Time and Randomness

Build a nonnegative Duration with an explicit unit:

Duration timeout = std.time.milliseconds(UInt64(250));
UInt64 micros = timeout.microseconds();

monotonic_now() is suitable for elapsed time and timeout calculations within one process. wall_now() returns time since the Unix epoch and may move when the system clock is adjusted. Either returns null when the target cannot provide the requested clock.

guard std.time.monotonic_now() is .some(start) else { return 1; }
// work
guard std.time.monotonic_now() is .some(end) else { return 2; }
guard end.duration_since(start) is .some(elapsed) else { return 3; }

Use std.random.fill_entropy(buffer) when bytes must come from the operating system. It returns false rather than substituting pseudorandom data when entropy is unavailable.

std.random.Generator(seed) is for tests, simulations, and other reproducible work. Equal seeds produce equal sequences, but the concrete algorithm is not a stable serialization format and is not cryptographically secure. Do not mutate one generator concurrently from several threads.