[babeltrace.git] / bindings / python / bt2 / bt2 / message_iterator.py

# The MIT License (MIT)
#
# Copyright (c) 2017 Philippe Proulx <pproulx@efficios.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

from bt2 import native_bt, object, utils
import bt2.message
import collections.abc
import bt2.component
import bt2


class _MessageIterator(collections.abc.Iterator):
    def _handle_status(self, status, gen_error_msg):
        if status == native_bt.MESSAGE_ITERATOR_STATUS_AGAIN:
            raise bt2.TryAgain
        elif status == native_bt.MESSAGE_ITERATOR_STATUS_END:
            raise bt2.Stop
        elif status < 0:
            raise bt2.Error(gen_error_msg)

    def __next__(self):
        raise NotImplementedError


class _GenericMessageIterator(object._SharedObject, _MessageIterator):
    def __init__(self, ptr):
            self._current_msgs = []
            self._at = 0
            super().__init__(ptr)

    def __next__(self):
        if len(self._current_msgs) == self._at:
            status, msgs = self._get_msg_range(self._ptr)
            self._handle_status(status,
                                'unexpected error: cannot advance the message iterator')
            self._current_msgs = msgs
            self._at = 0

        msg_ptr = self._current_msgs[self._at]
        self._at += 1

        return bt2.message._create_from_ptr(msg_ptr)


# This is created when a component wants to iterate on one of its input ports.
class _UserComponentInputPortMessageIterator(_GenericMessageIterator):
    _get_msg_range = staticmethod(native_bt.py3_self_component_port_input_get_msg_range)
    _get_ref = staticmethod(native_bt.self_component_port_input_message_iterator_get_ref)
    _put_ref = staticmethod(native_bt.self_component_port_input_message_iterator_put_ref)


# This is created when the user wants to iterate on a component's output port,
# from outside the graph.
class _OutputPortMessageIterator(_GenericMessageIterator):
    _get_msg_range = staticmethod(native_bt.py3_port_output_get_msg_range)
    _get_ref = staticmethod(native_bt.port_output_message_iterator_get_ref)
    _put_ref = staticmethod(native_bt.port_output_message_iterator_put_ref)


# This is extended by the user to implement component classes in Python.  It
# is created for a given output port when an input port message iterator is
# created on the input port on the other side of the connection.  It is also
# created when an output port message iterator is created on this output port.
#
# Its purpose is to feed the messages that should go out through this output
# port.
class _UserMessageIterator(_MessageIterator):
    def __new__(cls, ptr):
        # User iterator objects are always created by the native side,
        # that is, never instantiated directly by Python code.
        #
        # The native code calls this, then manually calls
        # self.__init__() without the `ptr` argument. The user has
        # access to self.component during this call, thanks to this
        # self._ptr argument being set.
        #
        # self._ptr is NOT owned by this object here, so there's nothing
        # to do in __del__().
        self = super().__new__(cls)
        self._ptr = ptr
        return self

    def _init_from_native(self, self_output_port_ptr):
        self_output_port = bt2.port._create_self_from_ptr_and_get_ref(
            self_output_port_ptr, native_bt.PORT_TYPE_OUTPUT)
        self.__init__(self_output_port)

    def __init__(self, output_port):
        pass

    @property
    def _component(self):
        return native_bt.py3_get_user_component_from_user_msg_iter(self._ptr)

    @property
    def addr(self):
        return int(self._ptr)

    def _finalize(self):
        pass

    def __next__(self):
        raise bt2.Stop

    def _next_from_native(self):
        # this can raise anything: it's catched by the native part
        try:
            msg = next(self)
        except StopIteration:
            raise bt2.Stop
        except:
            raise

        utils._check_type(msg, bt2.message._Message)

