bindings/python/bt2/bt2/component.py

   1 # The MIT License (MIT)
   2 #
   3 # Copyright (c) 2017 Philippe Proulx <pproulx@efficios.com>
   4 #
   5 # Permission is hereby granted, free of charge, to any person obtaining a copy
   6 # of this software and associated documentation files (the "Software"), to deal
   7 # in the Software without restriction, including without limitation the rights
   8 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   9 # copies of the Software, and to permit persons to whom the Software is
  10 # furnished to do so, subject to the following conditions:
  11 #
  12 # The above copyright notice and this permission notice shall be included in
  13 # all copies or substantial portions of the Software.
  14 #
  15 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21 # THE SOFTWARE.
  22
  23 from bt2 import native_bt, object, utils
  24 import bt2.message_iterator
  25 import collections.abc
  26 import bt2.values
  27 import traceback
  28 import bt2.port
  29 import sys
  30 import bt2
  31 import os
  32
  33
  34 _env_var = os.environ.get('BABELTRACE_PYTHON_BT2_NO_TRACEBACK')
  35 _NO_PRINT_TRACEBACK = _env_var == '1'
  36
  37
  38 # This class wraps a component class pointer. This component class could
  39 # have been created by Python code, but since we only have the pointer,
  40 # we can only wrap it in a generic way and lose the original Python
  41 # class.
  42 class _GenericComponentClass(object._Object):
  43     @property
  44     def name(self):
  45         name = native_bt.component_class_get_name(self._ptr)
  46         assert(name is not None)
  47         return name
  48
  49     @property
  50     def description(self):
  51         return native_bt.component_class_get_description(self._ptr)
  52
  53     @property
  54     def help(self):
  55         return native_bt.component_class_get_help(self._ptr)
  56
  57     def __eq__(self, other):
  58         if not isinstance(other, _GenericComponentClass):
  59             try:
  60                 if not issubclass(other, _UserComponent):
  61                     return False
  62             except TypeError:
  63                 return False
  64
  65         return self.addr == other.addr
  66
  67
  68 class _GenericSourceComponentClass(_GenericComponentClass):
  69     pass
  70
  71
  72 class _GenericFilterComponentClass(_GenericComponentClass):
  73     pass
  74
  75
  76 class _GenericSinkComponentClass(_GenericComponentClass):
  77     pass
  78
  79
  80 def _handle_component_status(status, gen_error_msg):
  81     if status == native_bt.COMPONENT_STATUS_END:
  82         raise bt2.Stop
  83     elif status == native_bt.COMPONENT_STATUS_AGAIN:
  84         raise bt2.TryAgain
  85     elif status == native_bt.COMPONENT_STATUS_UNSUPPORTED:
  86         raise bt2.UnsupportedFeature
  87     elif status == native_bt.COMPONENT_STATUS_REFUSE_PORT_CONNECTION:
  88         raise bt2.PortConnectionRefused
  89     elif status == native_bt.COMPONENT_STATUS_GRAPH_IS_CANCELED:
  90         raise bt2.GraphCanceled
  91     elif status < 0:
  92         raise bt2.Error(gen_error_msg)
  93
  94
  95 class _PortIterator(collections.abc.Iterator):
  96     def __init__(self, comp_ports):
  97         self._comp_ports = comp_ports
  98         self._at = 0
  99
 100     def __next__(self):
 101         if self._at == len(self._comp_ports):
 102             raise StopIteration
 103
 104         comp_ports = self._comp_ports
 105         comp_ptr = comp_ports._component._ptr
 106         port_ptr = comp_ports._get_port_at_index_fn(comp_ptr, self._at)
 107         assert(port_ptr)
 108
 109         if comp_ports._is_private:
 110             port_pub_ptr = native_bt.port_from_private(port_ptr)
 111             name = native_bt.port_get_name(port_pub_ptr)
 112             native_bt.put(port_pub_ptr)
 113         else:
 114             name = native_bt.port_get_name(port_ptr)
 115
 116         assert(name is not None)
 117         native_bt.put(port_ptr)
 118         self._at += 1
 119         return name
 120
 121
