Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 960 insertions, 0 deletions

diff --git a/vendor/lock_api/src/mutex.rs b/vendor/lock_api/src/mutex.rs
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+// Copyright 2018 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 mutex.
+///
+/// Types implementing this trait can be used by `Mutex` to form a safe and
+/// fully-functioning mutex type.
+///
+/// # Safety
+///
+/// Implementations of this trait must ensure that the mutex is actually
+/// exclusive: a lock can't be acquired while the mutex is already locked.
+pub unsafe trait RawMutex {
+    /// Initial value for an unlocked mutex.
+    // 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 this mutex, blocking the current thread until it is able to do so.
+    fn lock(&self);
+
+    /// Attempts to acquire this mutex without blocking. Returns `true`
+    /// if the lock was successfully acquired and `false` otherwise.
+    fn try_lock(&self) -> bool;
+
+    /// Unlocks this mutex.
+    ///
+    /// # Safety
+    ///
+    /// This method may only be called if the mutex is held in the current context, i.e. it must
+    /// be paired with a successful call to [`lock`], [`try_lock`], [`try_lock_for`] or [`try_lock_until`].
+    ///
+    /// [`lock`]: #tymethod.lock
+    /// [`try_lock`]: #tymethod.try_lock
+    /// [`try_lock_for`]: trait.RawMutexTimed.html#tymethod.try_lock_for
+    /// [`try_lock_until`]: trait.RawMutexTimed.html#tymethod.try_lock_until
+    unsafe fn unlock(&self);
+
+    /// Checks whether the mutex is currently locked.
+    #[inline]
+    fn is_locked(&self) -> bool {
+        let acquired_lock = self.try_lock();
+        if acquired_lock {
+            // Safety: The lock has been successfully acquired above.
+            unsafe {
+                self.unlock();
+            }
+        }
+        !acquired_lock
+    }
+}
+
+/// Additional methods for mutexes 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 RawMutexFair: RawMutex {
+    /// Unlocks this mutex using a fair unlock protocol.
+    ///
+    /// # Safety
+    ///
+    /// This method may only be called if the mutex is held in the current context, see
+    /// the documentation of [`unlock`].
+    ///
+    /// [`unlock`]: trait.RawMutex.html#tymethod.unlock
+    unsafe fn unlock_fair(&self);
+
+    /// Temporarily yields the mutex to a waiting thread if there is one.
+    ///
+    /// This method is functionally equivalent to calling `unlock_fair` followed
+    /// by `lock`, however it can be much more efficient in the case where there
+    /// are no waiting threads.
+    ///
+    /// # Safety
+    ///
+    /// This method may only be called if the mutex is held in the current context, see
+    /// the documentation of [`unlock`].
+    ///
+    /// [`unlock`]: trait.RawMutex.html#tymethod.unlock
+    unsafe fn bump(&self) {
+        self.unlock_fair();
+        self.lock();
+    }
+}
+
+/// Additional methods for mutexes 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 RawMutexTimed: RawMutex {
+    /// Duration type used for `try_lock_for`.
+    type Duration;
+
+    /// Instant type used for `try_lock_until`.
+    type Instant;
+
+    /// Attempts to acquire this lock until a timeout is reached.
+    fn try_lock_for(&self, timeout: Self::Duration) -> bool;
+
+    /// Attempts to acquire this lock until a timeout is reached.
+    fn try_lock_until(&self, timeout: Self::Instant) -> bool;
+}
+
+/// A mutual exclusion primitive useful for protecting shared data
+///
+/// This mutex will block threads waiting for the lock to become available. The
+/// mutex can also be statically initialized or created via a `new`
+/// constructor. Each mutex has a type parameter which represents the data that
+/// it is protecting. The data can only be accessed through the RAII guards
+/// returned from `lock` and `try_lock`, which guarantees that the data is only
+/// ever accessed when the mutex is locked.
