samples: add Python 3 sample script for ALSARawmidi

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

diff --git a/samples/rawmidi b/samples/rawmidi
new file mode 100755 (executable)
index 0000000..53c6bfe
--- /dev/null
+++ b/samples/rawmidi
@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+
+import gi
+gi.require_version('GLib', '2.0')
+gi.require_version('ALSACtl', '0.0')
+gi.require_version('ALSARawmidi', '0.0')
+from gi.repository import GLib, ALSACtl, ALSARawmidi
+
+from sys import exit
+from signal import SIGINT
+
+# Open ALSA Rawmidi chracter device in which a pair of input/output substreams
+# is available in the same subdevice ID.
+for card_id in ALSACtl.get_card_id_list():
+    for device_id in ALSARawmidi.get_device_id_list(card_id):
+        outputs = ALSARawmidi.get_subdevice_id_list(card_id, device_id,
+                                          ALSARawmidi.StreamDirection.OUTPUT)
+        inputs = ALSARawmidi.get_subdevice_id_list(card_id, device_id,
+                                          ALSARawmidi.StreamDirection.OUTPUT)
+        for subdevice_id in outputs:
+            if subdevice_id in inputs:
+                pair = ALSARawmidi.StreamPair.new()
+                modes = (ALSARawmidi.StreamPairInfoFlag.OUTPUT |
+                         ALSARawmidi.StreamPairInfoFlag.INPUT)
+                pair.open(card_id, device_id, subdevice_id, modes, 0)
+                break
+        else:
+            continue
+        break
+    else:
+        continue
+    break
+else:
+    print('ALSA Rawmidi devices not found.')
+    exit(1)
+
+# Retrieve the information of substream for both directions.
+for direction in (ALSARawmidi.StreamDirection.OUTPUT,
+                  ALSARawmidi.StreamDirection.INPUT):
+    info = pair.get_substream_info(direction)
+    print('The information of {} substream:'.format(direction.value_nick))
+    print('  direction:', info.get_property('direction').value_nick)
+    for prop in ('device-id', 'subdevice-id', 'card-id', 'id', 'name',
+                 'subdevice-name', 'subdevices-count', 'subdevices-avail'):
+        print('  {}: {}'.format(prop, info.get_property(prop)))
+    print('  flags:', info.get_property('flags').value_nicks)
+
+# Configure the substream for both directions.
+params = ALSARawmidi.SubstreamParams.new()
+for direction in (ALSARawmidi.StreamDirection.OUTPUT,
+                  ALSARawmidi.StreamDirection.INPUT):
+    params.set_property('buffer-size', 1024)
+    params.set_property('avail-min', 1)
+    params.set_property('active-sensing', False)
+    pair.set_substream_params(direction, params)
+    print('The parameter of {} substream.'.format(direction.value_nick))
+    for prop in ('buffer-size', 'avail-min', 'active-sensing'):
+        print('  {}: {}'.format(prop, params.get_property(prop)))
+
+# Register event handler.
+def handle_messages(pair):
+    print('Event:')
+    status = ALSARawmidi.SubstreamStatus.new()
+
+    status = pair.get_substream_status(ALSARawmidi.StreamDirection.INPUT, status)
+    avail = status.get_property('avail')
+    buf = pair.read_from_substream([0] * avail)
+    print('  {} bytes read.'.format(len(buf)))
+
+    status = pair.get_substream_status(ALSARawmidi.StreamDirection.OUTPUT, status)
+    avail = status.get_property('avail')
+    if avail < len(buf):
+        buf = buf[:avail]
+    pair.write_to_substream(buf)
+    print('  {} bytes written.'.format(len(buf)))
+pair.connect('handle-messages', handle_messages)
+
+# Create event dispatcher.
+dispatcher = GLib.MainLoop.new(None, False)
+src = pair.create_source()
+src.attach(dispatcher.get_context())
+
+# Register UNIX signal handler.
+def handle_unix_signal(dispatcher):
+    dispatcher.quit()
+GLib.unix_signal_add(GLib.PRIORITY_DEFAULT, SIGINT,
+                     handle_unix_signal, dispatcher)
+
+# Start to dispatch events.
+dispatcher.run()
+
+# Clean intermediate buffers.
+pair.drain_substream(ALSARawmidi.StreamDirection.INPUT)
+pair.drain_substream(ALSARawmidi.StreamDirection.OUTPUT)