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/* Copyright 2014 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 <cstring>
#include "mongo/base/data_view.h"
namespace mongo {
struct ZeroInitTag_t {
ZeroInitTag_t(){};
};
const ZeroInitTag_t kZeroInitTag;
template <typename Layout, typename ConstView, typename View>
class EncodedValueStorage {
protected:
EncodedValueStorage() {}
// This explicit constructor is provided to allow for easy zeroing
// during creation of a value. You might prefer this over an
// uninitialised value if the zeroed version provides a useful base
// state. Such cases might include a set of counters that begin at
// zero, flags that start off false or a larger structure where some
// significant portion of storage falls into those kind of use cases.
// Use this where you might have used calloc(1, sizeof(type)) in C.
//
// The added value of providing it as a constructor lies in the ability
// of subclasses to easily inherit a zeroed base state during
// initialization.
explicit EncodedValueStorage(ZeroInitTag_t) {
std::memset(_data, 0, sizeof(_data));
}
public:
View view() {
return _data;
}
ConstView constView() const {
return _data;
}
operator View() {
return view();
}
operator ConstView() const {
return constView();
}
private:
char _data[sizeof(Layout)];
};
} // namespace mongo
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