39 lines
1.3 KiB
Python
39 lines
1.3 KiB
Python
from ctypes import c_void_p
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from django.contrib.gis.geos.error import GEOSException
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class GEOSBase(object):
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"""
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Base object for GEOS objects that has a pointer access property
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that controls access to the underlying C pointer.
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"""
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# Initially the pointer is NULL.
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_ptr = None
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# Default allowed pointer type.
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ptr_type = c_void_p
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# Pointer access property.
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def _get_ptr(self):
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# Raise an exception if the pointer isn't valid don't
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# want to be passing NULL pointers to routines --
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# that's very bad.
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if self._ptr:
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return self._ptr
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else:
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raise GEOSException('NULL GEOS %s pointer encountered.' % self.__class__.__name__)
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def _set_ptr(self, ptr):
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# Only allow the pointer to be set with pointers of the
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# compatible type or None (NULL).
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if ptr is None or isinstance(ptr, self.ptr_type):
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self._ptr = ptr
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else:
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raise TypeError('Incompatible pointer type')
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# Property for controlling access to the GEOS object pointers. Using
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# this raises an exception when the pointer is NULL, thus preventing
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# the C library from attempting to access an invalid memory location.
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ptr = property(_get_ptr, _set_ptr)
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