[FFmpeg-devel] [PATCH 1/7] [GSoC] lavf: add directory listing API

[Michael Niedermayer]

On Fri, Mar 20, 2015 at 11:26:34PM +0100, Michael Niedermayer wrote:
> On Fri, Mar 20, 2015 at 10:31:56PM +0100, Lukasz Marek wrote:
> > On 20.03.2015 14:55, Michael Niedermayer wrote:
> > >On Fri, Mar 20, 2015 at 03:01:56AM +0100, Mariusz Szczepańczyk wrote:
> > >>From: Lukasz Marek <lukasz.m.luki2 at gmail.com>
> > >>  /**
> > >>+ * Open directory for reading.
> > >>+ *
> > >>+ * @param s       directory read context. Pointer to a NULL pointer must be passed.
> > >>+ * @param url     directory to be listed.
> > >>+ * @param options protocol options.
> > >>+ * @return >=0 on success or negative on error.
> > >>+ */
> > >>+int avio_open_dir(void **s, const char *url, AVDictionary **options);
> > >
> > >why void ** ? and not a more specific type ?
> > >a more specific type would allow the compiler to check types
> > 
> > I can't remember exactly why, but as far as I remember
> > it could be URLContext, but it is not a public struct.
> 
> > Also, creating dummy struct, to have it stored as void * inside is
> > not much better, but maybe it is. (the same as AVIOContext stores it
> > in void *opaque)
> 
> I think the type should not be void ** when in fact theres only one
> type that is valid and allowed
> Its different if it would be intended to allow multiple types
> 
> The goal is that a user application cannot mistakely pass the wrong
> type
> If a struct was used, the layout of that struct does not need to be
> defined in a public header so it can be a URLContext

to clarify this as it maybe could be misunderstood
a public struct like AVDirectoryWhatever and that contains a
URLContext

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The bravest are surely those who have the clearest vision
of what is before them, glory and danger alike, and yet
notwithstanding go out to meet it. -- Thucydides
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