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Diffstat (limited to 'vendor/lock_api/src/rwlock.rs')
| -rw-r--r-- | vendor/lock_api/src/rwlock.rs | 2883 |
1 files changed, 0 insertions, 2883 deletions
diff --git a/vendor/lock_api/src/rwlock.rs b/vendor/lock_api/src/rwlock.rs deleted file mode 100644 index cf9e8aa..0000000 --- a/vendor/lock_api/src/rwlock.rs +++ /dev/null @@ -1,2883 +0,0 @@ -// Copyright 2016 Amanieu d'Antras -// -// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or -// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or -// http://opensource.org/licenses/MIT>, at your option. This file may not be -// copied, modified, or distributed except according to those terms. - -use core::cell::UnsafeCell; -use core::fmt; -use core::marker::PhantomData; -use core::mem; -use core::ops::{Deref, DerefMut}; - -#[cfg(feature = "arc_lock")] -use alloc::sync::Arc; -#[cfg(feature = "arc_lock")] -use core::mem::ManuallyDrop; -#[cfg(feature = "arc_lock")] -use core::ptr; - -#[cfg(feature = "owning_ref")] -use owning_ref::StableAddress; - -#[cfg(feature = "serde")] -use serde::{Deserialize, Deserializer, Serialize, Serializer}; - -/// Basic operations for a reader-writer lock. -/// -/// Types implementing this trait can be used by `RwLock` to form a safe and -/// fully-functioning `RwLock` type. -/// -/// # Safety -/// -/// Implementations of this trait must ensure that the `RwLock` is actually -/// exclusive: an exclusive lock can't be acquired while an exclusive or shared -/// lock exists, and a shared lock can't be acquire while an exclusive lock -/// exists. -pub unsafe trait RawRwLock { - /// Initial value for an unlocked `RwLock`. - // A “non-constant” const item is a legacy way to supply an initialized value to downstream - // static items. Can hopefully be replaced with `const fn new() -> Self` at some point. - #[allow(clippy::declare_interior_mutable_const)] - const INIT: Self; - - /// Marker type which determines whether a lock guard should be `Send`. Use - /// one of the `GuardSend` or `GuardNoSend` helper types here. - type GuardMarker; - - /// Acquires a shared lock, blocking the current thread until it is able to do so. - fn lock_shared(&self); - - /// Attempts to acquire a shared lock without blocking. - fn try_lock_shared(&self) -> bool; - - /// Releases a shared lock. - /// - /// # Safety - /// - /// This method may only be called if a shared lock is held in the current context. - unsafe fn unlock_shared(&self); - - /// Acquires an exclusive lock, blocking the current thread until it is able to do so. - fn lock_exclusive(&self); - - /// Attempts to acquire an exclusive lock without blocking. - fn try_lock_exclusive(&self) -> bool; - - /// Releases an exclusive lock. - /// - /// # Safety - /// - /// This method may only be called if an exclusive lock is held in the current context. - unsafe fn unlock_exclusive(&self); - - /// Checks if this `RwLock` is currently locked in any way. - #[inline] - fn is_locked(&self) -> bool { - let acquired_lock = self.try_lock_exclusive(); - if acquired_lock { - // Safety: A lock was successfully acquired above. - unsafe { - self.unlock_exclusive(); - } - } - !acquired_lock - } - - /// Check if this `RwLock` is currently exclusively locked. - fn is_locked_exclusive(&self) -> bool { - let acquired_lock = self.try_lock_shared(); - if acquired_lock { - // Safety: A shared lock was successfully acquired above. - unsafe { - self.unlock_shared(); - } - } - !acquired_lock - } -} - -/// Additional methods for RwLocks which support fair unlocking. -/// -/// Fair unlocking means that a lock is handed directly over to the next waiting -/// thread if there is one, without giving other threads the opportunity to -/// "steal" the lock in the meantime. This is typically slower than unfair -/// unlocking, but may be necessary in certain circumstances. -pub unsafe trait RawRwLockFair: RawRwLock { - /// Releases a shared lock using a fair unlock protocol. - /// - /// # Safety - /// - /// This method may only be called if a shared lock is held in the current context. - unsafe fn unlock_shared_fair(&self); - - /// Releases an exclusive lock using a fair unlock protocol. - /// - /// # Safety - /// - /// This method may only be called if an exclusive lock is held in the current context. - unsafe fn unlock_exclusive_fair(&self); - - /// Temporarily yields a shared lock to a waiting thread if there is one. - /// - /// This method is functionally equivalent to calling `unlock_shared_fair` followed - /// by `lock_shared`, however it can be much more efficient in the case where there - /// are no waiting threads. - /// - /// # Safety - /// - /// This method may only be called if a shared lock is held in the current context. - unsafe fn bump_shared(&self) { - self.unlock_shared_fair(); - self.lock_shared(); - } - - /// Temporarily yields an exclusive lock to a waiting thread if there is one. - /// - /// This method is functionally equivalent to calling `unlock_exclusive_fair` followed - /// by `lock_exclusive`, however it can be much more efficient in the case where there - /// are no waiting threads. - /// - /// # Safety - /// - /// This method may only be called if an exclusive lock is held in the current context. - unsafe fn bump_exclusive(&self) { - self.unlock_exclusive_fair(); - self.lock_exclusive(); - } -} - -/// Additional methods for RwLocks which support atomically downgrading an -/// exclusive lock to a shared lock. -pub unsafe trait RawRwLockDowngrade: RawRwLock { - /// Atomically downgrades an exclusive lock into a shared lock without - /// allowing any thread to take an exclusive lock in the meantime. - /// - /// # Safety - /// - /// This method may only be called if an exclusive lock is held in the current context. - unsafe fn downgrade(&self); -} - -/// Additional methods for RwLocks which support locking with timeouts. -/// -/// The `Duration` and `Instant` types are specified as associated types so that -/// this trait is usable even in `no_std` environments. -pub unsafe trait RawRwLockTimed: RawRwLock { - /// Duration type used for `try_lock_for`. - type Duration; - - /// Instant type used for `try_lock_until`. - type Instant; - - /// Attempts to acquire a shared lock until a timeout is reached. - fn try_lock_shared_for(&self, timeout: Self::Duration) -> bool; - - /// Attempts to acquire a shared lock until a timeout is reached. - fn try_lock_shared_until(&self, timeout: Self::Instant) -> bool; - - /// Attempts to acquire an exclusive lock until a timeout is reached. - fn try_lock_exclusive_for(&self, timeout: Self::Duration) -> bool; - - /// Attempts to acquire an exclusive lock until a timeout is reached. - fn try_lock_exclusive_until(&self, timeout: Self::Instant) -> bool; -} - -/// Additional methods for RwLocks which support recursive read locks. -/// -/// These are guaranteed to succeed without blocking if -/// another read lock is held at the time of the call. This allows a thread -/// to recursively lock a `RwLock`. However using this method can cause -/// writers to starve since readers no longer block if a writer is waiting -/// for the lock. -pub unsafe trait RawRwLockRecursive: RawRwLock { - /// Acquires a shared lock without deadlocking in case of a recursive lock. - fn lock_shared_recursive(&self); - - /// Attempts to acquire a shared lock without deadlocking in case of a recursive lock. - fn try_lock_shared_recursive(&self) -> bool; -} - -/// Additional methods for RwLocks which support recursive read locks and timeouts. -pub unsafe trait RawRwLockRecursiveTimed: RawRwLockRecursive + RawRwLockTimed { - /// Attempts to acquire a shared lock until a timeout is reached, without - /// deadlocking in case of a recursive lock. - fn try_lock_shared_recursive_for(&self, timeout: Self::Duration) -> bool; - - /// Attempts to acquire a shared lock until a timeout is reached, without - /// deadlocking in case of a recursive lock. - fn try_lock_shared_recursive_until(&self, timeout: Self::Instant) -> bool; -} - -/// Additional methods for RwLocks which support atomically upgrading a shared -/// lock to an exclusive lock. -/// -/// This requires acquiring a special "upgradable read lock" instead of a -/// normal shared lock. There may only be one upgradable lock at any time, -/// otherwise deadlocks could occur when upgrading. -pub unsafe trait RawRwLockUpgrade: RawRwLock { - /// Acquires an upgradable lock, blocking the current thread until it is able to do so. - fn lock_upgradable(&self); - - /// Attempts to acquire an upgradable lock without blocking. - fn try_lock_upgradable(&self) -> bool; - - /// Releases an upgradable lock. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn unlock_upgradable(&self); - - /// Upgrades an upgradable lock to an exclusive lock. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn upgrade(&self); - - /// Attempts to upgrade an upgradable lock to an exclusive lock without - /// blocking. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn try_upgrade(&self) -> bool; -} - -/// Additional methods for RwLocks which support upgradable locks and fair -/// unlocking. -pub unsafe trait RawRwLockUpgradeFair: RawRwLockUpgrade + RawRwLockFair { - /// Releases an upgradable lock using a fair unlock protocol. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn unlock_upgradable_fair(&self); - - /// Temporarily yields an upgradable lock to a waiting thread if there is one. - /// - /// This method is functionally equivalent to calling `unlock_upgradable_fair` followed - /// by `lock_upgradable`, however it can be much more efficient in the case where there - /// are no waiting threads. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn bump_upgradable(&self) { - self.unlock_upgradable_fair(); - self.lock_upgradable(); - } -} - -/// Additional methods for RwLocks which support upgradable locks and lock -/// downgrading. -pub unsafe trait RawRwLockUpgradeDowngrade: RawRwLockUpgrade + RawRwLockDowngrade { - /// Downgrades an upgradable lock to a shared lock. