Function poll_parse_clock

src/poll.rs:22–62

(
    ctx: &VmCtx,
    sub_clock: SubscriptionClock,
    precision: u64,
    min_timeout: &mut Option<Timestamp>,
    timeouts: &mut Vec<(u64, Timestamp)>,
    userdata: u64,
)

#[external_methods(push, checked_sub, try_into, subscription_clock_abstime)]
#[external_calls(Some)]
pub fn poll_parse_clock(
    ctx: &VmCtx,
    sub_clock: SubscriptionClock,
    precision: u64,
    min_timeout: &mut Option<Timestamp>,
    timeouts: &mut Vec<(u64, Timestamp)>,
    userdata: u64,
) -> RuntimeResult<()> {
    // if the subscription is a clock, check if it is the shortest timeout.
    // let clock = subscription_clock.id;
    match sub_clock.id.try_into()? {
        // TODO: what clock source does posix poll use for timeouts? Will a relative
        //       realtime be significantly different than monotonic?
        ClockId::Monotonic | ClockId::Realtime => {
            let now = wasi_clock_time_get(ctx, sub_clock.id, precision)?;
            let timeout: Timestamp = if sub_clock.flags.subscription_clock_abstime() {
                // if this is an absolute timeout, we need to wait the difference
                // between now and the timeout
                // This will also perform a checked cast to an i32, which will
                sub_clock.timeout.checked_sub(now).ok_or(Eoverflow)?
            } else {
                sub_clock.timeout
            };

            if let Some(m_timeout) = min_timeout {
                if timeout < *m_timeout {
                    *min_timeout = Some(timeout);
                }
            } else {
                *min_timeout = Some(timeout);
            }

            timeouts.push((userdata, timeout));
            Ok(())
        }
        // we don't support timeouts on other clock types
        _ => {
            return Err(Einval);
        }
    }
}

#[with_ghost_var(trace: &mut Trace)]
#[requires(ctx_safe(ctx))]