 122 class _ComponentPorts(collections.abc.Mapping):
 123     def __init__(self, is_private, component,
 124                  get_port_by_name_fn, get_port_at_index_fn,
 125                  get_port_count_fn):
 126         self._is_private = is_private
 127         self._component = component
 128         self._get_port_by_name_fn = get_port_by_name_fn
 129         self._get_port_at_index_fn = get_port_at_index_fn
 130         self._get_port_count_fn = get_port_count_fn
 131
 132     def __getitem__(self, key):
 133         utils._check_str(key)
 134         port_ptr = self._get_port_by_name_fn(self._component._ptr, key)
 135
 136         if port_ptr is None:
 137             raise KeyError(key)
 138
 139         if self._is_private:
 140             return bt2.port._create_private_from_ptr(port_ptr)
 141         else:
 142             return bt2.port._create_from_ptr(port_ptr)
 143
 144     def __len__(self):
 145         if self._is_private:
 146             pub_ptr = native_bt.component_from_private(self._component._ptr)
 147             count = self._get_port_count_fn(pub_ptr)
 148             native_bt.put(pub_ptr)
 149         else:
 150             count = self._get_port_count_fn(self._component._ptr)
 151
 152         assert(count >= 0)
 153         return count
 154
 155     def __iter__(self):
 156         return _PortIterator(self)
 157
 158
 159 # This class holds the methods which are common to both generic
 160 # component objects and Python user component objects. They use the
 161 # internal native _ptr, however it was set, to call native API
 162 # functions.
 163 class _Component:
 164     @property
 165     def name(self):
 166         name = native_bt.component_get_name(self._ptr)
 167         assert(name is not None)
 168         return name
 169
 170     @property
 171     def graph(self):
 172         ptr = native_bt.component_get_graph(self._ptr)
 173         assert(ptr)
 174         return bt2.Graph._create_from_ptr(ptr)
 175
 176     @property
 177     def component_class(self):
 178         cc_ptr = native_bt.component_get_class(self._ptr)
 179         assert(cc_ptr)
 180         return _create_generic_component_class_from_ptr(cc_ptr)
 181
 182     def __eq__(self, other):
 183         if not hasattr(other, 'addr'):
 184             return False
 185
 186         return self.addr == other.addr
 187
 188
 189 class _SourceComponent(_Component):
 190     pass
 191
 192
 193 class _FilterComponent(_Component):
 194     pass
 195
 196
 197 class _SinkComponent(_Component):
 198     pass
 199
 200
 201 # This is analogous to _GenericSourceComponentClass, but for source
 202 # component objects.
 203 class _GenericSourceComponent(object._Object, _SourceComponent):
 204     @property
 205     def output_ports(self):
 206         return _ComponentPorts(False, self,
 207                                native_bt.component_source_get_output_port_by_name,
 208                                native_bt.component_source_get_output_port_by_index,
 209                                native_bt.component_source_get_output_port_count)
 210
 211
 212 # This is analogous to _GenericFilterComponentClass, but for filter
 213 # component objects.
 214 class _GenericFilterComponent(object._Object, _FilterComponent):
 215     @property
 216     def output_ports(self):
 217         return _ComponentPorts(False, self,
 218                                native_bt.component_filter_get_output_port_by_name,
 219                                native_bt.component_filter_get_output_port_by_index,
 220                                native_bt.component_filter_get_output_port_count)
 221
 222     @property
 223     def input_ports(self):
 224         return _ComponentPorts(False, self,
 225                                native_bt.component_filter_get_input_port_by_name,
 226                                native_bt.component_filter_get_input_port_by_index,
 227                                native_bt.component_filter_get_input_port_count)
 228
 229
 230 # This is analogous to _GenericSinkComponentClass, but for sink
 231 # component objects.
