bt2: Add bindings for trace classes

[babeltrace.git] / tests / bindings / python / bt2 / utils.py

diff --git a/tests/bindings/python/bt2/utils.py b/tests/bindings/python/bt2/utils.py
new file mode 100644 (file)
index 0000000..768462e
--- /dev/null
+++ b/tests/bindings/python/bt2/utils.py
@@ -0,0 +1,40 @@
+import bt2
+
+# Run callable `func` in the context of a component's __init__ method.  The
+# callable is passed the Component being instantiated.
+#
+# The value returned by the callable is returned by run_in_component_init.
+
+def run_in_component_init(func):
+    class MySink(bt2._UserSinkComponent):
+        def __init__(self, params):
+            nonlocal res_bound
+            res_bound = func(self)
+
+        def _consume(self):
+            pass
+
+    g = bt2.Graph()
+    res_bound = None
+    g.add_component(MySink, 'comp')
+
+    # We deliberately use a different variable for returning the result than
+    # the variable bound to the MySink.__init__ context and delete res_bound.
+    # The MySink.__init__ context stays alive until the end of the program, so
+    # if res_bound were to still point to our result, it would contribute an
+    # unexpected reference to the refcount of the result, from the point of view
+    # of the user of this function.  It would then affect destruction tests,
+    # for example, which want to test what happens when the refcount of a Python
+    # object reaches 0.
+
+    res = res_bound
+    del res_bound
+    return res
+
+# Create an empty trace class with default values.
+
+def get_default_trace_class():
+    def f(comp_self):
+        return comp_self._create_trace_class()
+
+    return run_in_component_init(f)