mini_midi/
lib.rs

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use std::iter;

/// A MIDI channel.
#[derive(Debug)]
pub enum Channel {
    Channel1,
    Channel2,
    Channel3,
    Channel4,
    Channel5,
    Channel6,
    Channel7,
    Channel8,
    Channel9,
    Channel10,
    Channel11,
    Channel12,
    Channel13,
    Channel14,
    Channel15,
    Channel16,
}

impl From<u8> for Channel {
    fn from(value: u8) -> Self {
        match value {
            0 => Self::Channel1,
            1 => Self::Channel2,
            2 => Self::Channel3,
            3 => Self::Channel4,
            4 => Self::Channel5,
            5 => Self::Channel6,
            6 => Self::Channel7,
            7 => Self::Channel8,
            8 => Self::Channel9,
            9 => Self::Channel10,
            10 => Self::Channel11,
            11 => Self::Channel12,
            12 => Self::Channel13,
            13 => Self::Channel14,
            14 => Self::Channel15,
            _ => Self::Channel16,
        }
    }
}

impl Into<u8> for &Channel {
    fn into(self) -> u8 {
        match self.as_ref() {
            Channel::Channel1 => 0,
            Channel::Channel2 => 1,
            Channel::Channel3 => 2,
            Channel::Channel4 => 3,
            Channel::Channel5 => 4,
            Channel::Channel6 => 5,
            Channel::Channel7 => 6,
            Channel::Channel8 => 7,
            Channel::Channel9 => 8,
            Channel::Channel10 => 9,
            Channel::Channel11 => 10,
            Channel::Channel12 => 11,
            Channel::Channel13 => 12,
            Channel::Channel14 => 13,
            Channel::Channel15 => 14,
            Channel::Channel16 => 15,
        }
    }
}

impl AsRef<Channel> for Channel {
    fn as_ref(&self) -> &Channel {
        self
    }
}

/// A MIDI message.  
/// Refer to [this table](https://midi.org/expanded-midi-1-0-messages-list)
/// for more info.
#[derive(Debug)]
pub enum Message<'a> {
    // TODO: Implement a struct for 7-bit values
    // TODO: Implement an enum for notes
    NoteOff(Channel, u8, u8),
    NoteOn(Channel, u8, u8),
    PolyphonicAftertouch(Channel, u8, u8),
    /* TODO: Implement MIDI spec table 3
    https://midi.org/midi-1-0-control-change-messages */
    ControlOrModeChange(Channel, u8, u8),
    ProgramChange(Channel, u8),
    Aftertouch(Channel, u8),
    PitchBendChange(Channel, u8, u8),
    SystemExclusive(&'a [u8]),
    // TODO: Determine whether to implement the quarter frame (242)
    SongPositionPointer(u8, u8),
    SongSelect(u8),
    TuneRequest,
    TimingClock,
    Start,
    Continue,
    Stop,
    ActiveSensing,
    SystemReset,
}

impl<'a> From<&'a [u8]> for Message<'a> {
    fn from(value: &'a [u8]) -> Self {
        let first_byte = if value.len() >= 1 {
            value[0]
        } else {
            panic!("A MIDI message can't be zero bytes long!");
        };

        let get_second_byte = || {
            if value.len() >= 2 {
                value[1]
            } else {
                // TODO: Add an error message
                panic!("No second byte present!")
            }
        };

        let get_third_byte = || {
            if value.len() >= 3 {
                value[2]
            } else {
                panic!("No third byte present!")
            }
        };

        match first_byte {
            128..=143 => Self::NoteOff(
                Channel::from(first_byte - 128),
                get_second_byte(),
                get_third_byte(),
            ),
            144..=159 => Self::NoteOn(
                Channel::from(first_byte - 144),
                get_second_byte(),
                get_third_byte(),
            ),
            160..=175 => Self::PolyphonicAftertouch(
                Channel::from(first_byte - 145),
                get_second_byte(),
                get_third_byte(),
            ),
            176..=191 => Self::ControlOrModeChange(
                Channel::from(first_byte - 176),
                get_second_byte(),
                get_third_byte(),
            ),
            192..=207 => Self::ProgramChange(Channel::from(first_byte - 192), get_second_byte()),
            208..=223 => Self::Aftertouch(Channel::from(first_byte - 208), get_second_byte()),
            224..=239 => Self::PitchBendChange(
                Channel::from(first_byte),
                get_second_byte(),
                get_third_byte(),
            ),
            240 => Self::SystemExclusive(&value[1..value.len() - 1]),
            242 => Self::SongPositionPointer(get_second_byte(), get_third_byte()),
            243 => Self::SongSelect(get_second_byte()),
            246 => Self::TuneRequest,
            248 => Self::TimingClock,
            250 => Self::Start,
            251 => Self::Continue,
            252 => Self::Stop,
            254 => Self::ActiveSensing,
            255 => Self::SystemReset,
            // TODO: Add error handling
            _ => panic!("Invalid MIDI message!"),
        }
    }
}

impl<'a> Into<Vec<u8>> for Message<'a> {
    fn into(self) -> Vec<u8> {
        fn c_to_u8(channel: &Channel) -> u8 {
            Into::<u8>::into(channel)
        }

        match self {
            Message::NoteOff(ref channel, note, velocity) => {
                vec![128u8 + c_to_u8(channel), note, velocity]
            }
            Message::NoteOn(ref channel, note, velocity) => {
                vec![144u8 + c_to_u8(channel), note, velocity]
            }
            Message::PolyphonicAftertouch(ref channel, note, pressure) => {
                vec![160u8 + c_to_u8(channel), note, pressure]
            }
            Message::ControlOrModeChange(ref channel, byte2, byte3) => {
                vec![176u8 + c_to_u8(channel), byte2, byte3]
            }
            Message::ProgramChange(ref channel, program) => {
                vec![192u8 + c_to_u8(channel), program]
            }
            Message::Aftertouch(ref channel, pressure) => {
                vec![208u8 + c_to_u8(channel), pressure]
            }
            Message::PitchBendChange(ref channel, lsb, msb) => {
                vec![224u8 + c_to_u8(channel), lsb, msb]
            }
            Message::SystemExclusive(data) => iter::once(240u8)
                .chain(data.to_owned())
                .chain(iter::once(247u8))
                .collect(),
            Message::SongPositionPointer(lsb, msb) => {
                vec![242u8, lsb, msb]
            }
            Message::SongSelect(song) => {
                vec![243u8, song]
            }
            Message::TuneRequest => {
                vec![246u8]
            }
            Message::TimingClock => {
                vec![248u8]
            }
            Message::Start => {
                vec![250u8]
            }
            Message::Continue => {
                vec![251u8]
            }
            Message::Stop => {
                vec![252u8]
            }
            Message::ActiveSensing => {
                vec![254u8]
            }
            Message::SystemReset => {
                vec![255u8]
            }
            _ => todo!(),
        }
    }
}