On 28 January 2015 at 12:55, Savolainen, Petri (NSN - FI/Espoo)
<petri.savolai...@nsn.com> wrote:
>
>
>> -----Original Message-----
>> From: ext Ola Liljedahl [mailto:ola.liljed...@linaro.org]
>> Sent: Wednesday, January 28, 2015 1:29 PM
>> To: Savolainen, Petri (NSN - FI/Espoo)
>> Cc: LNG ODP Mailman List
>> Subject: Re: [lng-odp] odp_cpumask.h
>>
>> On 28 January 2015 at 12:21, Savolainen, Petri (NSN - FI/Espoo)
>> <petri.savolai...@nsn.com> wrote:
>> >
>> >
>> >> -----Original Message-----
>> >> From: lng-odp-boun...@lists.linaro.org [mailto:lng-odp-
>> >> boun...@lists.linaro.org] On Behalf Of ext Ola Liljedahl
>> >> Sent: Wednesday, January 28, 2015 12:48 PM
>> >> To: LNG ODP Mailman List
>> >> Subject: [lng-odp] odp_cpumask.h
>> >>
>> >> * @param str Output buffer
>> >> * @param len Size of string length (incl. ending zero)
>> >> */
>> >> void odp_cpumask_to_str(const odp_cpumask_t *mask, char *str, int len);
>> >>
>> >> Why don't we use size_t for the"len" parameter?
>> >>
>> >> -- Ola
>> >
>> >
>> > It's an object size, so it can be changed to size_t (similar to e.g.
>> snprintf()).
>> >
>> > Packet data len/offsets, buffer sizes, packet/bytes counts etc, should
>> be uintxx_t - but object sizes should be size_t.
>> >
>> >
>> > Answer to: What happens if len < output length? Maybe we copy the
>> snprintf definition (except output also ending zero). Return number chars
>> written (incl. str ending zero), otherwise return number of chars that
>> would have been outputted (return >len and clip output).
>> This is more complicated to check for and goes against the convention
>> of returning <0 for errors.
>> I would prefer my suggestion with returning -(minimum required buffer
>> size), there's a clear separation between success and error.
>>
>> And that we add a define with a suggested buffer size which will be
>> usable when the CPU mask is full (all bits set), this seems to be 128
>> when using Linux cpu_set_t for the implementation. Of course ODP could
>> use a smaller max size as well.
>
>
> About error from functions that return len. I'd have input param and return
> type the same, so that compiler don't complain when comparing those (maybe
> your audio was breaking on call yesterday on that part).
No I didn't hear, my wifi router stopped working and had to be reset...
>
> e.g.
>
> size_t odp_cpumask_to_str(const odp_cpumask_t *mask, char *str, size_t len);
Better to use ssize_t then?
>
>
> size_t len, out;
> char str[SIZE];
>
> len = sizeof(str);
>
> out = odp_cpumask_to_str(mask, str, len);
>
> if (out > len) {
Simple yes. But we just defined the convention that we use negative
values to indicate failures. Why not follow that here?
To use positive values to indicate both success and error conditions
seems confusing to me. snprintf is not a good example here.
> printf("output needs %z chars", out);
> ABORT();
> }
>
>
> -Petri
>
>
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