tools lib traceevent: Add trace_seq_reset()

Sometimes it'd be useful if existing trace_seq can be reused.  But
currently it's impossible since there's no API to reset the trace_seq.
Let's add trace_seq_reset() for this case.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1370323231-14022-5-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/event-parse.h

@@ -69,6 +69,7 @@ struct trace_seq {
 };
 
 void trace_seq_init(struct trace_seq *s);
+void trace_seq_reset(struct trace_seq *s);
 void trace_seq_destroy(struct trace_seq *s);
 
 extern int trace_seq_printf(struct trace_seq *s, const char *fmt, ...)

tools/lib/traceevent/trace-seq.c

@@ -48,6 +48,19 @@ void trace_seq_init(struct trace_seq *s)
 	s->buffer = malloc_or_die(s->buffer_size);
 }
 
+/**
+ * trace_seq_reset - re-initialize the trace_seq structure
+ * @s: a pointer to the trace_seq structure to reset
+ */
+void trace_seq_reset(struct trace_seq *s)
+{
+	if (!s)
+		return;
+	TRACE_SEQ_CHECK(s);
+	s->len = 0;
+	s->readpos = 0;
+}
+
 /**
  * trace_seq_destroy - free up memory of a trace_seq
  * @s: a pointer to the trace_seq to free the buffer