On Tue, 11 Sep 2007 05:09:58 -0700, Tim wrote:
> On Sep 10, 3:31 pm, Marc 'BlackJack' Rintsch <[EMAIL PROTECTED]> wrote:
>> On Mon, 10 Sep 2007 11:38:50 -0700, Tim wrote:
>> > How do I memcpy from a pointer to an array of floats in python?
>>
>> > I get errors: NameError: global name 'row' is not defined
>>
>> Well than the (global) name `row` is not defined. Quite clear message,
>> isn't it? ;-)
>>
>> > I want to be able to get the row[i] array element. In C I would
>> > normally place the address of row as the first argument.
>>
>> > cdll.msvcrt.memcpy( row, pData, 256 )
>>
>> > If I define row as the following I also get the following error:
>>
>> > row = ones( TOTAL_PARAMETER_ENTRIES, dtype=float )
>>
>> > ArgumentError: argument 1: <type 'exceptions.TypeError'>: Don't know
>> > how to convert parameter 1
>>
>> You don't give enough information so we have to guess. For example I
>> guess the `ones()` function comes from one of the packages `numeric`,
>> `numarray` or `numpy`!?
>>
>> This function returns a Python object. You can't use arbitrary Python
>> objects with `ctypes`. `memcpy` expects a pointer not an object.
>
> Can I initialize something in Python that I can get access to it's
> pointer?
"It's pointer"? Then you have a pointer to a structure that represents
the Python object but still no idea what data is at that pointer. This is
an implementation detail of the Python version and of the particular
object.
> Here is what I would like to write:
>
> shared_memory_pointer = windll.kernel32.MapViewOfFile(hMapObject,
> FILE_MAP_ALL_ACCESS,
> 0, 0, TABLE_SHMEMSIZE)
>
> memcpy( self.data, shared_memory_pointer, my_size )
I haven't tested but it should be possible to declare the return type of
`windll.kernel32.MapViewOfFile()` as ``ctypes.POINTER(ctypes.c_double *
256)`` and then do:
test_data = numpy.ones(1000)
shared_memory_pointer.contents[0:256] = test_data[0:256]
Ciao,
Marc 'BlackJack' Rintsch
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