cytpes **int

[Gabriel Genellina]

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)

-- 
Gabriel Genellina