Add ALSA midi input support.

2 files changed, 253 insertions, 0 deletions

diff --git a/drumgizmo/input/alsamidi.cc b/drumgizmo/input/alsamidi.cc
new file mode 100644
index 0000000..068ea2b
--- /dev/null
+++ b/drumgizmo/input/alsamidi.cc
@@ -0,0 +1,196 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            alsamidi.cc
+ *
+ *  Copyright 2021 Volker Fischer (github.com/corrados)
+ ****************************************************************************/
+
+/*
+ *  This file is part of DrumGizmo.
+ *
+ *  DrumGizmo is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU Lesser General Public License as published by
+ *  the Free Software Foundation; either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  DrumGizmo 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 Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public License
+ *  along with DrumGizmo; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#include <iostream>
+#include <cassert>
+
+#include "cpp11fix.h" // required for c++11
+#include "alsamidi.h"
+
+struct AlsaMidiInitError
+{
+	int const code;
+	const std::string msg;
+
+	AlsaMidiInitError(int op_code, const std::string& msg)
+		: code{op_code}
+		, msg{msg}
+	{
+	}
+
+	static inline void test(int code, const std::string& msg)
+	{
+		if(code < 0)
+		{
+			throw AlsaMidiInitError(code, msg);
+		}
+	}
+};
+
+AlsaMidiInputEngine::AlsaMidiInputEngine()
+	: AudioInputEngineMidi{}
+	, in_port(0)
+	, seq_handle{nullptr}
+	, pos{0u}
+	, events{}
+{
+}
+
+AlsaMidiInputEngine::~AlsaMidiInputEngine()
+{
+	if(seq_handle != nullptr)
+	{
+		snd_seq_close(seq_handle);
+	}
+}
+
+bool AlsaMidiInputEngine::init(const Instruments& instruments)
+{
+	if(!loadMidiMap(midimap_file, instruments))
+	{
+		std::cerr << "[AlsaMidiInputEngine] Failed to parse midimap '"
+		          << midimap_file << "'\n";
+		return false;
+	}
+
+	// try to initialize alsa MIDI
+	try
+	{
+		// it is not allowed to block in the run() function, therefore we
+		// have to use a non-blocking mode
+		int value = snd_seq_open(&seq_handle, "default",
+		                         SND_SEQ_OPEN_INPUT, SND_SEQ_NONBLOCK);
+		AlsaMidiInitError::test(value, "snd_seq_open");
+
+		value = snd_seq_set_client_name(seq_handle, "drumgizmo");
+		AlsaMidiInitError::test(value, "snd_seq_set_client_name");
+
+		in_port =
+			snd_seq_create_simple_port(seq_handle, "listen:in",
+			                           SND_SEQ_PORT_CAP_WRITE |
+			                           SND_SEQ_PORT_CAP_SUBS_WRITE,
+			                           SND_SEQ_PORT_TYPE_APPLICATION);
+		AlsaMidiInitError::test(in_port, "snd_seq_create_simple_port");
+	}
+	catch(AlsaMidiInitError const& error)
+	{
+		std::cerr << "[AlsaMidiInputEngine] " << error.msg
+		          << " failed: " << snd_strerror(error.code) << std::endl;
+		return false;
+	}
+
+	return true;
+}
+
+void AlsaMidiInputEngine::setParm(const std::string& parm,
+                                  const std::string& value)
+{
+	if(parm == "midimap")
+	{
+		// apply midimap filename
+		midimap_file = value;
+	}
+	else
+	{
+		std::cerr << "[AlsaMidiInputEngine] Unsupported parameter '" << parm
+		          << "'\n";
+	}
+}
+
+bool AlsaMidiInputEngine::start()
+{
+	return true;
+}
+
+void AlsaMidiInputEngine::stop()
+{
+}
+
+void AlsaMidiInputEngine::pre()
+{
+}
+
+void AlsaMidiInputEngine::run(size_t pos, size_t len,
+                              std::vector<event_t>& events)
+{
+	assert(events.empty());
+	snd_seq_event_t* ev = NULL;
+	if ( snd_seq_event_input(seq_handle, &ev) >= 0 )
+	{
+		// TODO Better solution needed: The ALSA MIDI event structure does
+		// not seem to contain the raw MIDI data, therefore we have to re-create
+		// the raw MIDI data based on the ALSA sequence event information.
+		std::vector<uint8_t> midi_buffer(3, 0);
+		bool message_type_handled = true;
+
+		switch(ev->type)
+		{
+		case SND_SEQ_EVENT_NOTEON:
+			midi_buffer[0] = ev->data.note.channel + 0x90; // NoteOn
+			midi_buffer[1] = ev->data.note.note;
+			midi_buffer[2] = ev->data.note.velocity;
+			break;
+
+		case SND_SEQ_EVENT_NOTEOFF:
+			midi_buffer[0] = ev->data.note.channel + 0x80; // NoteOff
+			midi_buffer[1] = ev->data.note.note;
+			midi_buffer[2] = ev->data.note.off_velocity;
+			break;
+
+		case SND_SEQ_EVENT_KEYPRESS:
+			midi_buffer[0] = ev->data.note.channel + 0xA0; // NoteAftertouch
+			midi_buffer[1] = ev->data.note.note;
+			midi_buffer[2] = ev->data.note.velocity;
+			break;
+
+		case SND_SEQ_EVENT_CONTROLLER:
+			midi_buffer[0] = ev->data.control.channel + 0xB0; // ControlChange
+			midi_buffer[1] = ev->data.control.param;
+			midi_buffer[2] = ev->data.control.value;
+			break;
+
+		default:
+			// unkown message type, ignore the message
+			message_type_handled = false;
+			break;
+		}
+
+		if(message_type_handled)
+		{
+			// since we do not want to introduce any additional delay for the
+			// MIDI processing, we set the offset to zero
+			processNote(midi_buffer.data(), midi_buffer.size(), 0, events);
+		}
+	}
+	snd_seq_free_event(ev);
+}
+
+void AlsaMidiInputEngine::post()
+{
+}
+
+bool AlsaMidiInputEngine::isFreewheeling() const
+{
+	return true;
+}
diff --git a/drumgizmo/input/alsamidi.h b/drumgizmo/input/alsamidi.h
new file mode 100644
index 0000000..73e0fc8
--- /dev/null
+++ b/drumgizmo/input/alsamidi.h
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            alsamidi.h
+ *
+ *  Copyright 2021 Volker Fischer (github.com/corrados)
+ ****************************************************************************/
+
+/*
+ *  This file is part of DrumGizmo.
+ *
+ *  DrumGizmo is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU Lesser General Public License as published by
+ *  the Free Software Foundation; either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  DrumGizmo 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 Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public License
+ *  along with DrumGizmo; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#pragma once
+#include <memory>
+#include <alsa/asoundlib.h>
+
+#include "audioinputenginemidi.h"
+#include "midimapper.h"
+#include "midimapparser.h"
+
+class AlsaMidiInputEngine
+	: public AudioInputEngineMidi
+{
+public:
+	AlsaMidiInputEngine();
+	~AlsaMidiInputEngine();
+
+	// based on AudioInputEngineMidi
+	bool init(const Instruments& instruments) override;
+	void setParm(const std::string& parm, const std::string& value) override;
+	bool start() override;
+	void stop() override;
+	void pre() override;
+	void run(size_t pos, size_t len, std::vector<event_t>& events) override;
+	void post() override;
+	bool isFreewheeling() const override;
+
+private:
+	int in_port;
+	snd_seq_t* seq_handle;
+
+	std::string midimap_file;
+	std::size_t pos;
+	std::vector<event_t> events;
+};