Class: MIDI::IO::MIDIFile

Inherits:
Object
  • Object
show all
Defined in:
lib/midilib/io/midifile.rb

Overview

A MIDIFile parses a MIDI file and calls methods when it sees MIDI events. Most of the methods are stubs. To do anything interesting with the events, override these methods (those between the “The rest of these are NOPs by default” and “End of NOPs” comments).

See SeqReader for a subclass that uses these methods to create Event objects.

Direct Known Subclasses

SeqReader

Constant Summary collapse

MThd_BYTE_ARRAY =

“MThd”

[77, 84, 104, 100]
MTrk_BYTE_ARRAY =

“MTrk”

[77, 84, 114, 107]
NUM_DATA_BYTES =

This array is indexed by the high half of a status byte. Its value is either the number of bytes needed (1 or 2) for a channel message, or 0 if it’s not a channel message.

[
  0, 0, 0, 0, 0, 0, 0, 0, # 0x00 - 0x70
  2, 2, 2, 2, 1, 1, 2, 0  # 0x80 - 0xf0
]

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ MIDIFile

Returns a new instance of MIDIFile.



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# File 'lib/midilib/io/midifile.rb', line 29

def initialize
  @no_merge = false
  @skip_init = true
  @io = nil
  @bytes_to_be_read = 0
  @msg_buf = nil
end

Instance Attribute Details

#bytes_to_be_read ⇒ Object

Current time, from delta-time in MIDI file # Number of delta-time ticks so far # Counts number of bytes expected # true means continued sysex are not collapsed # true if initial garbage should be skipped



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# File 'lib/midilib/io/midifile.rb', line 24

def bytes_to_be_read
  @bytes_to_be_read
end

#curr_ticks ⇒ Object

Current time, from delta-time in MIDI file # Number of delta-time ticks so far # Counts number of bytes expected # true means continued sysex are not collapsed # true if initial garbage should be skipped



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# File 'lib/midilib/io/midifile.rb', line 24

def curr_ticks
  @curr_ticks
end

#no_merge ⇒ Object

Current time, from delta-time in MIDI file # Number of delta-time ticks so far # Counts number of bytes expected # true means continued sysex are not collapsed # true if initial garbage should be skipped



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# File 'lib/midilib/io/midifile.rb', line 24

def no_merge
  @no_merge
end

#raw_data ⇒ Object

Current time, from delta-time in MIDI file # Number of delta-time ticks so far # Counts number of bytes expected # true means continued sysex are not collapsed # true if initial garbage should be skipped



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# File 'lib/midilib/io/midifile.rb', line 24

def raw_data
  @raw_data
end

#raw_time_stamp_data ⇒ Object

Raw data info



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# File 'lib/midilib/io/midifile.rb', line 27

def raw_time_stamp_data
  @raw_time_stamp_data
end

#raw_var_num_data ⇒ Object

Current time, from delta-time in MIDI file # Number of delta-time ticks so far # Counts number of bytes expected # true means continued sysex are not collapsed # true if initial garbage should be skipped



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# File 'lib/midilib/io/midifile.rb', line 24

def raw_var_num_data
  @raw_var_num_data
end

#skip_init ⇒ Object

Current time, from delta-time in MIDI file # Number of delta-time ticks so far # Counts number of bytes expected # true means continued sysex are not collapsed # true if initial garbage should be skipped



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# File 'lib/midilib/io/midifile.rb', line 24

def skip_init
  @skip_init
end

#ticks_so_far ⇒ Object

Current time, from delta-time in MIDI file # Number of delta-time ticks so far # Counts number of bytes expected # true means continued sysex are not collapsed # true if initial garbage should be skipped



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# File 'lib/midilib/io/midifile.rb', line 24

def ticks_so_far
  @ticks_so_far
end

Instance Method Details

#arbitrary(msg) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 132

def arbitrary(msg)
end

#bad_byte(c) ⇒ Object

Handle an unexpected byte.



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# File 'lib/midilib/io/midifile.rb', line 268

def bad_byte(c)
  error(format('unexpected byte: 0x%02x', c))
end

#chan_message(running, status, c1, c2) ⇒ Object

Handle a channel message (note on, note off, etc.)



