[misc] Add function to add a relative time to current clock

src/misc.c

@@ -27,6 +27,7 @@
 #endif
 
 #include <stdlib.h>
+#include <unistd.h>
 #include <string.h>
 #include <ctype.h>
 #include <errno.h>
@@ -928,6 +929,21 @@ timespec_cmp(struct timespec time1, struct timespec time2)
     return 0;
 }
 
+struct timespec
+timespec_reltoabs(struct timespec relative)
+{
+  struct timespec absolute;
+
+#if _POSIX_TIMERS > 0
+  clock_gettime(CLOCK_REALTIME, &absolute);
+#else
+  struct timeval tv;
+  gettimeofday(&tv, NULL);
+  TIMEVAL_TO_TIMESPEC(&tv, &absolute);
+#endif
+  return timespec_add(absolute, relative);
+}
+
 #if defined(HAVE_MACH_CLOCK) || defined(HAVE_MACH_TIMER)
 
 #include <mach/mach_time.h> /* mach_absolute_time */