+pub struct Mutex<R, T: ?Sized> {
+    raw: R,
+    data: UnsafeCell<T>,
+}
+
+unsafe impl<R: RawMutex + Send, T: ?Sized + Send> Send for Mutex<R, T> {}
+unsafe impl<R: RawMutex + Sync, T: ?Sized + Send> Sync for Mutex<R, T> {}
+
+impl<R: RawMutex, T> Mutex<R, T> {
+    /// Creates a new mutex in an unlocked state ready for use.
+    #[cfg(has_const_fn_trait_bound)]
+    #[inline]
+    pub const fn new(val: T) -> Mutex<R, T> {
+        Mutex {
+            raw: R::INIT,
+            data: UnsafeCell::new(val),
+        }
+    }
+
+    /// Creates a new mutex in an unlocked state ready for use.
+    #[cfg(not(has_const_fn_trait_bound))]
+    #[inline]
+    pub fn new(val: T) -> Mutex<R, T> {
+        Mutex {
+            raw: R::INIT,
+            data: UnsafeCell::new(val),
+        }
+    }
+
+    /// Consumes this mutex, returning the underlying data.
+    #[inline]
+    pub fn into_inner(self) -> T {
+        self.data.into_inner()
+    }
+}
+
+impl<R, T> Mutex<R, T> {
+    /// Creates a new mutex based on a pre-existing raw mutex.
+    ///
+    /// This allows creating a mutex in a constant context on stable Rust.
+    #[inline]
+    pub const fn const_new(raw_mutex: R, val: T) -> Mutex<R, T> {
+        Mutex {
+            raw: raw_mutex,
+            data: UnsafeCell::new(val),
+        }
+    }
+}
+
+impl<R: RawMutex, T: ?Sized> Mutex<R, T> {
+    /// Creates a new `MutexGuard` without checking if the mutex is locked.
+    ///
+    /// # Safety
+    ///
+    /// This method must only be called if the thread logically holds 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_guard_unchecked(&self) -> MutexGuard<'_, R, T> {
+        MutexGuard {
+            mutex: self,
+            marker: PhantomData,
+        }
+    }
+
+    /// Acquires a mutex, blocking the current thread until it is able to do so.
+    ///
+    /// This function will block the local thread until it is available to acquire
+    /// the mutex. Upon returning, the thread is the only thread with the mutex
+    /// held. An RAII guard is returned to allow scoped unlock of the lock. When
+    /// the guard goes out of scope, the mutex will be unlocked.
+    ///
+    /// Attempts to lock a mutex in the thread which already holds the lock will
+    /// result in a deadlock.
+    #[inline]
+    pub fn lock(&self) -> MutexGuard<'_, R, T> {
+        self.raw.lock();
+        // SAFETY: The lock is held, as required.
+        unsafe { self.make_guard_unchecked() }
+    }
+
+    /// Attempts to acquire this lock.
+    ///
+    /// If the lock could not be acquired at this time, then `None` is returned.
+    /// Otherwise, an RAII guard is returned. The lock will be unlocked when the
+    /// guard is dropped.
+    ///
+    /// This function does not block.
+    #[inline]
+    pub fn try_lock(&self) -> Option<MutexGuard<'_, R, T>> {
+        if self.raw.try_lock() {
+            // SAFETY: The lock is held, as required.
+            Some(unsafe { self.make_guard_unchecked() })
+        } else {
+            None
+        }
+    }
+
+    /// Returns a mutable reference to the underlying data.
+    ///
+    /// Since this call borrows the `Mutex` 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 the mutex is currently locked.
+    #[inline]
+    pub fn is_locked(&self) -> bool {
+        self.raw.is_locked()
+    }
+
+    /// Forcibly unlocks the mutex.
+    ///
+    /// This is useful when combined with `mem::forget` to hold a lock without
+    /// the need to maintain a `MutexGuard` object alive, for example when
+    /// dealing with FFI.
+    ///
+    /// # Safety
+    ///
+    /// This method must only be called if the current thread logically owns a
+    /// `MutexGuard` but that guard has been discarded using `mem::forget`.
+    /// Behavior is undefined if a mutex is unlocked when not locked.
