add emper::nanosleep similar to nanosleep(3)

emper/Emper.cpp

@@ -5,6 +5,7 @@
 #include <cassert>
 #include <cerrno>
 #include <cstdint>
+#include <ctime>
 #include <stdexcept>
 #include <utility>
 
@@ -182,16 +183,25 @@ void yield() {
 	runtime->yield();
 }
 
-auto sleep(unsigned int seconds) -> bool {
+static auto _sleep(emper::io::AlarmFuture::Timespec& ts) -> bool {
 	if constexpr (!emper::IO) {
 		DIE_MSG("sleep requires emper::io");
 	}
 
-	emper::io::AlarmFuture::Timespec ts = {.tv_sec = seconds, .tv_nsec = 0};
 	emper::io::AlarmFuture alarm(ts);
 	int32_t res = alarm.submitAndWait();
 
 	return res == -ETIME;
 }
 
+auto sleep(unsigned int seconds) -> bool {
+	emper::io::AlarmFuture::Timespec ts = {.tv_sec = seconds, .tv_nsec = 0};
+	return _sleep(ts);
+}
+
+auto nanosleep(const struct timespec* rqtp) -> bool {
+	emper::io::AlarmFuture::Timespec ts = {.tv_sec = rqtp->tv_sec, .tv_nsec = rqtp->tv_nsec};
+	return _sleep(ts);
+}
+
 }	 // namespace emper

emper/include/emper.hpp

@@ -56,5 +56,6 @@ void destroy_runtime();
 void yield();
 
 auto sleep(unsigned int seconds) -> bool;
+auto nanosleep(const struct timespec* rqtp) -> bool;
 
 }	 // namespace emper