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-rw-r--r--src/basic/time-util.h13
-rw-r--r--src/test/test-time.c15
2 files changed, 26 insertions, 2 deletions
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;
+}
diff --git a/src/test/test-time.c b/src/test/test-time.c
index 8896b2c92b..ca44f81f9c 100644
--- a/src/test/test-time.c
+++ b/src/test/test-time.c
@@ -176,9 +176,19 @@ static void test_get_timezones(void) {
r = get_timezones(&zones);
assert_se(r == 0);
- STRV_FOREACH(zone, zones) {
+ STRV_FOREACH(zone, zones)
assert_se(timezone_is_valid(*zone));
- }
+}
+
+static void test_usec_add(void) {
+ assert_se(usec_add(0, 0) == 0);
+ assert_se(usec_add(1, 4) == 5);
+ assert_se(usec_add(USEC_INFINITY, 5) == USEC_INFINITY);
+ assert_se(usec_add(5, USEC_INFINITY) == USEC_INFINITY);
+ assert_se(usec_add(USEC_INFINITY-5, 2) == USEC_INFINITY-3);
+ assert_se(usec_add(USEC_INFINITY-2, 2) == USEC_INFINITY);
+ assert_se(usec_add(USEC_INFINITY-1, 2) == USEC_INFINITY);
+ assert_se(usec_add(USEC_INFINITY, 2) == USEC_INFINITY);
}
int main(int argc, char *argv[]) {
@@ -190,6 +200,7 @@ int main(int argc, char *argv[]) {
test_format_timespan(USEC_PER_SEC);
test_timezone_is_valid();
test_get_timezones();
+ test_usec_add();
return 0;
}