use std::fmt::Debug;
use lock_api::RawRwLock;
use crate::key::Keyable;
use crate::lockable::{Lockable, RawLock, Sharable};
use super::{ReadLock, RwLock, RwLockReadGuard, RwLockReadRef};
unsafe impl<T: Send, R: RawRwLock + Send + Sync> Lockable for ReadLock<'_, T, R> {
type Guard<'g>
= RwLockReadRef<'g, T, R>
where
Self: 'g;
fn get_ptrs<'a>(&'a self, ptrs: &mut Vec<&'a dyn RawLock>) {
ptrs.push(self.as_ref());
}
unsafe fn guard(&self) -> Self::Guard<'_> {
RwLockReadRef::new(self.as_ref())
}
}
unsafe impl<T: Send, R: RawRwLock + Send + Sync> Sharable for ReadLock<'_, T, R> {
type ReadGuard<'g>
= RwLockReadRef<'g, T, R>
where
Self: 'g;
unsafe fn read_guard(&self) -> Self::Guard<'_> {
RwLockReadRef::new(self.as_ref())
}
}
#[mutants::skip]
impl<T: ?Sized + Debug, R: RawRwLock> Debug for ReadLock<'_, T, R> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// safety: this is just a try lock, and the value is dropped
// immediately after, so there's no risk of blocking ourselves
// or any other threads
if let Some(value) = unsafe { self.try_lock_no_key() } {
f.debug_struct("ReadLock").field("data", &&*value).finish()
} else {
struct LockedPlaceholder;
impl Debug for LockedPlaceholder {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str("<locked>")
}
}
f.debug_struct("ReadLock")
.field("data", &LockedPlaceholder)
.finish()
}
}
}
impl<'l, T, R> From<&'l RwLock<T, R>> for ReadLock<'l, T, R> {
fn from(value: &'l RwLock<T, R>) -> Self {
Self::new(value)
}
}
impl<T: ?Sized, R> AsRef<RwLock<T, R>> for ReadLock<'_, T, R> {
fn as_ref(&self) -> &RwLock<T, R> {
self.0
}
}
impl<'l, T, R> ReadLock<'l, T, R> {
/// Creates a new `ReadLock` which accesses the given [`RwLock`]
///
/// # Examples
///
/// ```
/// use happylock::{rwlock::ReadLock, RwLock};
///
/// let lock = RwLock::new(5);
/// let read_lock = ReadLock::new(&lock);
/// ```
#[must_use]
pub const fn new(rwlock: &'l RwLock<T, R>) -> Self {
Self(rwlock)
}
}
impl<T: ?Sized, R: RawRwLock> ReadLock<'_, T, R> {
/// Locks the underlying [`RwLock`] with shared read access, blocking the
/// current thread until it can be acquired.
///
/// The calling thread will be blocked until there are no more writers
/// which hold the lock. There may be other readers currently inside the
/// lock when this method returns.
///
/// Returns an RAII guard which will release this thread's shared access
/// once it is dropped.
///
/// Because this method takes a [`ThreadKey`], it's not possible for this
/// method to cause a deadlock.
///
/// # Examples
///
/// ```
/// use std::sync::Arc;
/// use std::thread;
/// use happylock::{RwLock, ThreadKey};
/// use happylock::rwlock::ReadLock;
///
/// let key = ThreadKey::get().unwrap();
/// let lock: &'static mut RwLock<_> = Box::leak(Box::new(RwLock::new(1)));
/// let reader = ReadLock::new(&lock);
///
/// let n = reader.lock(key);
/// assert_eq!(*n, 1);
/// ```
///
/// [`ThreadKey`]: `crate::ThreadKey`
pub fn lock<'s, 'key: 's, Key: Keyable + 'key>(
&'s self,
key: Key,
) -> RwLockReadGuard<'s, 'key, T, Key, R> {
self.0.read(key)
}
/// Attempts to acquire the underlying [`RwLock`] with shared read access
/// without blocking.
///
/// If the access could not be granted at this time, then `Err` is
/// returned. Otherwise, an RAII guard is returned which will release the
/// shared access when it is dropped.
///
/// This function does not provide any guarantees with respect to the
/// ordering of whether contentious readers or writers will acquire the
/// lock first.
///
/// # Errors
///
/// If the `RwLock` could not be acquired because it was already locked
/// exclusively, then an error will be returned containing the given key.
///
/// # Examples
///
/// ```
/// use happylock::{RwLock, ThreadKey};
/// use happylock::rwlock::ReadLock;
///
/// let key = ThreadKey::get().unwrap();
/// let lock = RwLock::new(1);
/// let reader = ReadLock::new(&lock);
///
/// match reader.try_lock(key) {
/// Ok(n) => assert_eq!(*n, 1),
/// Err(_) => unreachable!(),
/// };
/// ```
pub fn try_lock<'s, 'key: 's, Key: Keyable + 'key>(
&'s self,
key: Key,
) -> Result<RwLockReadGuard<'s, 'key, T, Key, R>, Key> {
self.0.try_read(key)
}
/// Attempts to create an exclusive lock without a key. Locking this
/// without exclusive access to the key is undefined behavior.
pub(crate) unsafe fn try_lock_no_key(&self) -> Option<RwLockReadRef<'_, T, R>> {
self.0.try_read_no_key()
}
/// Immediately drops the guard, and consequently releases the shared lock
/// on the underlying [`RwLock`].
///
/// This function is equivalent to calling [`drop`] on the guard, except
/// that it returns the key that was used to create it. Alternately, the
/// guard will be automatically dropped when it goes out of scope.
///
/// # Examples
///
/// ```
/// use happylock::{RwLock, ThreadKey};
/// use happylock::rwlock::ReadLock;
///
/// let key = ThreadKey::get().unwrap();
/// let lock = RwLock::new(0);
/// let reader = ReadLock::new(&lock);
///
/// let mut guard = reader.lock(key);
/// assert_eq!(*guard, 0);
/// let key = ReadLock::unlock(guard);
/// ```
pub fn unlock<'key, Key: Keyable + 'key>(guard: RwLockReadGuard<'_, 'key, T, Key, R>) -> Key {
RwLock::unlock_read(guard)
}
}
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