YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

//  This source code is licensed under the BSD-style license found in the

//  LICENSE file in the root directory of this source tree. An additional grant

//  of patent rights can be found in the PATENTS file in the same directory.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except

// in compliance with the License.  You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software distributed under the License

// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

// or implied.  See the License for the specific language governing permissions and limitations

// under the License.

//

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file. See the AUTHORS file for names of contributors.

//

// WriteBuffer is for managing memory allocation for one or more MemTables.

#pragma once

#include <atomic>

#include <memory>

#include "yb/rocksdb/memory_monitor.h"

namespace rocksdb {

class WriteBuffer {

 public:

  WriteBuffer(size_t _buffer_size,

              std::shared_ptr<MemoryMonitor> memory_monitor = nullptr)

    : buffer_size_(_buffer_size), memory_monitor_(memory_monitor) {}

  ~WriteBuffer() {}

  size_t memory_usage() const {

    return memory_used_.load(std::memory_order_relaxed);

  }

  size_t buffer_size() const { return buffer_size_; }

  // Should only be called from write thread

  bool ShouldFlush() const {

    return buffer_size() > 0 && memory_usage() >= buffer_size();

  }

  // Should only be called from write thread

  void ReserveMem(size_t mem) {

    memory_used_.fetch_add(mem, std::memory_order_relaxed);

    if (memory_monitor_) {

      memory_monitor_->ReservedMem(mem);

    }

  }

  void FreeMem(size_t mem) {

    memory_used_.fetch_sub(mem, std::memory_order_relaxed);

    if (memory_monitor_) {

      memory_monitor_->FreedMem(mem);

    }

  }

 private:

  const size_t buffer_size_;

  std::atomic<size_t> memory_used_{0};

  std::shared_ptr<MemoryMonitor> memory_monitor_;

  // No copying allowed

  WriteBuffer(const WriteBuffer&);

  void operator=(const WriteBuffer&);

};

}  // namespace rocksdb