/
midi.go
753 lines (576 loc) · 15.7 KB
/
midi.go
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// Copyright 2012 Joe Wass. All rights reserved.
// Use of this source code is governed by the MIT license
// which can be found in the LICENSE file.
// MIDI package
// A package for reading Standard Midi Files, written in Go.
// Joe Wass 2012
// joe@afandian.com
/*
* The main file.
* This contains the lexer, which does the job of scanning through the file.
*/
package midi
import (
"io"
)
// State of the MidiLexerCallback.
const (
// At the start of the MIDI file.
// Expect SMF Header chunk.
ExpectHeader = iota
// Expect a chunk. Any kind of chunk. Except MThd.
// But really, anything other than MTrk would be weird.
ExpectChunk = iota
// We're in a Track, expect a track event.
ExpectTrackEvent = iota
// This has to happen sooner or later.
Done = iota
)
// MidiLexer is a Standard Midi File Lexer.
// Pass this a ReadSeeker to a MIDI file and a callback that conforms to MidiLexerCallback
// and it'll run over the file, calling events on the callback.
type MidiLexer struct {
callback MidiLexerCallback
input io.ReadSeeker
// State of the parser, as per the above constants.
state int
// The location of the next chunk header that we expect to find as an offset from
// most recent Chunk header.
nextChunkHeader int64
}
// Construct a new MidiLexer
func NewMidiLexer(input io.ReadSeeker, callback MidiLexerCallback) *MidiLexer {
return &MidiLexer{callback: callback, input: input, state: ExpectHeader}
}
// Lex starts the MidiLexer running.
func (lexer *MidiLexer) Lex() error {
if lexer.callback == nil {
return NoCallback
}
if lexer.input == nil {
return NoReadSeeker
}
var finished bool = false
var err error
for {
finished, err = lexer.next()
if err != nil {
return err
}
if finished == true {
return nil
}
}
return nil
}
// next lexes the next item, calling appropriate callbacks.
// Finished only set true when finished correctly.
func (lexer *MidiLexer) next() (finished bool, err error) {
// Default for return values.
err = nil
finished = false
// The position in the file before the next lexing event happens.
// Useful in some cases
var currentPosition int64
currentPosition, err = lexer.input.Seek(0, 1)
if err != nil {
return
}
// See comments for state values above.
switch lexer.state {
case ExpectHeader:
{
//fmt.Println("ExpectHeader")
var chunkHeader ChunkHeader
chunkHeader, err = parseChunkHeader(lexer.input)
if chunkHeader.ChunkType != "MThd" {
err = ExpectedMthd
//fmt.Println("ChunkHeader error ", err)
return
}
var header HeaderData
header, err = parseHeaderData(lexer.input)
if err != nil {
//fmt.Println("HeaderData error ", err)
return
}
lexer.callback.Began()
lexer.callback.Header(header)
lexer.state = ExpectChunk
return
}
case ExpectChunk:
{
//fmt.Println("ExpectChunk")
var chunkHeader ChunkHeader
chunkHeader, err = parseChunkHeader(lexer.input)
//fmt.Println("Got chunk header", chunkHeader)
if err != nil {
// If we expect a chunk and we hit the end of the file, that's not so unexpected after all.
// The file has to end some time, and this is the correct boundary upon which to end it.
if err == UnexpectedEndOfFile {
lexer.state = Done
// TODO TEST
lexer.callback.Finished()
finished = true
err = nil
return
}
//fmt.Println("Chunk header error ", err)
return
}
lexer.callback.Track(chunkHeader)
lexer.nextChunkHeader = int64(chunkHeader.Length) + currentPosition
// If the header is of an unknown type, skip over it.
if chunkHeader.ChunkType != "MTrk" {
lexer.input.Seek(lexer.nextChunkHeader, 1)
// Then we expect another chunk.
lexer.state = ExpectChunk
lexer.nextChunkHeader = 0
} else {
// We have a MTrk
lexer.state = ExpectTrackEvent
}
return
}
case ExpectTrackEvent:
{
//fmt.Println("ExpectTrackEvent")
// Removed because there is an event to say 'end of chunk'.
// TODO: investigate. Could put this back for error cases.
// // If we're at the end of the chunk, change the state.
// if lexer.nextChunkHeader != 0 {
// // The chunk should end exactly on the chunk boundary, really.