 232 class _GenericSinkComponent(object._Object, _SinkComponent):
 233     @property
 234     def input_ports(self):
 235         return _ComponentPorts(False, self,
 236                                native_bt.component_sink_get_input_port_by_name,
 237                                native_bt.component_sink_get_input_port_by_index,
 238                                native_bt.component_sink_get_input_port_count)
 239
 240
 241 _COMP_CLS_TYPE_TO_GENERIC_COMP_PYCLS = {
 242     native_bt.COMPONENT_CLASS_TYPE_SOURCE: _GenericSourceComponent,
 243     native_bt.COMPONENT_CLASS_TYPE_FILTER: _GenericFilterComponent,
 244     native_bt.COMPONENT_CLASS_TYPE_SINK: _GenericSinkComponent,
 245 }
 246
 247
 248 _COMP_CLS_TYPE_TO_GENERIC_COMP_CLS_PYCLS = {
 249     native_bt.COMPONENT_CLASS_TYPE_SOURCE: _GenericSourceComponentClass,
 250     native_bt.COMPONENT_CLASS_TYPE_FILTER: _GenericFilterComponentClass,
 251     native_bt.COMPONENT_CLASS_TYPE_SINK: _GenericSinkComponentClass,
 252 }
 253
 254
 255 def _create_generic_component_from_ptr(ptr):
 256     comp_cls_type = native_bt.component_get_class_type(ptr)
 257     return _COMP_CLS_TYPE_TO_GENERIC_COMP_PYCLS[comp_cls_type]._create_from_ptr(ptr)
 258
 259
 260 def _create_generic_component_class_from_ptr(ptr):
 261     comp_cls_type = native_bt.component_class_get_type(ptr)
 262     return _COMP_CLS_TYPE_TO_GENERIC_COMP_CLS_PYCLS[comp_cls_type]._create_from_ptr(ptr)
 263
 264
 265 def _trim_docstring(docstring):
 266     lines = docstring.expandtabs().splitlines()
 267     indent = sys.maxsize
 268
 269     for line in lines[1:]:
 270         stripped = line.lstrip()
 271
 272         if stripped:
 273             indent = min(indent, len(line) - len(stripped))
 274
 275     trimmed = [lines[0].strip()]
 276
 277     if indent < sys.maxsize:
 278         for line in lines[1:]:
 279             trimmed.append(line[indent:].rstrip())
 280
 281     while trimmed and not trimmed[-1]:
 282         trimmed.pop()
 283
 284     while trimmed and not trimmed[0]:
 285         trimmed.pop(0)
 286
 287     return '\n'.join(trimmed)
 288
 289
 290 # Metaclass for component classes defined by Python code.
 291 #
 292 # The Python user can create a standard Python class which inherits one
 293 # of the three base classes (_UserSourceComponent, _UserFilterComponent,
 294 # or _UserSinkComponent). Those base classes set this class
 295 # (_UserComponentType) as their metaclass.
 296 #
 297 # Once the body of a user-defined component class is executed, this
 298 # metaclass is used to create and initialize the class. The metaclass
 299 # creates a native BT component class of the corresponding type and
 300 # associates it with this user-defined class. The metaclass also defines
 301 # class methods like the `name` and `description` properties to match
 302 # the _GenericComponentClass interface.
 303 #
 304 # The component class name which is used is either:
 305 #
 306 # * The `name` parameter of the class:
 307 #
 308 #       class MySink(bt2.SinkComponent, name='my-custom-sink'):
 309 #           ...
 310 #
 311 # * If the `name` class parameter is not used: the name of the class
 312 #   itself (`MySink` in the example above).
 313 #
 314 # The component class description which is used is the user-defined
 315 # class's docstring:
 316 #
 317 #     class MySink(bt2.SinkComponent):
 318 #         'Description goes here'
 319 #         ...
 320 #
 321 # A user-defined Python component class can have an __init__() method
 322 # which must at least accept the `params` and `name` arguments:
 323 #
 324 #     def __init__(self, params, name, something_else):
 325 #         ...
 326 #
 327 # The user-defined component class can also have a _finalize() method
 328 # (do NOT use __del__()) to be notified when the component object is
 329 # finalized.
 330 #
 331 # User-defined source and filter component classes must use the
 332 # `message_iterator_class` class parameter to specify the
 333 # message iterator class to use for this component class:
 334 #
 335 #     class MyMessageIterator(bt2._UserMessageIterator):
 336 #         ...
 337 #
 338 #     class MySource(bt2._UserSourceComponent,
 339 #                    message_iterator_class=MyMessageIterator):
 340 #         ...