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn downgrade_upgradable(&self); - - /// Downgrades an exclusive lock to an upgradable lock. - /// - /// # Safety - /// - /// This method may only be called if an exclusive lock is held in the current context. - unsafe fn downgrade_to_upgradable(&self); -} - -/// Additional methods for RwLocks which support upgradable locks and locking -/// with timeouts. -pub unsafe trait RawRwLockUpgradeTimed: RawRwLockUpgrade + RawRwLockTimed { - /// Attempts to acquire an upgradable lock until a timeout is reached. - fn try_lock_upgradable_for(&self, timeout: Self::Duration) -> bool; - - /// Attempts to acquire an upgradable lock until a timeout is reached. - fn try_lock_upgradable_until(&self, timeout: Self::Instant) -> bool; - - /// Attempts to upgrade an upgradable lock to an exclusive lock until a - /// timeout is reached. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn try_upgrade_for(&self, timeout: Self::Duration) -> bool; - - /// Attempts to upgrade an upgradable lock to an exclusive lock until a - /// timeout is reached. - /// - /// # Safety - /// - /// This method may only be called if an upgradable lock is held in the current context. - unsafe fn try_upgrade_until(&self, timeout: Self::Instant) -> bool; -} - -/// A reader-writer lock -/// -/// This type of lock allows a number of readers or at most one writer at any -/// point in time. The write portion of this lock typically allows modification -/// of the underlying data (exclusive access) and the read portion of this lock -/// typically allows for read-only access (shared access). -/// -/// The type parameter `T` represents the data that this lock protects. It is -/// required that `T` satisfies `Send` to be shared across threads and `Sync` to -/// allow concurrent access through readers. The RAII guards returned from the -/// locking methods implement `Deref` (and `DerefMut` for the `write` methods) -/// to allow access to the contained of the lock. -pub struct RwLock<R, T: ?Sized> { - raw: R, - data: UnsafeCell<T>, -} - -// Copied and modified from serde -#[cfg(feature = "serde")] -impl<R, T> Serialize for RwLock<R, T> -where - R: RawRwLock, - T: Serialize + ?Sized, -{ - fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> - where - S: Serializer, - { - self.read().serialize(serializer) - } -} - -#[cfg(feature = "serde")] -impl<'de, R, T> Deserialize<'de> for RwLock<R, T> -where - R: RawRwLock, - T: Deserialize<'de> + ?Sized, -{ - fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> - where - D: Deserializer<'de>, - { - Deserialize::deserialize(deserializer).map(RwLock::new) - } -} - -unsafe impl<R: RawRwLock + Send, T: ?Sized + Send> Send for RwLock<R, T> {} -unsafe impl<R: RawRwLock + Sync, T: ?Sized + Send + Sync> Sync for RwLock<R, T> {} - -impl<R: RawRwLock, T> RwLock<R, T> { - /// Creates a new instance of an `RwLock<T>` which is unlocked. - #[cfg(has_const_fn_trait_bound)] - #[inline] - pub const fn new(val: T) -> RwLock<R, T> { - RwLock { - data: UnsafeCell::new(val), - raw: R::INIT, - } - } - - /// Creates a new instance of an `RwLock<T>` which is unlocked. - #[cfg(not(has_const_fn_trait_bound))] - #[inline] - pub fn new(val: T) -> RwLock<R, T> { - RwLock { - data: UnsafeCell::new(val), - raw: R::INIT, - } - } - - /// Consumes this `RwLock`, returning the underlying data. - #[inline] - #[allow(unused_unsafe)] - pub fn into_inner(self) -> T { - unsafe { self.data.into_inner() } - } -} - -impl<R, T> RwLock<R, T> { - /// Creates a new new instance of an `RwLock<T>` based on a pre-existing - /// `RawRwLock<T>`. - /// - /// This allows creating a `RwLock<T>` in a constant context on stable - /// Rust. - #[inline] - pub const fn const_new(raw_rwlock: R, val: T) -> RwLock<R, T> { - RwLock { - data: UnsafeCell::new(val), - raw: raw_rwlock, - } - } -} - -impl<R: RawRwLock, T: ?Sized> RwLock<R, T> { - /// Creates a new `RwLockReadGuard` without checking if the lock is held. - /// - /// # Safety - /// - /// This method must only be called if the thread logically holds a read lock. - /// - /// This function does not increment the read count of the lock. Calling this function when a - /// guard has already been produced is undefined behaviour unless the guard was forgotten - /// with `mem::forget`.` - #[inline] - pub unsafe fn make_read_guard_unchecked(&self) -> RwLockReadGuard<'_, R, T> { - RwLockReadGuard { - rwlock: self, - marker: PhantomData, - } - } - - /// Creates a new `RwLockReadGuard` without checking if the lock is held. - /// - /// # Safety - /// - /// This method must only be called if the thread logically holds a write lock. - /// - /// Calling this function when a guard has already been produced is undefined behaviour unless - /// the guard was forgotten with `mem::forget`. - #[inline] - pub unsafe fn make_write_guard_unchecked(&self) -> RwLockWriteGuard<'_, R, T> { - RwLockWriteGuard { - rwlock: self, - marker: PhantomData, - } - } - - /// Locks this `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. - /// - /// Note that attempts to recursively acquire a read lock on a `RwLock` when - /// the current thread already holds one may result in a deadlock. - /// - /// Returns an RAII guard which will release this thread's shared access - /// once it is dropped. - #[inline] - pub fn read(&self) -> RwLockReadGuard<'_, R, T> { - self.raw.lock_shared(); - // SAFETY: The lock is held, as required. - unsafe { self.make_read_guard_unchecked() } - } - - /// Attempts to acquire this `RwLock` with shared read access. - /// - /// If the access could not be granted at this time, then `None` is returned. - /// Otherwise, an RAII guard is returned which will release the shared access - /// when it is dropped. - /// - /// This function does not block. - #[inline] - pub fn try_read(&self) -> Option<RwLockReadGuard<'_, R, T>> { - if self.raw.try_lock_shared() { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_read_guard_unchecked() }) - } else { - None - } - } - - /// Locks this `RwLock` with exclusive write access, blocking the current - /// thread until it can be acquired. - /// - /// This function will not return while other writers or other readers - /// currently have access to the lock. - /// - /// Returns an RAII guard which will drop the write access of this `RwLock` - /// when dropped. - #[inline] - pub fn write(&self) -> RwLockWriteGuard<'_, R, T> { - self.raw.lock_exclusive(); - // SAFETY: The lock is held, as required. - unsafe { self.make_write_guard_unchecked() } - } - - /// Attempts to lock this `RwLock` with exclusive write access. - /// - /// If the lock could not be acquired at this time, then `None` is returned. - /// Otherwise, an RAII guard is returned which will release the lock when - /// it is dropped. - /// - /// This function does not block. - #[inline] - pub fn try_write(&self) -> Option<RwLockWriteGuard<'_, R, T>> { - if self.raw.try_lock_exclusive() { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_write_guard_unchecked() }) - } else { - None - } - } - - /// Returns a mutable reference to the underlying data. - /// - /// Since this call borrows the `RwLock` mutably, no actual locking needs to - /// take place---the mutable borrow statically guarantees no locks exist. - #[inline] - pub fn get_mut(&mut self) -> &mut T { - unsafe { &mut *self.data.get() } - } - - /// Checks whether this `RwLock` is currently locked in any way. - #[inline] - pub fn is_locked(&self) -> bool { - self.raw.is_locked() - } - - /// Check if this `RwLock` is currently exclusively locked. - #[inline] - pub fn is_locked_exclusive(&self) -> bool { - self.raw.is_locked_exclusive() - } - - /// Forcibly unlocks a read lock. - /// - /// This is useful when combined with `mem::forget` to hold a lock without - /// the need to maintain a `RwLockReadGuard` object alive, for example when - /// dealing with FFI. - /// - /// # Safety - /// - /// This method must only be called if the current thread logically owns a - /// `RwLockReadGuard` but that guard has be discarded using `mem::forget`. - /// Behavior is undefined if a rwlock is read-unlocked when not read-locked. - #[inline] - pub unsafe fn force_unlock_read(&self) { - self.raw.unlock_shared(); - } - - /// Forcibly unlocks a write lock. - /// - /// This is useful when combined with `mem::forget` to hold a lock without - /// the need to maintain a `RwLockWriteGuard` object alive, for example when - /// dealing with FFI. - /// - /// # Safety - /// - /// This method must only be called if the current thread logically owns a - /// `RwLockWriteGuard` but that guard has be discarded using `mem::forget`. - /// Behavior is undefined if a rwlock is write-unlocked when not write-locked. - #[inline] - pub unsafe fn force_unlock_write(&self) { - self.raw.unlock_exclusive(); - } - - /// Returns the underlying raw reader-writer lock object. - /// - /// Note that you will most likely need to import the `RawRwLock` trait from - /// `lock_api` to be able to call functions on the raw - /// reader-writer lock. - /// - /// # Safety - /// - /// This method is unsafe because it allows unlocking a mutex while - /// still holding a reference to a lock guard. - pub unsafe fn raw(&self) -> &R { - &self.raw - } - - /// Returns a raw pointer to the underlying data. - /// - /// This is useful when combined with `mem::forget` to hold a lock without - /// the need to maintain a `RwLockReadGuard` or `RwLockWriteGuard` object - /// alive, for example when dealing with FFI. - /// - /// # Safety - /// - /// You must ensure that there are no data races when dereferencing the - /// returned pointer, for example if the current thread logically owns a - /// `RwLockReadGuard` or `RwLockWriteGuard` but that guard has been discarded - /// using `mem::forget`. - #[inline] - pub fn data_ptr(&self) -> *mut T { - self.data.get() - } - - /// Creates a new `RwLockReadGuard` without checking if the lock is held. - /// - /// # Safety - /// - /// This method must only be called if the thread logically holds a read lock. - /// - /// This function does not increment the read count of the lock. Calling this function when a - /// guard has already been produced is undefined behaviour unless the guard was forgotten - /// with `mem::forget`.