// if currentPosition == lexer.nextChunkHeader {
// lexer.state = ExpectChunk
// return false, nil
// } else if currentPosition > lexer.nextChunkHeader {
// //fmt.Println("Chunk end error ", err)
// return false, BadSizeChunk
// }
// }
// Time Delta
var time uint32
time, err = parseVarLength(lexer.input)
if err != nil {
//fmt.Println("Time delta error ", err)
return
}
// Message type, Message Channel
var mType, channel uint8
mType, channel, err = readStatusByte(lexer.input)
//fmt.Println("Track Event Type ", mType)
switch mType {
// NoteOff
case 0x8:
{
var pitch, velocity uint8
pitch, velocity, err = parseTwoUint7(lexer.input)
if err != nil {
//fmt.Println("NoteOff error ", err)
return
}
lexer.callback.NoteOff(channel, pitch, velocity, time)
}
// NoteOn
case 0x9:
{
var pitch, velocity uint8
pitch, velocity, err = parseTwoUint7(lexer.input)
if err != nil {
//fmt.Println("NoteOn error ", err)
return
}
lexer.callback.NoteOn(channel, pitch, velocity, time)
}
// Polyphonic Key Pressure
case 0xA:
{
var pitch, pressure uint8
pitch, pressure, err = parseTwoUint7(lexer.input)
if err != nil {
return
}
lexer.callback.PolyphonicAfterTouch(channel, pitch, pressure, time)
}
// Control Change or Channel Mode Message
case 0xB:
{
var controller, value uint8
controller, value, err = parseTwoUint7(lexer.input)
if err != nil {
return
}
// TODO split this into ChannelMode for values [120, 127]?
// TODO implement separate callbacks for each type of:
// - All sound off
// - Reset all controllers
// - Local control
// - All notes off
// Only if required. http://www.midi.org/techspecs/midimessages.php
// TODO TEST
lexer.callback.ControlChange(channel, controller, value, time)
return
}
// Program Change
case 0xC:
{
var program uint8
program, err = parseUint7(lexer.input)
if err != nil {
return
}
lexer.callback.ProgramChange(channel, program, time)
return
}
// Channel Pressure
case 0xD:
{
var value uint8
value, err = parseUint7(lexer.input)
if err != nil {
return
}
lexer.callback.ChannelAfterTouch(channel, value, time)
}
// Pitch Wheel
case 0xE:
{
// The value is a signed int (relative to centre), and absoluteValue is the actual value in the file.
var value int16
var absoluteValue uint16
value, absoluteValue, err = parsePitchWheelValue(lexer.input)
if err != nil {
return
}
lexer.callback.PitchWheel(channel, value, absoluteValue, time)
}
// System Common and System Real-Time / Meta
case 0xF:
{
// The 4-bit nibble called 'channel' isn't actually the channel in this case.
switch channel {
// Meta-events
case 0xF:
{
var command uint8
command, err = parseUint8(lexer.input)
if err != nil {
return
}
//fmt.Println("SystemCommon/RealTime command:", command)
// TODO: If every one of these takes a length, then take this outside.
// Will make for more more robust unknown types.
switch command {
// Sequence number
case 0x00:
{
//fmt.Println("seq no")
var length uint8
length, err = parseUint8(lexer.input)
if err != nil {
return
}
// Zero length sequences allowed according to http://home.roadrunner.com/~jgglatt/tech/midifile/seq.htm
if length == 0 {
lexer.callback.SequenceNumber(channel, 0, false, time)
return
}
// Otherwise length will be 2 to hold the uint16.
var sequenceNumber uint16
sequenceNumber, err = parseUint16(lexer.input)
if err != nil {
return
}
lexer.callback.SequenceNumber(channel, sequenceNumber, true, time)
return
}
// Text event
case 0x01:
{
//fmt.Println("Text")
var text string
text, err = parseText(lexer.input)
//fmt.Println("text value", text, err)
if err != nil {
return
}
lexer.callback.Text(channel, text, time)
return
}
// Copyright text event
case 0x02:
{
//fmt.Println("Copyright")
var text string
text, err = parseText(lexer.input)
if err != nil {
return
}
lexer.callback.CopyrightText(channel, text, time)
return
}
// Sequence or track name
case 0x03:
{
var text string
text, err = parseText(lexer.input)
if err != nil {
return
}
lexer.callback.SequenceName(channel, text, time)
return
}
// Track instrument name
case 0x04:
{
var text string
text, err = parseText(lexer.input)
if err != nil {
return
}
lexer.callback.TrackInstrumentName(channel, text, time)
return
}
// Lyric text
case 0x05:
{
var text string
text, err = parseText(lexer.input)
if err != nil {
return
}
lexer.callback.LyricText(channel, text, time)
return
}
// Marker text
case 0x06:
{
var text string
text, err = parseText(lexer.input)
if err != nil {
return
}
lexer.callback.MarkerText(channel, text, time)
return
}
// Cue point text
case 0x07:
{
var text string
text, err = parseText(lexer.input)
if err != nil {
return
}
lexer.callback.CuePointText(channel, text, time)
return
}
case 0x20:
{
// Obsolete 'MIDI Channel'
//fmt.Println("MIDI Channel obsolete")
var length uint32
length, err = parseVarLength(lexer.input)
if err != nil {
return
}
if length != 1 {
err = UnexpectedEventLengthError{"Midi Channel Event expected length 1"}
return
}
// This is the channel value.
