#MIDI

#Features

• Parse MThd / MTrk chunks into strongly-typed structures (MidiFile, Track, Event)
• Support for channel voice messages, meta events, SysEx, and common realtime messages
• Proper handling of variable-length quantities & running status (both parse & serialize)
• Serialize in‑memory structures back to a valid .mid byte stream
• Human‑readable printing (all core types implement Show)

#Installation

moon add CAIMEOX/midi

#Data Model

MidiFile { format: UInt16, division: UInt16, tracks: Array[Track] }
Track    { events: Array[Event] }
Event =>
  NoteOn(delta, channel, note, velocity)
| NoteOff(delta, channel, note, velocity)
| ControlChange(delta, channel, controller, value)
| ProgramChange(delta, channel, program)
| Aftertouch(delta, channel, value)
| PolyTouch(delta, channel, note, value)
| PitchWheel(delta, channel, pitch)          // signed 14-bit centered at 0
| Tempo(delta~ : UInt, microseconds~ : UInt)  // 0x51, in microseconds
| TimeSignature(delta~ : UInt, numerator~ : Byte, denominator~ : Byte, clocks_per_beat~ : Byte, thirty_seconds_per_quarter~ : Byte)  // 0x58, denominator is log(2)D
| KeySignature(delta~ : UInt, sf~ : Byte, mi~ : Byte)  // 0x59, sharp/flat and major/minor
| Meta(delta, meta_type, data[])             // raw meta payload
| SysEx(delta, data[])                       // payload (without trailing F7)
| Clock | Start | Continue | Stop | ActiveSensing | Reset

#Parsing

pub fn parse(bytes: Bytes) -> MidiFile raise ParseError

• Validates header chunk tag & size (MThd, size 6)
• Reads declared number of tracks
• Enforces track byte length boundaries
• Handles running status (channel messages may omit repeated status byte)

#Possible Errors (ParseError)

• InvalidHeader
• InvalidTrack
• UnexpectedEOF
• UnknownEventType
• InvalidData(String)

#Serialization

pub fn serialize(file: MidiFile) -> Bytes

• Emits canonical header (MThd, size 6)
• Encodes delta times as variable-length quantities
• Reuses running status for size optimization
• Restores 14-bit pitch wheel (adds 8192 offset internally)
• Writes SysEx with starting F0, length, payload, terminating F7

#Quick Usage Examples

#Parse & Inspect

fn demo(bytes: Bytes) raise @midi.ParseError {
  let mf = @midi.parse(bytes)
  println(mf.to_string()) // Uses Show impl to pretty print
}

#Roadmap Ideas

• Tick-to-time utilities
• Event builder DSL
• Track manipulation helpers (merge, filter, quantize)
• Event iteration utilities (by type, by channel, by time range)

#Contributing

#License