` - #[cfg(feature = "arc_lock")] - #[inline] - pub unsafe fn make_arc_read_guard_unchecked(self: &Arc<Self>) -> ArcRwLockReadGuard<R, T> { - ArcRwLockReadGuard { - rwlock: self.clone(), - marker: PhantomData, - } - } - - /// Creates a new `RwLockWriteGuard` without checking if the lock is held. - /// - /// # Safety - /// - /// This method must only be called if the thread logically holds a write lock. - /// - /// Calling this function when a guard has already been produced is undefined behaviour unless - /// the guard was forgotten with `mem::forget`. - #[cfg(feature = "arc_lock")] - #[inline] - pub unsafe fn make_arc_write_guard_unchecked(self: &Arc<Self>) -> ArcRwLockWriteGuard<R, T> { - ArcRwLockWriteGuard { - rwlock: self.clone(), - marker: PhantomData, - } - } - - /// Locks this `RwLock` with read access, through an `Arc`. - /// - /// This method is similar to the `read` method; however, it requires the `RwLock` to be inside of an `Arc` - /// and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn read_arc(self: &Arc<Self>) -> ArcRwLockReadGuard<R, T> { - self.raw.lock_shared(); - // SAFETY: locking guarantee is upheld - unsafe { self.make_arc_read_guard_unchecked() } - } - - /// Attempts to lock this `RwLock` with read access, through an `Arc`. - /// - /// This method is similar to the `try_read` method; however, it requires the `RwLock` to be inside of an - /// `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_read_arc(self: &Arc<Self>) -> Option<ArcRwLockReadGuard<R, T>> { - if self.raw.try_lock_shared() { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_read_guard_unchecked() }) - } else { - None - } - } - - /// Locks this `RwLock` with write access, through an `Arc`. - /// - /// This method is similar to the `write` method; however, it requires the `RwLock` to be inside of an `Arc` - /// and the resulting write guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn write_arc(self: &Arc<Self>) -> ArcRwLockWriteGuard<R, T> { - self.raw.lock_exclusive(); - // SAFETY: locking guarantee is upheld - unsafe { self.make_arc_write_guard_unchecked() } - } - - /// Attempts to lock this `RwLock` with writ access, through an `Arc`. - /// - /// This method is similar to the `try_write` method; however, it requires the `RwLock` to be inside of an - /// `Arc` and the resulting write guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_write_arc(self: &Arc<Self>) -> Option<ArcRwLockWriteGuard<R, T>> { - if self.raw.try_lock_exclusive() { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_write_guard_unchecked() }) - } else { - None - } - } -} - -impl<R: RawRwLockFair, T: ?Sized> RwLock<R, T> { - /// Forcibly unlocks a read lock using a fair unlock procotol. - /// - /// This is useful when combined with `mem::forget` to hold a lock without - /// the need to maintain a `RwLockReadGuard` object alive, for example when - /// dealing with FFI. - /// - /// # Safety - /// - /// This method must only be called if the current thread logically owns a - /// `RwLockReadGuard` but that guard has be discarded using `mem::forget`. - /// Behavior is undefined if a rwlock is read-unlocked when not read-locked. - #[inline] - pub unsafe fn force_unlock_read_fair(&self) { - self.raw.unlock_shared_fair(); - } - - /// Forcibly unlocks a write lock using a fair unlock procotol. - /// - /// This is useful when combined with `mem::forget` to hold a lock without - /// the need to maintain a `RwLockWriteGuard` object alive, for example when - /// dealing with FFI. - /// - /// # Safety - /// - /// This method must only be called if the current thread logically owns a - /// `RwLockWriteGuard` but that guard has be discarded using `mem::forget`. - /// Behavior is undefined if a rwlock is write-unlocked when not write-locked. - #[inline] - pub unsafe fn force_unlock_write_fair(&self) { - self.raw.unlock_exclusive_fair(); - } -} - -impl<R: RawRwLockTimed, T: ?Sized> RwLock<R, T> { - /// Attempts to acquire this `RwLock` with shared read access until a timeout - /// is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the shared access when it is dropped. - #[inline] - pub fn try_read_for(&self, timeout: R::Duration) -> Option<RwLockReadGuard<'_, R, T>> { - if self.raw.try_lock_shared_for(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_read_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with shared read access until a timeout - /// is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the shared access when it is dropped. - #[inline] - pub fn try_read_until(&self, timeout: R::Instant) -> Option<RwLockReadGuard<'_, R, T>> { - if self.raw.try_lock_shared_until(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_read_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with exclusive write access until a - /// timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the exclusive access when it is dropped. - #[inline] - pub fn try_write_for(&self, timeout: R::Duration) -> Option<RwLockWriteGuard<'_, R, T>> { - if self.raw.try_lock_exclusive_for(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_write_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with exclusive write access until a - /// timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the exclusive access when it is dropped. - #[inline] - pub fn try_write_until(&self, timeout: R::Instant) -> Option<RwLockWriteGuard<'_, R, T>> { - if self.raw.try_lock_exclusive_until(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_write_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with read access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_read_for` method; however, it requires the `RwLock` to be inside of an - /// `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_read_arc_for( - self: &Arc<Self>, - timeout: R::Duration, - ) -> Option<ArcRwLockReadGuard<R, T>> { - if self.raw.try_lock_shared_for(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_read_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with read access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_read_until` method; however, it requires the `RwLock` to be inside of - /// an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_read_arc_until( - self: &Arc<Self>, - timeout: R::Instant, - ) -> Option<ArcRwLockReadGuard<R, T>> { - if self.raw.try_lock_shared_until(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_read_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with write access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_write_for` method; however, it requires the `RwLock` to be inside of - /// an `Arc` and the resulting write guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_write_arc_for( - self: &Arc<Self>, - timeout: R::Duration, - ) -> Option<ArcRwLockWriteGuard<R, T>> { - if self.raw.try_lock_exclusive_for(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_write_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with read access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_write_until` method; however, it requires the `RwLock` to be inside of - /// an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_write_arc_until( - self: &Arc<Self>, - timeout: R::Instant, - ) -> Option<ArcRwLockWriteGuard<R, T>> { - if self.raw.try_lock_exclusive_until(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_write_guard_unchecked() }) - } else { - None - } - } -} - -impl<R: RawRwLockRecursive, T: ?Sized> RwLock<R, T> { - /// Locks this `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. - /// - /// Unlike `read`, this method is guaranteed to succeed without blocking if - /// another read lock is held at the time of the call. This allows a thread - /// to recursively lock a `RwLock`. However using this method can cause - /// writers to starve since readers no longer block if a writer is waiting - /// for the lock. - /// - /// Returns an RAII guard which will release this thread's shared access - /// once it is dropped. - #[inline] - pub fn read_recursive(&self) -> RwLockReadGuard<'_, R, T> { - self.raw.lock_shared_recursive(); - // SAFETY: The lock is held, as required. - unsafe { self.make_read_guard_unchecked() } - } - - /// Attempts to acquire this `RwLock` with shared read access. - /// - /// If the access could not be granted at this time, then `None` is returned. - /// Otherwise, an RAII guard is returned which will release the shared access - /// when it is dropped. - /// - /// This method is guaranteed to succeed if another read lock is held at the - /// time of the call. See the documentation for `read_recursive` for details. - /// - /// This function does not block. - #[inline] - pub fn try_read_recursive(&self) -> Option<RwLockReadGuard<'_, R, T>> { - if self.raw.try_lock_shared_recursive() { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_read_guard_unchecked() }) - } else { - None - } - } - - /// Locks this `RwLock` with shared read access, through an `Arc`. - /// - /// This method is similar to the `read_recursive` method; however, it requires the `RwLock` to be inside of - /// an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn read_arc_recursive(self: &Arc<Self>) -> ArcRwLockReadGuard<R, T> { - self.raw.lock_shared_recursive(); - // SAFETY: locking guarantee is upheld - unsafe { self.make_arc_read_guard_unchecked() } - } - - /// Attempts to lock this `RwLock` with shared read access, through an `Arc`. - /// - /// This method is similar to the `try_read_recursive` method; however, it requires the `RwLock` to be inside - /// of an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_read_recursive_arc(self: &Arc<Self>) -> Option<ArcRwLockReadGuard<R, T>> { - if self.raw.try_lock_shared_recursive() { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_read_guard_unchecked() }) - } else { - None - } - } -} - -impl<R: RawRwLockRecursiveTimed, T: ?Sized> RwLock<R, T> { - /// Attempts to acquire this `RwLock` with shared read access until a timeout - /// is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the shared access when it is dropped. - /// - /// This method is guaranteed to succeed without blocking if another read - /// lock is held at the time of the call. See the documentation for - /// `read_recursive` for details. - #[inline] - pub fn try_read_recursive_for( - &self, - timeout: R::Duration, - ) -> Option<RwLockReadGuard<'_, R, T>> { - if self.raw.try_lock_shared_recursive_for(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_read_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with shared read access until a timeout - /// is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the shared access when it is dropped. - #[inline] - pub fn try_read_recursive_until( - &self, - timeout: R::Instant, - ) -> Option<RwLockReadGuard<'_, R, T>> { - if self.raw.try_lock_shared_recursive_until(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_read_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to lock this `RwLock` with read access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_read_recursive_for` method; however, it requires the `RwLock` to be - /// inside of an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_read_arc_recursive_for( - self: &Arc<Self>, - timeout: R::Duration, - ) -> Option<ArcRwLockReadGuard<R, T>> { - if self.raw.try_lock_shared_recursive_for(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_read_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to lock this `RwLock` with read access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_read_recursive_until` method; however, it requires the `RwLock` to be - /// inside of an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_read_arc_recursive_until( - self: &Arc<Self>, - timeout: R::Instant, - ) -> Option<ArcRwLockReadGuard<R, T>> { - if self.raw.try_lock_shared_recursive_until(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_arc_read_guard_unchecked() }) - } else { - None - } - } -} - -impl<R: RawRwLockUpgrade, T: ?Sized> RwLock<R, T> { - /// Creates a new `RwLockUpgradableReadGuard` without checking if the lock is held. - /// - /// # Safety - /// - /// This method must only be called if the thread logically holds an upgradable read lock. - /// - /// This function does not increment the read count of the lock. Calling this function when a - /// guard has already been produced is undefined behaviour unless the guard was forgotten - /// with `mem::forget`.