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/**
* Copyright (C) 2013 10gen 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/>.
*/
namespace mongo {
/**
* The 'WireVersion' captures all "protocol events" the write protocol went through. A
* protocol event is a change in the syntax of messages on the wire or the semantics of
* existing messages. We may also add "logical" entries for releases, although that's not
* mandatory.
*
* We use the wire version to determine if two agents (a driver, a mongos, or a mongod) can
* interact. Each agent carries two versions, a 'max' and a 'min' one. If the two agents
* are on the same 'max' number, they stricly speak the same wire protocol and it is safe
* to allow them to communicate. If two agents' ranges do not intersect, they should not be
* allowed to communicate.
*
* If two agents have at least one version in common they can communicate, but one of the
* sides has to be ready to compensate for not being on its partner version.
*/
enum WireVersion {
// Everything before we started tracking.
RELEASE_2_4_AND_BEFORE = 0,
// The aggregation command may now be requested to return cursors.
AGG_RETURNS_CURSORS = 1,
};
// Latest version that the server accepts. This should always be at the latest entry in
// WireVersion.
static const int maxWireVersion = AGG_RETURNS_CURSORS;
// Minimum version that the server accepts. We should bump this whenever we don't want
// to allow communication with too old agents.
static const int minWireVersion = RELEASE_2_4_AND_BEFORE;
} // namespace mongo
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