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// snapshot.h
/**
* Copyright (C) 2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/util/assert_util.h"
namespace mongo {
class SnapshotId {
static const uint64_t kNullId = 0;
public:
SnapshotId() : _id(kNullId) {}
// 0 is NULL
explicit SnapshotId(uint64_t id) : _id(id) {
invariant(id != kNullId);
}
bool isNull() const {
return _id == kNullId;
}
bool operator==(const SnapshotId& other) const {
return _id == other._id;
}
bool operator!=(const SnapshotId& other) const {
return _id != other._id;
}
std::string toString() const {
return std::to_string(_id);
}
private:
uint64_t _id;
};
template <typename T>
class Snapshotted {
public:
Snapshotted() : _id(), _value() {}
Snapshotted(SnapshotId id, const T& value) : _id(id), _value(value) {}
void reset() {
*this = Snapshotted();
}
void setValue(const T& t) {
_value = t;
}
SnapshotId snapshotId() const {
return _id;
}
const T& value() const {
return _value;
}
T& value() {
return _value;
}
private:
SnapshotId _id;
T _value;
};
}
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