+    #[inline]
+    pub unsafe fn force_unlock(&self) {
+        self.raw.unlock();
+    }
+
+    /// Returns the underlying raw mutex object.
+    ///
+    /// Note that you will most likely need to import the `RawMutex` trait from
+    /// `lock_api` to be able to call functions on the raw mutex.
+    ///
+    /// # Safety
+    ///
+    /// This method is unsafe because it allows unlocking a mutex while
+    /// still holding a reference to a `MutexGuard`.
+    #[inline]
+    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 `MutexGuard` 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 `MutexGuard` but that guard has been discarded using `mem::forget`.
+    #[inline]
+    pub fn data_ptr(&self) -> *mut T {
+        self.data.get()
+    }
+
+    /// Creates a new `ArcMutexGuard` without checking if the mutex is locked.
+    ///
+    /// # Safety
+    ///
+    /// This method must only be called if the thread logically holds 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]
+    unsafe fn make_arc_guard_unchecked(self: &Arc<Self>) -> ArcMutexGuard<R, T> {
+        ArcMutexGuard {
+            mutex: self.clone(),
+            marker: PhantomData,
+        }
+    }
+
+    /// Acquires a lock through an `Arc`.
+    ///
+    /// This method is similar to the `lock` method; however, it requires the `Mutex` to be inside of an `Arc`
+    /// and the resulting mutex guard has no lifetime requirements.
+    #[cfg(feature = "arc_lock")]
+    #[inline]
+    pub fn lock_arc(self: &Arc<Self>) -> ArcMutexGuard<R, T> {
+        self.raw.lock();
+        // SAFETY: the locking guarantee is upheld
+        unsafe { self.make_arc_guard_unchecked() }
+    }
+
+    /// Attempts to acquire a lock through an `Arc`.
+    ///
+    /// This method is similar to the `try_lock` method; however, it requires the `Mutex` to be inside of an
+    /// `Arc` and the resulting mutex guard has no lifetime requirements.
+    #[cfg(feature = "arc_lock")]
+    #[inline]
+    pub fn try_lock_arc(self: &Arc<Self>) -> Option<ArcMutexGuard<R, T>> {
+        if self.raw.try_lock() {
+            // SAFETY: locking guarantee is upheld
+            Some(unsafe { self.make_arc_guard_unchecked() })
+        } else {
+            None
+        }
+    }
+}
+
+impl<R: RawMutexFair, T: ?Sized> Mutex<R, T> {
+    /// Forcibly unlocks the mutex using a fair unlock procotol.
+    ///
+    /// This is useful when combined with `mem::forget` to hold a lock without
+    /// the need to maintain a `MutexGuard` object alive, for example when
+    /// dealing with FFI.
+    ///
+    /// # Safety
+    ///
+    /// This method must only be called if the current thread logically owns a
+    /// `MutexGuard` but that guard has been discarded using `mem::forget`.
+    /// Behavior is undefined if a mutex is unlocked when not locked.
+    #[inline]
+    pub unsafe fn force_unlock_fair(&self) {
+        self.raw.unlock_fair();
+    }
+}
+
+impl<R: RawMutexTimed, T: ?Sized> Mutex<R, T> {
+    /// Attempts to acquire this lock until a timeout is reached.
+    ///
+    /// If the lock could not be acquired before the timeout expired, then
+    /// `None` is returned. Otherwise, an RAII guard is returned. The lock will
+    /// be unlocked when the guard is dropped.
+    #[inline]
+    pub fn try_lock_for(&self, timeout: R::Duration) -> Option<MutexGuard<'_, R, T>> {
+        if self.raw.try_lock_for(timeout) {
+            // SAFETY: The lock is held, as required.
+            Some(unsafe { self.make_guard_unchecked() })
+        } else {
+            None
+        }
+    }
+
+    /// Attempts to acquire this lock until a timeout is reached.
+    ///
+    /// If the lock could not be acquired before the timeout expired, then
+    /// `None` is returned. Otherwise, an RAII guard is returned. The lock will
+    /// be unlocked when the guard is dropped.
