tomFlowee
c63519fa47
The leveldb and univalue 3rd party libraries are not installed and not needed by anyone outside of the Hub. So move them there, making it easier for 3rd party usage.
67 lines
1.6 KiB
C++
67 lines
1.6 KiB
C++
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#ifndef STORAGE_LEVELDB_DB_SNAPSHOT_H_
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#define STORAGE_LEVELDB_DB_SNAPSHOT_H_
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#include "leveldb/db.h"
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namespace leveldb {
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class SnapshotList;
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// Snapshots are kept in a doubly-linked list in the DB.
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// Each SnapshotImpl corresponds to a particular sequence number.
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class SnapshotImpl : public Snapshot {
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public:
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SequenceNumber number_; // const after creation
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private:
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friend class SnapshotList;
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// SnapshotImpl is kept in a doubly-linked circular list
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SnapshotImpl* prev_;
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SnapshotImpl* next_;
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SnapshotList* list_; // just for sanity checks
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};
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class SnapshotList {
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public:
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SnapshotList() {
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list_.prev_ = &list_;
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list_.next_ = &list_;
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}
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bool empty() const { return list_.next_ == &list_; }
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SnapshotImpl* oldest() const { assert(!empty()); return list_.next_; }
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SnapshotImpl* newest() const { assert(!empty()); return list_.prev_; }
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const SnapshotImpl* New(SequenceNumber seq) {
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SnapshotImpl* s = new SnapshotImpl;
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s->number_ = seq;
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s->list_ = this;
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s->next_ = &list_;
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s->prev_ = list_.prev_;
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s->prev_->next_ = s;
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s->next_->prev_ = s;
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return s;
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}
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void Delete(const SnapshotImpl* s) {
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assert(s->list_ == this);
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s->prev_->next_ = s->next_;
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s->next_->prev_ = s->prev_;
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delete s;
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}
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private:
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// Dummy head of doubly-linked list of snapshots
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SnapshotImpl list_;
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};
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_DB_SNAPSHOT_H_
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