Re: [Qemu-devel] [PATCH v2 1/6] trace: add trace event iterator APIs

[Lluís Vilanova]

Daniel P Berrange writes:

> Currently methods which want to iterate over trace events,
> do so using the trace_event_count() and trace_event_id()
> methods. This leaks the concept of a single ID enum to
> the callers. There is an alternative trace_event_pattern()
> method which can be used in an iteration context, but its
> design is stateless, so is not easy to expand it in the
> future.

> This defines a formal iterator API will provide an future
> proof way of iterating over events.

> The iterator is also able to apply a pattern match filter
> to events, further removing the need for the pattern

> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
>  trace/control.c | 20 ++++++++++++++++++++
>  trace/control.h | 27 +++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+)

> diff --git a/trace/control.c b/trace/control.c
> index 05d85ac..b871727 100644
> --- a/trace/control.c
> +++ b/trace/control.c
> @@ -125,6 +125,26 @@ TraceEvent *trace_event_pattern(const char *pat, 
> TraceEvent *ev)
>      return NULL;
>  }
 
> +void trace_event_iter_init(TraceEventIter *iter, const char *pattern)
> +{
> +    iter->event = 0;
> +    iter->pattern = pattern;
> +}
> +
> +TraceEvent *trace_event_iter_next(TraceEventIter *iter)
> +{
> +    while (iter->event < TRACE_EVENT_COUNT) {
> +        if (!iter->pattern ||
> +            pattern_glob(iter->pattern,
> +                         
> trace_event_get_name(&(trace_events[iter->event])))) {
> +            return &(trace_events[iter->event]);

That's a picky one (feel free to ignore), but can you refactor
"&(trace_events[iter->event])" out into a variable? The long pattern_glob() call
is a bit hard to parse.


> +        }
> +        iter->event++;
> +    }
> +
> +    return NULL;
> +}
> +
>  void trace_list_events(void)
>  {
>      int i;
> diff --git a/trace/control.h b/trace/control.h
> index 27a16fc..c71b405 100644
> --- a/trace/control.h
> +++ b/trace/control.h
> @@ -13,6 +13,10 @@
>  #include "qemu-common.h"
>  #include "trace/generated-events.h"
 
> +typedef struct TraceEventIter {
> +    size_t event;

Shouldn't this be TraceEventID for consistence with "trace/control.h"? But if
you're going to drop TraceEventID in a later series feel free to ignore me.

Other than those two, the rest looks good to me.


Cheers,
  Lluis