statically know if the allocation size can benefit
// from it.
template <AllocationClient alloc_client = AllocationClient::kDefault>
void* AllocateAligned(size_t n, const AllocationPolicy* policy) {
GOOGLE_DCHECK_EQ(internal::AlignUpTo8(n), n); // Must be already aligned.
GOOGLE_DCHECK_GE(limit_, ptr_);
if (alloc_client == AllocationClient::kArray) {
if (void* res = TryAllocateFromCachedBlock(n)) {
return res;
}
}
if (PROTOBUF_PREDICT_FALSE(!HasSpace(n))) {
return AllocateAlignedFallback(n, policy);
}
return AllocateFromExisting(n);
}
private:
void* AllocateFromExisting(size_t n) {
void* ret = ptr_;
ptr_ += n;
#ifdef ADDRESS_SANITIZER
ASAN_UNPOISON_MEMORY_REGION(ret, n);
#endif // ADDRESS_SANITIZER
return ret;
}
// See comments on `cached_blocks_` member for details.
void ReturnArrayMemory(void* p, size_t size) {
// We only need to check for 32-bit platforms.
// In 64-bit platforms the minimum allocation size from Repeated*Field will
// be 16 guaranteed.
if (sizeof(void*) < 8) {
if (PROTOBUF_PREDICT_FALSE(size < 16)) return;
} else {
GOOGLE_DCHECK(size >= 16);
}
// We round down to the next smaller block in case the memory doesn't match
// the pattern we are looking for. eg, someone might have called Reserve()
// on the repeated field.
const size_t index = Bits::Log2FloorNonZero64(size) - 4;
if (PROTOBUF_PREDICT_FALSE(index >= cached_block_length_)) {
// We can't put this object on the freelist so make this object the
// freelist. It is guaranteed it is larger than the one we have, and
// large enough to hold another allocation of `size`.
CachedBlock** new_list = static_cast<CachedBlock**>(p);
size_t new_size = size / sizeof(CachedBlock*);
std::copy(cached_blocks_, cached_blocks_ + cached_block_length_,
new_list);
std::fill(new_list + cached_block_length_, new_list + new_size, nullptr);
cached_blocks_ = new_list;
// Make the size fit in uint8_t. This is the power of two, so we don't
// need anything larger.
cached_block_length_ =
static_cast<uint8_t>(std::min(size_t{64}, new_size));
return;
}
auto& cached_head = cached_blocks_[index];
auto* new_node = static_cast<CachedBlock*>(p);
new_node->next = cached_head;
cached_head = new_node;
#ifdef ADDRESS_SANITIZER
ASAN_POISON_MEMORY_REGION(p, size);
#endif // ADDRESS_SANITIZER
}
public:
// Allocate space if the current region provides enough space.
bool MaybeAllocateAligned(size_t n, void** out) {
GOOGLE_DCHECK_EQ(internal::AlignUpTo8(n), n); // Must be already aligned.
GOOGLE_DCHECK_GE(limit_, ptr_);
if (PROTOBUF_PREDICT_FALSE(!HasSpace(n))) return false;
*out = AllocateFromExisting(n);
return true;
}
std::pair<void*, CleanupNode*> AllocateAlignedWithCleanup(
size_t n, const AllocationPolicy* policy) {
GOOGLE_DCHECK_EQ(internal::AlignUpTo8(n), n); // Must be already aligned.
if (PROTOBUF_PREDICT_FALSE(!HasSpace(n + kCleanupSize))) {
return AllocateAlignedWithCleanupFallback(n, policy);
}
return AllocateFromExistingWithCleanupFallback(n);
}
private:
std::pair<void*, CleanupNode*> AllocateFromExistingWithCleanupFallback(
size_t n) {
void* ret = ptr_;
ptr_ += n;
limit_ -= kCleanupSize;
#ifdef ADDRESS_SANITIZER
ASAN_UNPOISON_MEMORY_REGION(ret, n);
ASAN_UNPOISON_MEMORY_REGION(limit_, kCleanupSize);
#endif // ADDRESS_SANITIZER
return CreatePair(ret, reinterpret_cast<CleanupNode*>(limit_));
}
public:
void AddCleanup(void* elem, void (*cleanup)(void*),
const AllocationPolicy* policy) {
auto res = AllocateAlignedWithCleanup(0, policy);
res.second->elem = elem;
res.second->cleanup = cleanup;
}
void* owner() const { return owner_; }
SerialArena* next() const { return next_; }
void set_next(SerialArena* next) { next_ = next; }
private:
friend class ThreadSafeArena;
friend class ArenaBenchmark;
// Creates a new SerialArena inside mem using the remaining memory as for
// future allocations.
