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

//  This source code is licensed under both the GPLv2 (found in the

//  COPYING file in the root directory) and Apache 2.0 License

//  (found in the LICENSE.Apache file in the root directory).

//

// 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.

#pragma once

#include <string>

#include <utility>

#include "rocksdb/slice.h"

#include "rocksdb/types.h"

namespace ROCKSDB_NAMESPACE {

// A helper class useful for DBImpl::Get()

class LookupKey {

 public:

  // Initialize *this for looking up user_key at a snapshot with

  // the specified sequence number.

  LookupKey(const Slice& _user_key, SequenceNumber sequence,

            const Slice* ts = nullptr);

  ~LookupKey();

  // Return a key suitable for lookup in a MemTable.

  Slice memtable_key() const {

    return Slice(start_, static_cast<size_t>(end_ - start_));

  }

  // Return an internal key (suitable for passing to an internal iterator)

  Slice internal_key() const {

    return Slice(kstart_, static_cast<size_t>(end_ - kstart_));

  }

  // Return the user key.

  // If user-defined timestamp is enabled, then timestamp is included in the

  // result.

  Slice user_key() const {

    return Slice(kstart_, static_cast<size_t>(end_ - kstart_ - 8));

  }

 private:

  // We construct a char array of the form:

  //    klength  varint32               <-- start_

  //    userkey  char[klength]          <-- kstart_

  //    tag      uint64

  //                                    <-- end_

  // The array is a suitable MemTable key.

  // The suffix starting with "userkey" can be used as an InternalKey.

  const char* start_;

  const char* kstart_;

  const char* end_;

  char space_[200];  // Avoid allocation for short keys

  // No copying allowed

  LookupKey(const LookupKey&);

  void operator=(const LookupKey&);

};

inline LookupKey::~LookupKey() {

  if (start_ != space_) delete[] start_;

}

}  // namespace ROCKSDB_NAMESPACE