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
  27 def run_in_component_init(func):
  28     class MySink(bt2._UserSinkComponent):
  29         def __init__(self, params, obj):
  30             nonlocal res_bound
  31             res_bound = func(self)
  32
  33         def _user_consume(self):
  34             pass
  35
  36     g = bt2.Graph()
  37     res_bound = None
  38     g.add_component(MySink, 'comp')
  39
  40     # We deliberately use a different variable for returning the result than
  41     # the variable bound to the MySink.__init__ context and delete res_bound.
  42     # The MySink.__init__ context stays alive until the end of the program, so
  43     # if res_bound were to still point to our result, it would contribute an
  44     # unexpected reference to the refcount of the result, from the point of view
  45     # of the user of this function.  It would then affect destruction tests,
  46     # for example, which want to test what happens when the refcount of a Python
  47     # object reaches 0.
  48
  49     res = res_bound
  50     del res_bound
  51     return res
  52
  53
  54 # Create an empty trace class with default values.
  55
  56
  57 def get_default_trace_class():
  58     def f(comp_self):
  59         return comp_self._create_trace_class()
  60
  61     return run_in_component_init(f)