rocksdb/db/snapshot.h
Dhruba Borthakur a143ef9b38 Change namespace from leveldb to rocksdb
Summary:
Change namespace from leveldb to rocksdb. This allows a single
application to link in open-source leveldb code as well as
rocksdb code into the same process.

Test Plan: compile rocksdb

Reviewers: emayanke

Reviewed By: emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D13287
2013-10-04 11:59:26 -07:00

86 lines
2.1 KiB
C++

// 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.
#ifndef STORAGE_LEVELDB_DB_SNAPSHOT_H_
#define STORAGE_LEVELDB_DB_SNAPSHOT_H_
#include "rocksdb/db.h"
namespace rocksdb {
class SnapshotList;
// Snapshots are kept in a doubly-linked list in the DB.
// Each SnapshotImpl corresponds to a particular sequence number.
class SnapshotImpl : public Snapshot {
public:
SequenceNumber number_; // const after creation
private:
friend class SnapshotList;
// SnapshotImpl is kept in a doubly-linked circular list
SnapshotImpl* prev_;
SnapshotImpl* next_;
SnapshotList* list_; // just for sanity checks
};
class SnapshotList {
public:
SnapshotList() {
list_.prev_ = &list_;
list_.next_ = &list_;
list_.number_ = 0xFFFFFFFFL; // placeholder marker, for debugging
}
bool empty() const { return list_.next_ == &list_; }
SnapshotImpl* oldest() const { assert(!empty()); return list_.next_; }
SnapshotImpl* newest() const { assert(!empty()); return list_.prev_; }
const SnapshotImpl* New(SequenceNumber seq) {
SnapshotImpl* s = new SnapshotImpl;
s->number_ = seq;
s->list_ = this;
s->next_ = &list_;
s->prev_ = list_.prev_;
s->prev_->next_ = s;
s->next_->prev_ = s;
return s;
}
void Delete(const SnapshotImpl* s) {
assert(s->list_ == this);
s->prev_->next_ = s->next_;
s->next_->prev_ = s->prev_;
delete s;
}
// retrieve all snapshot numbers. They are sorted in ascending order.
void getAll(std::vector<SequenceNumber>& ret) {
if (empty()) return;
SnapshotImpl* s = &list_;
while (s->next_ != &list_) {
ret.push_back(s->next_->number_);
s = s ->next_;
}
}
// get the sequence number of the most recent snapshot
const SequenceNumber GetNewest() {
if (empty()) {
return 0;
}
return newest()->number_;
}
private:
// Dummy head of doubly-linked list of snapshots
SnapshotImpl list_;
};
} // namespace rocksdb
#endif // STORAGE_LEVELDB_DB_SNAPSHOT_H_