From 53f555b6f6b0a9fb58a781e40e3db67924a2a9c8 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 1 Feb 2016 16:13:51 +0100
Subject: util: add usec_add() which adds two usec_t values with overflow
 handling

---
 src/basic/time-util.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'src/basic/time-util.h')

diff --git a/src/basic/time-util.h b/src/basic/time-util.h
index 7321e3c670..b37d5ad5dc 100644
--- a/src/basic/time-util.h
+++ b/src/basic/time-util.h
@@ -127,3 +127,16 @@ time_t mktime_or_timegm(struct tm *tm, bool utc);
 struct tm *localtime_or_gmtime_r(const time_t *t, struct tm *tm, bool utc);
 
 unsigned long usec_to_jiffies(usec_t usec);
+
+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;
+}
-- 
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