static SerialArena* New(SerialArena::Memory mem, void* owner,
ThreadSafeArenaStats* stats);
// Free SerialArena returning the memory passed in to New
template <typename Deallocator>
Memory Free(Deallocator deallocator);
// Blocks are variable length malloc-ed objects. The following structure
// describes the common header for all blocks.
struct Block {
Block(Block* next, size_t size) : next(next), size(size), start(nullptr) {}
char* Pointer(size_t n) {
GOOGLE_DCHECK(n <= size);
return reinterpret_cast<char*>(this) + n;
}
Block* const next;
const size_t size;
CleanupNode* start;
// data follows
};
void* owner_; // &ThreadCache of this thread;
Block* head_; // Head of linked list of blocks.
SerialArena* next_; // Next SerialArena in this linked list.
size_t space_used_ = 0; // Necessary for metrics.
std::atomic<size_t> space_allocated_;
// Next pointer to allocate from. Always 8-byte aligned. Points inside
// head_ (and head_->pos will always be non-canonical). We keep these
// here to reduce indirection.
char* ptr_;
// Limiting address up to which memory can be allocated from the head block.
char* limit_;
// For holding sampling information. The pointer is owned by the
// ThreadSafeArena that holds this serial arena.
ThreadSafeArenaStats* arena_stats_;
// Repeated*Field and Arena play together to reduce memory consumption by
// reusing blocks. Currently, natural growth of the repeated field types makes
// them allocate blocks of size `8 + 2^N, N>=3`.
// When the repeated field grows returns the previous block and we put it in
// this free list.
// `cached_blocks_[i]` points to the free list for blocks of size `8+2^(i+3)`.
// The array of freelists is grown when needed in `ReturnArrayMemory()`.
struct CachedBlock {
// Simple linked list.
CachedBlock* next;
};
uint8_t cached_block_length_ = 0;
CachedBlock** cached_blocks_ = nullptr;
// Constructor is private as only New() should be used.
inline SerialArena(Block* b, void* owner, ThreadSafeArenaStats* stats);
void* AllocateAlignedFallback(size_t n, const AllocationPolicy* policy);
std::pair<void*, CleanupNode*> AllocateAlignedWithCleanupFallback(
size_t n, const AllocationPolicy* policy);
void AllocateNewBlock(size_t n, const AllocationPolicy* policy);
std::pair<void*, CleanupNode*> CreatePair(void* ptr, CleanupNode* node) {
return {ptr, node};
}
public:
static constexpr size_t kBlockHeaderSize = AlignUpTo8(sizeof(Block));
static constexpr size_t kCleanupSize = AlignUpTo8(sizeof(CleanupNode));
};
// Tag type used to invoke the constructor of message-owned arena.
// Only message-owned arenas use this constructor for creation.
// Such constructors are internal implementation details of the library.
struct MessageOwned {
explicit MessageOwned() = default;
};
// This class provides the core Arena memory allocation library. Different
// implementations only need to implement the public interface below.
// Arena is not a template type as that would only be useful if all protos
// in turn would be templates, which will/cannot happen. However separating
// the memory allocation part from the cruft of the API users expect we can
// use #ifdef the select the best implementation based on hardware / OS.
class PROTOBUF_EXPORT ThreadSafeArena {
public:
ThreadSafeArena() { Init(); }
// Constructor solely used by message-owned arena.
ThreadSafeArena(internal::MessageOwned) : tag_and_id_(kMessageOwnedArena) {
Init();
}
ThreadSafeArena(char* mem, size_t size) { InitializeFrom(mem, size); }
explicit ThreadSafeArena(void* mem, size_t size,
const AllocationPolicy& policy) {
InitializeWithPolicy(mem, size, policy);
}
// 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.
