rocksdb/db/db_iter.h

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// Copyright (c) 2013, 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.
//
// 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 <stdint.h>
#include "rocksdb/db.h"
#include "db/dbformat.h"
#include "util/arena.h"
#include "util/autovector.h"
namespace rocksdb {
class Arena;
class DBIter;
// Return a new iterator that converts internal keys (yielded by
// "*internal_iter") that were live at the specified "sequence" number
// into appropriate user keys.
extern Iterator* NewDBIterator(
Env* env,
const Options& options,
const Comparator *user_key_comparator,
Iterator* internal_iter,
const SequenceNumber& sequence,
const Slice* iterate_upper_bound = nullptr);
// A wrapper iterator which wraps DB Iterator and the arena, with which the DB
// iterator is supposed be allocated. This class is used as an entry point of
// a iterator hierarchy whose memory can be allocated inline. In that way,
// accessing the iterator tree can be more cache friendly. It is also faster
// to allocate.
class ArenaWrappedDBIter : public Iterator {
public:
virtual ~ArenaWrappedDBIter();
// Get the arena to be used to allocate memory for DBIter to be wrapped,
// as well as child iterators in it.
virtual Arena* GetArena() { return &arena_; }
// Set the DB Iterator to be wrapped
virtual void SetDBIter(DBIter* iter);
// Set the internal iterator wrapped inside the DB Iterator. Usually it is
// a merging iterator.
virtual void SetIterUnderDBIter(Iterator* iter);
virtual bool Valid() const override;
virtual void SeekToFirst() override;
virtual void SeekToLast() override;
virtual void Seek(const Slice& target) override;
virtual void Next() override;
virtual void Prev() override;
virtual Slice key() const override;
virtual Slice value() const override;
virtual Status status() const override;
void RegisterCleanup(CleanupFunction function, void* arg1, void* arg2);
private:
DBIter* db_iter_;
Arena arena_;
};
// Generate the arena wrapped iterator class.
extern ArenaWrappedDBIter* NewArenaWrappedDbIterator(
Env* env, const Options& options, const Comparator* user_key_comparator,
const SequenceNumber& sequence, const Slice* iterate_upper_bound = nullptr);
} // namespace rocksdb