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"""Run-time calculation of offset into Python Numeric (old) structures
Numeric Python, by fortuitous chance, puts the one thing
we need precisely as the first value in the structure beyond the
PyObject * header, so that it's exactly that many bytes from the
pointer value for the object...
"""
import ctypes
def dataPointerFunction( ):
"""Calculate the data-pointer offset in the Numeric object header"""
offset = object.__basicsize__
from_address = ctypes.c_void_p.from_address
def dataPointer( data):
"""Return pointer-to-data + offset"""
return from_address( id( data ) + offset ).value
return dataPointer
dataPointer = dataPointerFunction()
if __name__ == "__main__":
import Numeric
test = Numeric.arange( 0,200, 1,'i' )
aType = ctypes.c_int * 200
test2 = aType.from_address( dataPointer( test ) )
assert test == test2, (test,test2)
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