Re: [PATCH V4 4/8] libgpiod: Add rust wrapper crate

[Viresh Kumar <viresh.kumar@linaro.org>]

On 27-07-22, 10:57, Kent Gibson wrote:
> On Fri, Jul 08, 2022 at 05:04:57PM +0530, Viresh Kumar wrote:
 
> > +    /// Get the number of events the buffers stores.
> 
> stores -> contains
> 
> The capacity indicates the number that can be stored.
> This field indicates the number the buffer currently contains.
> 
> And, as mentioned above, rename to len(), and return value should be
> usize.
> 
> Add a set_len() method to replace the max_events parameter in
> LineRequest::read_edge_event() to handle the unusual case where the user
> only wants to partially fill the buffer.

So capacity is max that can be stored, len is what is currently present. What
read_edge_event() needs is how much we want it to read, which should be <=
capacity.

If we remove the parameter to read_edge_event(), then it must fetch the value
from the buffer itself, which should be buffer.capacity() if user hasn't called
set_len(), else it will be that special value the user sets.

What do you want to call the value (to be added as a field to struct
EdgeEventBuffer) and the helper routine to fetch it ?

Maybe we should name it "max_events" and call the helpers as max_events() and
set_max_events() instead of set_len()?

> > +    pub fn get_num_events(&self) -> u32 {
> > +        unsafe { bindings::gpiod_edge_event_buffer_get_num_events(self.buffer()) as u32 }
> > +    }
> > +}

-- 
viresh