cytpes **int

[Diez B. Roggisch]

Gabriel Genellina schrieb:
> En Mon, 28 Apr 2008 18:55:15 -0300, Diez B. Roggisch 
> <deets at nospam.web.de> escribió:
>> VernM schrieb:
>>> I am using ctypes to wrap a set of functions in a DLL. It has been
>>> going very well, and I am very impressed with ctypes. I want to call a
>>> c function with a signature of: void func(int **cube), where the array
>>> if ints in cube is modified by func. I want to setup cube with int
>>> values, and access them after the call to func. I unerstand how to
>>> setup the ctypes array, but how do I pass **cube to the function, and
>>> how do I access the results?
>>
>> it should be simple.
>>
>> use something like (untestet):
>>
>> b = POINTER(c_int)()
>> func(byref(b))
> 
> [snip two other similar alternatives]
> 
> That's true for "a pointer to a pointer to int", and it's valid if the 
> functions references **b or b[0][0] - but in this case int** probably 
> means "[pointer to] an array of arrays of int" and presumibly the 
> function will try to access b[3][2] (or whatever indices are in range).
> The duality pointer/array in C is dangerous when defining interfases - 
> you have to know how the value is intended to be accessed.
> (I assume the function modifies the integer values, but not the pointers 
> themselves)
> 
> # build an array of 10x10 ints
> Arr10int = c_int * 10
> Pint = POINTER(c_int)
> PPint = POINTER(Pint)
> Arr10pint = Pint * 10
> a = Arr10pint()
> for i in range(10):
>     a[i] = Arr10int()
> ... initialize the array ...
> ... load the function ...
> # call the function
> somefunction.argtypes = (PPint,)
> somefunction.restype = None
> somefunction(a)
> 

Yup, you are right - I somehow missed the access description and thought 
of the pointer-to-a-pointer as out-parameter-spec.

Diez