1 files changed, 234 insertions, 0 deletions
diff --git a/vendor/tokio/src/sync/rwlock/owned_write_guard.rs b/vendor/tokio/src/sync/rwlock/owned_write_guard.rs
new file mode 100644
index 000000000..91b659524
--- /dev/null
+++ b/vendor/tokio/src/sync/rwlock/owned_write_guard.rs
@@ -0,0 +1,234 @@
+use crate::sync::rwlock::owned_read_guard::OwnedRwLockReadGuard;
+use crate::sync::rwlock::owned_write_guard_mapped::OwnedRwLockMappedWriteGuard;
+use crate::sync::rwlock::RwLock;
+use std::fmt;
+use std::marker::PhantomData;
+use std::mem::{self, ManuallyDrop};
+use std::ops;
+use std::sync::Arc;
+
+/// Owned RAII structure used to release the exclusive write access of a lock when
+/// dropped.
+///
+/// This structure is created by the [`write_owned`] method
+/// on [`RwLock`].
+///
+/// [`write_owned`]: method@crate::sync::RwLock::write_owned
+/// [`RwLock`]: struct@crate::sync::RwLock
+pub struct OwnedRwLockWriteGuard<T: ?Sized> {
+    pub(super) permits_acquired: u32,
+    // ManuallyDrop allows us to destructure into this field without running the destructor.
+    pub(super) lock: ManuallyDrop<Arc<RwLock<T>>>,
+    pub(super) data: *mut T,
+    pub(super) _p: PhantomData<T>,
+}
+
+impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
+    /// Make a new [`OwnedRwLockMappedWriteGuard`] for a component of the locked
+    /// data.
+    ///
+    /// This operation cannot fail as the `OwnedRwLockWriteGuard` passed in
+    /// already locked the data.
+    ///
+    /// This is an associated function that needs to be used as
+    /// `OwnedRwLockWriteGuard::map(..)`. A method would interfere with methods
+    /// of the same name on the contents of the locked data.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Arc;
+    /// use tokio::sync::{RwLock, OwnedRwLockWriteGuard};
+    ///
+    /// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    /// struct Foo(u32);
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let lock = Arc::new(RwLock::new(Foo(1)));
+    ///
+    /// {
+    ///     let lock = Arc::clone(&lock);
+    ///     let mut mapped = OwnedRwLockWriteGuard::map(lock.write_owned().await, |f| &mut f.0);
+    ///     *mapped = 2;
+    /// }
+    ///
+    /// assert_eq!(Foo(2), *lock.read().await);
+    /// # }
+    /// ```
+    #[inline]
+    pub fn map<F, U: ?Sized>(mut this: Self, f: F) -> OwnedRwLockMappedWriteGuard<T, U>
+    where
+        F: FnOnce(&mut T) -> &mut U,
+    {
+        let data = f(&mut *this) as *mut U;
+        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
+        let permits_acquired = this.permits_acquired;
+        // NB: Forget to avoid drop impl from being called.
+        mem::forget(this);
+        OwnedRwLockMappedWriteGuard {
+            permits_acquired,
+            lock: ManuallyDrop::new(lock),
+            data,
+            _p: PhantomData,
+        }
+    }
+
+    /// Attempts to make  a new [`OwnedRwLockMappedWriteGuard`] for a component
+    /// of the locked data. The original guard is returned if the closure
+    /// returns `None`.
+    ///
+    /// This operation cannot fail as the `OwnedRwLockWriteGuard` passed in
+    /// already locked the data.
+    ///
+    /// This is an associated function that needs to be
+    /// used as `OwnedRwLockWriteGuard::try_map(...)`. A method would interfere
+    /// with methods of the same name on the contents of the locked data.
