Re: [ctypes-users] copying/slicing ctypes arrays, (c_ulong *n)()

[Ray S. <rj...@bl...>]

At 10:09 PM 2/2/2005 +0100, Thomas Heller wrote:
>RayS <ra...@bl...> writes:
>
> > Alternatively, do you expect to implement the acceptance of Python
> > objects which implement the buffer interface in the near future?
>
>I hope to be able to make a new release this or next week.  So far, I
>think objects implementing the buffer interface should *not* be allowed
>as function parameters, but *buffer objects* should be.  The reason is
>that the former would break too much code.
>
>IIUC, you should then be able to call buffer() on a Numeric array
>instance and pass that to a function, or call buffer() on the _data
>member of a Numarray array instance.
>
>The buffer() object has been changed in Python 2.4 (or was it even 2.3?)
>so that it retrieves the memory block address from the original object
>each time it is needed, instead of getting it once and then storing it
>permanently.  So it should be even safe if the original object changes
>its internal memory block.

Ahh, thanks for the insight.

 >>> import Numeric, string
 >>> N=Numeric.zeros((100,), Numeric.Float)
 >>> repr(N.__copy__)
'<built-in method __copy__ of array object at 0x007B10B8>'
 >>> buffer(N, 0, 0)
<read-only buffer for 0x007B10B8, ptr 0x00809A98, size 0 at 0x0082B0D0>
 >>> buffer(N, 50, 50)
<read-only buffer for 0x007B10B8, ptr 0x00809ACA, size 50 at 0x00828E98>
 >>> string.split(buf.__repr__())[5]
'0x00809A98,'
 >>> int(string.split(buf.__repr__())[5][:-1], 16)
8428184

I presume (!) that the ptr address could be passed to ctypes.memmove()
At least, I'll try; memmove() does work fine with numarray.info address.

The desire is to write form the ctypes DLL call into the Numeric array, so 
actually using the buffer(N) is out.

Ray