melrōse musical expression player

package io import ( "bufio" "io" "log" ) const ( noteoff byte = 0b10000000 noteon byte = 0b10010000 command_mask byte = 0b11110000 iscommand_mask byte = 0b10000000 channel_mask byte = 0b00001111 controlchange byte = 0xB0 // 10110000 , 176 ) type Message struct { command byte channel byte parameter1 byte parameter2 byte } var noMessage = Message{} func WriteMessage(status int64, data1 int64, data2 int64, w io.Writer) error { data := []byte{byte(status & 0xFF), byte(data1 & 0xFF), byte(data2 & 0xFF)} _, err := w.Write(data) return err } func ReadMessage(r *bufio.Reader) (Message, error) { for { b, err := r.ReadByte() if err != nil { return noMessage, err } switch b & command_mask { case noteon: note, err := r.ReadByte() if err != nil { return noMessage, err } velocity, err := r.ReadByte() if err != nil { return noMessage, err } return Message{command: noteon, channel: b & channel_mask, parameter1: note, parameter2: velocity}, nil case noteoff: note, err := r.ReadByte() if err != nil { return noMessage, err } velocity, err := r.ReadByte() if err != nil { return noMessage, err } return Message{command: noteoff, channel: b & channel_mask, parameter1: note, parameter2: velocity}, nil case controlchange: p1, err := r.ReadByte() if err != nil { return noMessage, err } p2, err := r.ReadByte() if err != nil { return noMessage, err } return Message{command: controlchange, parameter1: p1, parameter2: p2}, nil default: log.Printf("unknown command: %b (%d)\n", b, b) // consume data bytes for seenCommand := false; !seenCommand; { data, err := r.ReadByte() if err != nil { return noMessage, err } if data&iscommand_mask == iscommand_mask { r.UnreadByte() break } } } } }