perf evswitch: Move switch logic to use in other tools

Now other tools that want switching can use an evswitch for that, just
set it up and add it to the PERF_RECORD_SAMPLE processing function.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: William Cohen <wcohen@redhat.com>
Link: https://lkml.kernel.org/n/tip-b1trj1q97qwfv251l66q3noj@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/Build

@@ -9,6 +9,7 @@ perf-y += event.o
 perf-y += evlist.o
 perf-y += evsel.o
 perf-y += evsel_fprintf.o
+perf-y += evswitch.o
 perf-y += find_bit.o
 perf-y += get_current_dir_name.o
 perf-y += kallsyms.o

tools/perf/util/evswitch.c

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2019, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
+
+#include "evswitch.h"
+
+bool evswitch__discard(struct evswitch *evswitch, struct evsel *evsel)
+{
+	if (evswitch->on && evswitch->discarding) {
+		if (evswitch->on != evsel)
+			return true;
+
+		evswitch->discarding = false;
+
+		if (!evswitch->show_on_off_events)
+			return true;
+
+		return false;
+	}
+
+	if (evswitch->off && !evswitch->discarding) {
+		if (evswitch->off != evsel)
+			return false;
+
+		evswitch->discarding = true;
+
+		if (!evswitch->show_on_off_events)
+			return true;
+	}
+
+	return false;
+}

tools/perf/util/evswitch.h

@@ -13,4 +13,6 @@ struct evswitch {
 	bool	     show_on_off_events;
 };
 
+bool evswitch__discard(struct evswitch *evswitch, struct evsel *evsel);
+
 #endif /* __PERF_EVSWITCH_H */