~ThreadSafeArena();
uint64_t Reset();
uint64_t SpaceAllocated() const;
uint64_t SpaceUsed() const;
template <AllocationClient alloc_client = AllocationClient::kDefault>
void* AllocateAligned(size_t n, const std::type_info* type) {
SerialArena* arena;
if (PROTOBUF_PREDICT_TRUE(!alloc_policy_.should_record_allocs() &&
GetSerialArenaFast(&arena))) {
return arena->AllocateAligned<alloc_client>(n, AllocPolicy());
} else {
return AllocateAlignedFallback(n, type);
}
}
void ReturnArrayMemory(void* p, size_t size) {
SerialArena* arena;
if (PROTOBUF_PREDICT_TRUE(GetSerialArenaFast(&arena))) {
arena->ReturnArrayMemory(p, size);
}
}
// This function allocates n bytes if the common happy case is true and
// returns true. Otherwise does nothing and returns false. This strange
// semantics is necessary to allow callers to program functions that only
// have fallback function calls in tail position. This substantially improves
// code for the happy path.
PROTOBUF_NDEBUG_INLINE bool MaybeAllocateAligned(size_t n, void** out) {
SerialArena* arena;
if (PROTOBUF_PREDICT_TRUE(!alloc_policy_.should_record_allocs() &&
GetSerialArenaFromThreadCache(&arena))) {
return arena->MaybeAllocateAligned(n, out);
}
return false;
}
std::pair<void*, SerialArena::CleanupNode*> AllocateAlignedWithCleanup(
size_t n, const std::type_info* type);
// Add object pointer and cleanup function pointer to the list.
void AddCleanup(void* elem, void (*cleanup)(void*));
// Checks whether this arena is message-owned.
PROTOBUF_ALWAYS_INLINE bool IsMessageOwned() const {
return tag_and_id_ & kMessageOwnedArena;
}
private:
// Unique for each arena. Changes on Reset().
uint64_t tag_and_id_ = 0;
// The LSB of tag_and_id_ indicates if the arena is message-owned.
enum : uint64_t { kMessageOwnedArena = 1 };
TaggedAllocationPolicyPtr alloc_policy_; // Tagged pointer to AllocPolicy.
static_assert(std::is_trivially_destructible<SerialArena>{},
"SerialArena needs to be trivially destructible.");
// Pointer to a linked list of SerialArena.
std::atomic<SerialArena*> threads_;
std::atomic<SerialArena*> hint_; // Fast thread-local block access
const AllocationPolicy* AllocPolicy() const { return alloc_policy_.get(); }
void InitializeFrom(void* mem, size_t size);
void InitializeWithPolicy(void* mem, size_t size, AllocationPolicy policy);
void* AllocateAlignedFallback(size_t n, const std::type_info* type);
std::pair<void*, SerialArena::CleanupNode*>
AllocateAlignedWithCleanupFallback(size_t n, const std::type_info* type);
void Init();
void SetInitialBlock(void* mem, size_t size);
// Delete or Destruct all objects owned by the arena.
void CleanupList();
inline uint64_t LifeCycleId() const {
return tag_and_id_ & ~kMessageOwnedArena;
}
inline void CacheSerialArena(SerialArena* serial) {
thread_cache().last_serial_arena = serial;
thread_cache().last_lifecycle_id_seen = tag_and_id_;
// TODO(haberman): evaluate whether we would gain efficiency by getting rid
// of hint_. It's the only write we do to ThreadSafeArena in the allocation
// path, which will dirty the cache line.
hint_.store(serial, std::memory_order_release);
}
PROTOBUF_NDEBUG_INLINE bool GetSerialArenaFast(SerialArena** arena) {
if (GetSerialArenaFromThreadCache(arena)) return true;
// Check whether we own the last accessed SerialArena on this arena. This
// fast path optimizes the case where a single thread uses multiple arenas.