// Just forget this one.
_, err = parseUint8(lexer.input)
if err != nil {
return
}
}
case 0x21:
{
// Obsolete 'MIDI Port'
//fmt.Println("MIDI PORT obsolete")
var length uint32
length, err = parseVarLength(lexer.input)
if err != nil {
return
}
if length != 1 {
err = UnexpectedEventLengthError{"MIDI Port Event expected length 1"}
return
}
// This is the port value.
// Just forget this one.
_, err = parseUint8(lexer.input)
if err != nil {
return
}
}
// End of track
case 0x2F:
{
var length uint32
length, err = parseVarLength(lexer.input)
if err != nil {
return
}
if length != 0 {
err = UnexpectedEventLengthError{"EndOfTrack expected length 0"}
return
}
lexer.callback.EndOfTrack(channel, time)
// Expect the next chunk event.
lexer.state = ExpectChunk
return false, nil
}
// Set tempo
case 0x51:
{
// TODO TEST
var length uint32
length, err = parseVarLength(lexer.input)
if err != nil {
return
}
if length != 3 {
err = UnexpectedEventLengthError{"Tempo expected length 3"}
return
}
var microsecondsPerCrotchet uint32
microsecondsPerCrotchet, err = parseUint24(lexer.input)
if err != nil {
return
}
// Also beats per minute
var bpm uint32
bpm = 60000000 / microsecondsPerCrotchet
lexer.callback.Tempo(bpm, microsecondsPerCrotchet, time)
}
// Time signature
case 0x58:
{
var length uint32
length, err = parseVarLength(lexer.input)
if err != nil {
return
}
if length != 4 {
err = UnexpectedEventLengthError{"TimeSignature expected length 4"}
return
}
// TODO TEST
var numerator uint8
numerator, err = parseUint8(lexer.input)
if err != nil {
return
}
var denomenator uint8
denomenator, err = parseUint8(lexer.input)
if err != nil {
return
}
var clocksPerClick uint8
clocksPerClick, err = parseUint8(lexer.input)
if err != nil {
return
}
var demiSemiQuaverPerQuarter uint8
demiSemiQuaverPerQuarter, err = parseUint8(lexer.input)
if err != nil {
return
}
//fmt.Println("TimeSignature event", numerator, denomenator, clocksPerClick, demiSemiQuaverPerQuarter, time)
lexer.callback.TimeSignature(numerator, denomenator, clocksPerClick, demiSemiQuaverPerQuarter, time)
return false, nil
}
// Key signature
case 0x59:
{
// TODO TEST
var length uint32
var sharpsOrFlats int8
var mode uint8
length, err = parseVarLength(lexer.input)
if err != nil {
return
}
if length != 2 {
err = UnexpectedEventLengthError{"KeySignature expected length 2"}
return
}
// Signed int, positive is sharps, negative is flats.
sharpsOrFlats, err = parseInt8(lexer.input)
if err != nil {
return
}
// Mode is Major or Minor.
mode, err = parseUint8(lexer.input)
if err != nil {
return
}
key, resultMode := keySignatureFromSharpsOrFlats(sharpsOrFlats, mode)
lexer.callback.KeySignature(key, resultMode, sharpsOrFlats)
}
// Sequencer specific info
case 0x7F:
{
//fmt.Println("0x7F")
}
// Timing clock
case 0xF8:
{
//fmt.Println("0xF8")
}
// Start current sequence
case 0xFA:
{
//fmt.Println("0xFA")
}
// Continue stopped sequence where left off
case 0xFB:
{
//fmt.Println("0xFB")
}
// Stop sequence
case 0xFc:
{
//fmt.Println("0xFc")
}
default:
//fmt.Println("Unrecognised meta command", command)
}
}
default:
//fmt.Println("Unrecognised message type", mType)
}
//
}
// This covers all cases.
// Now we need to see if we're at the end of a Track Data chunk.
default:
{
var length uint32
length, err = parseVarLength(lexer.input)
if err != nil {
return
}
//fmt.Println("Type Unrecognised", mType, "length", length)
// Read length of chunk
for i := uint32(0); i < length; i++ {
_, err = parseUint8(lexer.input)
if err != nil {
return
}
}
}
}
}
case Done:
{
// The event that raised this will already have returned false to say it's stopped ticking.
// Just keep returning false.
finished = true
return
}
}
return
}