test: Add Python GATT client example

This patch introduces test/example-gatt-client which implements a simple
D-Bus client application for a remote Heart Rate service.

test/example-gatt-client

@@ -0,0 +1,218 @@
+#!/usr/bin/python
+
+import argparse
+import dbus
+import gobject
+import sys
+
+from dbus.mainloop.glib import DBusGMainLoop
+
+bus = None
+mainloop = None
+
+BLUEZ_SERVICE_NAME = 'org.bluez'
+DBUS_OM_IFACE =      'org.freedesktop.DBus.ObjectManager'
+DBUS_PROP_IFACE =    'org.freedesktop.DBus.Properties'
+
+GATT_SERVICE_IFACE = 'org.bluez.GattService1'
+GATT_CHRC_IFACE =    'org.bluez.GattCharacteristic1'
+
+HR_SVC_UUID =        '0000180d-0000-1000-8000-00805f9b34fb'
+HR_MSRMT_UUID =      '00002a37-0000-1000-8000-00805f9b34fb'
+BODY_SNSR_LOC_UUID = '00002a38-0000-1000-8000-00805f9b34fb'
+HR_CTRL_PT_UUID =    '00002a39-0000-1000-8000-00805f9b34fb'
+
+# The objects that we interact with.
+hr_service = None
+hr_msrmt_chrc = None
+body_snsr_loc_chrc = None
+hr_ctrl_pt_chrc = None
+
+
+def generic_error_cb(error):
+    print('D-Bus call failed: ' + str(error))
+    mainloop.quit()
+
+
+def body_sensor_val_to_str(val):
+    if val == 0:
+        return 'Other'
+    if val == 1:
+        return 'Chest'
+    if val == 2:
+        return 'Wrist'
+    if val == 3:
+        return 'Finger'
+    if val == 4:
+        return 'Hand'
+    if val == 5:
+        return 'Ear Lobe'
+    if val == 6:
+        return 'Foot'
+
+    return 'Reserved value'
+
+
+def sensor_contact_val_to_str(val):
+    if val == 0 or val == 1:
+        return 'not supported'
+    if val == 2:
+        return 'no contact detected'
+    if val == 3:
+        return 'contact detected'
+
+    return 'invalid value'
+
+
+def body_sensor_val_cb(value):
+    if len(value) != 1:
+        print('Invalid body sensor location value: ' + repr(value))
+        return
+
+    print('Body sensor location value: ' + body_sensor_val_to_str(value[0]))
+
+
+def hr_msrmt_start_notify_cb():
+    print('HR Measurement notifications enabled')
+
+
+def hr_msrmt_changed_cb(iface, changed_props, invalidated_props):
+    if iface != GATT_CHRC_IFACE:
+        return
+
+    if not len(changed_props):
+        return
+
+    value = changed_props.get('Value', None)
+    if not value:
+        return
+
+    print('New HR Measurement')
+
+    flags = value[0]
+    value_format = flags & 0x01
+    sc_status = (flags >> 1) & 0x03
+    ee_status = flags & 0x08
+
+    if value_format == 0x00:
+        hr_msrmt = value[1]
+        next_ind = 2
+    else:
+        hr_msrmt = value[1] | (value[2] << 8)
+        next_ind = 3
+
+    print('\tHR: ' + str(int(hr_msrmt)))
+    print('\tSensor Contact status: ' +
+          sensor_contact_val_to_str(sc_status))
+
+    if ee_status:
+        print('\tEnergy Expended: ' + str(int(value[next_ind])))
+
+
+def start_client():
+    # Read the Body Sensor Location value and print it asynchronously.
+    body_snsr_loc_chrc[0].ReadValue(reply_handler=body_sensor_val_cb,
+                                    error_handler=generic_error_cb,
+                                    dbus_interface=GATT_CHRC_IFACE)
+
+    # Listen to PropertiesChanged signals from the Heart Measurement
+    # Characteristic.
+    hr_msrmt_prop_iface = dbus.Interface(hr_msrmt_chrc[0], DBUS_PROP_IFACE)
+    hr_msrmt_prop_iface.connect_to_signal("PropertiesChanged",
+                                          hr_msrmt_changed_cb)
+
+    # Subscribe to Heart Rate Measurement notifications.
+    hr_msrmt_chrc[0].StartNotify(reply_handler=hr_msrmt_start_notify_cb,
+                                 error_handler=generic_error_cb,
+                                 dbus_interface=GATT_CHRC_IFACE)
+
+
+def process_chrc(chrc_path):
+    chrc = bus.get_object(BLUEZ_SERVICE_NAME, chrc_path)
+    chrc_props = chrc.GetAll(GATT_CHRC_IFACE,
+                             dbus_interface=DBUS_PROP_IFACE)
+
+    uuid = chrc_props['UUID']
+
+    if uuid == HR_MSRMT_UUID:
+        global hr_msrmt_chrc
+        hr_msrmt_chrc = (chrc, chrc_props)
+    elif uuid == BODY_SNSR_LOC_UUID:
+        global body_snsr_loc_chrc
+        body_snsr_loc_chrc = (chrc, chrc_props)
+    elif uuid == HR_CTRL_PT_UUID:
+        global hr_ctrl_pt_chrc
+        hr_ctrl_pt_chrc = (chrc, chrc_props)
+    else:
+        print('Unrecognized characteristic: ' + uuid)
+
+    return True
+
+
+def process_hr_service(service_path):
+    service = bus.get_object(BLUEZ_SERVICE_NAME, service_path)
+    service_props = service.GetAll(GATT_SERVICE_IFACE,
+                                   dbus_interface=DBUS_PROP_IFACE)
+
+    uuid = service_props['UUID']
+
+    if uuid != HR_SVC_UUID:
+        print('Service is not a Heart Rate Service: ' + uuid)
+        return False
+
+    # Process the characteristics.
+    chrc_paths = service_props['Characteristics']
+    for chrc_path in chrc_paths:
+        process_chrc(chrc_path)
+
+    global hr_service
+    hr_service = (service, service_props, service_path)
+
+    return True
+
+
+def interfaces_removed_cb(object_path, interfaces):
+    if not hr_service:
+        return
+
+    if object_path == hr_service[2]:
+        print('Service was removed')
+        mainloop.quit()
+
+
+def main():
+    # Prase the service path from the arguments.
+    parser = argparse.ArgumentParser(
+            description='D-Bus Heart Rate Service client example')
+    parser.add_argument('service_path', metavar='<service-path>',
+                        type=dbus.ObjectPath, nargs=1,
+                        help='GATT service object path')
+    args = parser.parse_args()
+    service_path = args.service_path[0]
+
+    # Set up the main loop.
+    DBusGMainLoop(set_as_default=True)
+    global bus
+    bus = dbus.SystemBus()
+    global mainloop
+    mainloop = gobject.MainLoop()
+
+    om = dbus.Interface(bus.get_object(BLUEZ_SERVICE_NAME, '/'), DBUS_OM_IFACE)
+    om.connect_to_signal('InterfacesRemoved', interfaces_removed_cb)
+
+    try:
+        if not process_hr_service(service_path):
+            sys.exit(1)
+    except dbus.DBusException as e:
+        print e.message
+        sys.exit(1)
+
+    print 'Heart Rate Service ready'
+
+    start_client()
+
+    mainloop.run()
+
+
+if __name__ == '__main__':
+    main()