+
+inline void heartbeat_init(heartbeat_t *hb)
+{
+ *hb = 0ULL;
+}
+
+usec_t heartbeat_next(heartbeat_t *hb, usec_t tick)
+{
+ heartbeat_t now = now_monotonic_usec();
+ usec_t next = now - (now % tick) + tick;
+
+ while(now < next) {
+ sleep_usec(next - now);
+ now = now_monotonic_usec();
+ }
+
+ if(likely(*hb != 0ULL)) {
+ usec_t dt = now - *hb;
+ *hb = now;
+ if(unlikely(dt / tick > 1))
+ error("heartbeat missed between %llu usec and %llu usec", *hb, now);
+ return dt;
+ }
+ else {
+ *hb = now;
+ return 0ULL;
+ }
+}
+
+inline usec_t heartbeat_dt_usec(heartbeat_t *hb)
+{
+ if(!*hb)
+ return 0ULL;
+ return now_monotonic_usec() - *hb;
+}