+    #[inline]
+    pub fn try_lock_until(&self, timeout: R::Instant) -> Option<MutexGuard<'_, R, T>> {
+        if self.raw.try_lock_until(timeout) {
+            // SAFETY: The lock is held, as required.
+            Some(unsafe { self.make_guard_unchecked() })
+        } else {
+            None
+        }
+    }
+
+    /// Attempts to acquire this lock through an `Arc` until a timeout is reached.
+    ///
+    /// This method is similar to the `try_lock_for` method; however, it requires the `Mutex` to be inside of an
+    /// `Arc` and the resulting mutex guard has no lifetime requirements.
+    #[cfg(feature = "arc_lock")]
+    #[inline]
+    pub fn try_lock_arc_for(self: &Arc<Self>, timeout: R::Duration) -> Option<ArcMutexGuard<R, T>> {
+        if self.raw.try_lock_for(timeout) {
+            // SAFETY: locking guarantee is upheld
+            Some(unsafe { self.make_arc_guard_unchecked() })
+        } else {
+            None
+        }
+    }
+
+    /// Attempts to acquire this lock through an `Arc` until a timeout is reached.
+    ///
+    /// This method is similar to the `try_lock_until` method; however, it requires the `Mutex` to be inside of
+    /// an `Arc` and the resulting mutex guard has no lifetime requirements.
+    #[cfg(feature = "arc_lock")]
+    #[inline]
+    pub fn try_lock_arc_until(
+        self: &Arc<Self>,
+        timeout: R::Instant,
+    ) -> Option<ArcMutexGuard<R, T>> {
+        if self.raw.try_lock_until(timeout) {
+            // SAFETY: locking guarantee is upheld
+            Some(unsafe { self.make_arc_guard_unchecked() })
+        } else {
+            None
+        }
+    }
+}
+
+impl<R: RawMutex, T: ?Sized + Default> Default for Mutex<R, T> {
+    #[inline]
+    fn default() -> Mutex<R, T> {
+        Mutex::new(Default::default())
+    }
+}
+
+impl<R: RawMutex, T> From<T> for Mutex<R, T> {
+    #[inline]
+    fn from(t: T) -> Mutex<R, T> {
+        Mutex::new(t)
+    }
+}
+
+impl<R: RawMutex, T: ?Sized + fmt::Debug> fmt::Debug for Mutex<R, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.try_lock() {
+            Some(guard) => f.debug_struct("Mutex").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("Mutex")
+                    .field("data", &LockedPlaceholder)
+                    .finish()
+            }
+        }
+    }
+}
+
+// Copied and modified from serde
+#[cfg(feature = "serde")]
+impl<R, T> Serialize for Mutex<R, T>
+where
+    R: RawMutex,
+    T: Serialize + ?Sized,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        self.lock().serialize(serializer)
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de, R, T> Deserialize<'de> for Mutex<R, T>
+where
+    R: RawMutex,
+    T: Deserialize<'de> + ?Sized,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Deserialize::deserialize(deserializer).map(Mutex::new)
+    }
+}
+
+/// An RAII implementation of a "scoped lock" of a mutex. When this structure is
+/// dropped (falls out of scope), the lock will be unlocked.
+///
+/// The data protected by the mutex can be accessed through this guard via its
+/// `Deref` and `DerefMut` implementations.
+#[clippy::has_significant_drop]
+#[must_use = "if unused the Mutex will immediately unlock"]
+pub struct MutexGuard<'a, R: RawMutex, T: ?Sized> {
+    mutex: &'a Mutex<R, T>,
+    marker: PhantomData<(&'a mut T, R::GuardMarker)>,
+}
+
+unsafe impl<'a, R: RawMutex + Sync + 'a, T: ?Sized + Sync + 'a> Sync for MutexGuard<'a, R, T> {}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> MutexGuard<'a, R, T> {
+    /// Returns a reference to the original `Mutex` object.
+    pub fn mutex(s: &Self) -> &'a Mutex<R, T> {
+        s.mutex
+    }
+
+    /// Makes a new `MappedMutexGuard` for a component of the locked data.
