- enum { BILLION = 1000000000 };
-
- /* For overflow checking, use naive comparison if possible, widening
- to long double if double is not wide enough. Otherwise, use <=,
- not <, to avoid problems when TIME_T_MAX is less than SECONDS but
- compares equal to SECONDS after loss of precision when coercing
- from time_t to long double. This mishandles near-maximal values
- in some rare (perhaps theoretical) cases but that is better than
- undefined behavior. */
- bool overflow = ((time_t) ((double) TIME_T_MAX / 2) == TIME_T_MAX / 2
- ? TIME_T_MAX < seconds
- : (time_t) ((long double) TIME_T_MAX / 2) == TIME_T_MAX / 2
- ? TIME_T_MAX < (long double) seconds
- : TIME_T_MAX <= (long double) seconds);
-
- struct timespec ts_sleep;
-
- assert (0 <= seconds);
-
- /* Separate whole seconds from nanoseconds. */
- if (! overflow)
- {
- time_t floor_seconds = seconds;
- double ns = BILLION * (seconds - floor_seconds);
- ts_sleep.tv_sec = floor_seconds;
-
- /* Round up to the next whole number, if necessary, so that we
- always sleep for at least the requested amount of time. Assuming
- the default rounding mode, we don't have to worry about the
- rounding error when computing 'ns' above, since the error won't
- cause 'ns' to drop below an integer boundary. */
- ts_sleep.tv_nsec = ns;
- ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
-
- /* Normalize the interval length. nanosleep requires this. */
- if (BILLION <= ts_sleep.tv_nsec)
- {
- if (ts_sleep.tv_sec == TIME_T_MAX)
- overflow = true;
- else
- {
- ts_sleep.tv_sec++;
- ts_sleep.tv_nsec -= BILLION;
- }
- }
- }