usbd_midi/packet/
code_index_number.rs

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//! Enum representing the code index number of a packet.

use crate::packet::UsbMidiEventPacketError;

/// The Code Index Number(CIN) indicates the classification
/// of the bytes in the MIDI_x fields.
/// Code Index Number classifications.
#[derive(Debug, Clone, Copy, Eq, PartialEq)]
#[repr(u8)]
pub enum CodeIndexNumber {
    /// Miscellaneous function codes. Reserved for future extensions.
    MiscFunction = 0x00,
    /// Cable events. Reserved for future expansion.
    CableEvents = 0x1,
    /// Two-byte System Common messages like MTC, SongSelect, etc.
    SystemCommon2Bytes = 0x2,
    /// Three-byte System Common messages like SPP, etc.
    SystemCommon3Bytes = 0x3,
    /// SysEx starts or continues.
    SysexStartsOrContinues = 0x4,
    /// Single-byte System Common Message or SysEx ends with following single byte.
    SystemCommon1Byte = 0x5,
    /// SysEx ends with following two bytes.
    SysexEnds2Bytes = 0x6,
    /// SysEx ends with following three bytes.
    SysexEnds3Bytes = 0x7,
    /// Note-off.
    NoteOff = 0x8,
    /// Note-on.
    NoteOn = 0x9,
    /// Poly-KeyPress.
    PolyKeyPress = 0xA,
    /// Control Change.
    ControlChange = 0xB,
    /// Program Change.
    ProgramChange = 0xC,
    /// Channel Pressure.
    ChannelPressure = 0xD,
    /// PitchBend Change.
    PitchBendChange = 0xE,
    /// Single Byte.
    SingleByte = 0xF,
}

impl TryFrom<u8> for CodeIndexNumber {
    type Error = UsbMidiEventPacketError;

    fn try_from(value: u8) -> Result<Self, Self::Error> {
        match value {
            x if x == CodeIndexNumber::MiscFunction as u8 => Ok(CodeIndexNumber::MiscFunction),
            x if x == CodeIndexNumber::CableEvents as u8 => Ok(CodeIndexNumber::CableEvents),
            x if x == CodeIndexNumber::SystemCommon2Bytes as u8 => {
                Ok(CodeIndexNumber::SystemCommon2Bytes)
            }
            x if x == CodeIndexNumber::SystemCommon3Bytes as u8 => {
                Ok(CodeIndexNumber::SystemCommon3Bytes)
            }
            x if x == CodeIndexNumber::SysexStartsOrContinues as u8 => {
                Ok(CodeIndexNumber::SysexStartsOrContinues)
            }
            x if x == CodeIndexNumber::SystemCommon1Byte as u8 => {
                Ok(CodeIndexNumber::SystemCommon1Byte)
            }
            x if x == CodeIndexNumber::SysexEnds2Bytes as u8 => {
                Ok(CodeIndexNumber::SysexEnds2Bytes)
            }
            x if x == CodeIndexNumber::SysexEnds3Bytes as u8 => {
                Ok(CodeIndexNumber::SysexEnds3Bytes)
            }
            x if x == CodeIndexNumber::NoteOff as u8 => Ok(CodeIndexNumber::NoteOff),
            x if x == CodeIndexNumber::NoteOn as u8 => Ok(CodeIndexNumber::NoteOn),
            x if x == CodeIndexNumber::PolyKeyPress as u8 => Ok(CodeIndexNumber::PolyKeyPress),
            x if x == CodeIndexNumber::ControlChange as u8 => Ok(CodeIndexNumber::ControlChange),
            x if x == CodeIndexNumber::ProgramChange as u8 => Ok(CodeIndexNumber::ProgramChange),
            x if x == CodeIndexNumber::ChannelPressure as u8 => {
                Ok(CodeIndexNumber::ChannelPressure)
            }
            x if x == CodeIndexNumber::PitchBendChange as u8 => {
                Ok(CodeIndexNumber::PitchBendChange)
            }
            x if x == CodeIndexNumber::SingleByte as u8 => Ok(CodeIndexNumber::SingleByte),
            _ => Err(UsbMidiEventPacketError::InvalidCodeIndexNumber(value)),
        }
    }
}

impl CodeIndexNumber {
    /// Creates a new number from a MIDI event payload.
    ///
    /// The detection is based on the content and ignores the slice length.
    pub fn try_from_payload(payload: &[u8]) -> Result<Self, UsbMidiEventPacketError> {
        let Some(status) = payload.first() else {
            return Err(UsbMidiEventPacketError::EmptyPayload);
        };

        if *status < 0xF0 {
            match status & 0xF0 {
                0x80 => Ok(Self::NoteOff),
                0x90 => Ok(Self::NoteOn),
                0xA0 => Ok(Self::PolyKeyPress),
                0xB0 => Ok(Self::ControlChange),
                0xC0 => Ok(Self::ProgramChange),
                0xD0 => Ok(Self::ChannelPressure),
                0xE0 => Ok(Self::PitchBendChange),
                _ => {
                    if payload.len() > 1 && payload[1] == 0xF7 {
                        Ok(Self::SysexEnds2Bytes)
                    } else if payload.len() > 2 && payload[2] == 0xF7 {
                        Ok(Self::SysexEnds3Bytes)
                    } else if payload.len() == 1 {
                        Ok(Self::SingleByte)
                    } else if payload.len() > 2 {
                        Ok(Self::SysexStartsOrContinues)
                    } else {
                        Err(UsbMidiEventPacketError::InvalidPayloadSize)
                    }
                }
            }
        } else {
            match status {
                0xF0 => {
                    if payload.len() > 1 && payload[1] == 0xF7 {
                        Ok(Self::SysexEnds2Bytes)
                    } else if payload.len() > 2 && payload[2] == 0xF7 {
                        Ok(Self::SysexEnds3Bytes)
                    } else if payload.len() > 2 {
                        Ok(Self::SysexStartsOrContinues)
                    } else {
                        Err(UsbMidiEventPacketError::InvalidPayloadSize)
                    }
                }
                0xF1 | 0xF3 => Ok(Self::SystemCommon2Bytes),
                0xF2 => Ok(Self::SystemCommon3Bytes),
                0xF6 | 0xF7 => Ok(Self::SystemCommon1Byte),
                0xF8 | 0xF9 | 0xFA | 0xFB | 0xFC | 0xFE | 0xFF => Ok(Self::SingleByte),
                _ => Err(UsbMidiEventPacketError::InvalidPayloadStatus),
            }
        }
    }