        # Release the reference to the native part.
        ptr = msg._release()
        return int(ptr)

    # Validate that the presence or lack of presence of a
    # `default_clock_snapshot` value is valid in the context of `stream_class`.
    @staticmethod
    def _validate_default_clock_snapshot(stream_class, default_clock_snapshot):
        stream_class_has_default_clock_class = stream_class.default_clock_class is not None

        if stream_class_has_default_clock_class and default_clock_snapshot is None:
            raise bt2.Error(
                'stream class has a default clock class, default_clock_snapshot should not be None')

        if not stream_class_has_default_clock_class and default_clock_snapshot is not None:
            raise bt2.Error(
                'stream class has no default clock class, default_clock_snapshot should be None')

    def _create_event_message(self, event_class, packet, default_clock_snapshot=None):
        utils._check_type(event_class, bt2.event_class.EventClass)
        utils._check_type(packet, bt2.packet._Packet)
        self._validate_default_clock_snapshot(packet.stream.stream_class, default_clock_snapshot)

        if default_clock_snapshot is not None:
            utils._check_uint64(default_clock_snapshot)
            ptr = native_bt.message_event_create_with_default_clock_snapshot(
                self._ptr, event_class._ptr, packet._ptr, default_clock_snapshot)
        else:
            ptr = native_bt.message_event_create(
                self._ptr, event_class._ptr, packet._ptr)

        if ptr is None:
            raise bt2.CreationError('cannot create event message object')

        return bt2.message._EventMessage(ptr)

    def _create_message_iterator_inactivity_message(self, clock_class, clock_snapshot):
        utils._check_type(clock_class, bt2.clock_class._ClockClass)
        ptr = native_bt.message_message_iterator_inactivity_create(
            self._ptr, clock_class._ptr, clock_snapshot)

        if ptr is None:
            raise bt2.CreationError('cannot create inactivity message object')

        return bt2.message._MessageIteratorInactivityMessage(ptr)

    def _create_stream_beginning_message(self, stream):
        utils._check_type(stream, bt2.stream._Stream)

        ptr = native_bt.message_stream_beginning_create(self._ptr, stream._ptr)
        if ptr is None:
            raise bt2.CreationError('cannot create stream beginning message object')

        return bt2.message._StreamBeginningMessage(ptr)

    def _create_stream_activity_beginning_message(self, stream, default_clock_snapshot=None):
        utils._check_type(stream, bt2.stream._Stream)
        self._validate_default_clock_snapshot(stream.stream_class, default_clock_snapshot)

        ptr = native_bt.message_stream_activity_beginning_create(self._ptr, stream._ptr)

        if ptr is None:
            raise bt2.CreationError(
                'cannot create stream activity beginning message object')

        msg = bt2.message._StreamActivityBeginningMessage(ptr)

        if default_clock_snapshot is not None:
            msg._default_clock_snapshot = default_clock_snapshot

        return msg

    def _create_stream_activity_end_message(self, stream, default_clock_snapshot=None):
        utils._check_type(stream, bt2.stream._Stream)
        self._validate_default_clock_snapshot(stream.stream_class, default_clock_snapshot)

        ptr = native_bt.message_stream_activity_end_create(self._ptr, stream._ptr)

        if ptr is None:
            raise bt2.CreationError(
                'cannot create stream activity end message object')

        msg = bt2.message._StreamActivityEndMessage(ptr)

        if default_clock_snapshot is not None:
            msg._default_clock_snapshot = default_clock_snapshot

        return msg

    def _create_stream_end_message(self, stream):
        utils._check_type(stream, bt2.stream._Stream)

        ptr = native_bt.message_stream_end_create(self._ptr, stream._ptr)
        if ptr is None:
            raise bt2.CreationError('cannot create stream end message object')

        return bt2.message._StreamEndMessage(ptr)

    def _create_packet_beginning_message(self, packet, default_clock_snapshot=None):
        utils._check_type(packet, bt2.packet._Packet)

        if packet.stream.stream_class.packets_have_default_beginning_clock_snapshot:
            if default_clock_snapshot is None:
                raise ValueError("packet beginning messages in this stream must have a default clock snapshots")

