Project import generated by Copybara.
PiperOrigin-RevId: 237361882
Change-Id: I109a68f44db867b20f8c6a7732b0ce657133e52a
diff --git a/quic/core/quic_one_block_arena.h b/quic/core/quic_one_block_arena.h
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+// 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. DCHECK's
+// if an allocation out of the arena ever fails in debug builds; falls back to
+// heap allocation in release builds.
+
+#ifndef QUICHE_QUIC_CORE_QUIC_ONE_BLOCK_ARENA_H_
+#define QUICHE_QUIC_CORE_QUIC_ONE_BLOCK_ARENA_H_
+
+#include <cstdint>
+
+#include "base/macros.h"
+#include "net/third_party/quiche/src/quic/core/quic_arena_scoped_ptr.h"
+#include "net/third_party/quiche/src/quic/core/quic_types.h"
+#include "net/third_party/quiche/src/quic/platform/api/quic_bug_tracker.h"
+#include "net/third_party/quiche/src/quic/platform/api/quic_logging.h"
+
+namespace quic {
+
+template <uint32_t ArenaSize>
+class QuicOneBlockArena {
+ static const uint32_t kMaxAlign = 8;
+
+ public:
+ QuicOneBlockArena();
+ 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);
+
+ private:
+ // 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.
+ QUIC_ALIGNED(8) char storage_[ArenaSize];
+ // Current offset into the storage.
+ uint32_t offset_;
+};
+
+template <uint32_t ArenaSize>
+QuicOneBlockArena<ArenaSize>::QuicOneBlockArena() : offset_(0) {}
+
+template <uint32_t ArenaSize>
+template <typename T, typename... Args>
+QuicArenaScopedPtr<T> QuicOneBlockArena<ArenaSize>::New(Args&&... args) {
+ DCHECK_LT(AlignedSize<T>(), ArenaSize)
+ << "Object is too large for the arena.";
+ static_assert(QUIC_ALIGN_OF(T) > 1,
+ "Objects added to the arena must be at least 2B aligned.");
+ if (QUIC_PREDICT_FALSE(offset_ > ArenaSize - AlignedSize<T>())) {
+ QUIC_BUG << "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,
+ QuicArenaScopedPtr<T>::ConstructFrom::kArena);
+}
+
+// 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<1024>;
+
+} // namespace quic
+
+#endif // QUICHE_QUIC_CORE_QUIC_ONE_BLOCK_ARENA_H_
