perf evsel: Introduce append_filter() method

To allow building filters in evsel->filter, that will eventually be
applied via perf_evsel__apply_filter().

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-sjfoes3pycx7nlpmgedca13v@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.c

@@ -836,6 +836,23 @@ int perf_evsel__set_filter(struct perf_evsel *evsel, const char *filter)
 	return -1;
 }
 
+int perf_evsel__append_filter(struct perf_evsel *evsel,
+			      const char *op, const char *filter)
+{
+	char *new_filter;
+
+	if (evsel->filter == NULL)
+		return perf_evsel__set_filter(evsel, filter);
+
+	if (asprintf(&new_filter,"(%s) %s (%s)", evsel->filter, op, filter) > 0) {
+		free(evsel->filter);
+		evsel->filter = new_filter;
+		return 0;
+	}
+
+	return -1;
+}
+
 int perf_evsel__enable(struct perf_evsel *evsel, int ncpus, int nthreads)
 {
 	return perf_evsel__run_ioctl(evsel, ncpus, nthreads,

tools/perf/util/evsel.h

@@ -183,6 +183,8 @@ void perf_evsel__set_sample_id(struct perf_evsel *evsel,
 			       bool use_sample_identifier);
 
 int perf_evsel__set_filter(struct perf_evsel *evsel, const char *filter);
+int perf_evsel__append_filter(struct perf_evsel *evsel,
+			      const char *op, const char *filter);
 int perf_evsel__apply_filter(struct perf_evsel *evsel, int ncpus, int nthreads,
 			     const char *filter);
 int perf_evsel__enable(struct perf_evsel *evsel, int ncpus, int nthreads);