            utils._check_uint64(default_clock_snapshot)
            ptr = native_bt.message_packet_beginning_create_with_default_clock_snapshot(
                self._ptr, packet._ptr, default_clock_snapshot)
        else:
            if default_clock_snapshot is not None:
                raise ValueError("packet beginning messages in this stream must not have a default clock snapshots")

            ptr = native_bt.message_packet_beginning_create(self._ptr, packet._ptr)

        if ptr is None:
            raise bt2.CreationError('cannot create packet beginning message object')

        return bt2.message._PacketBeginningMessage(ptr)

    def _create_packet_end_message(self, packet, default_clock_snapshot=None):
        utils._check_type(packet, bt2.packet._Packet)

        if packet.stream.stream_class.packets_have_default_end_clock_snapshot:
            if default_clock_snapshot is None:
                raise ValueError("packet end messages in this stream must have a default clock snapshots")

            utils._check_uint64(default_clock_snapshot)
            ptr = native_bt.message_packet_end_create_with_default_clock_snapshot(
                self._ptr, packet._ptr, default_clock_snapshot)
        else:
            if default_clock_snapshot is not None:
                raise ValueError("packet end messages in this stream must not have a default clock snapshots")

            ptr = native_bt.message_packet_end_create(self._ptr, packet._ptr)

        if ptr is None:
            raise bt2.CreationError('cannot create packet end message object')

        return bt2.message._PacketEndMessage(ptr)

    def _create_discarded_events_message(self, stream, count=None,
                                         beg_clock_snapshot=None,
                                         end_clock_snapshot=None):
        utils._check_type(stream, bt2.stream._Stream)

        if beg_clock_snapshot is None and end_clock_snapshot is None:
            ptr = native_bt.message_discarded_events_create(self._ptr, stream._ptr)
        elif beg_clock_snapshot is not None and end_clock_snapshot is not None:
            utils._check_uint64(beg_clock_snapshot)
            utils._check_uint64(end_clock_snapshot)
            ptr = native_bt.message_discarded_events_create_with_default_clock_snapshots(
                self._ptr, stream._ptr, beg_clock_snapshot, end_clock_snapshot)
        else:
            raise ValueError('begin and end clock snapshots must be both provided or both omitted')

        if ptr is None:
            raise bt2.CreationError('cannot discarded events message object')

        msg = bt2.message._DiscardedEventsMessage(ptr)

        if count is not None:
            msg._count = count

        return msg

    def _create_discarded_packets_message(self, stream, count=None, beg_clock_snapshot=None, end_clock_snapshot=None):
        utils._check_type(stream, bt2.stream._Stream)

        if beg_clock_snapshot is None and end_clock_snapshot is None:
            ptr = native_bt.message_discarded_packets_create(self._ptr, stream._ptr)
        elif beg_clock_snapshot is not None and end_clock_snapshot is not None:
            utils._check_uint64(beg_clock_snapshot)
            utils._check_uint64(end_clock_snapshot)
            ptr = native_bt.message_discarded_packets_create_with_default_clock_snapshots(
                self._ptr, stream._ptr, beg_clock_snapshot, end_clock_snapshot)
        else:
            raise ValueError('begin and end clock snapshots must be both provided or both omitted')

        if ptr is None:
            raise bt2.CreationError('cannot discarded packets message object')

        msg = bt2.message._DiscardedPacketsMessage(ptr)