` - #[inline] - pub unsafe fn make_upgradable_guard_unchecked(&self) -> RwLockUpgradableReadGuard<'_, R, T> { - RwLockUpgradableReadGuard { - rwlock: self, - marker: PhantomData, - } - } - - /// Locks this `RwLock` with upgradable read access, blocking the current thread - /// until it can be acquired. - /// - /// The calling thread will be blocked until there are no more writers or other - /// upgradable reads 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. - #[inline] - pub fn upgradable_read(&self) -> RwLockUpgradableReadGuard<'_, R, T> { - self.raw.lock_upgradable(); - // SAFETY: The lock is held, as required. - unsafe { self.make_upgradable_guard_unchecked() } - } - - /// Attempts to acquire this `RwLock` with upgradable read access. - /// - /// If the access could not be granted at this time, then `None` is returned. - /// Otherwise, an RAII guard is returned which will release the shared access - /// when it is dropped. - /// - /// This function does not block. - #[inline] - pub fn try_upgradable_read(&self) -> Option<RwLockUpgradableReadGuard<'_, R, T>> { - if self.raw.try_lock_upgradable() { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_upgradable_guard_unchecked() }) - } else { - None - } - } - - /// Creates a new `ArcRwLockUpgradableReadGuard` without checking if the lock is held. - /// - /// # Safety - /// - /// This method must only be called if the thread logically holds an upgradable read lock. - /// - /// This function does not increment the read count of the lock. Calling this function when a - /// guard has already been produced is undefined behaviour unless the guard was forgotten - /// with `mem::forget`.` - #[cfg(feature = "arc_lock")] - #[inline] - pub unsafe fn make_upgradable_arc_guard_unchecked( - self: &Arc<Self>, - ) -> ArcRwLockUpgradableReadGuard<R, T> { - ArcRwLockUpgradableReadGuard { - rwlock: self.clone(), - marker: PhantomData, - } - } - - /// Locks this `RwLock` with upgradable read access, through an `Arc`. - /// - /// This method is similar to the `upgradable_read` method; however, it requires the `RwLock` to be - /// inside of an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn upgradable_read_arc(self: &Arc<Self>) -> ArcRwLockUpgradableReadGuard<R, T> { - self.raw.lock_upgradable(); - // SAFETY: locking guarantee is upheld - unsafe { self.make_upgradable_arc_guard_unchecked() } - } - - /// Attempts to lock this `RwLock` with upgradable read access, through an `Arc`. - /// - /// This method is similar to the `try_upgradable_read` method; however, it requires the `RwLock` to be - /// inside of an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_upgradable_read_arc(self: &Arc<Self>) -> Option<ArcRwLockUpgradableReadGuard<R, T>> { - if self.raw.try_lock_upgradable() { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_upgradable_arc_guard_unchecked() }) - } else { - None - } - } -} - -impl<R: RawRwLockUpgradeTimed, T: ?Sized> RwLock<R, T> { - /// Attempts to acquire this `RwLock` with upgradable read access until a timeout - /// is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the shared access when it is dropped. - #[inline] - pub fn try_upgradable_read_for( - &self, - timeout: R::Duration, - ) -> Option<RwLockUpgradableReadGuard<'_, R, T>> { - if self.raw.try_lock_upgradable_for(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_upgradable_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to acquire this `RwLock` with upgradable read access until a timeout - /// is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. Otherwise, an RAII guard is returned which will - /// release the shared access when it is dropped. - #[inline] - pub fn try_upgradable_read_until( - &self, - timeout: R::Instant, - ) -> Option<RwLockUpgradableReadGuard<'_, R, T>> { - if self.raw.try_lock_upgradable_until(timeout) { - // SAFETY: The lock is held, as required. - Some(unsafe { self.make_upgradable_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to lock this `RwLock` with upgradable access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_upgradable_read_for` method; however, it requires the `RwLock` to be - /// inside of an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_upgradable_read_arc_for( - self: &Arc<Self>, - timeout: R::Duration, - ) -> Option<ArcRwLockUpgradableReadGuard<R, T>> { - if self.raw.try_lock_upgradable_for(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_upgradable_arc_guard_unchecked() }) - } else { - None - } - } - - /// Attempts to lock this `RwLock` with upgradable access until a timeout is reached, through an `Arc`. - /// - /// This method is similar to the `try_upgradable_read_until` method; however, it requires the `RwLock` to be - /// inside of an `Arc` and the resulting read guard has no lifetime requirements. - #[cfg(feature = "arc_lock")] - #[inline] - pub fn try_upgradable_read_arc_until( - self: &Arc<Self>, - timeout: R::Instant, - ) -> Option<ArcRwLockUpgradableReadGuard<R, T>> { - if self.raw.try_lock_upgradable_until(timeout) { - // SAFETY: locking guarantee is upheld - Some(unsafe { self.make_upgradable_arc_guard_unchecked() }) - } else { - None - } - } -} - -impl<R: RawRwLock, T: ?Sized + Default> Default for RwLock<R, T> { - #[inline] - fn default() -> RwLock<R, T> { - RwLock::new(Default::default()) - } -} - -impl<R: RawRwLock, T> From<T> for RwLock<R, T> { - #[inline] - fn from(t: T) -> RwLock<R, T> { - RwLock::new(t) - } -} - -impl<R: RawRwLock, T: ?Sized + fmt::Debug> fmt::Debug for RwLock<R, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - match self.try_read() { - Some(guard) => f.debug_struct("RwLock").field("data", &&*guard).finish(), - None => { - struct LockedPlaceholder; - impl fmt::Debug for LockedPlaceholder { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.write_str("<locked>") - } - } - - f.debug_struct("RwLock") - .field("data", &LockedPlaceholder) - .finish() - } - } - } -} - -/// RAII structure used to release the shared read access of a lock when -/// dropped. -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct RwLockReadGuard<'a, R: RawRwLock, T: ?Sized> { - rwlock: &'a RwLock<R, T>, - marker: PhantomData<(&'a T, R::GuardMarker)>, -} - -unsafe impl<R: RawRwLock + Sync, T: Sync + ?Sized> Sync for RwLockReadGuard<'_, R, T> {} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T> { - /// Returns a reference to the original reader-writer lock object. - pub fn rwlock(s: &Self) -> &'a RwLock<R, T> { - s.rwlock - } - - /// Make a new `MappedRwLockReadGuard` for a component of the locked data. - /// - /// This operation cannot fail as the `RwLockReadGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `RwLockReadGuard::map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedRwLockReadGuard<'a, R, U> - where - F: FnOnce(&T) -> &U, - { - let raw = &s.rwlock.raw; - let data = f(unsafe { &*s.rwlock.data.get() }); - mem::forget(s); - MappedRwLockReadGuard { - raw, - data, - marker: PhantomData, - } - } - - /// Attempts to make a new `MappedRwLockReadGuard` for a component of the - /// locked data. Returns the original guard if the closure returns `None`. - /// - /// This operation cannot fail as the `RwLockReadGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `RwLockReadGuard::try_map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn try_map<U: ?Sized, F>(s: Self, f: F) -> Result<MappedRwLockReadGuard<'a, R, U>, Self> - where - F: FnOnce(&T) -> Option<&U>, - { - let raw = &s.rwlock.raw; - let data = match f(unsafe { &*s.rwlock.data.get() }) { - Some(data) => data, - None => return Err(s), - }; - mem::forget(s); - Ok(MappedRwLockReadGuard { - raw, - data, - marker: PhantomData, - }) - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is safe because `&mut` guarantees that there exist no other - /// references to the data protected by the `RwLock`. - #[inline] - pub fn unlocked<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_shared(); - } - defer!(s.rwlock.raw.lock_shared()); - f() - } -} - -impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// By default, `RwLock` is unfair and allow the current thread to re-lock - /// the `RwLock` before another has the chance to acquire the lock, even if - /// that thread has been blocked on the `RwLock` for a long time. This is - /// the default because it allows much higher throughput as it avoids - /// forcing a context switch on every `RwLock` unlock. This can result in one - /// thread acquiring a `RwLock` many more times than other threads. - /// - /// However in some cases it can be beneficial to ensure fairness by forcing - /// the lock to pass on to a waiting thread if there is one. This is done by - /// using this method instead of dropping the `RwLockReadGuard` normally. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_shared_fair(); - } - mem::forget(s); - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// The `RwLock` is unlocked a fair unlock protocol. - /// - /// This is safe because `&mut` guarantees that there exist no other - /// references to the data protected by the `RwLock`. - #[inline] - pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_shared_fair(); - } - defer!