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use std::mem;
use std::sync;
use std::sync::atomic;
#[derive(Debug)]
pub struct ReadGuard<'rh, T: ?Sized> {
pub(super) t: &'rh T,
pub(super) epoch: usize,
pub(super) handle: &'rh sync::atomic::AtomicUsize,
}
impl<'rh, T: ?Sized> ReadGuard<'rh, T> {
pub(super) fn map_ref<F, U: ?Sized>(self, f: F) -> ReadGuard<'rh, U>
where
F: for<'a> FnOnce(&'a T) -> &'a U,
{
let rg = ReadGuard {
t: f(self.t),
epoch: self.epoch,
handle: self.handle,
};
mem::forget(self);
rg
}
pub(super) fn map_opt<F, U: ?Sized>(self, f: F) -> Option<ReadGuard<'rh, U>>
where
F: for<'a> FnOnce(&'a T) -> Option<&'a U>,
{
let rg = Some(ReadGuard {
t: f(self.t)?,
epoch: self.epoch,
handle: self.handle,
});
mem::forget(self);
rg
}
}
impl<'rh, T: ?Sized> AsRef<T> for ReadGuard<'rh, T> {
fn as_ref(&self) -> &T {
self.t
}
}
impl<'rh, T: ?Sized> std::ops::Deref for ReadGuard<'rh, T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.t
}
}
impl<'rh, T: ?Sized> Drop for ReadGuard<'rh, T> {
fn drop(&mut self) {
self.handle.store(
(self.epoch + 1) | 1usize << (mem::size_of::<usize>() * 8 - 1),
atomic::Ordering::Release,
);
}
}