Re: How to get binary data to callback function

On 22/12/2009, Nikolaus Rath <[email protected]> wrote:
>
> When I define a callback function with a prototype of
>
>    ctypes.CFUNCTYPE(None, ctypes.c_char_p, ctypes.c_int)

You have the prototype wrong, c_char_p is for null-terminated strings:

<http://docs.python.org/library/ctypes.html#ctypes.c_char_p>

You want to use `ctypes.POINTER(ctypes.c_char)` instead for the definition.

> The function receives a true Python string. However, my data isn't
> actually \0 terminated, and I would like to call string_at(par1, par2)
> to get the binary data. But how do I get ctypes to pass the c_char_p
> object to my function, rather than the unwrapped string?

The python callback function you write also needs to pass the second
(size) argument to string_at which will otherwise assume
null-termination.

Martin

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