wait_on_address 0.1.6

Cross-platform atomic wait and wake (aka futex) functionality.
Documentation 
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use std::{
    hint::spin_loop,
    sync::atomic::{AtomicU32, AtomicU64},
    time::Duration,
};

use crate::private::AtomicWaitImpl;

/// Whether this thread is allowed to block and use synchronization primitives.
#[inline(always)]
fn can_block() -> bool {
    thread_local! {
        static CAN_BLOCK: bool = web_sys::window().is_none();
    }

    CAN_BLOCK.with(|x| *x)
}

#[cfg(not(nightly))]
impl AtomicWaitImpl for AtomicU32 {
    type AtomicInner = u32;

    fn wait_timeout(&self, value: Self::AtomicInner, timeout: Option<Duration>) {
        if can_block() {
            crate::condvar_table::wait(
                self as *const _ as *const _,
                || self.load(std::sync::atomic::Ordering::Acquire) == value,
                timeout,
            );
        } else {
            spin_loop();
        }
    }

    fn notify_all(&self) {
        crate::condvar_table::notify_all(self as *const _ as *const _);
    }

    fn notify_one(&self) {
        crate::condvar_table::notify_one(self as *const _ as *const _);
    }
}

#[cfg(not(nightly))]
impl AtomicWaitImpl for AtomicU64 {
    type AtomicInner = u64;

    fn wait_timeout(&self, value: Self::AtomicInner, timeout: Option<Duration>) {
        if can_block() {
            crate::condvar_table::wait(
                self as *const _ as *const _,
                || self.load(std::sync::atomic::Ordering::Acquire) == value,
                timeout,
            );
        } else {
            spin_loop();
        }
    }

    fn notify_all(&self) {
        crate::condvar_table::notify_all(self as *const _ as *const _);
    }

    fn notify_one(&self) {
        crate::condvar_table::notify_one(self as *const _ as *const _);
    }
}

#[cfg(nightly)]
impl AtomicWaitImpl for AtomicU32 {
    type AtomicInner = u32;

    fn wait_timeout(&self, value: Self::AtomicInner, timeout: Option<Duration>) {
        unsafe {
            if can_block() {
                std::arch::wasm32::memory_atomic_wait32(
                    self as *const _ as *mut _,
                    value as i32,
                    timeout
                        .map(|x| x.as_nanos().min(i64::MAX as u128) as i64)
                        .unwrap_or(i64::MAX),
                );
            } else {
                spin_loop();
            }
        }
    }

    fn notify_all(&self) {
        unsafe {
            std::arch::wasm32::memory_atomic_notify(self as *const _ as *mut _, u32::MAX);
        };
    }

    fn notify_one(&self) {
        unsafe {
            std::arch::wasm32::memory_atomic_notify(self as *const _ as *mut _, 1);
        };
    }
}

#[cfg(nightly)]
impl AtomicWaitImpl for AtomicU64 {
    type AtomicInner = u64;

    fn wait_timeout(&self, value: Self::AtomicInner, timeout: Option<Duration>) {
        unsafe {
            if can_block() {
                std::arch::wasm32::memory_atomic_wait64(
                    self as *const _ as *mut _,
                    value as i64,
                    timeout
                        .map(|x| x.as_nanos().min(i64::MAX as u128) as i64)
                        .unwrap_or(i64::MAX),
                );
            } else {
                spin_loop();
            }
        }
    }

    fn notify_all(&self) {
        unsafe {
            std::arch::wasm32::memory_atomic_notify(self as *const _ as *mut _, u32::MAX);
        };
    }

    fn notify_one(&self) {
        unsafe {
            std::arch::wasm32::memory_atomic_notify(self as *const _ as *mut _, 1);
        };
    }
}