[v3,01/18] trace: add trace event iterator APIs

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 <berrange@redhat.com>
---
 trace/control.c | 21 +++++++++++++++++++++
 trace/control.h | 27 +++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

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.

an -> a
future proof -> future-proof

> 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 <berrange@redhat.com>

As for patch contents:

Reviewed-by: Lluís Vilanova <vilanova@ac.upc.edu>


> ---
>  trace/control.c | 21 +++++++++++++++++++++
>  trace/control.h | 27 +++++++++++++++++++++++++++
>  2 files changed, 48 insertions(+)

> diff --git a/trace/control.c b/trace/control.c
> index 05d85ac..1a96049 100644
> --- a/trace/control.c
> +++ b/trace/control.c
> @@ -125,6 +125,27 @@ 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) {
> +        TraceEvent *ev = &(trace_events[iter->event]);
> +        iter->event++;
> +        if (!iter->pattern ||
> +            pattern_glob(iter->pattern,
> +                         trace_event_get_name(ev))) {
> +            return ev;
> +        }
> +    }
> +
> +    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;
> +    const char *pattern;
> +} TraceEventIter;
 
>  /**
>   * TraceEventID:
> @@ -25,6 +29,29 @@
>   */
>  enum TraceEventID;
 
> +
> +/**
> + * trace_event_iter_init:
> + * @iter: the event iterator struct
> + * @pattern: optional pattern to filter events on name
> + *
> + * Initialize the event iterator struct @iter,
> + * optionally using @pattern to filter out events
> + * with non-matching names.
> + */
> +void trace_event_iter_init(TraceEventIter *iter, const char *pattern);
> +
> +/**
> + * trace_event_iter_next:
> + * @iter: the event iterator struct
> + *
> + * Get the next event, if any. When this returns NULL,
> + * the iterator should no longer be used.
> + *
> + * Returns: the next event, or NULL if no more events exist
> + */
> +TraceEvent *trace_event_iter_next(TraceEventIter *iter);
> +
>  /**
>   * trace_event_id:
>   * @id: Event identifier.
> -- 
> 2.7.4