YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

// 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.

//

#ifndef YB_ROCKSDB_DB_FILE_NUMBERS_H

#define YB_ROCKSDB_DB_FILE_NUMBERS_H

#include <unordered_set>

#include <boost/container/small_vector.hpp>

#include "yb/rocksdb/util/mutexlock.h"

namespace rocksdb {

typedef uint64_t FileNumber;

typedef std::unordered_multiset<FileNumber> FileNumberSet;

class VersionSet;

// Utility interface used by FileNumbersHolder and FileNumbersProvider (see below).

class FileNumberAdderRemover {

 public:

  virtual void AddFileNumber(FileNumber file_number) = 0;

  virtual void RemoveFileNumber(FileNumber file_number) = 0;

  virtual ~FileNumberAdderRemover() {}

};

// RAII wrapper which holds file numbers and passes them to adder_remover_->RemoveFileNumber

// when destroyed. Also calls adder_remover_->AddFileNumber on copy.

class FileNumbersHolder {

 public:

  FileNumbersHolder(const FileNumbersHolder& rhs) :

    adder_remover_(rhs.adder_remover_), file_numbers_(rhs.file_numbers_) {

    HoldFileNumbers();

  }

  FileNumbersHolder& operator=(const FileNumbersHolder& rhs) {

    if (&rhs != this) {

      Reset();

      adder_remover_ = rhs.adder_remover_;

      file_numbers_ = rhs.file_numbers_;

      HoldFileNumbers();

    }

    return *this;

  }

  // Default constructor creates empty holder which is not intended to add any file numbers.

  FileNumbersHolder() {}

  // Creates holder which can be used to add file numbers.

  explicit FileNumbersHolder(FileNumberAdderRemover* remover) : adder_remover_(remover) {}

  FileNumbersHolder(FileNumbersHolder&& rhs)

      : adder_remover_(rhs.adder_remover_),

        file_numbers_(std::move(rhs.file_numbers_)) {

    rhs.file_numbers_.clear();

  }

  FileNumbersHolder& operator=(FileNumbersHolder&& rhs) {

    if (&rhs != this) {

      Reset();

      adder_remover_ = std::move(rhs.adder_remover_);

      file_numbers_ = std::move(rhs.file_numbers_);

      rhs.file_numbers_.clear();

    }

    return *this;

  }

  ~FileNumbersHolder() {

    Reset();

  }

  void Reset() {

    for (auto file_number : file_numbers_) {

      adder_remover_->RemoveFileNumber(file_number);

    }

    file_numbers_.clear();

  }

  // Returns last number added.

  FileNumber Last() { return file_numbers_.back(); }

  // Preallocate capacity in internal file numbers storage.

  void Reserve(size_t capacity) {

    file_numbers_.reserve(capacity);

  }

  void Add(FileNumber file_number) {

    file_numbers_.emplace_back(file_number);

  }

  std::string ToString() const;

 private:

  void HoldFileNumbers() {

    for (auto file_number : file_numbers_) {

      adder_remover_->AddFileNumber(file_number);

    }

  }

  FileNumberAdderRemover* adder_remover_ = nullptr;

  boost::container::small_vector<FileNumber, 1> file_numbers_;

};

// Utility class providing functionality to get new file numbers from VersionSet. File numbers

// returned are wrapped in FileNumbersHolder and stored in internal storage. Once wrapper is

// destroyed, corresponding file numbers will be removed from internal storage. Also provides a

// function to check whether specific file number is contained in internal storage.

// See DBImpl::pending_outputs_ description for more details on usage and application.

class FileNumbersProvider : public FileNumberAdderRemover {

 public:

  explicit FileNumbersProvider(VersionSet* versions)

      : versions_(versions) {}

  // Requests new file number from VersionSet, stores it and returns wrapped in a holder.

  FileNumbersHolder NewFileNumber();

  // Create empty holder to which file numbers could be added later using NewFileNumber.

  FileNumbersHolder CreateHolder();

  // Requests new file number from VersionSet, stores it and adds to holder.

  FileNumber NewFileNumber(FileNumbersHolder* holder);

  // Check whether we have have file_number in internal storage.

  bool HasFileNumber(FileNumber file_number) const;

  // Add file_number to internal storage.

  void AddFileNumber(FileNumber file_number) override;

  // Remove file_number from internal storage.

  void RemoveFileNumber(FileNumber file_number) override;

  std::string ToString() const;

 private:

  VersionSet* versions_;

  mutable SpinMutex mutex_;

  FileNumberSet fset_;

};

}  // namespace rocksdb

#endif  // YB_ROCKSDB_DB_FILE_NUMBERS_H