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//! Implementation of an atomic u64 cell. On 64 bit platforms, this is a
//! re-export of `AtomicU64`. On 32 bit platforms, this is implemented using a
//! `Mutex`.
pub(crate) use self::imp::AtomicU64;
// `AtomicU64` can only be used on targets with `target_has_atomic` is 64 or greater.
// Once `cfg_target_has_atomic` feature is stable, we can replace it with
// `#[cfg(target_has_atomic = "64")]`.
// Refs: https://github.com/rust-lang/rust/tree/master/src/librustc_target
#[cfg(not(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc")))]
mod imp {
pub(crate) use std::sync::atomic::AtomicU64;
}
#[cfg(any(target_arch = "arm", target_arch = "mips", target_arch = "powerpc"))]
mod imp {
use std::sync::atomic::Ordering;
use std::sync::Mutex;
#[derive(Debug)]
pub(crate) struct AtomicU64 {
inner: Mutex<u64>,
}
impl AtomicU64 {
pub(crate) fn new(val: u64) -> AtomicU64 {
AtomicU64 {
inner: Mutex::new(val),
}
}
pub(crate) fn load(&self, _: Ordering) -> u64 {
*self.inner.lock().unwrap()
}
pub(crate) fn store(&self, val: u64, _: Ordering) {
*self.inner.lock().unwrap() = val;
}
pub(crate) fn fetch_or(&self, val: u64, _: Ordering) -> u64 {
let mut lock = self.inner.lock().unwrap();
let prev = *lock;
*lock = prev | val;
prev
}
pub(crate) fn compare_and_swap(&self, old: u64, new: u64, _: Ordering) -> u64 {
let mut lock = self.inner.lock().unwrap();
let prev = *lock;
if prev != old {
return prev;
}
*lock = new;
prev
}
}
}
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