        if count is not None:
            msg._count = count

        return msg
Commit	Line	Data
	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
	25	import collections.abc
	26	import bt2.component
	27	import bt2
	28
	29
	30	class _MessageIterator(collections.abc.Iterator):
	31	def _handle_status(self, status, gen_error_msg):
	32	if status == native_bt.MESSAGE_ITERATOR_STATUS_AGAIN:
	33	raise bt2.TryAgain
	34	elif status == native_bt.MESSAGE_ITERATOR_STATUS_END:
	35	raise bt2.Stop
	36	elif status < 0:
	37	raise bt2.Error(gen_error_msg)
	38
	39	def __next__(self):
	40	raise NotImplementedError
	41
	42
	43	class _GenericMessageIterator(object._SharedObject, _MessageIterator):
	44	def __init__(self, ptr):
	45	self._current_msgs = []
	46	self._at = 0
	47	super().__init__(ptr)
	48
	49	def __next__(self):
	50	if len(self._current_msgs) == self._at:
	51	status, msgs = self._get_msg_range(self._ptr)
	52	self._handle_status(status,
	53	'unexpected error: cannot advance the message iterator')
	54	self._current_msgs = msgs
	55	self._at = 0
	56
	57	msg_ptr = self._current_msgs[self._at]
	58	self._at += 1
	59
	60	return bt2.message._create_from_ptr(msg_ptr)
	61
	62
	63	# This is created when a component wants to iterate on one of its input ports.
	64	class _UserComponentInputPortMessageIterator(_GenericMessageIterator):
	65	_get_msg_range = staticmethod(native_bt.py3_self_component_port_input_get_msg_range)
	66	_get_ref = staticmethod(native_bt.self_component_port_input_message_iterator_get_ref)
	67	_put_ref = staticmethod(native_bt.self_component_port_input_message_iterator_put_ref)
	68
	69
	70	# This is created when the user wants to iterate on a component's output port,
	71	# from outside the graph.
	72	class _OutputPortMessageIterator(_GenericMessageIterator):
	73	_get_msg_range = staticmethod(native_bt.py3_port_output_get_msg_range)
	74	_get_ref = staticmethod(native_bt.port_output_message_iterator_get_ref)
	75	_put_ref = staticmethod(native_bt.port_output_message_iterator_put_ref)
	76
	77
	78	# This is extended by the user to implement component classes in Python. It
	79	# is created for a given output port when an input port message iterator is
	80	# created on the input port on the other side of the connection. It is also
	81	# created when an output port message iterator is created on this output port.
	82	#
	83	# Its purpose is to feed the messages that should go out through this output
	84	# port.
	85	class _UserMessageIterator(_MessageIterator):
	86	def __new__(cls, ptr):
	87	# User iterator objects are always created by the native side,
	88	# that is, never instantiated directly by Python code.
	89	#
	90	# The native code calls this, then manually calls
	91	# self.__init__() without the `ptr` argument. The user has
	92	# access to self.component during this call, thanks to this
	93	# self._ptr argument being set.
	94	#
	95	# self._ptr is NOT owned by this object here, so there's nothing
	96	# to do in __del__().
	97	self = super().__new__(cls)
	98	self._ptr = ptr
	99	return self
	100
	101	def _init_from_native(self, self_output_port_ptr):
	102	self_output_port = bt2.port._create_self_from_ptr_and_get_ref(
	103	self_output_port_ptr, native_bt.PORT_TYPE_OUTPUT)
	104	self.__init__(self_output_port)
	105
	106	def __init__(self, output_port):
	107	pass
	108
	109	@property
	110	def _component(self):
	111	return native_bt.py3_get_user_component_from_user_msg_iter(self._ptr)
	112
	113	@property
	114	def addr(self):
	115	return int(self._ptr)
	116
	117	def _finalize(self):
	118	pass
	119
	120	def __next__(self):
	121	raise bt2.Stop
	122
	123	def _next_from_native(self):
	124	# this can raise anything: it's catched by the native part
	125	try:
	126	msg = next(self)
	127	except StopIteration:
	128	raise bt2.Stop
	129	except:
	130	raise
	131
	132	utils._check_type(msg, bt2.message._Message)
	133
	134	# Release the reference to the native part.
