Re-organize sources

[babeltrace.git] / src / bindings / python / bt2 / bt2 / object.py

diff --git a/src/bindings/python/bt2/bt2/object.py b/src/bindings/python/bt2/bt2/object.py
new file mode 100644 (file)
index 0000000..218965d
--- /dev/null
+++ b/src/bindings/python/bt2/bt2/object.py
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+# The MIT License (MIT)
+#
+# Copyright (c) 2017 Philippe Proulx <pproulx@efficios.com>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+
+class _BaseObject:
+    # Ensure that the object always has _ptr set, even if it throws during
+    # construction.
+
+    def __new__(cls, *args, **kwargs):
+        obj = super().__new__(cls)
+        obj._ptr = None
+        return obj
+
+    def __init__(self, ptr):
+        self._ptr = ptr
+
+    @property
+    def addr(self):
+        return int(self._ptr)
+
+    def __repr__(self):
+        return '<{}.{} object @ {}>'.format(self.__class__.__module__,
+                                            self.__class__.__name__,
+                                            hex(self.addr))
+
+    def __copy__(self):
+        raise NotImplementedError
+
+    def __deepcopy__(self, memo):
+        raise NotImplementedError
+
+
+# A Python object that is itself not refcounted, but is wholly owned by an
+# object that is itself refcounted (a _SharedObject).  A Babeltrace unique
+# object gets destroyed once its owner gets destroyed (its refcount drops to
+# 0).
+#
+# In the Python bindings, to avoid having to deal with issues with the lifetime
+# of unique objects, we make it so acquiring a reference on a unique object
+# acquires a reference on its owner.
+
+class _UniqueObject(_BaseObject):
+
+    # Create a _UniqueObject.
+    #
+    #   - ptr: SWIG Object, pointer to the unique object.
+    #   - owner_ptr: SWIG Object, pointer to the owner of the unique
+    #     object.  A new reference is acquired.
+    #   - owner_get_ref: Callback to get a reference on the owner
+    #   - owner_put_ref: Callback to put a reference on the owner.
+
+    @classmethod
+    def _create_from_ptr_and_get_ref(cls, ptr, owner_ptr,
+                                     owner_get_ref, owner_put_ref):
+        obj = cls.__new__(cls)
+
+        obj._ptr = ptr
+        obj._owner_ptr = owner_ptr
+        obj._owner_get_ref = owner_get_ref
+        obj._owner_put_ref = owner_put_ref
+
+        obj._owner_get_ref(obj._owner_ptr)
+
+        return obj
+
+    def __del__(self):
+        self._owner_put_ref(self._owner_ptr)
+
+
+# Python object that owns a reference to a Babeltrace object.
+class _SharedObject(_BaseObject):
+
+    # Get a new reference on ptr.
+    #
+    # This must be implemented by subclasses to work correctly with a pointer
+    # of the native type they wrap.
+
+    @staticmethod
+    def _get_ref(ptr):
+        raise NotImplementedError
+
+    # Put a reference on ptr.
+    #
+    # This must be implemented by subclasses to work correctly with a pointer
+    # of the native type they wrap.
+
+    @staticmethod
+    def _put_ref(ptr):
+        raise NotImplementedError
+
+    # Create a _SharedObject from an existing reference.
+    #
+    # This assumes that the caller owns a reference to the Babeltrace object
+    # and transfers this ownership to the newly created Python object.
+
+    @classmethod
+    def _create_from_ptr(cls, ptr_owned):
+        obj = cls.__new__(cls)
+        obj._ptr = ptr_owned
+        return obj
+
+    # Like _create_from_ptr, but acquire a new reference rather than
+    # stealing the caller's reference.
+
+    @classmethod
+    def _create_from_ptr_and_get_ref(cls, ptr):
+        obj = cls._create_from_ptr(ptr)
+        cls._get_ref(obj._ptr)
+        return obj
+
+    def _release(self):
+        """Return the wrapped pointer, transfer its ownership to the
+        caller."""
+        ptr = self._ptr
+        self._ptr = None
+        return ptr
+
+    def __del__(self):
+        self._put_ref(self._ptr)