AlsaBridge.cpp
author František Kučera <franta-hg@frantovo.cz>
Mon, 21 Dec 2020 16:44:39 +0100
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lock in AlsaBridge
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/**
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 * DJM-Fix
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 * Copyright © 2020 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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#include <iostream>
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#include <stdexcept>
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#include <thread>
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#include <mutex>
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#include <atomic>
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#include <alsa/asoundlib.h>
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#include "AlsaBridge.h"
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namespace djmfix {
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namespace alsa {
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class AlsaBridgeImpl : public AlsaBridge, private djmfix::MidiSender {
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private:
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	djmfix::DJMFix* djmFix;
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	snd_rawmidi_t* input;
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	snd_rawmidi_t* output;
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	std::thread receivingThread;
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	std::recursive_mutex midiMutex;
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	std::atomic<bool> stopped{false};
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	void run() {
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		while (!stopped) {
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			{
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				std::lock_guard<std::recursive_mutex> lock(midiMutex);
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				// TODO: poll
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				uint8_t buffer[256];
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				ssize_t length = snd_rawmidi_read(input, buffer, sizeof (buffer));
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				if (length > 0 && length <= sizeof (buffer)) {
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					// TODO: multiple messages combined together?
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					djmFix->receive(MidiMessage(buffer, buffer + length));
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				}
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			}
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			std::this_thread::sleep_for(std::chrono::milliseconds(100));
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		}
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	}
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public:
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	AlsaBridgeImpl(djmfix::DJMFix* djmFix, const std::string& deviceName) : djmFix(djmFix) {
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		if (djmFix == nullptr) throw std::invalid_argument("need a djmFix for AlsaBridge");
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		int error = snd_rawmidi_open(&input, &output, deviceName.c_str(), SND_RAWMIDI_NONBLOCK);
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		if (error) throw std::invalid_argument("unable to open ALSA device");
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		djmFix->setMidiSender(this);
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	}
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	virtual ~AlsaBridgeImpl() {
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		// TODO: do not use raw/exclusive access to the device
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		snd_rawmidi_close(input);
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		snd_rawmidi_close(output);
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		std::cerr << "~AlsaBridgeImpl()" << std::endl; // TODO: do not mess STDIO
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	}
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	virtual void start() override {
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		djmFix->start();
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		receivingThread = std::thread(&AlsaBridgeImpl::run, this);
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	}
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	virtual void stop() override {
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		stopped = true;
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		receivingThread.join();
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		djmFix->stop();
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	}
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	virtual void send(MidiMessage midiMessage) override {
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		std::lock_guard<std::recursive_mutex> lock(midiMutex);
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		ssize_t length = snd_rawmidi_write(output, midiMessage.data(), midiMessage.size());
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		std::cerr << "AlsaBridgeImpl::send(): length = " << length << std::endl; // TODO: do not mess STDIO
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	}
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};
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AlsaBridge* create(djmfix::DJMFix* djmFix, const std::string& deviceName) {
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	return new AlsaBridgeImpl(djmFix, deviceName);
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}
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}
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}