/usr/include/google/protobuf
Edit: /usr/include/google/protobuf/arena_impl.h (14316B)
// 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_IMPL_H__
#define GOOGLE_PROTOBUF_ARENA_IMPL_H__
#include
#include
#include
#include
#ifdef ADDRESS_SANITIZER
#include
#endif // ADDRESS_SANITIZER
#include
namespace google {
namespace protobuf {
namespace internal {
inline size_t AlignUpTo8(size_t n) {
// Align n to next multiple of 8 (from Hacker's Delight, Chapter 3.)
return (n + 7) & static_cast(-8);
}
using LifecycleId = int64_t;
// 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 ArenaImpl {
public:
struct Options {
size_t start_block_size;
size_t max_block_size;
char* initial_block;
size_t initial_block_size;
void* (*block_alloc)(size_t);
void (*block_dealloc)(void*, size_t);
template
explicit Options(const O& options)
: start_block_size(options.start_block_size),
max_block_size(options.max_block_size),
initial_block(options.initial_block),
initial_block_size(options.initial_block_size),
block_alloc(options.block_alloc),
block_dealloc(options.block_dealloc) {}
};
template
explicit ArenaImpl(const O& options) : options_(options) {
if (options_.initial_block != NULL && options_.initial_block_size > 0) {
GOOGLE_CHECK_GE(options_.initial_block_size, sizeof(Block))
<< ": Initial block size too small for header.";
initial_block_ = reinterpret_cast(options_.initial_block);
} else {
initial_block_ = NULL;
}
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.
~ArenaImpl();
uint64 Reset();
uint64 SpaceAllocated() const;
uint64 SpaceUsed() const;
void* AllocateAligned(size_t n) {
SerialArena* arena;
if (PROTOBUF_PREDICT_TRUE(GetSerialArenaFast(&arena))) {
return arena->AllocateAligned(n);
} else {
return AllocateAlignedFallback(n);
}
}
// 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_ALWAYS_INLINE bool MaybeAllocateAligned(size_t n, void** out) {
SerialArena* a;
if (PROTOBUF_PREDICT_TRUE(GetSerialArenaFromThreadCache(&a))) {
return a->MaybeAllocateAligned(n, out);
}
return false;
}
void* AllocateAlignedAndAddCleanup(size_t n, void (*cleanup)(void*));
// Add object pointer and cleanup function pointer to the list.
void AddCleanup(void* elem, void (*cleanup)(void*));
private:
friend class ArenaBenchmark;
void* AllocateAlignedFallback(size_t n);
void* AllocateAlignedAndAddCleanupFallback(size_t n, void (*cleanup)(void*));
void AddCleanupFallback(void* elem, void (*cleanup)(void*));
// 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.
};
// Cleanup uses a chunked linked list, to reduce pointer chasing.
struct CleanupChunk {
static size_t SizeOf(size_t i) {
return sizeof(CleanupChunk) + (sizeof(CleanupNode) * (i - 1));
}
size_t size; // Total elements in the list.
CleanupChunk* next; // Next node in the list.
CleanupNode nodes[1]; // True length is |size|.
};
class Block;
// A thread-unsafe Arena that can only be used within its owning thread.
class PROTOBUF_EXPORT SerialArena {
public:
// The allocate/free methods here are a little strange, since SerialArena is
// allocated inside a Block which it also manages. This is to avoid doing
// an extra allocation for the SerialArena itself.
// Creates a new SerialArena inside Block* and returns it.
static SerialArena* New(Block* b, void* owner, ArenaImpl* arena);
// Destroys this SerialArena, freeing all blocks with the given dealloc
// function, except any block equal to |initial_block|.
static uint64 Free(SerialArena* serial, Block* initial_block,
void (*block_dealloc)(void*, size_t));
void CleanupList();
uint64 SpaceUsed() const;
bool HasSpace(size_t n) { return n <= static_cast(limit_ - ptr_); }
void* AllocateAligned(size_t n) {
GOOGLE_DCHECK_EQ(internal::AlignUpTo8(n), n); // Must be already aligned.
