blob: 6a07f8057657d5daf9ec6500b5563edbb2817803 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
|
// 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 "include/db.h"
namespace leveldb {
class SnapshotList;
// Snapshots are kept in a doubly-linked list in the DB.
// Each Snapshot corresponds to a particular sequence number.
class Snapshot {
public:
SequenceNumber number_; // const after creation
private:
friend class SnapshotList;
// Snapshot is kept in a doubly-linked circular list
Snapshot* prev_;
Snapshot* next_;
SnapshotList* list_; // just for sanity checks
};
class SnapshotList {
public:
SnapshotList() {
list_.prev_ = &list_;
list_.next_ = &list_;
}
bool empty() const { return list_.next_ == &list_; }
Snapshot* oldest() const { assert(!empty()); return list_.next_; }
Snapshot* newest() const { assert(!empty()); return list_.prev_; }
const Snapshot* New(SequenceNumber seq) {
Snapshot* s = new Snapshot;
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 Snapshot* s) {
assert(s->list_ == this);
s->prev_->next_ = s->next_;
s->next_->prev_ = s->prev_;
delete s;
}
private:
// Dummy head of doubly-linked list of snapshots
Snapshot list_;
};
}
#endif // STORAGE_LEVELDB_DB_SNAPSHOT_H_
|
