use std::sync::atomic::AtomicUsize;use std::sync::atomic::Ordering::SeqCst;#[cfg(any(test, feature = "test-support"))]use std::time::Duration; #[cfg(any(test, feature = "test-support"))]use futures::Future; #[cfg(any(test, feature = "test-support"))]use smol::future::FutureExt; pub use util::*; /// A helper trait for building complex objects with imperative conditionals in a fluent style.pub trait FluentBuilder {    /// Imperatively modify self with the given closure.    fn map<U>(self, f: impl FnOnce(Self) -> U) -> U    where        Self: Sized,    {        f(self)    }     /// Conditionally modify self with the given closure.    fn when(self, condition: bool, then: impl FnOnce(Self) -> Self) -> Self    where        Self: Sized,    {        self.map(|this| if condition { then(this) } else { this })    }     /// Conditionally modify self with the given closure.    fn when_else(        self,        condition: bool,        then: impl FnOnce(Self) -> Self,        else_fn: impl FnOnce(Self) -> Self,    ) -> Self    where        Self: Sized,    {        self.map(|this| if condition { then(this) } else { else_fn(this) })    }     /// Conditionally unwrap and modify self with the given closure, if the given option is Some.    fn when_some<T>(self, option: Option<T>, then: impl FnOnce(Self, T) -> Self) -> Self    where        Self: Sized,    {        self.map(|this| {            if let Some(value) = option {                then(this, value)            } else {                this            }        })    }    /// Conditionally unwrap and modify self with the given closure, if the given option is None.    fn when_none<T>(self, option: &Option<T>, then: impl FnOnce(Self) -> Self) -> Self    where        Self: Sized,    {        self.map(|this| {            if let Some(_) = option {                this            } else {                then(this)            }        })    }} #[cfg(any(test, feature = "test-support"))]pub async fn timeout<F, T>(timeout: Duration, f: F) -> Result<T, ()>where    F: Future<Output = T>,{    let timer = async {        smol::Timer::after(timeout).await;        Err(())    };    let future = async move { Ok(f.await) };    timer.race(future).await} /// Increment the given atomic counter if it is not zero./// Return the new value of the counter.pub(crate) fn atomic_incr_if_not_zero(counter: &AtomicUsize) -> usize {    let mut loaded = counter.load(SeqCst);    loop {        if loaded == 0 {            return 0;        }        match counter.compare_exchange_weak(loaded, loaded + 1, SeqCst, SeqCst) {            Ok(x) => return x + 1,            Err(actual) => loaded = actual,        }    }}