    /// Returns the size of the MIDI_x event payload in bytes.
    pub fn payload_size(&self) -> usize {
        match self {
            Self::SystemCommon1Byte | Self::SingleByte => 1,
            Self::SystemCommon2Bytes
            | Self::SysexEnds2Bytes
            | Self::ProgramChange
            | Self::ChannelPressure => 2,
            Self::SystemCommon3Bytes
            | Self::SysexEnds3Bytes
            | Self::SysexStartsOrContinues
            | Self::NoteOff
            | Self::NoteOn
            | Self::PolyKeyPress
            | Self::ControlChange
            | Self::PitchBendChange => 3,

            // These variants are reserved for future use.
            // We assume the maximum length of 3 bytes so that no data can get lost.
            Self::MiscFunction | Self::CableEvents => 3,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    macro_rules! encode_payload_test {
        ($($id:ident: $value:expr,)*) => {
            $(
                #[test]
                fn $id() {
                    let (payload, expected) = $value;
                    let cin = CodeIndexNumber::try_from_payload(&payload);
                    assert_eq!(cin, expected);
                }
            )*
        }
    }

    encode_payload_test! {
        note_off: ([0x80, 60, 64], Ok(CodeIndexNumber::NoteOff)),
        note_on: ([0x90, 60, 64], Ok(CodeIndexNumber::NoteOn)),
        poly_key_press: ([0xA0, 48, 32], Ok(CodeIndexNumber::PolyKeyPress)),
        control_change: ([0xB0, 10, 127], Ok(CodeIndexNumber::ControlChange)),
        program_change: ([0xC0, 5], Ok(CodeIndexNumber::ProgramChange)),
        channel_pressure: ([0xD0, 54], Ok(CodeIndexNumber::ChannelPressure)),
        pitch_bend: ([0xE0, 32, 96], Ok(CodeIndexNumber::PitchBendChange)),
        mtc_quarter_frame: ([0xF1, 12], Ok(CodeIndexNumber::SystemCommon2Bytes)),
        song_position_pointer: ([0xF2, 3, 8], Ok(CodeIndexNumber::SystemCommon3Bytes)),
        song_select: ([0xF3, 15], Ok(CodeIndexNumber::SystemCommon2Bytes)),
        tune_request: ([0xF6], Ok(CodeIndexNumber::SystemCommon1Byte)),
        timing_clock: ([0xF8], Ok(CodeIndexNumber::SingleByte)),
        tick: ([0xF9], Ok(CodeIndexNumber::SingleByte)),
        start: ([0xFA], Ok(CodeIndexNumber::SingleByte)),
        continue_: ([0xFB], Ok(CodeIndexNumber::SingleByte)),
        stop: ([0xFC], Ok(CodeIndexNumber::SingleByte)),
        active_sensing: ([0xFE], Ok(CodeIndexNumber::SingleByte)),
        system_reset: ([0xFF], Ok(CodeIndexNumber::SingleByte)),
        sysex_starts: ([0xF0, 1, 2], Ok(CodeIndexNumber::SysexStartsOrContinues)),
        sysex_starts_1byte: ([0xF0], Err(UsbMidiEventPacketError::InvalidPayloadSize)),
        sysex_starts_2bytes: ([0xF0, 1], Err(UsbMidiEventPacketError::InvalidPayloadSize)),
        sysex_continues_1byte: ([1], Ok(CodeIndexNumber::SingleByte)),
        sysex_continues_2bytes: ([1, 2], Err(UsbMidiEventPacketError::InvalidPayloadSize)),
        sysex_continues_3bytes: ([1, 2, 3], Ok(CodeIndexNumber::SysexStartsOrContinues)),
        sysex_ends_1byte: ([0xF7], Ok(CodeIndexNumber::SystemCommon1Byte)),
        sysex_ends_2bytes: ([1, 0xF7], Ok(CodeIndexNumber::SysexEnds2Bytes)),
        sysex_ends_3bytes: ([1, 2, 0xF7], Ok(CodeIndexNumber::SysexEnds3Bytes)),
        sysex_2bytes: ([0xF0, 0xF7], Ok(CodeIndexNumber::SysexEnds2Bytes)),
        sysex_3bytes: ([0xF0, 1, 0xF7], Ok(CodeIndexNumber::SysexEnds3Bytes)),
        undefined_f4: ([0xF4], Err(UsbMidiEventPacketError::InvalidPayloadStatus)),
        undefined_f5: ([0xF5], Err(UsbMidiEventPacketError::InvalidPayloadStatus)),
        empty: ([], Err(UsbMidiEventPacketError::EmptyPayload)),
    }
}