+    ///
+    /// This operation cannot fail as the `MutexGuard` passed
+    /// in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be
+    /// used as `MutexGuard::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) -> MappedMutexGuard<'a, R, U>
+    where
+        F: FnOnce(&mut T) -> &mut U,
+    {
+        let raw = &s.mutex.raw;
+        let data = f(unsafe { &mut *s.mutex.data.get() });
+        mem::forget(s);
+        MappedMutexGuard {
+            raw,
+            data,
+            marker: PhantomData,
+        }
+    }
+
+    /// Attempts to make a new `MappedMutexGuard` for a component of the
+    /// locked data. The original guard is returned if the closure returns `None`.
+    ///
+    /// This operation cannot fail as the `MutexGuard` passed
+    /// in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be
+    /// used as `MutexGuard::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<MappedMutexGuard<'a, R, U>, Self>
+    where
+        F: FnOnce(&mut T) -> Option<&mut U>,
+    {
+        let raw = &s.mutex.raw;
+        let data = match f(unsafe { &mut *s.mutex.data.get() }) {
+            Some(data) => data,
+            None => return Err(s),
+        };
+        mem::forget(s);
+        Ok(MappedMutexGuard {
+            raw,
+            data,
+            marker: PhantomData,
+        })
+    }
+
+    /// Temporarily unlocks the mutex to execute the given function.
+    ///
+    /// This is safe because `&mut` guarantees that there exist no other
+    /// references to the data protected by the mutex.
+    #[inline]
+    pub fn unlocked<F, U>(s: &mut Self, f: F) -> U
+    where
+        F: FnOnce() -> U,
+    {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.unlock();
+        }
+        defer!(s.mutex.raw.lock());
+        f()
+    }
+
+    /// Leaks the mutex guard and returns a mutable reference to the data
+    /// protected by the mutex.
+    ///
+    /// This will leave the `Mutex` in a locked state.
+    #[inline]
+    pub fn leak(s: Self) -> &'a mut T {
+        let r = unsafe { &mut *s.mutex.data.get() };
+        mem::forget(s);
+        r
+    }
+}
+
+impl<'a, R: RawMutexFair + 'a, T: ?Sized + 'a> MutexGuard<'a, R, T> {
+    /// Unlocks the mutex using a fair unlock protocol.
+    ///
+    /// By default, mutexes are unfair and allow the current thread to re-lock
+    /// the mutex before another has the chance to acquire the lock, even if
+    /// that thread has been blocked on the mutex for a long time. This is the
+    /// default because it allows much higher throughput as it avoids forcing a
+    /// context switch on every mutex unlock. This can result in one thread
+    /// acquiring a mutex 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 `MutexGuard` normally.
+    #[inline]
+    pub fn unlock_fair(s: Self) {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.unlock_fair();
+        }
+        mem::forget(s);
+    }
+
+    /// Temporarily unlocks the mutex to execute the given function.
+    ///
+    /// The mutex is unlocked using a fair unlock protocol.
+    ///
+    /// This is safe because `&mut` guarantees that there exist no other
+    /// references to the data protected by the mutex.
+    #[inline]
+    pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
+    where
+        F: FnOnce() -> U,
+    {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.unlock_fair();
+        }
+        defer!(s.mutex.raw.lock());
+        f()
+    }
+
+    /// Temporarily yields the mutex to a waiting thread if there is one.
+    ///
+    /// This method is functionally equivalent to calling `unlock_fair` followed
+    /// by `lock`, however it can be much more efficient in the case where there
+    /// are no waiting threads.
+    #[inline]
+    pub fn bump(s: &mut Self) {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.bump();
+        }
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Deref for MutexGuard<'a, R, T> {
+    type Target = T;
+    #[inline]
+    fn deref(&self) -> &T {
+        unsafe { &*self.mutex.data.get() }
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> DerefMut for MutexGuard<'a, R, T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.mutex.data.get() }
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Drop for MutexGuard<'a, R, T> {
+    #[inline]
+    fn drop(&mut self) {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            self.mutex.raw.unlock();
+        }
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug for MutexGuard<'a, R, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display for MutexGuard<'a, R, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+#[cfg(feature = "owning_ref")]
+unsafe impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> StableAddress for MutexGuard<'a, R, T> {}
+
+/// An RAII mutex guard returned by the `Arc` locking operations on `Mutex`.
