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Move MIDI parsing up from ALSA driver to platform independent driver.
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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)
<[email protected]>
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@ibrahn
ibrahn committed Jun 25, 2024
1 parent 6b281c0 commit 607c5ec
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Showing 8 changed files with 332 additions and 316 deletions.
199 changes: 139 additions & 60 deletions core/os/midi_driver.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
68 changes: 61 additions & 7 deletions core/os/midi_driver.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -42,19 +42,73 @@ class MIDIDriver {
static MIDIDriver *singleton;
static uint8_t last_received_message;

protected:
// Categories of message for parser logic.
enum class MessageCategory {
Data,
Voice,
SysExBegin,
SystemCommon, // excluding System Exclusive Begin/End
SysExEnd,
RealTime,
};

// Convert midi data to InputEventMIDI and send it to Input.
// p_data_len is the length of the buffer passed at p_data, this must be
// at least equal to the data required by the passed message type, but
// may be larger. Only the required data will be read.
static void send_event(int p_device_index, uint8_t p_status,
const uint8_t *p_data = nullptr, size_t p_data_len = 0);

class Parser {
public:
Parser() = default;
Parser(int p_device_index) :
device_index{ p_device_index } {}
virtual ~Parser() = default;

// Push a byte of MIDI stream. Any completed messages will be
// forwarded to MIDIDriver::send_event.
void parse_fragment(uint8_t p_fragment);

static MessageCategory category(uint8_t p_midi_fragment);

// If the byte is a Voice Message status byte return the contained
// channel number, otherwise zero.
static uint8_t channel(uint8_t p_status_byte);

// If the byte is a status byte for a message with a fixed number of
// additional data bytes, return the number expected, otherwise zero.
static size_t expected_data(uint8_t p_status_byte);
static size_t expected_data(MIDIMessage p_msg_type);

// If the fragment is a status byte return the message type
// represented, otherwise MIDIMessage::NONE.
static MIDIMessage status_to_msg_enum(uint8_t p_status_byte);

private:
int device_index = 0;

static constexpr size_t DATA_BUFFER_SIZE = 2;

uint8_t status_byte = 0;
uint8_t data_buffer[DATA_BUFFER_SIZE] = { 0 };
size_t received_data_len = 0;
bool skipping_sys_ex = false;
};

PackedStringArray connected_input_names;

public:
static MIDIDriver *get_singleton();
void set_singleton();

MIDIDriver();
virtual ~MIDIDriver() = default;

virtual Error open() = 0;
virtual void close() = 0;

virtual PackedStringArray get_connected_inputs();

static void receive_input_packet(int device_index, uint64_t timestamp, uint8_t *data, uint32_t length);

MIDIDriver();
virtual ~MIDIDriver() {}
PackedStringArray get_connected_inputs() const;
};

#endif // MIDI_DRIVER_H
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