ThreadCache* tc = &thread_cache();
SerialArena* serial = hint_.load(std::memory_order_acquire);
if (PROTOBUF_PREDICT_TRUE(serial != nullptr && serial->owner() == tc)) {
*arena = serial;
return true;
}
return false;
}
PROTOBUF_NDEBUG_INLINE bool GetSerialArenaFromThreadCache(
SerialArena** arena) {
// If this thread already owns a block in this arena then try to use that.
// This fast path optimizes the case where multiple threads allocate from
// the same arena.
ThreadCache* tc = &thread_cache();
if (PROTOBUF_PREDICT_TRUE(tc->last_lifecycle_id_seen == tag_and_id_)) {
*arena = tc->last_serial_arena;
return true;
}
return false;
}
SerialArena* GetSerialArenaFallback(void* me);
template <typename Functor>
void PerSerialArena(Functor fn) {
// By omitting an Acquire barrier we ensure that any user code that doesn't
// properly synchronize Reset() or the destructor will throw a TSAN warning.
SerialArena* serial = threads_.load(std::memory_order_relaxed);
for (; serial; serial = serial->next()) fn(serial);
}
// Releases all memory except the first block which it returns. The first
// block might be owned by the user and thus need some extra checks before
// deleting.
SerialArena::Memory Free(size_t* space_allocated);
#ifdef _MSC_VER
#pragma warning(disable : 4324)
#endif
struct alignas(kCacheAlignment) ThreadCache {
#if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL)
// If we are using the ThreadLocalStorage class to store the ThreadCache,
// then the ThreadCache's default constructor has to be responsible for
// initializing it.
ThreadCache()
: next_lifecycle_id(0),
last_lifecycle_id_seen(-1),
last_serial_arena(nullptr) {}
#endif
// Number of per-thread lifecycle IDs to reserve. Must be power of two.
// To reduce contention on a global atomic, each thread reserves a batch of
// IDs. The following number is calculated based on a stress test with
// ~6500 threads all frequently allocating a new arena.
static constexpr size_t kPerThreadIds = 256;
// Next lifecycle ID available to this thread. We need to reserve a new
// batch, if `next_lifecycle_id & (kPerThreadIds - 1) == 0`.
uint64_t next_lifecycle_id;
// The ThreadCache is considered valid as long as this matches the
// lifecycle_id of the arena being used.
uint64_t last_lifecycle_id_seen;
SerialArena* last_serial_arena;
};
// Lifecycle_id can be highly contended variable in a situation of lots of
// arena creation. Make sure that other global variables are not sharing the
// cacheline.
#ifdef _MSC_VER
#pragma warning(disable : 4324)
#endif
struct alignas(kCacheAlignment) CacheAlignedLifecycleIdGenerator {
std::atomic<LifecycleIdAtomic> id;
};
static CacheAlignedLifecycleIdGenerator lifecycle_id_generator_;
#if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL)
// iOS does not support __thread keyword so we use a custom thread local
// storage class we implemented.
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 PROTOBUF_THREAD_LOCAL ThreadCache thread_cache_;
static ThreadCache& thread_cache() { return thread_cache_; }
#endif
ThreadSafeArenaStatsHandle arena_stats_;
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ThreadSafeArena);
// All protos have pointers back to the arena hence Arena must have
// pointer stability.
ThreadSafeArena(ThreadSafeArena&&) = delete;
ThreadSafeArena& operator=(ThreadSafeArena&&) = delete;
public:
// kBlockHeaderSize is sizeof(Block), aligned up to the nearest multiple of 8
// to protect the invariant that pos is always at a multiple of 8.
static constexpr size_t kBlockHeaderSize = SerialArena::kBlockHeaderSize;
static constexpr size_t kSerialArenaSize =
(sizeof(SerialArena) + 7) & static_cast<size_t>(-8);
static_assert(kBlockHeaderSize % 8 == 0,
"kBlockHeaderSize must be a multiple of 8.");
static_assert(kSerialArenaSize % 8 == 0,
"kSerialArenaSize must be a multiple of 8.");
};
} // namespace internal
} // namespace protobuf
} // namespace google
#include <google/protobuf/port_undef.inc>
#endif // GOOGLE_PROTOBUF_ARENA_IMPL_H__