+
+static inline usec_t usec_add(usec_t a, usec_t b) {
+ usec_t c;
+
+ /* Adds two time values, and makes sure USEC_INFINITY as input results as USEC_INFINITY in output, and doesn't
+ * overflow. */
+
+ c = a + b;
+ if (c < a || c < b) /* overflow check */
+ return USEC_INFINITY;
+
+ return c;
+}
+
+static inline usec_t usec_sub(usec_t timestamp, int64_t delta) {
+ if (delta < 0)
+ return usec_add(timestamp, (usec_t) (-delta));
+
+ if (timestamp == USEC_INFINITY) /* Make sure infinity doesn't degrade */
+ return USEC_INFINITY;
+
+ if (timestamp < (usec_t) delta)
+ return 0;
+
+ return timestamp - delta;
+}