(s.rwlock.raw.lock_shared()); - f() - } - - /// Temporarily yields the `RwLock` to a waiting thread if there is one. - /// - /// This method is functionally equivalent to calling `unlock_fair` followed - /// by `read`, however it can be much more efficient in the case where there - /// are no waiting threads. - #[inline] - pub fn bump(s: &mut Self) { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.bump_shared(); - } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for RwLockReadGuard<'a, R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.rwlock.data.get() } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for RwLockReadGuard<'a, R, T> { - #[inline] - fn drop(&mut self) { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - self.rwlock.raw.unlock_shared(); - } - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug for RwLockReadGuard<'a, R, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display - for RwLockReadGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -#[cfg(feature = "owning_ref")] -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress for RwLockReadGuard<'a, R, T> {} - -/// An RAII rwlock guard returned by the `Arc` locking operations on `RwLock`. -/// -/// This is similar to the `RwLockReadGuard` struct, except instead of using a reference to unlock the `RwLock` -/// it uses an `Arc<RwLock>`. This has several advantages, most notably that it has an `'static` lifetime. -#[cfg(feature = "arc_lock")] -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct ArcRwLockReadGuard<R: RawRwLock, T: ?Sized> { - rwlock: Arc<RwLock<R, T>>, - marker: PhantomData<R::GuardMarker>, -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: ?Sized> ArcRwLockReadGuard<R, T> { - /// Returns a reference to the rwlock, contained in its `Arc`. - pub fn rwlock(s: &Self) -> &Arc<RwLock<R, T>> { - &s.rwlock - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is functionally identical to the `unlocked` method on [`RwLockReadGuard`]. - #[inline] - pub fn unlocked<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_shared(); - } - defer!(s.rwlock.raw.lock_shared()); - f() - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockFair, T: ?Sized> ArcRwLockReadGuard<R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// This is functionally identical to the `unlock_fair` method on [`RwLockReadGuard`]. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_shared_fair(); - } - - // SAFETY: ensure the Arc has its refcount decremented - let mut s = ManuallyDrop::new(s); - unsafe { ptr::drop_in_place(&mut s.rwlock) }; - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is functionally identical to the `unlocked_fair` method on [`RwLockReadGuard`]. - #[inline] - pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_shared_fair(); - } - defer!(s.rwlock.raw.lock_shared()); - f() - } - - /// Temporarily yields the `RwLock` to a waiting thread if there is one. - /// - /// This is functionally identical to the `bump` method on [`RwLockReadGuard`]. - #[inline] - pub fn bump(s: &mut Self) { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.bump_shared(); - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: ?Sized> Deref for ArcRwLockReadGuard<R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.rwlock.data.get() } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: ?Sized> Drop for ArcRwLockReadGuard<R, T> { - #[inline] - fn drop(&mut self) { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - self.rwlock.raw.unlock_shared(); - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: fmt::Debug + ?Sized> fmt::Debug for ArcRwLockReadGuard<R, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: fmt::Display + ?Sized> fmt::Display for ArcRwLockReadGuard<R, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -/// RAII structure used to release the exclusive write access of a lock when -/// dropped. -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct RwLockWriteGuard<'a, R: RawRwLock, T: ?Sized> { - rwlock: &'a RwLock<R, T>, - marker: PhantomData<(&'a mut T, R::GuardMarker)>, -} - -unsafe impl<R: RawRwLock + Sync, T: Sync + ?Sized> Sync for RwLockWriteGuard<'_, R, T> {} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> { - /// Returns a reference to the original reader-writer lock object. - pub fn rwlock(s: &Self) -> &'a RwLock<R, T> { - s.rwlock - } - - /// Make a new `MappedRwLockWriteGuard` for a component of the locked data. - /// - /// This operation cannot fail as the `RwLockWriteGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `RwLockWriteGuard::map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedRwLockWriteGuard<'a, R, U> - where - F: FnOnce(&mut T) -> &mut U, - { - let raw = &s.rwlock.raw; - let data = f(unsafe { &mut *s.rwlock.data.get() }); - mem::forget(s); - MappedRwLockWriteGuard { - raw, - data, - marker: PhantomData, - } - } - - /// Attempts to make a new `MappedRwLockWriteGuard` for a component of the - /// locked data. The original guard is return if the closure returns `None`. - /// - /// This operation cannot fail as the `RwLockWriteGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `RwLockWriteGuard::try_map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn try_map<U: ?Sized, F>(s: Self, f: F) -> Result<MappedRwLockWriteGuard<'a, R, U>, Self> - where - F: FnOnce(&mut T) -> Option<&mut U>, - { - let raw = &s.rwlock.raw; - let data = match f(unsafe { &mut *s.rwlock.data.get() }) { - Some(data) => data, - None => return Err(s), - }; - mem::forget(s); - Ok(MappedRwLockWriteGuard { - raw, - data, - marker: PhantomData, - }) - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is safe because `&mut` guarantees that there exist no other - /// references to the data protected by the `RwLock`. - #[inline] - pub fn unlocked<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockReadGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_exclusive(); - } - defer!(s.rwlock.raw.lock_exclusive()); - f() - } -} - -impl<'a, R: RawRwLockDowngrade + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> { - /// Atomically downgrades a write lock into a read lock without allowing any - /// writers to take exclusive access of the lock in the meantime. - /// - /// Note that if there are any writers currently waiting to take the lock - /// then other readers may not be able to acquire the lock even if it was - /// downgraded. - pub fn downgrade(s: Self) -> RwLockReadGuard<'a, R, T> { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.downgrade(); - } - let rwlock = s.rwlock; - mem::forget(s); - RwLockReadGuard { - rwlock, - marker: PhantomData, - } - } -} - -impl<'a, R: RawRwLockUpgradeDowngrade + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> { - /// Atomically downgrades a write lock into an upgradable read lock without allowing any - /// writers to take exclusive access of the lock in the meantime. - /// - /// Note that if there are any writers currently waiting to take the lock - /// then other readers may not be able to acquire the lock even if it was - /// downgraded. - pub fn downgrade_to_upgradable(s: Self) -> RwLockUpgradableReadGuard<'a, R, T> { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.downgrade_to_upgradable(); - } - let rwlock = s.rwlock; - mem::forget(s); - RwLockUpgradableReadGuard { - rwlock, - marker: PhantomData, - } - } -} - -impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// By default, `RwLock` is unfair and allow the current thread to re-lock - /// the `RwLock` before another has the chance to acquire the lock, even if - /// that thread has been blocked on the `RwLock` for a long time. This is - /// the default because it allows much higher throughput as it avoids - /// forcing a context switch on every `RwLock` unlock. This can result in one - /// thread acquiring a `RwLock` many more times than other threads. - /// - /// However in some cases it can be beneficial to ensure fairness by forcing - /// the lock to pass on to a waiting thread if there is one. This is done by - /// using this method instead of dropping the `RwLockWriteGuard` normally. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.unlock_exclusive_fair(); - } - mem::forget(s); - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// The `RwLock` is unlocked a fair unlock protocol. - /// - /// This is safe because `&mut` guarantees that there exist no other - /// references to the data protected by the `RwLock`. - #[inline] - pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.unlock_exclusive_fair(); - } - defer!(s.rwlock.raw.lock_exclusive()); - f() - } - - /// Temporarily yields the `RwLock` to a waiting thread if there is one. - /// - /// This method is functionally equivalent to calling `unlock_fair` followed - /// by `write`, however it can be much more efficient in the case where there - /// are no waiting threads. - #[inline] - pub fn bump(s: &mut Self) { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.bump_exclusive(); - } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for RwLockWriteGuard<'a, R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.rwlock.data.get() } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> DerefMut for RwLockWriteGuard<'a, R, T> { - #[inline] - fn deref_mut(&mut self) -> &mut T { - unsafe { &mut *self.rwlock.data.get() } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for RwLockWriteGuard<'a, R, T> { - #[inline] - fn drop(&mut self) { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - self.rwlock.raw.unlock_exclusive(); - } - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug for RwLockWriteGuard<'a, R, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display - for RwLockWriteGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -#[cfg(feature = "owning_ref")] -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress for RwLockWriteGuard<'a, R, T> {} - -/// An RAII rwlock guard returned by the `Arc` locking operations on `RwLock`. -/// This is similar to the `RwLockWriteGuard` struct, except instead of using a reference to unlock the `RwLock` -/// it uses an `Arc<RwLock>`. This has several advantages, most notably that it has an `'static` lifetime. -#[cfg(feature = "arc_lock")] -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct ArcRwLockWriteGuard<R: RawRwLock, T: ?Sized> { - rwlock: Arc<RwLock<R, T>>, - marker: PhantomData<R::GuardMarker>, -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: ?Sized> ArcRwLockWriteGuard<R, T> { - /// Returns a reference to the rwlock, contained in its `Arc`. - pub fn rwlock(s: &Self) -> &Arc<RwLock<R, T>> { - &s.rwlock - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is functionally equivalent to the `unlocked` method on [`RwLockWriteGuard`]. - #[inline] - pub fn unlocked<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockWriteGuard always holds a shared lock. - unsafe { - s.rwlock.raw.unlock_exclusive(); - } - defer!