blob: 02aae871e0299c2d11419146813754909a002920 [file] [log] [blame]
// Copyright (c) 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// An arena that consists of a single inlined block of |ArenaSize|. Useful to
// avoid repeated calls to malloc/new and to improve memory locality.
// QUICHE_DCHECK's if an allocation out of the arena ever fails in debug builds;
// falls back to heap allocation in release builds.
#include <cstdint>
#include "quic/core/quic_arena_scoped_ptr.h"
#include "quic/core/quic_types.h"
#include "quic/platform/api/quic_bug_tracker.h"
#include "quic/platform/api/quic_logging.h"
namespace quic {
template <uint32_t ArenaSize>
class QUIC_EXPORT_PRIVATE QuicOneBlockArena {
static const uint32_t kMaxAlign = 8;
QuicOneBlockArena() : offset_(0) {}
QuicOneBlockArena(const QuicOneBlockArena&) = delete;
QuicOneBlockArena& operator=(const QuicOneBlockArena&) = delete;
// Instantiates an object of type |T| with |args|. |args| are perfectly
// forwarded to |T|'s constructor. The returned pointer's lifetime is
// controlled by QuicArenaScopedPtr.
template <typename T, typename... Args>
QuicArenaScopedPtr<T> New(Args&&... args) {
QUICHE_DCHECK_LT(AlignedSize<T>(), ArenaSize)
<< "Object is too large for the arena.";
static_assert(alignof(T) > 1,
"Objects added to the arena must be at least 2B aligned.");
if (QUIC_PREDICT_FALSE(offset_ > ArenaSize - AlignedSize<T>())) {
<< "Ran out of space in QuicOneBlockArena at " << this
<< ", max size was " << ArenaSize << ", failing request was "
<< AlignedSize<T>() << ", end of arena was " << offset_;
return QuicArenaScopedPtr<T>(new T(std::forward<Args>(args)...));
void* buf = &storage_[offset_];
new (buf) T(std::forward<Args>(args)...);
offset_ += AlignedSize<T>();
return QuicArenaScopedPtr<T>(buf,
// Returns the size of |T| aligned up to |kMaxAlign|.
template <typename T>
static inline uint32_t AlignedSize() {
return ((sizeof(T) + (kMaxAlign - 1)) / kMaxAlign) * kMaxAlign;
// Actual storage.
// Subtle/annoying: the value '8' must be coded explicitly into the alignment
// declaration for MSVC.
alignas(8) char storage_[ArenaSize];
// Current offset into the storage.
uint32_t offset_;
// QuicConnections currently use around 1KB of polymorphic types which would
// ordinarily be on the heap. Instead, store them inline in an arena.
using QuicConnectionArena = QuicOneBlockArena<1152>;
} // namespace quic