 341 #
 342 # This message iterator class must inherit
 343 # bt2._UserMessageIterator, and it must define the _get() and
 344 # _next() methods. The message iterator class can also define an
 345 # __init__() method: this method has access to the original Python
 346 # component object which was used to create it as the `component`
 347 # property. The message iterator class can also define a
 348 # _finalize() method (again, do NOT use __del__()): this is called when
 349 # the message iterator is (really) destroyed.
 350 #
 351 # When the user-defined class is destroyed, this metaclass's __del__()
 352 # method is called: the native BT component class pointer is put (not
 353 # needed anymore, at least not by any Python code since all references
 354 # are dropped for __del__() to be called).
 355 class _UserComponentType(type):
 356     # __new__() is used to catch custom class parameters
 357     def __new__(meta_cls, class_name, bases, attrs, **kwargs):
 358         return super().__new__(meta_cls, class_name, bases, attrs)
 359
 360     def __init__(cls, class_name, bases, namespace, **kwargs):
 361         super().__init__(class_name, bases, namespace)
 362
 363         # skip our own bases; they are never directly instantiated by the user
 364         own_bases = (
 365             '_UserComponent',
 366             '_UserFilterSinkComponent',
 367             '_UserSourceComponent',
 368             '_UserFilterComponent',
 369             '_UserSinkComponent',
 370         )
 371
 372         if class_name in own_bases:
 373             return
 374
 375         comp_cls_name = kwargs.get('name', class_name)
 376         utils._check_str(comp_cls_name)
 377         comp_cls_descr = None
 378         comp_cls_help = None
 379
 380         if hasattr(cls, '__doc__') and cls.__doc__ is not None:
 381             utils._check_str(cls.__doc__)
 382             docstring = _trim_docstring(cls.__doc__)
 383             lines = docstring.splitlines()
 384
 385             if len(lines) >= 1:
 386                 comp_cls_descr = lines[0]
 387
 388             if len(lines) >= 3:
 389                 comp_cls_help = '\n'.join(lines[2:])
 390
 391         iter_cls = kwargs.get('message_iterator_class')
 392
 393         if _UserSourceComponent in bases:
 394             _UserComponentType._set_iterator_class(cls, iter_cls)
 395             cc_ptr = native_bt.py3_component_class_source_create(cls,
 396                                                                  comp_cls_name,
 397                                                                  comp_cls_descr,
 398                                                                  comp_cls_help)
 399         elif _UserFilterComponent in bases:
 400             _UserComponentType._set_iterator_class(cls, iter_cls)
 401             cc_ptr = native_bt.py3_component_class_filter_create(cls,
 402                                                                  comp_cls_name,
 403                                                                  comp_cls_descr,
 404                                                                  comp_cls_help)
 405         elif _UserSinkComponent in bases:
 406             if not hasattr(cls, '_consume'):
 407                 raise bt2.IncompleteUserClass("cannot create component class '{}': missing a _consume() method".format(class_name))
 408
 409             cc_ptr = native_bt.py3_component_class_sink_create(cls,
 410                                                                comp_cls_name,
 411                                                                comp_cls_descr,
 412                                                                comp_cls_help)
 413         else:
 414             raise bt2.IncompleteUserClass("cannot find a known component class base in the bases of '{}'".format(class_name))
 415
 416         if cc_ptr is None:
 417             raise bt2.CreationError("cannot create component class '{}'".format(class_name))
 418
 419         cls._cc_ptr = cc_ptr
 420
 421     def _init_from_native(cls, comp_ptr, params_ptr):
 422         # create instance, not user-initialized yet
 423         self = cls.__new__(cls)
 424
 425         # pointer to native private component object (weak/borrowed)
 426         self._ptr = comp_ptr
 427
 428         # call user's __init__() method
 429         if params_ptr is not None:
 430             native_bt.get(params_ptr)
 431             params = bt2.values._create_from_ptr(params_ptr)
 432         else:
 433             params = None
 434
 435         self.__init__(params)
 436         return self
 437
 438     def __call__(cls, *args, **kwargs):
