src/MQTT.h
author František Kučera <franta-hg@frantovo.cz>
Fri, 06 May 2022 21:54:09 +0200
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/**
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 * Relational pipes
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 * Copyright © 2022 František Kučera (Frantovo.cz, GlobalCode.info)
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 *
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 * This program is free software: you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation, version 3 of the License.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program. If not, see <http://www.gnu.org/licenses/>.
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 */
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#pragma once
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#include <mqueue.h>
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#include <string>
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#include <stdexcept>
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#include <cstring>
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namespace relpipe {
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namespace in {
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namespace mqtt {
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class MQTT {
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private:
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	const static size_t MSG_SIZE = 8192; // TODO: configurable/dynamic
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	std::string queueName;
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	mqd_t handle = -2;
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	bool unlinkOnClose = false;
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	MQTT(std::string queueName, mqd_t handle, bool unlinkOnClose) : queueName(queueName), handle(handle), unlinkOnClose(unlinkOnClose) {
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	}
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public:
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	virtual ~MQTT() {
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		if (handle >= 0) mq_close(handle);
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		if (unlinkOnClose) mq_unlink(queueName.c_str());
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	}
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	static MQTT* open(std::string queueName, bool unlinkOnClose = false) {
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		mqd_t handle = mq_open(queueName.c_str(), O_RDONLY | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
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		if (handle >= 0) return new MQTT(queueName, handle, unlinkOnClose);
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		else throw std::logic_error("Unable to open MQTT: " + queueName + " error: " + strerror(errno));
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	}
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	void send(std::string message) {
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		int result = mq_send(handle, message.c_str(), message.size(), 0);
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		if (result) throw std::logic_error("Unable to send message to" + queueName + " error: " + strerror(errno));
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	}
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	std::string receive() {
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		char buffer[MSG_SIZE + 1];
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		memset(buffer, 0, MSG_SIZE + 1);
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		ssize_t msgSize = mq_receive(handle, buffer, MSG_SIZE, nullptr);
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		if (msgSize > sizeof (buffer))throw std::logic_error("Invalid MQTT message size.");
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		else if (msgSize >= 0) return std::string(buffer, msgSize);
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		else throw std::logic_error("Unable to receive MQTT message from " + queueName + " error: " + strerror(errno));
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	}
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};
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}
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}
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}