| 1 | # SPDX-License-Identifier: MIT |
| 2 | # |
| 3 | # Copyright (c) 2017 Philippe Proulx <pproulx@efficios.com> |
| 4 | |
| 5 | |
| 6 | import abc |
| 7 | |
| 8 | |
| 9 | class _BaseObject: |
| 10 | # Ensure that the object always has _ptr set, even if it throws during |
| 11 | # construction. |
| 12 | |
| 13 | def __new__(cls, *args, **kwargs): |
| 14 | obj = super().__new__(cls) |
| 15 | obj._ptr = None |
| 16 | return obj |
| 17 | |
| 18 | def __init__(self, ptr): |
| 19 | self._ptr = ptr |
| 20 | |
| 21 | @property |
| 22 | def addr(self): |
| 23 | return int(self._ptr) |
| 24 | |
| 25 | def __repr__(self): |
| 26 | return "<{}.{} object @ {}>".format( |
| 27 | self.__class__.__module__, self.__class__.__name__, hex(self.addr) |
| 28 | ) |
| 29 | |
| 30 | def __copy__(self): |
| 31 | raise NotImplementedError |
| 32 | |
| 33 | def __deepcopy__(self, memo): |
| 34 | raise NotImplementedError |
| 35 | |
| 36 | |
| 37 | # A Python object that is itself not refcounted, but is wholly owned by an |
| 38 | # object that is itself refcounted (a _SharedObject). A Babeltrace unique |
| 39 | # object gets destroyed once its owner gets destroyed (its refcount drops to |
| 40 | # 0). |
| 41 | # |
| 42 | # In the Python bindings, to avoid having to deal with issues with the lifetime |
| 43 | # of unique objects, we make it so acquiring a reference on a unique object |
| 44 | # acquires a reference on its owner. |
| 45 | |
| 46 | |
| 47 | class _UniqueObject(_BaseObject): |
| 48 | # Create a _UniqueObject. |
| 49 | # |
| 50 | # - ptr: SWIG Object, pointer to the unique object. |
| 51 | # - owner_ptr: SWIG Object, pointer to the owner of the unique |
| 52 | # object. A new reference is acquired. |
| 53 | # - owner_get_ref: Callback to get a reference on the owner |
| 54 | # - owner_put_ref: Callback to put a reference on the owner. |
| 55 | |
| 56 | @classmethod |
| 57 | def _create_from_ptr_and_get_ref(cls, ptr, owner_ptr, owner_get_ref, owner_put_ref): |
| 58 | obj = cls.__new__(cls) |
| 59 | |
| 60 | obj._ptr = ptr |
| 61 | obj._owner_ptr = owner_ptr |
| 62 | obj._owner_get_ref = owner_get_ref |
| 63 | obj._owner_put_ref = owner_put_ref |
| 64 | |
| 65 | obj._owner_get_ref(obj._owner_ptr) |
| 66 | |
| 67 | return obj |
| 68 | |
| 69 | def __del__(self): |
| 70 | self._owner_put_ref(self._owner_ptr) |
| 71 | |
| 72 | |
| 73 | # Python object that owns a reference to a Babeltrace object. |
| 74 | class _SharedObject(_BaseObject, abc.ABC): |
| 75 | # Get a new reference on ptr. |
| 76 | # |
| 77 | # This must be implemented by subclasses to work correctly with a pointer |
| 78 | # of the native type they wrap. |
| 79 | |
| 80 | @staticmethod |
| 81 | @abc.abstractmethod |
| 82 | def _get_ref(ptr): |
| 83 | raise NotImplementedError |
| 84 | |
| 85 | # Put a reference on ptr. |
| 86 | # |
| 87 | # This must be implemented by subclasses to work correctly with a pointer |
| 88 | # of the native type they wrap. |
| 89 | |
| 90 | @staticmethod |
| 91 | @abc.abstractmethod |
| 92 | def _put_ref(ptr): |
| 93 | raise NotImplementedError |
| 94 | |
| 95 | # Create a _SharedObject from an existing reference. |
| 96 | # |
| 97 | # This assumes that the caller owns a reference to the Babeltrace object |
| 98 | # and transfers this ownership to the newly created Python object. |
| 99 | |
| 100 | @classmethod |
| 101 | def _create_from_ptr(cls, ptr_owned): |
| 102 | obj = cls.__new__(cls) |
| 103 | obj._ptr = ptr_owned |
| 104 | return obj |
| 105 | |
| 106 | # Like _create_from_ptr, but acquire a new reference rather than |
| 107 | # stealing the caller's reference. |
| 108 | |
| 109 | @classmethod |
| 110 | def _create_from_ptr_and_get_ref(cls, ptr): |
| 111 | obj = cls._create_from_ptr(ptr) |
| 112 | cls._get_ref(obj._ptr) |
| 113 | return obj |
| 114 | |
| 115 | def __del__(self): |
| 116 | self._put_ref(self._ptr) |