Add rewrite of midi.c in python

Work was done in 2012, and came from here:
    https://codereview.appspot.com/7016046/

diff --git a/python/midi.py b/python/midi.py
new file mode 100644 (file)
index 0000000..45c2553
--- /dev/null
+++ b/python/midi.py
@@ -0,0 +1,199 @@
+# This file is part of LilyPond, the GNU music typesetter.
+#
+# Copyright (C) 2001--2012 Han-Wen Nienhuys <hanwen@xs4all.nl>
+#           Jan Nieuwenhuizen <janneke@gnu.org>
+#
+#
+# LilyPond is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# LilyPond is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with LilyPond.  If not, see <http://www.gnu.org/licenses/>.
+
+# import midi
+# s = open ("s.midi").read ()
+# midi.parse_track (s)
+# midi.parse (s)
+#
+#
+# returns a MIDI file as the tuple
+#
+#  ((format, division), TRACKLIST)          # division (>0) = TPQN*4
+#                                           # or (<0) TBD
+#
+# each track is an EVENTLIST, where EVENT is
+#
+#   (time, (type, ARG1, [ARG2]))            # time = cumulative delta time
+                                            # MIDI event: 
+                                            #   type = MIDI status+channel >= x80
+                                            # META-event  = xFF:
+                                            #   type = meta-event type <= x7F
+                                            #   ARG1 = length
+                                            #   ARG2 = data
+
+import array
+import struct
+
+class error (Exception): pass
+
+# class warning (Exception): pass
+
+def _add_constants ():
+    channelVoiceMessages = (
+        (0x80, "NOTE_OFF"),
+        (0x90, "NOTE_ON"),
+        (0xA0, "POLYPHONIC_KEY_PRESSURE"),
+        (0xB0, "CONTROLLER_CHANGE"),
+        (0xC0, "PROGRAM_CHANGE"),
+        (0xD0, "CHANNEL_KEY_PRESSURE"),
+        (0xE0, "PITCH_BEND"),
+    )
+    channelModeMessages = (
+        (0x78, "ALL_SOUND_OFF"),
+        (0x79, "RESET_ALL_CONTROLLERS"),
+        (0x7A, "LOCAL_CONTROL"),
+        (0x7B, "ALL_NOTES_OFF"),
+        (0x7C, "OMNI_MODE_OFF"),
+        (0x7D, "OMNI_MODE_ON"),
+        (0x7E, "MONO_MODE_ON"),
+        (0x7F, "POLY_MODE_ON"),
+    )
+    metaEvents = (
+        (0x00, "SEQUENCE_NUMBER"),
+        (0x01, "TEXT_EVENT"),
+        (0x02, "COPYRIGHT_NOTICE"),
+        (0x03, "SEQUENCE_TRACK_NAME"),
+        (0x04, "INSTRUMENT_NAME"),
+        (0x05, "LYRIC"),        #renamed LYRIC_DISPLAY MIDI RP-26
+        (0x06, "MARKER"),
+        (0x07, "CUE_POINT"),
+        (0x08, "PROGRAM_NAME"), #added MIDI RP-19
+        (0X09, "DEVICE_NAME"),  #added MIDI RP-19 
+        (0x20, "MIDI_CHANNEL_PREFIX"),
+        (0x21, "MIDI_PORT"),
+        (0x2F, "END_OF_TRACK"),
+        (0x51, "SET_TEMPO"),
+        (0x54, "SMTPE_OFFSET"),
+        (0x58, "TIME_SIGNATURE"),
+        (0x59, "KEY_SIGNATURE"),
+        (0x60, "XMF_PATCH_TYPE_PREFIX"),    #added MIDI RP-32
+        (0x7F, "SEQUENCER_SPECIFIC_META_EVENT"),
+        (0xFF, "META_EVENT"),
+    )
+    globals().update((desc, msg) for msg, desc in
+                       channelVoiceMessages + channelModeMessages + metaEvents)
+
+_add_constants ()
+
+def _get_variable_length_number (nextbyte, getbyte):
+    sum = 0
+    while nextbyte >= 0x80:
+        sum = (sum + (nextbyte & 0x7F)) << 7
+        nextbyte = getbyte()
+    return sum + nextbyte
+
+def _first_command_is_repeat(status, nextbyte, getbyte):
+    raise error('the first midi command in the track is a repeat')
+
+def _read_two_bytes (status, nextbyte, getbyte):
+    return status, nextbyte
+
+def _read_three_bytes (status, nextbyte, getbyte):
+    return status, nextbyte, getbyte()
+
+def _read_string (nextbyte, getbyte):
+    length = _get_variable_length_number (nextbyte, getbyte)
+    return ''.join(chr(getbyte()) for i in xrange(length))
+
+def _read_f0_byte (status, nextbyte, getbyte):
+    if status == 0xff:
+        return status, nextbyte, _read_string(getbyte(), getbyte)
+    return status, _read_string(nextbyte, getbyte)
+
+_read_midi_event = (
+    _first_command_is_repeat,  #  0
+    None,  # 10
+    None,  # 20
+    None,  # 30
+    None,  # 40
+    None,  # 50
+    None,  # 60 data entry???
