Move MIDI parsing up from ALSA driver to platform independent driver.

Aims for more consistent MIDI support across Windows, MacOS, Linux and
to provide a base for adding MIDI drivers for other platforms.
Reworks the MIDIDriverALSAMidi MIDI parsing implementation as a platform
independent version in MIDIDriver::Parser.
Uses MIDIDriver::Parser to provide running status support in MacOS
MIDIDriverCoreMidi.
Collects connected input names at open, ensuring devices indices reported
in events match names in array returned from get_connected_inputs.

Fixes #77035.
Fixes #79811.

With code review changes by: A Thousand Ships (she/her)
<96648715+AThousandShips@users.noreply.github.com>

1 files changed, 139 insertions, 60 deletions

diff --git a/core/os/midi_driver.cpp b/core/os/midi_driver.cpp
index 6870c84b49..6c748b1498 100644
--- a/core/os/midi_driver.cpp
+++ b/core/os/midi_driver.cpp
@@ -38,88 +38,167 @@ MIDIDriver *MIDIDriver::get_singleton() {
 	return singleton;
 }
 
-void MIDIDriver::set_singleton() {
+MIDIDriver::MIDIDriver() {
 	singleton = this;
 }
 
-void MIDIDriver::receive_input_packet(int device_index, uint64_t timestamp, uint8_t *data, uint32_t length) {
-	Ref<InputEventMIDI> event;
-	event.instantiate();
-	event->set_device(device_index);
-	uint32_t param_position = 1;
-
-	if (length >= 1) {
-		if (data[0] >= 0xF0) {
-			// channel does not apply to system common messages
-			event->set_channel(0);
-			event->set_message(MIDIMessage(data[0]));
-			last_received_message = data[0];
-		} else if ((data[0] & 0x80) == 0x00) {
-			// running status
-			event->set_channel(last_received_message & 0xF);
-			event->set_message(MIDIMessage(last_received_message >> 4));
-			param_position = 0;
+MIDIDriver::MessageCategory MIDIDriver::Parser::category(uint8_t p_midi_fragment) {
+	if (p_midi_fragment >= 0xf8) {
+		return MessageCategory::RealTime;
+	} else if (p_midi_fragment >= 0xf0) {
+		// System Exclusive begin/end are specified as System Common Category
+		// messages, but we separate them here and give them their own categories
+		// as their behavior is significantly different.
+		if (p_midi_fragment == 0xf0) {
+			return MessageCategory::SysExBegin;
+		} else if (p_midi_fragment == 0xf7) {
+			return MessageCategory::SysExEnd;
+		}
+		return MessageCategory::SystemCommon;
+	} else if (p_midi_fragment >= 0x80) {
+		return MessageCategory::Voice;
+	}
+	return MessageCategory::Data;
+}
+
+MIDIMessage MIDIDriver::Parser::status_to_msg_enum(uint8_t p_status_byte) {
+	if (p_status_byte & 0x80) {
+		if (p_status_byte < 0xf0) {
+			return MIDIMessage(p_status_byte >> 4);
 		} else {
-			event->set_channel(data[0] & 0xF);
-			event->set_message(MIDIMessage(data[0] >> 4));
-			param_position = 1;
-			last_received_message = data[0];
+			return MIDIMessage(p_status_byte);
 		}
 	}
+	return MIDIMessage::NONE;
+}
 
-	switch (event->get_message()) {
-		case MIDIMessage::AFTERTOUCH:
-			if (length >= 2 + param_position) {
-				event->set_pitch(data[param_position]);
-				event->set_pressure(data[param_position + 1]);
-			}
-			break;
+size_t MIDIDriver::Parser::expected_data(uint8_t p_status_byte) {
+	return expected_data(status_to_msg_enum(p_status_byte));
+}
 
+size_t MIDIDriver::Parser::expected_data(MIDIMessage p_msg_type) {
+	switch (p_msg_type) {
+		case MIDIMessage::NOTE_OFF:
+		case MIDIMessage::NOTE_ON:
+		case MIDIMessage::AFTERTOUCH:
 		case MIDIMessage::CONTROL_CHANGE:
-			if (length >= 2 + param_position) {
-				event->set_controller_number(data[param_position]);
-				event->set_controller_value(data[param_position + 1]);
-			}
-			break;
+		case MIDIMessage::PITCH_BEND:
+		case MIDIMessage::SONG_POSITION_POINTER:
+			return 2;
+		case MIDIMessage::PROGRAM_CHANGE:
+		case MIDIMessage::CHANNEL_PRESSURE:
+		case MIDIMessage::QUARTER_FRAME:
+		case MIDIMessage::SONG_SELECT:
+			return 1;
+		default:
+			return 0;
+	}
+}
 