+///
+/// This is similar to the `MutexGuard` struct, except instead of using a reference to unlock the `Mutex` it
+/// uses an `Arc<Mutex>`. 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 Mutex will immediately unlock"]
+pub struct ArcMutexGuard<R: RawMutex, T: ?Sized> {
+    mutex: Arc<Mutex<R, T>>,
+    marker: PhantomData<*const ()>,
+}
+
+#[cfg(feature = "arc_lock")]
+unsafe impl<R: RawMutex + Send + Sync, T: Send + ?Sized> Send for ArcMutexGuard<R, T> where
+    R::GuardMarker: Send
+{
+}
+#[cfg(feature = "arc_lock")]
+unsafe impl<R: RawMutex + Sync, T: Sync + ?Sized> Sync for ArcMutexGuard<R, T> where
+    R::GuardMarker: Sync
+{
+}
+
+#[cfg(feature = "arc_lock")]
+impl<R: RawMutex, T: ?Sized> ArcMutexGuard<R, T> {
+    /// Returns a reference to the `Mutex` this is guarding, contained in its `Arc`.
+    #[inline]
+    pub fn mutex(s: &Self) -> &Arc<Mutex<R, T>> {
+        &s.mutex
+    }
+
+    /// Unlocks the mutex and returns the `Arc` that was held by the [`ArcMutexGuard`].
+    #[inline]
+    pub fn into_arc(s: Self) -> Arc<Mutex<R, T>> {
+        // Safety: Skip our Drop impl and manually unlock the mutex.
+        let arc = unsafe { ptr::read(&s.mutex) };
+        mem::forget(s);
+        unsafe {
+            arc.raw.unlock();
+        }
+        arc
+    }
+
+    /// Temporarily unlocks the mutex to execute the given function.
+    ///
+    /// This is safe because `&mut` guarantees that there exist no other
+    /// references to the data protected by the mutex.
+    #[inline]
+    pub fn unlocked<F, U>(s: &mut Self, f: F) -> U
+    where
+        F: FnOnce() -> U,
+    {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.unlock();
+        }
+        defer!(s.mutex.raw.lock());
+        f()
+    }
+}
+
+#[cfg(feature = "arc_lock")]
+impl<R: RawMutexFair, T: ?Sized> ArcMutexGuard<R, T> {
+    /// Unlocks the mutex using a fair unlock protocol.
+    ///
+    /// This is functionally identical to the `unlock_fair` method on [`MutexGuard`].
+    #[inline]
+    pub fn unlock_fair(s: Self) {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.unlock_fair();
+        }
+
+        // SAFETY: make sure the Arc gets it reference decremented
+        let mut s = ManuallyDrop::new(s);
+        unsafe { ptr::drop_in_place(&mut s.mutex) };
+    }
+
+    /// Temporarily unlocks the mutex to execute the given function.
+    ///
+    /// This is functionally identical to the `unlocked_fair` method on [`MutexGuard`].
+    #[inline]
+    pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
+    where
+        F: FnOnce() -> U,
+    {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.unlock_fair();
+        }
+        defer!(s.mutex.raw.lock());
+        f()
+    }
+
+    /// Temporarily yields the mutex to a waiting thread if there is one.
+    ///
+    /// This is functionally identical to the `bump` method on [`MutexGuard`].
