/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    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 Server Side 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.
 */

#include "mongo/db/operation_id.h"

#include "mongo/util/assert_util.h"

namespace mongo {

OperationIdSlot UniqueOperationIdRegistry::acquireSlot() {
    stdx::lock_guard lk(_mutex);

    // Make sure the set isn't absolutely enormous. If it is, something else is wrong,
    // and the loop below could fail.
    invariant(_activeIds.size() < (1 << 20));

    while (true) {
        auto opId = _nextOpId++;
        if (!_nextOpId) {
            _nextOpId = 1U;
        }
        const auto&& [it, ok] = _activeIds.insert(opId);
        if (ok) {
            return OperationIdSlot(*it, shared_from_this());
        }
    }
}

void UniqueOperationIdRegistry::_releaseSlot(OperationId id) {
    stdx::lock_guard lk(_mutex);
    invariant(_activeIds.erase(id));
}

}  // namespace mongo