perf streams: Get the evsel_streams by evsel_idx

In previous patch, we have created evsel_streams array.

This patch returns the specified evsel_streams according to the
evsel_idx.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20201009022845.13141-3-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/stream.c

@@ -162,3 +162,16 @@ struct evlist_streams *evlist__create_streams(struct evlist *evlist,
 
 	return els;
 }
+
+struct evsel_streams *evsel_streams__entry(struct evlist_streams *els,
+					   int evsel_idx)
+{
+	struct evsel_streams *es = els->ev_streams;
+
+	for (int i = 0; i < els->nr_evsel; i++) {
+		if (es[i].evsel_idx == evsel_idx)
+			return &es[i];
+	}
+
+	return NULL;
+}

tools/perf/util/stream.h

@@ -27,4 +27,7 @@ void evlist_streams__delete(struct evlist_streams *els);
 struct evlist_streams *evlist__create_streams(struct evlist *evlist,
 					      int nr_streams_max);
 
+struct evsel_streams *evsel_streams__entry(struct evlist_streams *els,
+					   int evsel_idx);
+
 #endif /* __PERF_STREAM_H */