+    #[inline]
+    pub fn bump(s: &mut Self) {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.mutex.raw.bump();
+        }
+    }
+}
+
+#[cfg(feature = "arc_lock")]
+impl<R: RawMutex, T: ?Sized> Deref for ArcMutexGuard<R, T> {
+    type Target = T;
+    #[inline]
+    fn deref(&self) -> &T {
+        unsafe { &*self.mutex.data.get() }
+    }
+}
+
+#[cfg(feature = "arc_lock")]
+impl<R: RawMutex, T: ?Sized> DerefMut for ArcMutexGuard<R, T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.mutex.data.get() }
+    }
+}
+
+#[cfg(feature = "arc_lock")]
+impl<R: RawMutex, T: ?Sized> Drop for ArcMutexGuard<R, T> {
+    #[inline]
+    fn drop(&mut self) {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            self.mutex.raw.unlock();
+        }
+    }
+}
+
+/// An RAII mutex guard returned by `MutexGuard::map`, which can point to a
+/// subfield of the protected data.
+///
+/// The main difference between `MappedMutexGuard` and `MutexGuard` 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 Mutex will immediately unlock"]
+pub struct MappedMutexGuard<'a, R: RawMutex, T: ?Sized> {
+    raw: &'a R,
+    data: *mut T,
+    marker: PhantomData<&'a mut T>,
+}
+
+unsafe impl<'a, R: RawMutex + Sync + 'a, T: ?Sized + Sync + 'a> Sync
+    for MappedMutexGuard<'a, R, T>
+{
+}
+unsafe impl<'a, R: RawMutex + 'a, T: ?Sized + Send + 'a> Send for MappedMutexGuard<'a, R, T> where
+    R::GuardMarker: Send
+{
+}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> MappedMutexGuard<'a, R, T> {
+    /// Makes a new `MappedMutexGuard` for a component of the locked data.
+    ///
+    /// This operation cannot fail as the `MappedMutexGuard` passed
+    /// in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be
+    /// used as `MappedMutexGuard::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) -> MappedMutexGuard<'a, R, U>
+    where
+        F: FnOnce(&mut T) -> &mut U,
+    {
+        let raw = s.raw;
+        let data = f(unsafe { &mut *s.data });
+        mem::forget(s);
+        MappedMutexGuard {
+            raw,
+            data,
+            marker: PhantomData,
+        }
+    }
+
+    /// Attempts to make a new `MappedMutexGuard` for a component of the
+    /// locked data. The original guard is returned if the closure returns `None`.
+    ///
+    /// This operation cannot fail as the `MappedMutexGuard` passed
+    /// in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be
+    /// used as `MappedMutexGuard::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<MappedMutexGuard<'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(MappedMutexGuard {
+            raw,
+            data,
+            marker: PhantomData,
+        })
+    }
+}
+
+impl<'a, R: RawMutexFair + 'a, T: ?Sized + 'a> MappedMutexGuard<'a, R, T> {
+    /// Unlocks the mutex using a fair unlock protocol.
+    ///
+    /// By default, mutexes are unfair and allow the current thread to re-lock
+    /// the mutex before another has the chance to acquire the lock, even if
+    /// that thread has been blocked on the mutex for a long time. This is the
+    /// default because it allows much higher throughput as it avoids forcing a
+    /// context switch on every mutex unlock. This can result in one thread
+    /// acquiring a mutex 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 `MutexGuard` normally.
+    #[inline]
+    pub fn unlock_fair(s: Self) {
+        // Safety: A MutexGuard always holds the lock.
+        unsafe {
+            s.raw.unlock_fair();
+        }
+        mem::forget(s);
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Deref for MappedMutexGuard<'a, R, T> {
+    type Target = T;
+    #[inline]
+    fn deref(&self) -> &T {
+        unsafe { &*self.data }
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> DerefMut for MappedMutexGuard<'a, R, T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.data }
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Drop for MappedMutexGuard<'a, R, T> {
+    #[inline]
+    fn drop(&mut self) {
+        // Safety: A MappedMutexGuard always holds the lock.
+        unsafe {
+            self.raw.unlock();
+        }
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug for MappedMutexGuard<'a, R, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+impl<'a, R: RawMutex + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display
+    for MappedMutexGuard<'a, R, T>
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+#[cfg(feature = "owning_ref")]
+unsafe impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> StableAddress for MappedMutexGuard<'a, R, T> {}