On 30.10.20 г. 3:57 ч., Steven Rostedt wrote:
On Thu, 29 Oct 2020 16:49:03 +0200 "Yordan Karadzhov (VMware)" <y.karadz@xxxxxxxxx> wrote:Maybe I don't understand your idea very well, but I think what you suggest has very different behavior. What I want is the implementation of the interface to stay in the same header file (libkshark.h). In the future we can add more interfaces but this will be again in the same header (libkshark.h).Maybe I got confused ;-) Is there going to be different interface structures? Why the "void *" and not just supply a "struct kshark_data_stream *"?
Hi Steven,Yes, my idea is that in the future we may decide to change something in the interface, or to have a second completely different interface, while we may still need to keep the interface version that we have now for backward compatibility.
That way at least you have some kind of type checking when tasks move things around. I try to avoid using "void *" because it can easily be the source of unwanted bugs, due to the lack of type checking.
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?
Thanks a lot!
Yordan
-- Steve
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