	135	ptr = msg._release()
	136	return int(ptr)
	137
	138	# Validate that the presence or lack of presence of a
	139	# `default_clock_snapshot` value is valid in the context of `stream_class`.
	140	@staticmethod
	141	def _validate_default_clock_snapshot(stream_class, default_clock_snapshot):
	142	stream_class_has_default_clock_class = stream_class.default_clock_class is not None
	143
	144	if stream_class_has_default_clock_class and default_clock_snapshot is None:
	145	raise bt2.Error(
	146	'stream class has a default clock class, default_clock_snapshot should not be None')
	147
	148	if not stream_class_has_default_clock_class and default_clock_snapshot is not None:
	149	raise bt2.Error(
	150	'stream class has no default clock class, default_clock_snapshot should be None')
	151
	152	def _create_event_message(self, event_class, packet, default_clock_snapshot=None):
	153	utils._check_type(event_class, bt2.event_class.EventClass)
	154	utils._check_type(packet, bt2.packet._Packet)
	155	self._validate_default_clock_snapshot(packet.stream.stream_class, default_clock_snapshot)
	156
	157	if default_clock_snapshot is not None:
	158	utils._check_uint64(default_clock_snapshot)
	159	ptr = native_bt.message_event_create_with_default_clock_snapshot(
	160	self._ptr, event_class._ptr, packet._ptr, default_clock_snapshot)
	161	else:
	162	ptr = native_bt.message_event_create(
	163	self._ptr, event_class._ptr, packet._ptr)
	164
	165	if ptr is None:
	166	raise bt2.CreationError('cannot create event message object')
	167
	168	return bt2.message._EventMessage(ptr)
	169
	170	def _create_message_iterator_inactivity_message(self, clock_class, clock_snapshot):
	171	utils._check_type(clock_class, bt2.clock_class._ClockClass)
	172	ptr = native_bt.message_message_iterator_inactivity_create(
	173	self._ptr, clock_class._ptr, clock_snapshot)
	174
	175	if ptr is None:
	176	raise bt2.CreationError('cannot create inactivity message object')
	177
	178	return bt2.message._MessageIteratorInactivityMessage(ptr)
	179
	180	def _create_stream_beginning_message(self, stream):
	181	utils._check_type(stream, bt2.stream._Stream)
	182
	183	ptr = native_bt.message_stream_beginning_create(self._ptr, stream._ptr)
	184	if ptr is None:
	185	raise bt2.CreationError('cannot create stream beginning message object')
	186
	187	return bt2.message._StreamBeginningMessage(ptr)
	188
	189	def _create_stream_activity_beginning_message(self, stream, default_clock_snapshot=None):
	190	utils._check_type(stream, bt2.stream._Stream)
	191	self._validate_default_clock_snapshot(stream.stream_class, default_clock_snapshot)
	192
	193	ptr = native_bt.message_stream_activity_beginning_create(self._ptr, stream._ptr)
	194
	195	if ptr is None:
	196	raise bt2.CreationError(
	197	'cannot create stream activity beginning message object')
	198
	199	msg = bt2.message._StreamActivityBeginningMessage(ptr)
	200
	201	if default_clock_snapshot is not None:
	202	msg._default_clock_snapshot = default_clock_snapshot
	203
	204	return msg
	205
	206	def _create_stream_activity_end_message(self, stream, default_clock_snapshot=None):
	207	utils._check_type(stream, bt2.stream._Stream)
	208	self._validate_default_clock_snapshot(stream.stream_class, default_clock_snapshot)
	209
	210	ptr = native_bt.message_stream_activity_end_create(self._ptr, stream._ptr)
	211
	212	if ptr is None:
	213	raise bt2.CreationError(
	214	'cannot create stream activity end message object')
	215
	216	msg = bt2.message._StreamActivityEndMessage(ptr)
	217
	218	if default_clock_snapshot is not None:
	219	msg._default_clock_snapshot = default_clock_snapshot
	220
	221	return msg
	222
	223	def _create_stream_end_message(self, stream):
	224	utils._check_type(stream, bt2.stream._Stream)
	225
	226	ptr = native_bt.message_stream_end_create(self._ptr, stream._ptr)
	227	if ptr is None:
	228	raise bt2.CreationError('cannot create stream end message object')
	229
