rpc: adds json_add_timeiso helper

common/json.c

@@ -827,6 +827,22 @@ void json_add_time(struct json_stream *result, const char *fieldname,
 	json_add_string(result, fieldname, timebuf);
 }
 
+void json_add_timeiso(struct json_stream *result,
+		      const char *fieldname,
+		      struct timeabs *time)
+{
+	char iso8601_msec_fmt[sizeof("YYYY-mm-ddTHH:MM:SS.%03dZ")];
+	char iso8601_s[sizeof("YYYY-mm-ddTHH:MM:SS.nnnZ")];
+
+	strftime(iso8601_msec_fmt, sizeof(iso8601_msec_fmt),
+		 "%FT%T.%%03dZ", gmtime(&time->ts.tv_sec));
+	snprintf(iso8601_s, sizeof(iso8601_s),
+		 iso8601_msec_fmt, (int) time->ts.tv_nsec / 1000000);
+
+	json_add_string(result, fieldname, iso8601_s);
+}
+
+
 void json_add_tok(struct json_stream *result, const char *fieldname,
                   const jsmntok_t *tok, const char *buffer)
 {

common/json.h

@@ -201,6 +201,11 @@ void json_add_timeabs(struct json_stream *result, const char *fieldname,
 void json_add_time(struct json_stream *result, const char *fieldname,
 			  struct timespec ts);
 
+/* Add ISO_8601 timestamp string, i.e. "2019-09-07T15:50+01:00" */
+void json_add_timeiso(struct json_stream *result,
+		      const char *fieldname,
+		      struct timeabs *time);
+
 /* Add any json token */
 void json_add_tok(struct json_stream *result, const char *fieldname,
                   const jsmntok_t *tok, const char *buffer);