godot/drivers/alsamidi/midi_driver_alsamidi.cpp

/*************************************************************************/
/*  midi_driver_alsamidi.cpp                                             */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
/*                      https://godotengine.org                          */
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/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
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#ifdef ALSAMIDI_ENABLED

#include "midi_driver_alsamidi.h"

#include "core/os/os.h"
#include "core/print_string.h"

#include <errno.h>

static int get_message_size(uint8_t message) {
	switch (message & 0xF0) {
		case 0x80: // note off
		case 0x90: // note on
		case 0xA0: // aftertouch
		case 0xB0: // continuous controller
			return 3;

		case 0xC0: // patch change
		case 0xD0: // channel pressure
		case 0xE0: // pitch bend
			return 2;
	}

	return 256;
}

void MIDIDriverALSAMidi::thread_func(void *p_udata) {
	MIDIDriverALSAMidi *md = (MIDIDriverALSAMidi *)p_udata;
	uint64_t timestamp = 0;
	uint8_t buffer[256];
	int expected_size = 255;
	int bytes = 0;

	while (!md->exit_thread) {
		int ret;

		md->lock();

		for (int i = 0; i < md->connected_inputs.size(); i++) {
			snd_rawmidi_t *midi_in = md->connected_inputs[i];
			do {
				uint8_t byte = 0;
				ret = snd_rawmidi_read(midi_in, &byte, 1);
				if (ret < 0) {
					if (ret != -EAGAIN) {
						ERR_PRINTS("snd_rawmidi_read error: " + String(snd_strerror(ret)));
					}
				} else {
					if (byte & 0x80) {
						// Flush previous packet if there is any
						if (bytes) {
							md->receive_input_packet(timestamp, buffer, bytes);
							bytes = 0;
						}
						expected_size = get_message_size(byte);
					}

					if (bytes < 256) {
						buffer[bytes++] = byte;
						// If we know the size of the current packet receive it if it reached the expected size
						if (bytes >= expected_size) {
							md->receive_input_packet(timestamp, buffer, bytes);
							bytes = 0;
						}
					}
				}
			} while (ret > 0);
		}

		md->unlock();

		OS::get_singleton()->delay_usec(1000);
	}
}

Error MIDIDriverALSAMidi::open() {

	void **hints;

	if (snd_device_name_hint(-1, "rawmidi", &hints) < 0)
		return ERR_CANT_OPEN;

	int i = 0;
	for (void **n = hints; *n != NULL; n++) {
		char *name = snd_device_name_get_hint(*n, "NAME");

		if (name != NULL) {
			snd_rawmidi_t *midi_in;
			int ret = snd_rawmidi_open(&midi_in, NULL, name, SND_RAWMIDI_NONBLOCK);
			if (ret >= 0) {
				connected_inputs.insert(i++, midi_in);
			}
		}

		if (name != NULL)
			free(name);
	}
	snd_device_name_free_hint(hints);

	mutex = Mutex::create();
	exit_thread = false;
	thread = Thread::create(MIDIDriverALSAMidi::thread_func, this);

	return OK;
}

void MIDIDriverALSAMidi::close() {

	if (thread) {
		exit_thread = true;
		Thread::wait_to_finish(thread);

		memdelete(thread);
		thread = NULL;
	}

	if (mutex) {
		memdelete(mutex);
		mutex = NULL;
	}

	for (int i = 0; i < connected_inputs.size(); i++) {
		snd_rawmidi_t *midi_in = connected_inputs[i];
		snd_rawmidi_close(midi_in);
	}
	connected_inputs.clear();
}

void MIDIDriverALSAMidi::lock() const {

	if (mutex)
		mutex->lock();
}

void MIDIDriverALSAMidi::unlock() const {

	if (mutex)
		mutex->unlock();
}

PoolStringArray MIDIDriverALSAMidi::get_connected_inputs() {

	PoolStringArray list;

	lock();
	for (int i = 0; i < connected_inputs.size(); i++) {
		snd_rawmidi_t *midi_in = connected_inputs[i];
		snd_rawmidi_info_t *info;

		snd_rawmidi_info_malloc(&info);
		snd_rawmidi_info(midi_in, info);
		list.push_back(snd_rawmidi_info_get_name(info));
		snd_rawmidi_info_free(info);
	}
	unlock();

	return list;
}

MIDIDriverALSAMidi::MIDIDriverALSAMidi() {

	mutex = NULL;
	thread = NULL;

	exit_thread = false;
}

MIDIDriverALSAMidi::~MIDIDriverALSAMidi() {

	close();
}

#endif // ALSAMIDI_ENABLED