d52a474c1e7337aefafb40e78c8a6a2d03947646
[babeltrace.git] / tests / bindings / python / bt2 / utils.py
1 #
2 # Copyright (C) 2019 EfficiOS Inc.
3 #
4 # This program is free software; you can redistribute it and/or
5 # modify it under the terms of the GNU General Public License
6 # as published by the Free Software Foundation; only version 2
7 # of the License.
8 #
9 # This program is distributed in the hope that it will be useful,
10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 # GNU General Public License for more details.
13 #
14 # You should have received a copy of the GNU General Public License
15 # along with this program; if not, write to the Free Software
16 # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 #
18
19 import bt2
20
21 # Run callable `func` in the context of a component's __init__ method. The
22 # callable is passed the Component being instantiated.
23 #
24 # The value returned by the callable is returned by run_in_component_init.
25
26 def run_in_component_init(func):
27 class MySink(bt2._UserSinkComponent):
28 def __init__(self, params):
29 nonlocal res_bound
30 res_bound = func(self)
31
32 def _consume(self):
33 pass
34
35 g = bt2.Graph()
36 res_bound = None
37 g.add_component(MySink, 'comp')
38
39 # We deliberately use a different variable for returning the result than
40 # the variable bound to the MySink.__init__ context and delete res_bound.
41 # The MySink.__init__ context stays alive until the end of the program, so
42 # if res_bound were to still point to our result, it would contribute an
43 # unexpected reference to the refcount of the result, from the point of view
44 # of the user of this function. It would then affect destruction tests,
45 # for example, which want to test what happens when the refcount of a Python
46 # object reaches 0.
47
48 res = res_bound
49 del res_bound
50 return res
51
52 # Create an empty trace class with default values.
53
54 def get_default_trace_class():
55 def f(comp_self):
56 return comp_self._create_trace_class()
57
58 return run_in_component_init(f)
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