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/**
* 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.
*/
#pragma once
#include "mongo/base/status_with.h"
#include "mongo/transport/message_compressor_base.h"
#include "mongo/transport/session.h"
#include <vector>
namespace mongo {
class BSONObj;
class BSONObjBuilder;
class Message;
class MessageCompressorRegistry;
class MessageCompressorManager {
MessageCompressorManager(const MessageCompressorManager&) = delete;
MessageCompressorManager& operator=(const MessageCompressorManager&) = delete;
public:
/*
* Default constructor. Uses the global MessageCompressorRegistry.
*/
MessageCompressorManager();
/*
* Constructs a manager from a specific MessageCompressorRegistry - used by the unit tests
* to test various registry configurations.
*/
explicit MessageCompressorManager(MessageCompressorRegistry* factory);
MessageCompressorManager(MessageCompressorManager&&) = default;
MessageCompressorManager& operator=(MessageCompressorManager&&) = default;
/*
* Called by a client constructing an isMaster request. This function will append the result
* of _registry->getCompressorNames() to the BSONObjBuilder as a BSON array. If no compressors
* are configured, it won't append anything.
*/
void clientBegin(BSONObjBuilder* output);
/*
* Called by a client that has received an isMaster response (received after calling
* clientBegin) and wants to finish negotiating compression.
*
* This looks for a BSON array called "compression" with the server's list of
* requested algorithms. The first algorithm in that array will be used in subsequent calls
* to compressMessage.
*/
void clientFinish(const BSONObj& input);
/*
* Called by a server that has received an isMaster request.
*
* If no compressors are configured that match those requested by the client, then it will
* not append anything to the BSONObjBuilder output.
*/
void serverNegotiate(const boost::optional<std::vector<StringData>>& clientCompressors,
BSONObjBuilder*);
/*
* Returns a new Message containing the compressed contentx of 'msg'. If compressorId is null,
* then it selects the first negotiated compressor. Otherwise, it uses the compressor with the
* given identifier. It is intended that this value echo back a value returned as the out
* parameter value for compressorId from a call to decompressMessage.
*
* If _negotiated is empty (meaning compression was not negotiated or is not supported), then
* it will return a ref-count bumped copy of the input message.
*
* If an error occurs in the compressor, it will return a Status error.
*/
StatusWith<Message> compressMessage(const Message& msg,
const MessageCompressorId* compressorId = nullptr);
/*
* Returns a new Message containing the decompressed copy of the input message.
*
* If the compressor specified in the input message is not supported, it will return a Status
* error.
*
* If an error occurs in the compressor, it will return a Status error.
*
* This can be called before Compression is negotiated with the client. This class has a
* pointer to the global MessageCompressorRegistry and can lookup any message's compressor
* by ID number through that registry. As long as the compressor has been enabled process-wide,
* it can decompress any message without negotiation.
*
* If the 'compressorId' parameter is non-null, it will be populated with the compressor
* used. If 'decompressMessage' returns succesfully, then that value can be fed back into
* compressMessage, ensuring that the same compressor is used on both sides of a conversation.
*/
StatusWith<Message> decompressMessage(const Message& msg,
MessageCompressorId* compressorId = nullptr);
static MessageCompressorManager& forSession(const transport::SessionHandle& session);
private:
std::vector<MessageCompressorBase*> _negotiated;
MessageCompressorRegistry* _registry;
};
} // namespace mongo
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