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# File 'lib/midilib/io/midifile.rb', line 309

def chan_message(running, status, c1, c2)
  @raw_data = []
  @raw_data << status unless running
  @raw_data << c1
  @raw_data << c2

  chan = status & 0x0f

  case (status & 0xf0)
  when NOTE_OFF
    note_off(chan, c1, c2)
  when NOTE_ON
    note_on(chan, c1, c2)
  when POLY_PRESSURE
    pressure(chan, c1, c2)
  when CONTROLLER
    controller(chan, c1, c2)
  when PITCH_BEND
    pitch_bend(chan, c1, c2)
  when PROGRAM_CHANGE
    program(chan, c1)
  when CHANNEL_PRESSURE
    chan_pressure(chan, c1)
  else
    error("illegal chan message 0x#{format('%02x', (status & 0xf0))}\n")
  end
end

#chan_pressure(chan, press) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 99

def chan_pressure(chan, press)
end

#controller(chan, control, value) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 90

def controller(chan, control, value)
end

#end_track ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 78

def end_track
end

#eot ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 117

def eot
end

#error(str) ⇒ Object

The default error handler.



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# File 'lib/midilib/io/midifile.rb', line 64

def error(str)
  loc = @io.tell - 1
  raise "#{self.class.name} error at byte #{loc} (0x#{'%02x' % loc}): #{str}"
end

#get_bytes(n) ⇒ Object

Return the next n bytes from @io as an array.



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# File 'lib/midilib/io/midifile.rb', line 57

def get_bytes(n)
  buf = []
  n.times { buf << getc }
  buf
end

#getc ⇒ Object

This default getc implementation tries to read a single byte from io and returns it as an integer.



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# File 'lib/midilib/io/midifile.rb', line 51

def getc
  @bytes_to_be_read -= 1
  @io.readbyte
end

#handle_arbitrary(msg) ⇒ Object

Copy message into raw data array, then call arbitrary().



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# File 'lib/midilib/io/midifile.rb', line 344

def handle_arbitrary(msg)
  @raw_data = msg.dup
  arbitrary(msg)
end

#handle_sysex(msg) ⇒ Object

Copy message into raw data array, then call sysex().



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# File 'lib/midilib/io/midifile.rb', line 338

def handle_sysex(msg)
  @raw_data = msg.dup
  sysex(msg)
end

#header(format, ntrks, division) ⇒ Object

MIDI header.



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# File 'lib/midilib/io/midifile.rb', line 72

def header(format, ntrks, division)
end

#key_signature(sharpflat, is_minor) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 129

def key_signature(sharpflat, is_minor)
end

#meta_event(type) ⇒ Object

Handle a meta event.



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# File 'lib/midilib/io/midifile.rb', line 273

def meta_event(type)
  m = msg # Copy of internal message buffer

  # Create raw data array
  @raw_data = []
  @raw_data << META_EVENT
  @raw_data << type
  @raw_data << @raw_var_num_data
  @raw_data << m
  @raw_data.flatten!

  case type
  when META_SEQ_NUM
    sequence_number((m[0] << 8) + m[1])
  when META_TEXT, META_COPYRIGHT, META_SEQ_NAME, META_INSTRUMENT,
       META_LYRIC, META_MARKER, META_CUE, 0x08, 0x09, 0x0a,
       0x0b, 0x0c, 0x0d, 0x0e, 0x0f
    text(type, m)
  when META_TRACK_END
    eot
  when META_SET_TEMPO
    tempo((m[0] << 16) + (m[1] << 8) + m[2])
  when META_SMPTE
    smpte(m[0], m[1], m[2], m[3], m[4])
  when META_TIME_SIG
    time_signature(m[0], m[1], m[2], m[3])
  when META_KEY_SIG
    key_signature(m[0], !(m[1] == 0))
  when META_SEQ_SPECIF
    sequencer_specific(type, m)
  else
    meta_misc(type, m)
  end
end

#meta_misc(type, msg) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 105

def meta_misc(type, msg)
end

#msg ⇒ Object

Return a copy of the internal message buffer.