(s.rwlock.raw.lock_exclusive()); - f() - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockDowngrade, T: ?Sized> ArcRwLockWriteGuard<R, T> { - /// Atomically downgrades a write lock into a read lock without allowing any - /// writers to take exclusive access of the lock in the meantime. - /// - /// This is functionally equivalent to the `downgrade` method on [`RwLockWriteGuard`]. - pub fn downgrade(s: Self) -> ArcRwLockReadGuard<R, T> { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.downgrade(); - } - - // SAFETY: prevent the arc's refcount from changing using ManuallyDrop and ptr::read - let s = ManuallyDrop::new(s); - let rwlock = unsafe { ptr::read(&s.rwlock) }; - - ArcRwLockReadGuard { - rwlock, - marker: PhantomData, - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgradeDowngrade, T: ?Sized> ArcRwLockWriteGuard<R, T> { - /// Atomically downgrades a write lock into an upgradable read lock without allowing any - /// writers to take exclusive access of the lock in the meantime. - /// - /// This is functionally identical to the `downgrade_to_upgradable` method on [`RwLockWriteGuard`]. - pub fn downgrade_to_upgradable(s: Self) -> ArcRwLockUpgradableReadGuard<R, T> { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.downgrade_to_upgradable(); - } - - // SAFETY: same as above - let s = ManuallyDrop::new(s); - let rwlock = unsafe { ptr::read(&s.rwlock) }; - - ArcRwLockUpgradableReadGuard { - rwlock, - marker: PhantomData, - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockFair, T: ?Sized> ArcRwLockWriteGuard<R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// This is functionally equivalent to the `unlock_fair` method on [`RwLockWriteGuard`]. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.unlock_exclusive_fair(); - } - - // SAFETY: prevent the Arc from leaking memory - let mut s = ManuallyDrop::new(s); - unsafe { ptr::drop_in_place(&mut s.rwlock) }; - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is functionally equivalent to the `unlocked_fair` method on [`RwLockWriteGuard`]. - #[inline] - pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.unlock_exclusive_fair(); - } - defer!(s.rwlock.raw.lock_exclusive()); - f() - } - - /// Temporarily yields the `RwLock` to a waiting thread if there is one. - /// - /// This method is functionally equivalent to the `bump` method on [`RwLockWriteGuard`]. - #[inline] - pub fn bump(s: &mut Self) { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - s.rwlock.raw.bump_exclusive(); - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: ?Sized> Deref for ArcRwLockWriteGuard<R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.rwlock.data.get() } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: ?Sized> DerefMut for ArcRwLockWriteGuard<R, T> { - #[inline] - fn deref_mut(&mut self) -> &mut T { - unsafe { &mut *self.rwlock.data.get() } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: ?Sized> Drop for ArcRwLockWriteGuard<R, T> { - #[inline] - fn drop(&mut self) { - // Safety: An RwLockWriteGuard always holds an exclusive lock. - unsafe { - self.rwlock.raw.unlock_exclusive(); - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: fmt::Debug + ?Sized> fmt::Debug for ArcRwLockWriteGuard<R, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLock, T: fmt::Display + ?Sized> fmt::Display for ArcRwLockWriteGuard<R, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -/// RAII structure used to release the upgradable read access of a lock when -/// dropped. -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct RwLockUpgradableReadGuard<'a, R: RawRwLockUpgrade, T: ?Sized> { - rwlock: &'a RwLock<R, T>, - marker: PhantomData<(&'a T, R::GuardMarker)>, -} - -unsafe impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + Sync + 'a> Sync - for RwLockUpgradableReadGuard<'a, R, T> -{ -} - -impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> { - /// Returns a reference to the original reader-writer lock object. - pub fn rwlock(s: &Self) -> &'a RwLock<R, T> { - s.rwlock - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is safe because `&mut` guarantees that there exist no other - /// references to the data protected by the `RwLock`. - #[inline] - pub fn unlocked<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.unlock_upgradable(); - } - defer!(s.rwlock.raw.lock_upgradable()); - f() - } - - /// Atomically upgrades an upgradable read lock lock into an exclusive write lock, - /// blocking the current thread until it can be acquired. - pub fn upgrade(s: Self) -> RwLockWriteGuard<'a, R, T> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.upgrade(); - } - let rwlock = s.rwlock; - mem::forget(s); - RwLockWriteGuard { - rwlock, - marker: PhantomData, - } - } - - /// Tries to atomically upgrade an upgradable read lock into an exclusive write lock. - /// - /// If the access could not be granted at this time, then the current guard is returned. - pub fn try_upgrade(s: Self) -> Result<RwLockWriteGuard<'a, R, T>, Self> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - if unsafe { s.rwlock.raw.try_upgrade() } { - let rwlock = s.rwlock; - mem::forget(s); - Ok(RwLockWriteGuard { - rwlock, - marker: PhantomData, - }) - } else { - Err(s) - } - } -} - -impl<'a, R: RawRwLockUpgradeFair + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// By default, `RwLock` is unfair and allow the current thread to re-lock - /// the `RwLock` before another has the chance to acquire the lock, even if - /// that thread has been blocked on the `RwLock` for a long time. This is - /// the default because it allows much higher throughput as it avoids - /// forcing a context switch on every `RwLock` unlock. This can result in one - /// thread acquiring a `RwLock` many more times than other threads. - /// - /// However in some cases it can be beneficial to ensure fairness by forcing - /// the lock to pass on to a waiting thread if there is one. This is done by - /// using this method instead of dropping the `RwLockUpgradableReadGuard` normally. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.unlock_upgradable_fair(); - } - mem::forget(s); - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// The `RwLock` is unlocked a fair unlock protocol. - /// - /// This is safe because `&mut` guarantees that there exist no other - /// references to the data protected by the `RwLock`. - #[inline] - pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.unlock_upgradable_fair(); - } - defer!(s.rwlock.raw.lock_upgradable()); - f() - } - - /// Temporarily yields the `RwLock` to a waiting thread if there is one. - /// - /// This method is functionally equivalent to calling `unlock_fair` followed - /// by `upgradable_read`, however it can be much more efficient in the case where there - /// are no waiting threads. - #[inline] - pub fn bump(s: &mut Self) { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.bump_upgradable(); - } - } -} - -impl<'a, R: RawRwLockUpgradeDowngrade + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> { - /// Atomically downgrades an upgradable read lock lock into a shared read lock - /// without allowing any writers to take exclusive access of the lock in the - /// meantime. - /// - /// Note that if there are any writers currently waiting to take the lock - /// then other readers may not be able to acquire the lock even if it was - /// downgraded. - pub fn downgrade(s: Self) -> RwLockReadGuard<'a, R, T> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.downgrade_upgradable(); - } - let rwlock = s.rwlock; - mem::forget(s); - RwLockReadGuard { - rwlock, - marker: PhantomData, - } - } - - /// First, atomically upgrades an upgradable read lock lock into an exclusive write lock, - /// blocking the current thread until it can be acquired. - /// - /// Then, calls the provided closure with an exclusive reference to the lock's data. - /// - /// Finally, atomically downgrades the lock back to an upgradable read lock. - /// The closure's return value is wrapped in `Some` and returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `upgrade` which takes the guard by value. - pub fn with_upgraded<Ret, F: FnOnce(&mut T) -> Ret>(&mut self, f: F) -> Ret { - unsafe { - self.rwlock.raw.upgrade(); - } - - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_to_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - f(unsafe { &mut *self.rwlock.data.get() }) - } - - /// First, tries to atomically upgrade an upgradable read lock into an exclusive write lock. - /// - /// If the access could not be granted at this time, then `None` is returned. - /// - /// Otherwise, calls the provided closure with an exclusive reference to the lock's data, - /// and finally downgrades the lock back to an upgradable read lock. - /// The closure's return value is wrapped in `Some` and returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `try_upgrade` which takes the guard by value. - pub fn try_with_upgraded<Ret, F: FnOnce(&mut T) -> Ret>(&mut self, f: F) -> Option<Ret> { - if unsafe { self.rwlock.raw.try_upgrade() } { - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_to_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - Some(f(unsafe { &mut *self.rwlock.data.get() })) - } else { - None - } - } -} - -impl<'a, R: RawRwLockUpgradeTimed + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> { - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// the current guard is returned. - pub fn try_upgrade_for( - s: Self, - timeout: R::Duration, - ) -> Result<RwLockWriteGuard<'a, R, T>, Self> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - if unsafe { s.rwlock.raw.try_upgrade_for(timeout) } { - let rwlock = s.rwlock; - mem::forget(s); - Ok(RwLockWriteGuard { - rwlock, - marker: PhantomData, - }) - } else { - Err(s) - } - } - - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// the current guard is returned. - #[inline] - pub fn try_upgrade_until( - s: