How to write partial of a buffer which was returned from a C function to a file?

Jach Fong jfong at
Thu Apr 12 04:11:48 EDT 2018

This is the first time I am using python-list to interact with 
comp.lang.python forum (because there are so many spam when using 
browser to view it) so forgive me if something goes wrong.

Python already treat the returned buffer as 'bytes'. The problem is 
Python don't know its size (or decides it wrong:-).


Cameron Simpson at 2018/4/12 PM 02:28 wrote:
> On 11Apr2018 21:16, jfong at <jfong at> wrote:
>> This C function returns a buffer which I declared it as a 
>> ctypes.c_char_p. The buffer has size 0x10000 bytes long and the valid 
>> data may vary from a few bytes to the whole size.
> Could you show us the function?
>> In every call I know how much the valid data size is, but I suppose I 
>> can't use slice to get it because there may be zero byte in it. What 
>> to do?
> Why not just return bytes? Allocate one of the correct size and copy the 
> bytes into it, then return?
> Of course it is all hard to say without seeing some actual code.
> Cheers,
> Cameron Simpson <cs at>

This email has been checked for viruses by Avast antivirus software.

More information about the Python-list mailing list