+    None,  # 70 all notes off???
+    _read_three_bytes, # 80 note off
+    _read_three_bytes, # 90 note on
+    _read_three_bytes, # a0 poly aftertouch
+    _read_three_bytes, # b0 control
+    _read_two_bytes,  # c0 prog change
+    _read_two_bytes, # d0 ch aftertouch
+    _read_three_bytes, # e0 pitchwheel range
+    _read_f0_byte,   # f0
+)
+
+def _parse_track_body (data, clocks_max):
+    # This seems to be the fastest way of getting bytes in order as integers.
+    dataiter = iter(array.array('B', data))
+    getbyte = dataiter.next
+
+    time = 0
+    status = 0
+    try:
+        for nextbyte in dataiter:
+            time += _get_variable_length_number (nextbyte, getbyte)
+            if clocks_max and time > clocks_max:
+                break
+            nextbyte = getbyte()
+            if nextbyte >= 0x80:
+                status = nextbyte
+                nextbyte = getbyte()
+            yield time, _read_midi_event[status >> 4] (status, nextbyte, getbyte)
+    except StopIteration:
+        # If the track ended just before the start of an event, the for loop
+        # will exit normally. If it ends anywhere else, we end up here.
+        print len(list(dataiter))
+        raise error('a track ended in the middle of a MIDI command')
+
+def _parse_hunk (data, pos, type, magic):
+    if data[pos:pos+4] != magic:
+        raise error ('expected %r, got %r' % (magic, data[pos:pos+4]))
+    try:
+        length, = struct.unpack ('>I', data[pos+4:pos+8])
+    except struct.error:
+        raise error ('the %s header is truncated (may be an incomplete download)' % type)
+    endpos = pos + 8 + length
+    data = data[pos+8:endpos]
+    if len(data) != length:
+        raise error('the %s is truncated (may be an incomplete download)' % type)
+    return data, endpos
+
+def _parse_tracks (midi, pos, num_tracks, clocks_max):
+    if num_tracks > 256:
+        raise error('too many tracks: %d' % num_tracks)
+    for i in xrange(num_tracks):
+        trackdata, pos = _parse_hunk (midi, pos, 'track', 'MTrk')
+        yield list (_parse_track_body (trackdata, clocks_max))
+    # if pos < len(midi):
+    #     warn
+
+def parse_track (track, clocks_max=None):
+    track_body, end = _parse_hunk (track, 0, 'track', 'MTrk')
+    # if end < len(track):
+    #     warn
+    return list (_parse_track_body (track_body, clocks_max))
+
+def parse (midi, clocks_max=None):
+    header, first_track_pos = _parse_hunk(midi, 0, 'file', 'MThd')
+    try:
+        format, num_tracks, division = struct.unpack ('>3H', header[:6])
+    except struct.error:
+        raise error('the file header is too short')
+#  if division < 0:
+#    raise error ('cannot handle non-metrical time')
+    tracks = list (_parse_tracks (midi, first_track_pos, num_tracks, clocks_max))
+    return (format, division*4), tracks