+    ///
+    /// [`RwLockMappedWriteGuard`]: struct@crate::sync::RwLockMappedWriteGuard
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Arc;
+    /// use tokio::sync::{RwLock, OwnedRwLockWriteGuard};
+    ///
+    /// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    /// struct Foo(u32);
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let lock = Arc::new(RwLock::new(Foo(1)));
+    ///
+    /// {
+    ///     let guard = Arc::clone(&lock).write_owned().await;
+    ///     let mut guard = OwnedRwLockWriteGuard::try_map(guard, |f| Some(&mut f.0)).expect("should not fail");
+    ///     *guard = 2;
+    /// }
+    ///
+    /// assert_eq!(Foo(2), *lock.read().await);
+    /// # }
+    /// ```
+    #[inline]
+    pub fn try_map<F, U: ?Sized>(
+        mut this: Self,
+        f: F,
+    ) -> Result<OwnedRwLockMappedWriteGuard<T, U>, Self>
+    where
+        F: FnOnce(&mut T) -> Option<&mut U>,
+    {
+        let data = match f(&mut *this) {
+            Some(data) => data as *mut U,
+            None => return Err(this),
+        };
+        let permits_acquired = this.permits_acquired;
+        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
+        // NB: Forget to avoid drop impl from being called.
+        mem::forget(this);
+        Ok(OwnedRwLockMappedWriteGuard {
+            permits_acquired,
+            lock: ManuallyDrop::new(lock),
+            data,
+            _p: PhantomData,
+        })
+    }
+
+    /// Converts this `OwnedRwLockWriteGuard` into an
+    /// `OwnedRwLockMappedWriteGuard`. This method can be used to store a
+    /// non-mapped guard in a struct field that expects a mapped guard.
+    ///
+    /// This is equivalent to calling `OwnedRwLockWriteGuard::map(guard, |me| me)`.
+    #[inline]
+    pub fn into_mapped(this: Self) -> OwnedRwLockMappedWriteGuard<T> {
+        Self::map(this, |me| me)
+    }
+
+    /// Atomically downgrades a write lock into a read lock without allowing
+    /// any writers to take exclusive access of the lock in the meantime.
+    ///
+    /// **Note:** This won't *necessarily* allow any additional readers to acquire
+    /// locks, since [`RwLock`] is fair and it is possible that a writer is next
+    /// in line.
+    ///
+    /// Returns an RAII guard which will drop this read access of the `RwLock`
+    /// when dropped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use tokio::sync::RwLock;
+    /// # use std::sync::Arc;
+    /// #
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let lock = Arc::new(RwLock::new(1));
+    ///
+    /// let n = lock.clone().write_owned().await;
+    ///
+    /// let cloned_lock = lock.clone();
+    /// let handle = tokio::spawn(async move {
+    ///     *cloned_lock.write_owned().await = 2;
+    /// });
+    ///
+    /// let n = n.downgrade();
+    /// assert_eq!(*n, 1, "downgrade is atomic");
+    ///
+    /// drop(n);
+    /// handle.await.unwrap();
+    /// assert_eq!(*lock.read().await, 2, "second writer obtained write lock");
+    /// # }
+    /// ```
+    pub fn downgrade(mut self) -> OwnedRwLockReadGuard<T> {
+        let lock = unsafe { ManuallyDrop::take(&mut self.lock) };
+        let data = self.data;
+
+        // Release all but one of the permits held by the write guard
+        lock.s.release((self.permits_acquired - 1) as usize);
+        // NB: Forget to avoid drop impl from being called.
+        mem::forget(self);
+        OwnedRwLockReadGuard {
+            lock: ManuallyDrop::new(lock),
+            data,
+            _p: PhantomData,
+        }
+    }
+}
+
+impl<T: ?Sized> ops::Deref for OwnedRwLockWriteGuard<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.data }
+    }
+}
+
+impl<T: ?Sized> ops::DerefMut for OwnedRwLockWriteGuard<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.data }
+    }
+}
+
+impl<T: ?Sized> fmt::Debug for OwnedRwLockWriteGuard<T>
+where
+    T: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+impl<T: ?Sized> fmt::Display for OwnedRwLockWriteGuard<T>
+where
+    T: fmt::Display,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(&**self, f)
+    }
+}
+
+impl<T: ?Sized> Drop for OwnedRwLockWriteGuard<T> {
+    fn drop(&mut self) {
+        self.lock.s.release(self.permits_acquired as usize);
+        unsafe { ManuallyDrop::drop(&mut self.lock) };
+    }
+}