Self, - timeout: R::Instant, - ) -> Result<RwLockWriteGuard<'a, R, T>, Self> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - if unsafe { s.rwlock.raw.try_upgrade_until(timeout) } { - let rwlock = s.rwlock; - mem::forget(s); - Ok(RwLockWriteGuard { - rwlock, - marker: PhantomData, - }) - } else { - Err(s) - } - } -} - -impl<'a, R: RawRwLockUpgradeTimed + RawRwLockUpgradeDowngrade + 'a, T: ?Sized + 'a> - RwLockUpgradableReadGuard<'a, R, T> -{ - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. - /// - /// Otherwise, calls the provided closure with an exclusive reference to the lock's data, - /// and finally downgrades the lock back to an upgradable read lock. - /// The closure's return value is wrapped in `Some` and returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `try_upgrade_for` which takes the guard by value. - pub fn try_with_upgraded_for<Ret, F: FnOnce(&mut T) -> Ret>( - &mut self, - timeout: R::Duration, - f: F, - ) -> Option<Ret> { - if unsafe { self.rwlock.raw.try_upgrade_for(timeout) } { - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - Some(f(unsafe { &mut *self.rwlock.data.get() })) - } else { - None - } - } - - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. - /// - /// Otherwise, calls the provided closure with an exclusive reference to the lock's data, - /// and finally downgrades the lock back to an upgradable read lock. - /// The closure's return value is wrapped in `Some` and returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `try_upgrade_until` which takes the guard by value. - pub fn try_with_upgraded_until<Ret, F: FnOnce(&mut T) -> Ret>( - &mut self, - timeout: R::Instant, - f: F, - ) -> Option<Ret> { - if unsafe { self.rwlock.raw.try_upgrade_until(timeout) } { - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - Some(f(unsafe { &mut *self.rwlock.data.get() })) - } else { - None - } - } -} - -impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> Deref for RwLockUpgradableReadGuard<'a, R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.rwlock.data.get() } - } -} - -impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> Drop for RwLockUpgradableReadGuard<'a, R, T> { - #[inline] - fn drop(&mut self) { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - self.rwlock.raw.unlock_upgradable(); - } - } -} - -impl<'a, R: RawRwLockUpgrade + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug - for RwLockUpgradableReadGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -impl<'a, R: RawRwLockUpgrade + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display - for RwLockUpgradableReadGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -#[cfg(feature = "owning_ref")] -unsafe impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> StableAddress - for RwLockUpgradableReadGuard<'a, R, T> -{ -} - -/// An RAII rwlock guard returned by the `Arc` locking operations on `RwLock`. -/// This is similar to the `RwLockUpgradableReadGuard` struct, except instead of using a reference to unlock the -/// `RwLock` it uses an `Arc<RwLock>`. This has several advantages, most notably that it has an `'static` -/// lifetime. -#[cfg(feature = "arc_lock")] -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct ArcRwLockUpgradableReadGuard<R: RawRwLockUpgrade, T: ?Sized> { - rwlock: Arc<RwLock<R, T>>, - marker: PhantomData<R::GuardMarker>, -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgrade, T: ?Sized> ArcRwLockUpgradableReadGuard<R, T> { - /// Returns a reference to the rwlock, contained in its original `Arc`. - pub fn rwlock(s: &Self) -> &Arc<RwLock<R, T>> { - &s.rwlock - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is functionally identical to the `unlocked` method on [`RwLockUpgradableReadGuard`]. - #[inline] - pub fn unlocked<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.unlock_upgradable(); - } - defer!(s.rwlock.raw.lock_upgradable()); - f() - } - - /// Atomically upgrades an upgradable read lock lock into an exclusive write lock, - /// blocking the current thread until it can be acquired. - pub fn upgrade(s: Self) -> ArcRwLockWriteGuard<R, T> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.upgrade(); - } - - // SAFETY: avoid incrementing or decrementing the refcount using ManuallyDrop and reading the Arc out - // of the struct - let s = ManuallyDrop::new(s); - let rwlock = unsafe { ptr::read(&s.rwlock) }; - - ArcRwLockWriteGuard { - rwlock, - marker: PhantomData, - } - } - - /// Tries to atomically upgrade an upgradable read lock into an exclusive write lock. - /// - /// If the access could not be granted at this time, then the current guard is returned. - pub fn try_upgrade(s: Self) -> Result<ArcRwLockWriteGuard<R, T>, Self> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - if unsafe { s.rwlock.raw.try_upgrade() } { - // SAFETY: same as above - let s = ManuallyDrop::new(s); - let rwlock = unsafe { ptr::read(&s.rwlock) }; - - Ok(ArcRwLockWriteGuard { - rwlock, - marker: PhantomData, - }) - } else { - Err(s) - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgradeFair, T: ?Sized> ArcRwLockUpgradableReadGuard<R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// This is functionally identical to the `unlock_fair` method on [`RwLockUpgradableReadGuard`]. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.unlock_upgradable_fair(); - } - - // SAFETY: make sure we decrement the refcount properly - let mut s = ManuallyDrop::new(s); - unsafe { ptr::drop_in_place(&mut s.rwlock) }; - } - - /// Temporarily unlocks the `RwLock` to execute the given function. - /// - /// This is functionally equivalent to the `unlocked_fair` method on [`RwLockUpgradableReadGuard`]. - #[inline] - pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U - where - F: FnOnce() -> U, - { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.unlock_upgradable_fair(); - } - defer!(s.rwlock.raw.lock_upgradable()); - f() - } - - /// Temporarily yields the `RwLock` to a waiting thread if there is one. - /// - /// This method is functionally equivalent to calling `bump` on [`RwLockUpgradableReadGuard`]. - #[inline] - pub fn bump(s: &mut Self) { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.bump_upgradable(); - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgradeDowngrade, T: ?Sized> ArcRwLockUpgradableReadGuard<R, T> { - /// Atomically downgrades an upgradable read lock lock into a shared read lock - /// without allowing any writers to take exclusive access of the lock in the - /// meantime. - /// - /// Note that if there are any writers currently waiting to take the lock - /// then other readers may not be able to acquire the lock even if it was - /// downgraded. - pub fn downgrade(s: Self) -> ArcRwLockReadGuard<R, T> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - s.rwlock.raw.downgrade_upgradable(); - } - - // SAFETY: use ManuallyDrop and ptr::read to ensure the refcount is not changed - let s = ManuallyDrop::new(s); - let rwlock = unsafe { ptr::read(&s.rwlock) }; - - ArcRwLockReadGuard { - rwlock, - marker: PhantomData, - } - } - - /// First, atomically upgrades an upgradable read lock lock into an exclusive write lock, - /// blocking the current thread until it can be acquired. - /// - /// Then, calls the provided closure with an exclusive reference to the lock's data. - /// - /// Finally, atomically downgrades the lock back to an upgradable read lock. - /// The closure's return value is returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `upgrade` which takes the guard by value. - pub fn with_upgraded<Ret, F: FnOnce(&mut T) -> Ret>(&mut self, f: F) -> Ret { - unsafe { - self.rwlock.raw.upgrade(); - } - - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - f(unsafe { &mut *self.rwlock.data.get() }) - } - - /// First, tries to atomically upgrade an upgradable read lock into an exclusive write lock. - /// - /// If the access could not be granted at this time, then `None` is returned. - /// - /// Otherwise, calls the provided closure with an exclusive reference to the lock's data, - /// and finally downgrades the lock back to an upgradable read lock. - /// The closure's return value is wrapped in `Some` and returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `try_upgrade` which takes the guard by value. - pub fn try_with_upgraded<Ret, F: FnOnce(&mut T) -> Ret>(&mut self, f: F) -> Option<Ret> { - if unsafe { self.rwlock.raw.try_upgrade() } { - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - Some(f(unsafe { &mut *self.rwlock.data.get() })) - } else { - None - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgradeTimed, T: ?Sized> ArcRwLockUpgradableReadGuard<R, T> { - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// the current guard is returned. - pub fn try_upgrade_for( - s: Self, - timeout: R::Duration, - ) -> Result<ArcRwLockWriteGuard<R, T>, Self> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - if unsafe { s.rwlock.raw.try_upgrade_for(timeout) } { - // SAFETY: same as above - let s = ManuallyDrop::new(s); - let rwlock = unsafe { ptr::read(&s.rwlock) }; - - Ok(ArcRwLockWriteGuard { - rwlock, - marker: PhantomData, - }) - } else { - Err(s) - } - } - - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// the current guard is returned. - #[inline] - pub fn try_upgrade_until( - s: Self, - timeout: R::Instant, - ) -> Result<ArcRwLockWriteGuard<R, T>, Self> { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - if unsafe { s.rwlock.raw.try_upgrade_until(timeout) } { - // SAFETY: same as above - let s = ManuallyDrop::new(s); - let rwlock = unsafe { ptr::read(&s.rwlock) }; - - Ok(ArcRwLockWriteGuard { - rwlock, - marker: PhantomData, - }) - } else { - Err(s) - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgradeTimed + RawRwLockUpgradeDowngrade, T: ?Sized> - ArcRwLockUpgradableReadGuard<R, T> -{ - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. - /// - /// Otherwise, calls the provided closure with an exclusive reference to the lock's data, - /// and finally downgrades the lock back to an upgradable read lock. - /// The closure's return value is wrapped in `Some` and returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `try_upgrade_for` which takes the guard by value. - pub fn try_with_upgraded_for<Ret, F: FnOnce(&mut T) -> Ret>( - &mut self, - timeout: R::Duration, - f: F, - ) -> Option<Ret> { - if unsafe { self.rwlock.raw.try_upgrade_for(timeout) } { - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - Some(f(unsafe { &mut *self.rwlock.data.get() })) - } else { - None - } - } - - /// Tries to atomically upgrade an upgradable read lock into an exclusive - /// write lock, until a timeout is reached. - /// - /// If the access could not be granted before the timeout expires, then - /// `None` is returned. - /// - /// Otherwise, calls the provided closure with an exclusive reference to the lock's data, - /// and finally downgrades the lock back to an upgradable read lock. - /// The closure's return value is wrapped in `Some` and returned. - /// - /// This function only requires a mutable reference to the guard, unlike - /// `try_upgrade_until` which takes the guard by value. - pub fn try_with_upgraded_until<Ret, F: FnOnce(&mut T) -> Ret>( - &mut self, - timeout: R::Instant, - f: F, - ) -> Option<Ret> { - if unsafe { self.rwlock.raw.try_upgrade_until(timeout) } { - // Safety: We just upgraded the lock, so we have mutable access to the data. - // This will restore the state the lock was in at the start of the function. - defer!