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# File 'lib/midilib/io/midifile.rb', line 434

def msg
  @msg_buf.dup
end

#msg_add(c) ⇒ Object

Add a byte to the current message buffer.



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# File 'lib/midilib/io/midifile.rb', line 416

def msg_add(c)
  @msg_buf << c
end

#msg_init ⇒ Object

Initialize the internal message buffer.



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# File 'lib/midilib/io/midifile.rb', line 429

def msg_init
  @msg_buf = []
end

#msg_read(n_bytes) ⇒ Object

Read and add a number of bytes to the message buffer. Return the last byte (so we can see if it’s an EOX or not).



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# File 'lib/midilib/io/midifile.rb', line 422

def msg_read(n_bytes)
  @msg_buf += get_bytes(n_bytes)
  @msg_buf.flatten!
  @msg_buf[-1]
end

#note_off(chan, note, vel) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 84

def note_off(chan, note, vel)
end

#note_on(chan, note, vel) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 81

def note_on(chan, note, vel)
end

#pitch_bend(chan, msb, lsb) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 93

def pitch_bend(chan, msb, lsb)
end

#pressure(chan, note, press) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 87

def pressure(chan, note, press)
end

#program(chan, program) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 96

def program(chan, program)
end

#read16 ⇒ Object

Read and return a sixteen bit value.



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# File 'lib/midilib/io/midifile.rb', line 350

def read16
  val = (getc << 8) + getc
  val = -(val & 0x7fff) if (val & 0x8000).nonzero?
  val
end

#read32 ⇒ Object

Read and return a 32-bit value.



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# File 'lib/midilib/io/midifile.rb', line 357

def read32
  val = (getc << 24) + (getc << 16) + (getc << 8) +
        getc
  val = -(val & 0x7fffffff) if (val & 0x80000000).nonzero?
  val
end

#read_from(io) ⇒ Object

The only public method. Each MIDI event in the file causes a method to be called.



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# File 'lib/midilib/io/midifile.rb', line 39

def read_from(io)
  error('must specify non-nil input stream') if io.nil?
  @io = io

  ntrks = read_header
  error('No tracks!') if ntrks <= 0

  ntrks.times { read_track }
end

#read_header ⇒ Object

Read a header chunk.



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# File 'lib/midilib/io/midifile.rb', line 166

def read_header
  @bytes_to_be_read = 0
  read_mt_header_string(MThd_BYTE_ARRAY, @skip_init) # "MThd"

  @bytes_to_be_read = read32
  format = read16
  ntrks = read16
  division = read16

  header(format, ntrks, division)

  # Flush any extra stuff, in case the length of the header is not 6
  if @bytes_to_be_read > 0
    get_bytes(@bytes_to_be_read)
    @bytes_to_be_read = 0
  end

  ntrks
end

#read_mt_header_string(bytes, skip) ⇒ Object

Read through ‘MThd’ or ‘MTrk’ header string. If skip is true, attempt to skip initial trash. If there is an error, #error is called.



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# File 'lib/midilib/io/midifile.rb', line 139

def read_mt_header_string(bytes, skip)
  b = []
  bytes_to_read = 4
  while true
    data = get_bytes(bytes_to_read)
    b += data
    error("unexpected EOF while trying to read header string #{s}") if b.length < 4

    # See if we found the bytes we're looking for
    return if b == bytes

    if skip # Try again with the next char
      i = b[1..-1].index(bytes[0])
      if i.nil?
        b = []
        bytes_to_read = 4
      else
        b = b[i..-1]
        bytes_to_read = 4 - i
      end
    else
      error("header string #{bytes.collect { |b| b.chr }.join} not found")
    end
  end
end

#read_track ⇒ Object

Read a track chunk.



