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use crate::inner::Inner;
use one_way_slot_map::SlotMapKey as Key;
use std::marker::PhantomData;
use std::mem::ManuallyDrop;
use std::sync::atomic;
use std::sync::atomic::AtomicPtr;
use std::sync::{self, Arc};
use std::{cell, fmt, mem};
mod guard;
pub use guard::ReadGuard;
mod factory;
pub use factory::ReadHandleFactory;
mod read_ref;
pub use read_ref::MapReadRef;
pub(crate) fn user_friendly<'a, T>(to_fix: &'a ManuallyDrop<T>) -> &'a T {
unsafe { &*(to_fix as *const ManuallyDrop<T> as *const T) }
}
pub struct ReadHandle<K, P, V>
where
K: Key<P>,
{
pub(crate) inner: sync::Arc<AtomicPtr<Inner<ManuallyDrop<V>>>>,
pub(crate) epochs: crate::Epochs,
epoch: sync::Arc<sync::atomic::AtomicUsize>,
epoch_i: usize,
my_epoch: sync::atomic::AtomicUsize,
_not_sync_no_feature: PhantomData<cell::Cell<()>>,
_phantom_p: PhantomData<P>,
_phantom_k: PhantomData<K>,
}
impl<K, P, V> Drop for ReadHandle<K, P, V>
where
K: Key<P>,
{
fn drop(&mut self) {
let e = self.epochs.lock().unwrap().remove(self.epoch_i);
assert!(Arc::ptr_eq(&e, &self.epoch));
}
}
impl<K, P, V> fmt::Debug for ReadHandle<K, P, V>
where
K: fmt::Debug + Key<P>,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ReadHandle")
.field("epochs", &self.epochs)
.field("epoch", &self.epoch)
.field("my_epoch", &self.my_epoch)
.finish()
}
}
impl<K, P, V> Clone for ReadHandle<K, P, V>
where
K: Key<P>,
{
fn clone(&self) -> Self {
ReadHandle::new(
sync::Arc::clone(&self.inner),
sync::Arc::clone(&self.epochs),
)
}
}
pub(crate) fn new<K, P, V>(
inner: Inner<ManuallyDrop<V>>,
epochs: crate::Epochs,
) -> ReadHandle<K, P, V>
where
K: Key<P>,
{
let store = Box::into_raw(Box::new(inner));
ReadHandle::new(sync::Arc::new(AtomicPtr::new(store)), epochs)
}
impl<K, P, V> ReadHandle<K, P, V>
where
K: Key<P>,
{
fn new(
inner: sync::Arc<AtomicPtr<Inner<ManuallyDrop<V>>>>,
epochs: crate::Epochs,
) -> Self {
let epoch = sync::Arc::new(atomic::AtomicUsize::new(0));
let epoch_i = epochs.lock().unwrap().insert(Arc::clone(&epoch));
Self {
epochs,
epoch,
epoch_i,
my_epoch: atomic::AtomicUsize::new(0),
inner,
_not_sync_no_feature: PhantomData,
_phantom_p: Default::default(),
_phantom_k: Default::default(),
}
}
pub fn factory(&self) -> ReadHandleFactory<K, P, V> {
ReadHandleFactory {
inner: sync::Arc::clone(&self.inner),
epochs: sync::Arc::clone(&self.epochs),
_phantom_p: Default::default(),
_phantom_k: Default::default(),
}
}
}
impl<K, P, V> ReadHandle<K, P, V>
where
K: Key<P>,
{
fn handle(&self) -> Option<ReadGuard<'_, Inner<ManuallyDrop<V>>>> {
let epoch = self.my_epoch.fetch_add(1, atomic::Ordering::Relaxed);
self.epoch.store(epoch + 1, atomic::Ordering::Release);
atomic::fence(atomic::Ordering::SeqCst);
let r_handle = self.inner.load(atomic::Ordering::Acquire);
let r_handle = unsafe { r_handle.as_ref() };
if let Some(r_handle) = r_handle {
Some(ReadGuard {
handle: &self.epoch,
epoch,
t: r_handle,
})
} else {
self.epoch.store(
(epoch + 1) | 1usize << (mem::size_of::<usize>() * 8 - 1),
atomic::Ordering::Release,
);
None
}
}
pub fn read(&self) -> Option<MapReadRef<'_, K, P, V>> {
let guard = self.handle()?;
if !guard.is_ready() {
return None;
}
Some(MapReadRef {
guard,
_phantom_k: Default::default(),
_phantom_p: Default::default(),
})
}
pub fn len(&self) -> usize {
self.read().map_or(0, |x| x.len())
}
pub fn is_empty(&self) -> bool {
self.read().map_or(true, |x| x.is_empty())
}
fn get_raw(&self, key: &K) -> Option<ReadGuard<'_, ManuallyDrop<V>>> {
let inner = self.handle()?;
if !inner.is_ready() {
return None;
}
inner.map_opt(|inner| inner.data.get_unbounded(key))
}
#[inline]
pub fn get<'rh>(&'rh self, key: &K) -> Option<ReadGuard<'rh, V>> {
Some(self.get_raw(key)?.map_ref(user_friendly))
}
pub fn is_destroyed(&self) -> bool {
self.handle().is_none()
}
pub fn contains_key(&self, key: &K) -> bool {
self.read().map_or(false, |x| x.contains_key(key))
}
}