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from ctypes import c_void_p
class CPointerBase:
"""
Base class for objects that have a pointer access property
that controls access to the underlying C pointer.
"""
_ptr = None # Initially the pointer is NULL.
ptr_type = c_void_p
destructor = None
null_ptr_exception_class = AttributeError
@property
def ptr(self):
# Raise an exception if the pointer isn't valid so that NULL pointers
# aren't passed to routines -- that's very bad.
if self._ptr:
return self._ptr
raise self.null_ptr_exception_class(
"NULL %s pointer encountered." % self.__class__.__name__
)
@ptr.setter
def ptr(self, ptr):
# Only allow the pointer to be set with pointers of the compatible
# type or None (NULL).
if not (ptr is None or isinstance(ptr, self.ptr_type)):
raise TypeError("Incompatible pointer type: %s." % type(ptr))
self._ptr = ptr
def __del__(self):
"""
Free the memory used by the C++ object.
"""
if self.destructor and self._ptr:
try:
self.destructor(self.ptr)
except (AttributeError, ImportError, TypeError):
pass # Some part might already have been garbage collected
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