 439         raise bt2.Error('cannot directly instantiate a user component from a Python module')
 440
 441     @staticmethod
 442     def _set_iterator_class(cls, iter_cls):
 443         if iter_cls is None:
 444             raise bt2.IncompleteUserClass("cannot create component class '{}': missing message iterator class".format(cls.__name__))
 445
 446         if not issubclass(iter_cls, bt2.message_iterator._UserMessageIterator):
 447             raise bt2.IncompleteUserClass("cannot create component class '{}': message iterator class does not inherit bt2._UserMessageIterator".format(cls.__name__))
 448
 449         if not hasattr(iter_cls, '__next__'):
 450             raise bt2.IncompleteUserClass("cannot create component class '{}': message iterator class is missing a __next__() method".format(cls.__name__))
 451
 452         cls._iter_cls = iter_cls
 453
 454     @property
 455     def name(cls):
 456         return native_bt.component_class_get_name(cls._cc_ptr)
 457
 458     @property
 459     def description(cls):
 460         return native_bt.component_class_get_description(cls._cc_ptr)
 461
 462     @property
 463     def help(cls):
 464         return native_bt.component_class_get_help(cls._cc_ptr)
 465
 466     @property
 467     def addr(cls):
 468         return int(cls._cc_ptr)
 469
 470     def _query_from_native(cls, query_exec_ptr, obj, params_ptr):
 471         # this can raise, in which case the native call to
 472         # bt_component_class_query() returns NULL
 473         if params_ptr is not None:
 474             native_bt.get(params_ptr)
 475             params = bt2.values._create_from_ptr(params_ptr)
 476         else:
 477             params = None
 478
 479         native_bt.get(query_exec_ptr)
 480         query_exec = bt2.QueryExecutor._create_from_ptr(query_exec_ptr)
 481
 482         # this can raise, but the native side checks the exception
 483         results = cls._query(query_exec, obj, params)
 484
 485         if results is NotImplemented:
 486             return results
 487
 488         # this can raise, but the native side checks the exception
 489         results = bt2.create_value(results)
 490
 491         if results is None:
 492             results_addr = int(native_bt.value_null)
 493         else:
 494             # return new reference
 495             results._get()
 496             results_addr = int(results._ptr)
 497
 498         return results_addr
 499
 500     def _query(cls, query_executor, obj, params):
 501         # BT catches this and returns NULL to the user
 502         return NotImplemented
 503
 504     def __eq__(self, other):
 505         if not hasattr(other, 'addr'):
 506             return False
 507
 508         return self.addr == other.addr
 509
 510     def __del__(cls):
 511         if hasattr(cls, '_cc_ptr'):
 512             native_bt.put(cls._cc_ptr)
 513
 514
 515 class _UserComponent(metaclass=_UserComponentType):
 516     @property
 517     def name(self):
 518         pub_ptr = native_bt.component_from_private(self._ptr)
 519         name = native_bt.component_get_name(pub_ptr)
 520         native_bt.put(pub_ptr)
 521         assert(name is not None)
 522         return name
 523
 524     @property
 525     def graph(self):
 526         pub_ptr = native_bt.component_from_private(self._ptr)
 527         ptr = native_bt.component_get_graph(pub_ptr)
 528         native_bt.put(pub_ptr)
 529         assert(ptr)
 530         return bt2.Graph._create_from_ptr(ptr)
 531
 532     @property
 533     def component_class(self):
 534         pub_ptr = native_bt.component_from_private(self._ptr)
 535         cc_ptr = native_bt.component_get_class(pub_ptr)
 536         native_bt.put(pub_ptr)
 537         assert(cc_ptr)
 538         return _create_generic_component_class_from_ptr(cc_ptr)
 539
 540     @property
 541     def addr(self):
 542         return int(self._ptr)
 543
 544     def __init__(self, params=None):
 545         pass
 546
 547     def _finalize(self):
 548         pass
 549
 550     def _accept_port_connection(self, port, other_port):
 551         return True
 552
 553     def _accept_port_connection_from_native(self, port_ptr, other_port_ptr):
 554         native_bt.get(port_ptr)
 555         native_bt.get(other_port_ptr)
 556         port = bt2.port._create_private_from_ptr(port_ptr)
 557         other_port = bt2.port._create_from_ptr(other_port_ptr)
 558         res = self._accept_port_connection(port, other_port_ptr)
 559
 560         if type(res) is not bool:
 561             raise TypeError("'{}' is not a 'bool' object")
 562
 563         return res
 564
