[PATCH v7 13/16] perf python: Add evlist metrics function

[Ian Rogers <irogers@google.com>]

The function returns a list of the names of metrics within the
evlist. For example:
```
>>> import perf
>>> perf.parse_metrics("TopdownL1").metrics()
['tma_bad_speculation', 'tma_frontend_bound', 'tma_backend_bound', 'tma_retiring']
```

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/python.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
index 6454f24cd810..c1eab506f55b 100644
--- a/tools/perf/util/python.c
+++ b/tools/perf/util/python.c
@@ -1293,6 +1293,33 @@ static PyObject *pyrf_evlist__all_cpus(struct pyrf_evlist *pevlist)
 	return (PyObject *)pcpu_map;
 }
 
+static PyObject *pyrf_evlist__metrics(struct pyrf_evlist *pevlist)
+{
+	PyObject *list = PyList_New(/*len=*/0);
+	struct rb_node *node;
+
+	if (!list)
+		return NULL;
+
+	for (node = rb_first_cached(&pevlist->evlist.metric_events.entries); node;
+	     node = rb_next(node)) {
+		struct metric_event *me = container_of(node, struct metric_event, nd);
+		struct list_head *pos;
+
+		list_for_each(pos, &me->head) {
+			struct metric_expr *expr = container_of(pos, struct metric_expr, nd);
+			PyObject *str = PyUnicode_FromString(expr->metric_name);
+
+			if (!str || PyList_Append(list, str) != 0) {
+				Py_DECREF(list);
+				return NULL;
+			}
+			Py_DECREF(str);
+		}
+	}
+	return list;
+}
+
 static PyObject *pyrf_evlist__mmap(struct pyrf_evlist *pevlist,
 				   PyObject *args, PyObject *kwargs)
 {
@@ -1521,6 +1548,12 @@ static PyMethodDef pyrf_evlist__methods[] = {
 		.ml_flags = METH_NOARGS,
 		.ml_doc	  = PyDoc_STR("CPU map union of all evsel CPU maps.")
 	},
+	{
+		.ml_name  = "metrics",
+		.ml_meth  = (PyCFunction)pyrf_evlist__metrics,
+		.ml_flags = METH_NOARGS,
+		.ml_doc	  = PyDoc_STR("List of metric names within the evlist.")
+	},
 	{
 		.ml_name  = "mmap",
 		.ml_meth  = (PyCFunction)pyrf_evlist__mmap,
-- 
2.50.0.727.gbf7dc18ff4-goog