perf time-utils: Add utility function to print time stamps in nanoseconds

Add a utility function to print nanosecond timestamps.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20190305144758.12397-11-andi@firstfloor.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/time-utils.c

@@ -453,6 +453,14 @@ int timestamp__scnprintf_usec(u64 timestamp, char *buf, size_t sz)
 	return scnprintf(buf, sz, "%"PRIu64".%06"PRIu64, sec, usec);
 }
 
+int timestamp__scnprintf_nsec(u64 timestamp, char *buf, size_t sz)
+{
+	u64 sec  = timestamp / NSEC_PER_SEC,
+	    nsec = timestamp % NSEC_PER_SEC;
+
+	return scnprintf(buf, sz, "%" PRIu64 ".%09" PRIu64, sec, nsec);
+}
+
 int fetch_current_timestamp(char *buf, size_t sz)
 {
 	struct timeval tv;

tools/perf/util/time-utils.h

@@ -30,6 +30,7 @@ int perf_time__parse_for_ranges(const char *str, struct perf_session *session,
 				int *range_size, int *range_num);
 
 int timestamp__scnprintf_usec(u64 timestamp, char *buf, size_t sz);
+int timestamp__scnprintf_nsec(u64 timestamp, char *buf, size_t sz);
 
 int fetch_current_timestamp(char *buf, size_t sz);