GOOGLE_DCHECK_GE(limit_, ptr_);
if (PROTOBUF_PREDICT_FALSE(!HasSpace(n))) {
return AllocateAlignedFallback(n);
}
void* ret = ptr_;
ptr_ += n;
#ifdef ADDRESS_SANITIZER
ASAN_UNPOISON_MEMORY_REGION(ret, n);
#endif // ADDRESS_SANITIZER
return ret;
}
// 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;
void* ret = ptr_;
ptr_ += n;
#ifdef ADDRESS_SANITIZER
ASAN_UNPOISON_MEMORY_REGION(ret, n);
#endif // ADDRESS_SANITIZER
*out = ret;
return true;
}
void AddCleanup(void* elem, void (*cleanup)(void*)) {
if (PROTOBUF_PREDICT_FALSE(cleanup_ptr_ == cleanup_limit_)) {
AddCleanupFallback(elem, cleanup);
return;
}
cleanup_ptr_->elem = elem;
cleanup_ptr_->cleanup = cleanup;
cleanup_ptr_++;
}
void* AllocateAlignedAndAddCleanup(size_t n, void (*cleanup)(void*)) {
void* ret = AllocateAligned(n);
AddCleanup(ret, cleanup);
return ret;
}
void* owner() const { return owner_; }
SerialArena* next() const { return next_; }
void set_next(SerialArena* next) { next_ = next; }
private:
void* AllocateAlignedFallback(size_t n);
void AddCleanupFallback(void* elem, void (*cleanup)(void*));
void CleanupListFallback();
ArenaImpl* arena_; // Containing arena.
void* owner_; // &ThreadCache of this thread;
Block* head_; // Head of linked list of blocks.
CleanupChunk* cleanup_; // Head of cleanup list.
SerialArena* next_; // Next SerialArena in this linked list.
// 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_;
char* limit_;
// Next CleanupList members to append to. These point inside cleanup_.
CleanupNode* cleanup_ptr_;
CleanupNode* cleanup_limit_;
};
// Blocks are variable length malloc-ed objects. The following structure
// describes the common header for all blocks.
class PROTOBUF_EXPORT Block {
public:
Block(size_t size, Block* next);
char* Pointer(size_t n) {
GOOGLE_DCHECK(n <= size_);
return reinterpret_cast(this) + n;
}
Block* next() const { return next_; }
size_t pos() const { return pos_; }
size_t size() const { return size_; }
void set_pos(size_t pos) { pos_ = pos; }
private:
Block* next_; // Next block for this thread.
size_t pos_;
size_t size_;
// data follows
};
struct 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() : last_lifecycle_id_seen(-1), last_serial_arena(NULL) {}
#endif
// The ThreadCache is considered valid as long as this matches the
// lifecycle_id of the arena being used.
LifecycleId last_lifecycle_id_seen;
SerialArena* last_serial_arena;
};
static std::atomic 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
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();
// Delete or Destruct all objects owned by the arena.
void CleanupList();
inline void CacheSerialArena(SerialArena* serial) {
thread_cache().last_serial_arena = serial;
thread_cache().last_lifecycle_id_seen = lifecycle_id_;
// TODO(haberman): evaluate whether we would gain efficiency by getting rid
// of hint_. It's the only write we do to ArenaImpl in the allocation path,
// which will dirty the cache line.
hint_.store(serial, std::memory_order_release);
}
std::atomic
threads_; // Pointer to a linked list of SerialArena.
std::atomic hint_; // Fast thread-local block access
std::atomic space_allocated_; // Total size of all allocated blocks.
Block* initial_block_; // If non-NULL, points to the block that came from
// user data.
Block* NewBlock(Block* last_block, size_t min_bytes);
SerialArena* GetSerialArena();
PROTOBUF_ALWAYS_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 != NULL && serial->owner() == tc)) {
*arena = serial;
return true;
}
return false;
}
PROTOBUF_ALWAYS_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 == lifecycle_id_)) {
*arena = tc->last_serial_arena;
return true;
}
return false;
}
SerialArena* GetSerialArenaFallback(void* me);
LifecycleId lifecycle_id_; // Unique for each arena. Changes on Reset().
Options options_;
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ArenaImpl);
// All protos have pointers back to the arena hence Arena must have
// pointer stability.
ArenaImpl(ArenaImpl&&) = delete;
ArenaImpl& operator=(ArenaImpl&&) = 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 const size_t kBlockHeaderSize =
(sizeof(Block) + 7) & static_cast(-8);
static const size_t kSerialArenaSize =
(sizeof(SerialArena) + 7) & static_cast(-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
#endif // GOOGLE_PROTOBUF_ARENA_IMPL_H__