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# File 'lib/midilib/io/midifile.rb', line 187

def read_track
  c = c1 = type = needed = 0
  sysex_continue = false  # True if last msg was unfinished
  running = false         # True when running status used
  status = 0              # (Possibly running) status byte

  @bytes_to_be_read = 0
  read_mt_header_string(MTrk_BYTE_ARRAY, false)

  @bytes_to_be_read = read32
  @curr_ticks = @ticks_so_far = 0

  start_track

  while @bytes_to_be_read > 0
    @curr_ticks = read_var_len # Delta time
    @ticks_so_far += @curr_ticks

    # Copy raw var num data into raw time stamp data
    @raw_time_stamp_data = @raw_var_num_data.dup

    c = getc # Read first byte

    error("didn't find expected continuation of a sysex") if sysex_continue && c != EOX

    if (c & 0x80).zero? # Running status?
      error('unexpected running status') if status.zero?
      running = true
    else
      status = c
      running = false
    end

    needed = NUM_DATA_BYTES[(status >> 4) & 0x0f]

    if needed.nonzero? # i.e., is it a channel message?
      c1 = running ? c : (getc & 0x7f)

      # The "& 0x7f" here may seem unnecessary, but I've seen
      # "bad" MIDI files that had, for example, volume bytes
      # with the upper bit set. This code should not harm
      # proper data.
      chan_message(running, status, c1,
                   needed > 1 ? (getc & 0x7f) : 0)
      next
    end

    case c
    when META_EVENT       # Meta event
      type = getc
      msg_init
      msg_read(read_var_len)
      meta_event(type)
    when SYSEX            # Start of system exclusive
      msg_init
      msg_add(SYSEX)
      c = msg_read(read_var_len)

      if c == EOX || !@no_merge
        handle_sysex(msg)
      else
        sysex_continue = true
      end
    when EOX              # Sysex continuation or arbitrary stuff
      msg_init unless sysex_continue
      c = msg_read(read_var_len)

      if !sysex_continue
        handle_arbitrary(msg)
      elsif c == EOX
        handle_sysex(msg)
        sysex_continue = false
      end
    else
      bad_byte(c)
    end
  end
  end_track
end

#read_var_len ⇒ Object

Read a varlen value.



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# File 'lib/midilib/io/midifile.rb', line 365

def read_var_len
  @raw_var_num_data = []
  c = getc
  @raw_var_num_data << c
  val = c
  if (val & 0x80).nonzero?
    val &= 0x7f
    while true
      c = getc
      @raw_var_num_data << c
      val = (val << 7) + (c & 0x7f)
      break if (c & 0x80).zero?
    end
  end
  val
end

#sequence_number(num) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 111

def sequence_number(num)
end

#sequencer_specific(type, msg) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 108

def sequencer_specific(type, msg)
end

#smpte(hour, min, sec, frame, fract) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 123

def smpte(hour, min, sec, frame, fract)
end

#start_track(bytes_to_be_read) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 75

def start_track(bytes_to_be_read)
end

#sysex(msg) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 102

def sysex(msg)
end

#tempo(microsecs) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 126

def tempo(microsecs)
end

#text(type, msg) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 114

def text(type, msg)
end

#time_signature(numer, denom, clocks, qnotes) ⇒ Object 



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# File 'lib/midilib/io/midifile.rb', line 120

def time_signature(numer, denom, clocks, qnotes)
end

#write16(val) ⇒ Object

Write a sixteen-bit value.



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# File 'lib/midilib/io/midifile.rb', line 383

def write16(val)
  val = (-val) | 0x8000 if val < 0
  putc((val >> 8) & 0xff)
  putc(val & 0xff)
end

#write32(val) ⇒ Object

Write a 32-bit value.



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# File 'lib/midilib/io/midifile.rb', line 390

def write32(val)
  val = (-val) | 0x80000000 if val < 0
  putc((val >> 24) & 0xff)
  putc((val >> 16) & 0xff)
  putc((val >> 8) & 0xff)
  putc(val & 0xff)
end

#write_var_len(val) ⇒ Object

Write a variable length value.



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# File 'lib/midilib/io/midifile.rb', line 399

def write_var_len(val)
  if val.zero?
    putc(0)
    return
  end

  buf = []

  buf << (val & 0x7f)
  while (value >>= 7) > 0
    buf << (val & 0x7f) | 0x80
  end

  buf.reverse.each { |b| putc(b) }
end