[Tutor] pass a memory pointer to a c function

[Nathan Smith]

Hello!


I actually managed to figure this out myself, but do have a related 
question (I hope you all don't mind!).

My solution was:

import ctypes

data=b/"some text"

x=bytearray(data)

Buffer = ctypes.c_char * len(x)

buf = Buffer.from_buffer(x)

addr=ctypes.addressof(buf)


Then pass addr to the c function.


My question is, do I need to free that buffer? Will python do it when 
the object is deleted?

Thanks

On 30/01/2022 01:34, Nathan Smith wrote:
> Hi list,
>
>
> Put simply, I have a c function which takes a memory pointer as one of 
> the arguments, "An unmanaged pointer to the memory location as an 
> IntPtr." which I am calling from a python program.
>
>
> I've done some digging and it looks like tempfile can write to the 
> memory, but can I use that to then get the pointer and pass it over?
>
> More digging seems to indicate id(obj) gets the memory location for 
> that object, but as it is a python object I'm guessing that is not 
> much use?
>
> What I want the function to receive is the memory pointer for the data 
> in the tempfile, rather than the python tempfile object.
>
>
> I've also figured out that ctypes.pointer(i) is probably what I want, 
> where i is a ctypes.c_int(python_int) of some kind, but getting py_int 
> to be the correct memory locations is my stumbling block
>
>
> Sorry in advance if my terms are off here, I'm only a passing c user and.
>
> I hope someone can point me in the right direction!
>
> Nathan
>
-- 

Best Wishes,

Nathan Smith, BSC


My Website: https://nathantech.net