(unsafe { self.rwlock.raw.downgrade_upgradable() }); - - // Safety: We upgraded the lock, so we have mutable access to the data. - // When this function returns, whether by drop or panic, - // the drop guard will downgrade it back to an upgradeable lock. - Some(f(unsafe { &mut *self.rwlock.data.get() })) - } else { - None - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgrade, T: ?Sized> Deref for ArcRwLockUpgradableReadGuard<R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.rwlock.data.get() } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgrade, T: ?Sized> Drop for ArcRwLockUpgradableReadGuard<R, T> { - #[inline] - fn drop(&mut self) { - // Safety: An RwLockUpgradableReadGuard always holds an upgradable lock. - unsafe { - self.rwlock.raw.unlock_upgradable(); - } - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgrade, T: fmt::Debug + ?Sized> fmt::Debug - for ArcRwLockUpgradableReadGuard<R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -#[cfg(feature = "arc_lock")] -impl<R: RawRwLockUpgrade, T: fmt::Display + ?Sized> fmt::Display - for ArcRwLockUpgradableReadGuard<R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -/// An RAII read lock guard returned by `RwLockReadGuard::map`, which can point to a -/// subfield of the protected data. -/// -/// The main difference between `MappedRwLockReadGuard` and `RwLockReadGuard` is that the -/// former doesn't support temporarily unlocking and re-locking, since that -/// could introduce soundness issues if the locked object is modified by another -/// thread. -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct MappedRwLockReadGuard<'a, R: RawRwLock, T: ?Sized> { - raw: &'a R, - data: *const T, - marker: PhantomData<&'a T>, -} - -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Sync for MappedRwLockReadGuard<'a, R, T> {} -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Send for MappedRwLockReadGuard<'a, R, T> where - R::GuardMarker: Send -{ -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> MappedRwLockReadGuard<'a, R, T> { - /// Make a new `MappedRwLockReadGuard` for a component of the locked data. - /// - /// This operation cannot fail as the `MappedRwLockReadGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `MappedRwLockReadGuard::map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedRwLockReadGuard<'a, R, U> - where - F: FnOnce(&T) -> &U, - { - let raw = s.raw; - let data = f(unsafe { &*s.data }); - mem::forget(s); - MappedRwLockReadGuard { - raw, - data, - marker: PhantomData, - } - } - - /// Attempts to make a new `MappedRwLockReadGuard` for a component of the - /// locked data. The original guard is return if the closure returns `None`. - /// - /// This operation cannot fail as the `MappedRwLockReadGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `MappedRwLockReadGuard::try_map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn try_map<U: ?Sized, F>(s: Self, f: F) -> Result<MappedRwLockReadGuard<'a, R, U>, Self> - where - F: FnOnce(&T) -> Option<&U>, - { - let raw = s.raw; - let data = match f(unsafe { &*s.data }) { - Some(data) => data, - None => return Err(s), - }; - mem::forget(s); - Ok(MappedRwLockReadGuard { - raw, - data, - marker: PhantomData, - }) - } -} - -impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> MappedRwLockReadGuard<'a, R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// By default, `RwLock` is unfair and allow the current thread to re-lock - /// the `RwLock` before another has the chance to acquire the lock, even if - /// that thread has been blocked on the `RwLock` for a long time. This is - /// the default because it allows much higher throughput as it avoids - /// forcing a context switch on every `RwLock` unlock. This can result in one - /// thread acquiring a `RwLock` many more times than other threads. - /// - /// However in some cases it can be beneficial to ensure fairness by forcing - /// the lock to pass on to a waiting thread if there is one. This is done by - /// using this method instead of dropping the `MappedRwLockReadGuard` normally. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: A MappedRwLockReadGuard always holds a shared lock. - unsafe { - s.raw.unlock_shared_fair(); - } - mem::forget(s); - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for MappedRwLockReadGuard<'a, R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.data } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for MappedRwLockReadGuard<'a, R, T> { - #[inline] - fn drop(&mut self) { - // Safety: A MappedRwLockReadGuard always holds a shared lock. - unsafe { - self.raw.unlock_shared(); - } - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug - for MappedRwLockReadGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display - for MappedRwLockReadGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -#[cfg(feature = "owning_ref")] -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress - for MappedRwLockReadGuard<'a, R, T> -{ -} - -/// An RAII write lock guard returned by `RwLockWriteGuard::map`, which can point to a -/// subfield of the protected data. -/// -/// The main difference between `MappedRwLockWriteGuard` and `RwLockWriteGuard` is that the -/// former doesn't support temporarily unlocking and re-locking, since that -/// could introduce soundness issues if the locked object is modified by another -/// thread. -#[clippy::has_significant_drop] -#[must_use = "if unused the RwLock will immediately unlock"] -pub struct MappedRwLockWriteGuard<'a, R: RawRwLock, T: ?Sized> { - raw: &'a R, - data: *mut T, - marker: PhantomData<&'a mut T>, -} - -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Sync - for MappedRwLockWriteGuard<'a, R, T> -{ -} -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Send + 'a> Send for MappedRwLockWriteGuard<'a, R, T> where - R::GuardMarker: Send -{ -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> MappedRwLockWriteGuard<'a, R, T> { - /// Make a new `MappedRwLockWriteGuard` for a component of the locked data. - /// - /// This operation cannot fail as the `MappedRwLockWriteGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `MappedRwLockWriteGuard::map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedRwLockWriteGuard<'a, R, U> - where - F: FnOnce(&mut T) -> &mut U, - { - let raw = s.raw; - let data = f(unsafe { &mut *s.data }); - mem::forget(s); - MappedRwLockWriteGuard { - raw, - data, - marker: PhantomData, - } - } - - /// Attempts to make a new `MappedRwLockWriteGuard` for a component of the - /// locked data. The original guard is return if the closure returns `None`. - /// - /// This operation cannot fail as the `MappedRwLockWriteGuard` passed - /// in already locked the data. - /// - /// This is an associated function that needs to be - /// used as `MappedRwLockWriteGuard::try_map(...)`. A method would interfere with methods of - /// the same name on the contents of the locked data. - #[inline] - pub fn try_map<U: ?Sized, F>(s: Self, f: F) -> Result<MappedRwLockWriteGuard<'a, R, U>, Self> - where - F: FnOnce(&mut T) -> Option<&mut U>, - { - let raw = s.raw; - let data = match f(unsafe { &mut *s.data }) { - Some(data) => data, - None => return Err(s), - }; - mem::forget(s); - Ok(MappedRwLockWriteGuard { - raw, - data, - marker: PhantomData, - }) - } -} - -impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> MappedRwLockWriteGuard<'a, R, T> { - /// Unlocks the `RwLock` using a fair unlock protocol. - /// - /// By default, `RwLock` is unfair and allow the current thread to re-lock - /// the `RwLock` before another has the chance to acquire the lock, even if - /// that thread has been blocked on the `RwLock` for a long time. This is - /// the default because it allows much higher throughput as it avoids - /// forcing a context switch on every `RwLock` unlock. This can result in one - /// thread acquiring a `RwLock` many more times than other threads. - /// - /// However in some cases it can be beneficial to ensure fairness by forcing - /// the lock to pass on to a waiting thread if there is one. This is done by - /// using this method instead of dropping the `MappedRwLockWriteGuard` normally. - #[inline] - pub fn unlock_fair(s: Self) { - // Safety: A MappedRwLockWriteGuard always holds an exclusive lock. - unsafe { - s.raw.unlock_exclusive_fair(); - } - mem::forget(s); - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for MappedRwLockWriteGuard<'a, R, T> { - type Target = T; - #[inline] - fn deref(&self) -> &T { - unsafe { &*self.data } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> DerefMut for MappedRwLockWriteGuard<'a, R, T> { - #[inline] - fn deref_mut(&mut self) -> &mut T { - unsafe { &mut *self.data } - } -} - -impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for MappedRwLockWriteGuard<'a, R, T> { - #[inline] - fn drop(&mut self) { - // Safety: A MappedRwLockWriteGuard always holds an exclusive lock. - unsafe { - self.raw.unlock_exclusive(); - } - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug - for MappedRwLockWriteGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -impl<'a, R: RawRwLock + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display - for MappedRwLockWriteGuard<'a, R, T> -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - (**self).fmt(f) - } -} - -#[cfg(feature = "owning_ref")] -unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress - for MappedRwLockWriteGuard<'a, R, T> -{ -} |