On Tue, 3 Nov 2020 15:38:33 +0200
"Yordan Karadzhov (VMware)" <y.karadz@xxxxxxxxx> wrote:
> What if we define the interface to start with an integer identifier?
>
> /** Data interface identifier. */
> typedef enum kshark_data_interface_id {
> /** An interface with unknown type. */
> KS_INVALIDE_INTERFACE,
>
> /** Generic interface suitable Ftrace data. */
> KS_GENERIC_DATA_INTERFACE,
> } kshark_data_interface_id;
>
> /**
> * Structure representing the interface of methods used to operate over
> * the data from a given stream.
> */
> struct kshark_generic_stream_interface {
> /** Interface version identifier. */
> int type; /* MUST BE FIRST ENTRY */
>
> /** Method used to retrieve the Process Id of the entry. */
> stream_get_int_func get_pid;
>
> /** Method used to retrieve the Event Id of the entry. */
> stream_get_int_func get_event_id;
>
> ....
>
> and it can be used like this:
>
> char *kshark_get_aux_field(const struct kshark_entry *entry)
> {
> struct kshark_generic_stream_interface *interface;
> struct kshark_data_stream *stream =
> kshark_get_stream_from_entry(entry);
>
> ....
>
> interface = stream->interface;
> if (interface->type == KS_GENERIC_DATA_INTERFACE &&
> interface->aux_field)
> return interface->aux_field(stream, entry);
>
> return NULL;
> }
>
> What do you think?
This was actually what I was getting at ;-)
That is a common practice in the Linux kernel.
-- Steve
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