 565     def _port_connected(self, port, other_port):
 566         pass
 567
 568     def _port_connected_from_native(self, port_ptr, other_port_ptr):
 569         native_bt.get(port_ptr)
 570         native_bt.get(other_port_ptr)
 571         port = bt2.port._create_private_from_ptr(port_ptr)
 572         other_port = bt2.port._create_from_ptr(other_port_ptr)
 573
 574         try:
 575             self._port_connected(port, other_port)
 576         except:
 577             if not _NO_PRINT_TRACEBACK:
 578                 traceback.print_exc()
 579
 580     def _port_disconnected(self, port):
 581         pass
 582
 583     def _port_disconnected_from_native(self, port_ptr):
 584         native_bt.get(port_ptr)
 585         port = bt2.port._create_private_from_ptr(port_ptr)
 586
 587         try:
 588             self._port_disconnected(port)
 589         except:
 590             if not _NO_PRINT_TRACEBACK:
 591                 traceback.print_exc()
 592
 593
 594 class _UserSourceComponent(_UserComponent, _SourceComponent):
 595     @property
 596     def _output_ports(self):
 597         return _ComponentPorts(True, self,
 598                                native_bt.private_component_source_get_output_private_port_by_name,
 599                                native_bt.private_component_source_get_output_private_port_by_index,
 600                                native_bt.component_source_get_output_port_count)
 601
 602     def _add_output_port(self, name):
 603         utils._check_str(name)
 604         fn = native_bt.private_component_source_add_output_private_port
 605         comp_status, priv_port_ptr = fn(self._ptr, name, None)
 606         _handle_component_status(comp_status,
 607                                  'cannot add output port to source component object')
 608         assert(priv_port_ptr)
 609         return bt2.port._create_private_from_ptr(priv_port_ptr)
 610
 611
 612 class _UserFilterComponent(_UserComponent, _FilterComponent):
 613     @property
 614     def _output_ports(self):
 615         return _ComponentPorts(True, self,
 616                                native_bt.private_component_filter_get_output_private_port_by_name,
 617                                native_bt.private_component_filter_get_output_private_port_by_index,
 618                                native_bt.component_filter_get_output_port_count)
 619
 620     @property
 621     def _input_ports(self):
 622         return _ComponentPorts(True, self,
 623                                native_bt.private_component_filter_get_input_private_port_by_name,
 624                                native_bt.private_component_filter_get_input_private_port_by_index,
 625                                native_bt.component_filter_get_input_port_count)
 626
 627     def _add_output_port(self, name):
 628         utils._check_str(name)
 629         fn = native_bt.private_component_filter_add_output_private_port
 630         comp_status, priv_port_ptr = fn(self._ptr, name, None)
 631         _handle_component_status(comp_status,
 632                                  'cannot add output port to filter component object')
 633         assert(priv_port_ptr)
 634         return bt2.port._create_private_from_ptr(priv_port_ptr)
 635
 636     def _add_input_port(self, name):
 637         utils._check_str(name)
 638         fn = native_bt.private_component_filter_add_input_private_port
 639         comp_status, priv_port_ptr = fn(self._ptr, name, None)
 640         _handle_component_status(comp_status,
 641                                  'cannot add input port to filter component object')
 642         assert(priv_port_ptr)
 643         return bt2.port._create_private_from_ptr(priv_port_ptr)
 644
 645
 646 class _UserSinkComponent(_UserComponent, _SinkComponent):
 647     @property
 648     def _input_ports(self):
 649         return _ComponentPorts(True, self,
 650                                native_bt.private_component_sink_get_input_private_port_by_name,
 651                                native_bt.private_component_sink_get_input_private_port_by_index,
 652                                native_bt.component_sink_get_input_port_count)
 653
 654     def _add_input_port(self, name):
 655         utils._check_str(name)
 656         fn = native_bt.private_component_sink_add_input_private_port
 657         comp_status, priv_port_ptr = fn(self._ptr, name, None)
 658         _handle_component_status(comp_status,
 659                                  'cannot add input port to sink component object')
 660         assert(priv_port_ptr)
 661         return bt2.port._create_private_from_ptr(priv_port_ptr)