	230	return bt2.message._StreamEndMessage(ptr)
	231
	232	def _create_packet_beginning_message(self, packet, default_clock_snapshot=None):
	233	utils._check_type(packet, bt2.packet._Packet)
	234
	235	if packet.stream.stream_class.packets_have_default_beginning_clock_snapshot:
	236	if default_clock_snapshot is None:
	237	raise ValueError("packet beginning messages in this stream must have a default clock snapshots")
	238
	239	utils._check_uint64(default_clock_snapshot)
	240	ptr = native_bt.message_packet_beginning_create_with_default_clock_snapshot(
	241	self._ptr, packet._ptr, default_clock_snapshot)
	242	else:
	243	if default_clock_snapshot is not None:
	244	raise ValueError("packet beginning messages in this stream must not have a default clock snapshots")
	245
	246	ptr = native_bt.message_packet_beginning_create(self._ptr, packet._ptr)
	247
	248	if ptr is None:
	249	raise bt2.CreationError('cannot create packet beginning message object')
	250
	251	return bt2.message._PacketBeginningMessage(ptr)
	252
	253	def _create_packet_end_message(self, packet, default_clock_snapshot=None):
	254	utils._check_type(packet, bt2.packet._Packet)
	255
	256	if packet.stream.stream_class.packets_have_default_end_clock_snapshot:
	257	if default_clock_snapshot is None:
	258	raise ValueError("packet end messages in this stream must have a default clock snapshots")
	259
	260	utils._check_uint64(default_clock_snapshot)
	261	ptr = native_bt.message_packet_end_create_with_default_clock_snapshot(
	262	self._ptr, packet._ptr, default_clock_snapshot)
	263	else:
	264	if default_clock_snapshot is not None:
	265	raise ValueError("packet end messages in this stream must not have a default clock snapshots")
	266
	267	ptr = native_bt.message_packet_end_create(self._ptr, packet._ptr)
	268
	269	if ptr is None:
	270	raise bt2.CreationError('cannot create packet end message object')
	271
	272	return bt2.message._PacketEndMessage(ptr)
	273
	274	def _create_discarded_events_message(self, stream, count=None,
	275	beg_clock_snapshot=None,
	276	end_clock_snapshot=None):
	277	utils._check_type(stream, bt2.stream._Stream)
	278
	279	if beg_clock_snapshot is None and end_clock_snapshot is None:
	280	ptr = native_bt.message_discarded_events_create(self._ptr, stream._ptr)
	281	elif beg_clock_snapshot is not None and end_clock_snapshot is not None:
	282	utils._check_uint64(beg_clock_snapshot)
	283	utils._check_uint64(end_clock_snapshot)
	284	ptr = native_bt.message_discarded_events_create_with_default_clock_snapshots(
	285	self._ptr, stream._ptr, beg_clock_snapshot, end_clock_snapshot)
	286	else:
	287	raise ValueError('begin and end clock snapshots must be both provided or both omitted')
	288
	289	if ptr is None:
	290	raise bt2.CreationError('cannot discarded events message object')
	291
	292	msg = bt2.message._DiscardedEventsMessage(ptr)
	293
	294	if count is not None:
	295	msg._count = count
	296
	297	return msg
	298
	299	def _create_discarded_packets_message(self, stream, count=None, beg_clock_snapshot=None, end_clock_snapshot=None):
	300	utils._check_type(stream, bt2.stream._Stream)
	301
	302	if beg_clock_snapshot is None and end_clock_snapshot is None:
	303	ptr = native_bt.message_discarded_packets_create(self._ptr, stream._ptr)
	304	elif beg_clock_snapshot is not None and end_clock_snapshot is not None:
	305	utils._check_uint64(beg_clock_snapshot)
	306	utils._check_uint64(end_clock_snapshot)
	307	ptr = native_bt.message_discarded_packets_create_with_default_clock_snapshots(
	308	self._ptr, stream._ptr, beg_clock_snapshot, end_clock_snapshot)
	309	else:
	310	raise ValueError('begin and end clock snapshots must be both provided or both omitted')
	311
	312	if ptr is None:
	313	raise bt2.CreationError('cannot discarded packets message object')
	314
	315	msg = bt2.message._DiscardedPacketsMessage(ptr)
	316
	317	if count is not None:
	318	msg._count = count
	319
	320	return msg
	321