-		case MIDIMessage::NOTE_ON:
+uint8_t MIDIDriver::Parser::channel(uint8_t p_status_byte) {
+	if (category(p_status_byte) == MessageCategory::Voice) {
+		return p_status_byte & 0x0f;
+	}
+	return 0;
+}
+
+void MIDIDriver::send_event(int p_device_index, uint8_t p_status,
+		const uint8_t *p_data, size_t p_data_len) {
+	const MIDIMessage msg = Parser::status_to_msg_enum(p_status);
+	ERR_FAIL_COND(p_data_len < Parser::expected_data(msg));
+
+	Ref<InputEventMIDI> event;
+	event.instantiate();
+	event->set_device(p_device_index);
+	event->set_channel(Parser::channel(p_status));
+	event->set_message(msg);
+	switch (msg) {
 		case MIDIMessage::NOTE_OFF:
-			if (length >= 2 + param_position) {
-				event->set_pitch(data[param_position]);
-				event->set_velocity(data[param_position + 1]);
-			}
+		case MIDIMessage::NOTE_ON:
+			event->set_pitch(p_data[0]);
+			event->set_velocity(p_data[1]);
 			break;
-
-		case MIDIMessage::PITCH_BEND:
-			if (length >= 2 + param_position) {
-				event->set_pitch((data[param_position + 1] << 7) | data[param_position]);
-			}
+		case MIDIMessage::AFTERTOUCH:
+			event->set_pitch(p_data[0]);
+			event->set_pressure(p_data[1]);
+			break;
+		case MIDIMessage::CONTROL_CHANGE:
+			event->set_controller_number(p_data[0]);
+			event->set_controller_value(p_data[1]);
 			break;
-
 		case MIDIMessage::PROGRAM_CHANGE:
-			if (length >= 1 + param_position) {
-				event->set_instrument(data[param_position]);
-			}
+			event->set_instrument(p_data[0]);
 			break;
-
 		case MIDIMessage::CHANNEL_PRESSURE:
-			if (length >= 1 + param_position) {
-				event->set_pressure(data[param_position]);
-			}
+			event->set_pressure(p_data[0]);
+			break;
+		case MIDIMessage::PITCH_BEND:
+			event->set_pitch((p_data[1] << 7) | p_data[0]);
 			break;
+		// QUARTER_FRAME, SONG_POSITION_POINTER, and SONG_SELECT not yet implemented.
 		default:
 			break;
 	}
-
-	Input *id = Input::get_singleton();
-	id->parse_input_event(event);
+	Input::get_singleton()->parse_input_event(event);
 }
 
-PackedStringArray MIDIDriver::get_connected_inputs() {
-	PackedStringArray list;
-	return list;
+void MIDIDriver::Parser::parse_fragment(uint8_t p_fragment) {
+	switch (category(p_fragment)) {
+		case MessageCategory::RealTime:
+			// Real-Time messages are single byte messages that can
+			// occur at any point and do not interrupt other messages.
+			// We pass them straight through.
+			MIDIDriver::send_event(device_index, p_fragment);
+			break;
+
+		case MessageCategory::SysExBegin:
+			status_byte = p_fragment;
+			skipping_sys_ex = true;
+			break;
+
+		case MessageCategory::SysExEnd:
+			status_byte = 0;
+			skipping_sys_ex = false;
+			break;
+
+		case MessageCategory::Voice:
+		case MessageCategory::SystemCommon:
+			skipping_sys_ex = false; // If we were in SysEx, assume it was aborted.
+			received_data_len = 0;
+			status_byte = 0;
+			ERR_FAIL_COND(expected_data(p_fragment) > DATA_BUFFER_SIZE);
+			if (expected_data(p_fragment) == 0) {
+				// No data bytes needed, post it now.
+				MIDIDriver::send_event(device_index, p_fragment);
+			} else {
+				status_byte = p_fragment;
+			}
+			break;
+
+		case MessageCategory::Data:
+			// We don't currently process SysEx messages, so ignore their data.
+			if (!skipping_sys_ex) {
+				const size_t expected = expected_data(status_byte);
+				if (received_data_len < expected) {
+					data_buffer[received_data_len] = p_fragment;
+					received_data_len++;
+					if (received_data_len == expected) {
+						MIDIDriver::send_event(device_index, status_byte,
+								data_buffer, expected);
+						received_data_len = 0;
+						// Voice messages can use 'running status', sending further
+						// messages without resending their status byte.
+						// For other messages types we clear the cached status byte.
+						if (category(status_byte) != MessageCategory::Voice) {
+							status_byte = 0;
+						}
+					}
+				}
+			}
+			break;
+	}
 }
 
-MIDIDriver::MIDIDriver() {
-	set_singleton();
+PackedStringArray MIDIDriver::get_connected_inputs() const {
+	return connected_input_names;
 }