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

Chris Angelico rosuav at gmail.com
Thu Apr 12 04:05:07 EDT 2018


On Thu, Apr 12, 2018 at 4:20 PM,  <jfong at ms4.hinet.net> wrote:
> Chris Angelico於 2018年4月12日星期四 UTC+8下午1時31分35秒寫道:
>> On Thu, Apr 12, 2018 at 2:16 PM,  <jfong at ms4.hinet.net> 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.
>> >
>> > 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?
>> >
>>
>> You suppose? Or have you tested it?
>>
>> ChrisA
>
> Yes, I had test it once before. Now, I re-do it again to make sure. After a call which returns 3 bytes of data, I use len(buf) to check the length and get the number 24. I can see the first 24 bytes of data by using buf[:30] but buf[24] will cause an "index out of range" error. I don't know how to see what the buf[24] exactly is but I suppose it might be a zero byte.
>

If you have 24 bytes, they're numbered 0 through 23. So there is no byte at 24.

ChrisA


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