Compiles MML to MIDI

midimck.rb

require_relative 'midifile'

TicksPerQuarter = 32
NoteOffsets = { 'c' => 0, 'd' => 2, 'e' => 4, 'f' => 5, 'g' => 7, 'a' => 9, 'b' => 11 }

class Track
	attr_reader :delay, :octave, :note, :velocity, :bytes, :default_delay
	attr_writer :delay, :octave, :note, :velocity, :bytes, :default_delay
	def initialize()
		@delay = 0
		@octave = 5
		@note = nil
		@velocity = 0x40
		@bytes = []
		@default_delay = TicksPerQuarter
	end
end


def error(msg)
	puts msg
	exit
end

def add(arr)
	arr.each { |byte| $midi_bytes << byte }
end

def track_add(arr)
	arr.each { |byte| $current_track.bytes << byte }
end

def parse_line(line)
	i = 0
	while i < line.length
		if line[i] =~ /[ABCDEFGHIJKLMNOPQRSTUVWXYZ]/
			if not $tracks.has_key? line[i]
				$tracks[line[i]] = Track.new()
			end
			$current_track = $tracks[line[i]]
			i += 1
		elsif line[i] == 'l'
			i += 1
			if line[i...line.length] =~ /^(\d+)/
				$current_track.default_delay = TicksPerQuarter * 4 / $1.to_i
				i += $1.length
			end
		elsif line[i] =~ /[abcdefg]/
			note_val = $current_track.octave * 12 + NoteOffsets[line[i]]
			i += 1
			if line[i] == '+'
				note_val += 1
				i += 1
			elsif line[i] == '-'
				note_val -= 1
				i += 1
			end
			if $current_track.note != nil
				track_add midi_event($current_track.delay, NoteOff, 0, $current_track.note, 0x40)
				track_add midi_event(0, NoteOn, 0, note_val, $current_track.velocity)
			else
				track_add midi_event($current_track.delay, NoteOn, 0, note_val, $current_track.velocity)
			end
			$current_track.note = note_val
			if line[i...line.length] =~ /^(\d+)/
				$current_track.delay = TicksPerQuarter * 4 / $1.to_i
				i += $1.length
			else
				$current_track.delay = $current_track.default_delay
			end
			dot_count = 0
			delay = $current_track.delay
			while line[i] == '.'
				dot_count += 1
				$current_track.delay += delay / (2 ** dot_count)
				i += 1
			end
		elsif line[i] == '<'
			$current_track.octave -= 1
			i += 1
		elsif line[i] == '>'
			$current_track.octave += 1
			i += 1
		elsif line[i] == 'o'
			i += 1
			if line[i...line.length] =~ /^(\d+)/
				$current_track.octave = $1.to_i
				i += $1.length
			end
		elsif line[i] == 'v'
			i += 1
			if line[i...line.length] =~ /^(\d+)/
				$current_track.velocity = $1.to_i
				i += $1.length
			end
		elsif line[i] == 'r'
			i += 1
			track_add midi_event($current_track.delay, NoteOff, 0, $current_track.note, 0x40)
			$current_track.note = nil
			if line[i...line.length] =~ /^(\d+)/
				$current_track.delay = TicksPerQuarter * 4 / $1.to_i
				i += $1.length
			else
				$current_track.delay = $current_track.default_delay
			end
			delay = $current_track.delay
			dot_count = 0
			while line[i] == '.'
				dot_count += 1
				$current_track.delay += delay / (2 ** dot_count)
				i += 1
			end
		elsif line[i] == 's' or line[i] == 'w'
			i += 1
			delay = $current_track.default_delay
			if line[i...line.length] =~ /^(\d+)/
				delay = TicksPerQuarter * 4 / $1.to_i
				i += $1.length
			end
			$current_track.delay += delay
			dot_count = 0
			while line[i] == '.'
				dot_count += 1
				$current_track.delay += delay / (2 ** dot_count)
				i += 1
			end
		elsif line[i...line.length] =~ /^@(\d+)/
			track_add midi_event($current_track.delay, ProgramChange, 0, $1.to_i)
			$current_track.delay = 0
			i += $1.length
		elsif line[i] == 't'
			i += 1
			if line[i...line.length] =~ /^(\d+)/
				microseconds = 1000000 / ($1.to_i / 60)
				arr = int_to_bytes(microseconds, 3)
				track_add midi_meta_event($current_track.delay, SetTempo, 03, *arr)
				$current_track.delay = 0
				i += $1.length
			end
		else
			i += 1
		end
	end
end

ARGV.each do |filename|
	mml_text = ''
	File.open(filename, 'r') do |file|
		mml_text = file.read()
	end

	$midi_bytes = []
	$tracks = {}
	$tracks['A'] = Track.new()
	$current_track = $tracks['A']

	mml_text.each_line do |line|
		if line =~ /^#TITLE +(.+)$/
			data = [ $1.bytes.length ] 
			$1.each_byte { |byte| data << byte }
			track_add midi_meta_event(0, TrackName, *data)
		else
			parse_line(line)
		end
	end

	add header(MultipleTracksSync, $tracks.length, TicksPerQuarter)
	for track in $tracks.values
		$current_track = track
		track_add midi_meta_event(0, EndTrack, 0)
		add track_header(track.bytes.length)
		add track.bytes
	end

	str = ''
	$midi_bytes.each { |byte| str += byte.chr }
	
	File.open(filename + '.mid', 'w') do |file|
		file.write(str)
	end
end