bt2: add `_Trace.cls` property
[babeltrace.git] / bindings / python / bt2 / bt2 / object.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
24 class _BaseObject:
25 # Ensure that the object always has _ptr set, even if it throws during
26 # construction.
27
28 def __new__(cls, *args, **kwargs):
29 obj = super().__new__(cls)
30 obj._ptr = None
31 return obj
32
33 def __init__(self, ptr):
34 self._ptr = ptr
35
36 @property
37 def addr(self):
38 return int(self._ptr)
39
40 def __repr__(self):
41 return '<{}.{} object @ {}>'.format(self.__class__.__module__,
42 self.__class__.__name__,
43 hex(self.addr))
44
45 def __copy__(self):
46 raise NotImplementedError
47
48 def __deepcopy__(self, memo):
49 raise NotImplementedError
50
51
52 # A Python object that is itself not refcounted, but is wholly owned by an
53 # object that is itself refcounted (a _SharedObject). A Babeltrace unique
54 # object gets destroyed once its owner gets destroyed (its refcount drops to
55 # 0).
56 #
57 # In the Python bindings, to avoid having to deal with issues with the lifetime
58 # of unique objects, we make it so acquiring a reference on a unique object
59 # acquires a reference on its owner.
60
61 class _UniqueObject(_BaseObject):
62
63 # Create a _UniqueObject.
64 #
65 # - ptr: SWIG Object, pointer to the unique object.
66 # - owner_ptr: SWIG Object, pointer to the owner of the unique
67 # object. A new reference is acquired.
68 # - owner_get_ref: Callback to get a reference on the owner
69 # - owner_put_ref: Callback to put a reference on the owner.
70
71 @classmethod
72 def _create_from_ptr_and_get_ref(cls, ptr, owner_ptr,
73 owner_get_ref, owner_put_ref):
74 obj = cls.__new__(cls)
75
76 obj._ptr = ptr
77 obj._owner_ptr = owner_ptr
78 obj._owner_get_ref = owner_get_ref
79 obj._owner_put_ref = owner_put_ref
80
81 obj._owner_get_ref(obj._owner_ptr)
82
83 return obj
84
85 def __del__(self):
86 self._owner_put_ref(self._owner_ptr)
87
88
89 # Python object that owns a reference to a Babeltrace object.
90 class _SharedObject(_BaseObject):
91
92 # Get a new reference on ptr.
93 #
94 # This must be implemented by subclasses to work correctly with a pointer
95 # of the native type they wrap.
96
97 @staticmethod
98 def _get_ref(ptr):
99 raise NotImplementedError
100
101 # Put a reference on ptr.
102 #
103 # This must be implemented by subclasses to work correctly with a pointer
104 # of the native type they wrap.
105
106 @staticmethod
107 def _put_ref(ptr):
108 raise NotImplementedError
109
110 # Create a _SharedObject from an existing reference.
111 #
112 # This assumes that the caller owns a reference to the Babeltrace object
113 # and transfers this ownership to the newly created Python object.
114
115 @classmethod
116 def _create_from_ptr(cls, ptr_owned):
117 obj = cls.__new__(cls)
118 obj._ptr = ptr_owned
119 return obj
120
121 # Like _create_from_ptr, but acquire a new reference rather than
122 # stealing the caller's reference.
123
124 @classmethod
125 def _create_from_ptr_and_get_ref(cls, ptr):
126 obj = cls._create_from_ptr(ptr)
127 cls._get_ref(obj._ptr)
128 return obj
129
130 def _release(self):
131 """Return the wrapped pointer, transfer its ownership to the
132 caller."""
133 ptr = self._ptr
134 self._ptr = None
135 return ptr
136
137 def __del__(self):
138 self._put_ref(self._ptr)
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