1 files changed, 144 insertions, 0 deletions
diff --git a/vendor/windows-core/src/event.rs b/vendor/windows-core/src/event.rs
new file mode 100644
index 00000000..3951ef2c
--- /dev/null
+++ b/vendor/windows-core/src/event.rs
@@ -0,0 +1,144 @@
+use super::*;
+use core::{iter::once, mem::transmute_copy};
+use std::sync::{Arc, RwLock};
+
+/// A type that you can use to declare and implement an event of a specified delegate type.
+///
+/// The implementation is thread-safe and designed to avoid contention between events being
+/// raised and delegates being added or removed.
+pub struct Event<T: Interface> {
+    delegates: RwLock<Option<Arc<[Delegate<T>]>>>,
+}
+
+unsafe impl<T: Interface> Send for Event<T> {}
+unsafe impl<T: Interface> Sync for Event<T> {}
+
+impl<T: Interface> Default for Event<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T: Interface> Event<T> {
+    /// Creates a new, empty `Event<T>`.
+    pub const fn new() -> Self {
+        Self {
+            delegates: RwLock::new(None),
+        }
+    }
+
+    /// Registers a delegate with the event object.
+    pub fn add(&self, delegate: &T) -> Result<i64> {
+        let new_delegate = Delegate::new(delegate)?;
+        let token = new_delegate.to_token();
+        let new_iter = once(new_delegate);
+        let mut guard = self.delegates.write().unwrap();
+
+        let new_list = if let Some(old_delegates) = guard.as_ref() {
+            Arc::from_iter(old_delegates.iter().cloned().chain(new_iter))
+        } else {
+            Arc::from_iter(new_iter)
+        };
+
+        let old_list = guard.replace(new_list);
+        drop(guard);
+        drop(old_list); // drop the old delegates _after_ releasing lock
+
+        Ok(token)
+    }
+
+    /// Revokes a delegate's registration from the event object.
+    pub fn remove(&self, token: i64) {
+        let mut guard = self.delegates.write().unwrap();
+        let mut old_list = None;
+        if let Some(old_delegates) = guard.as_ref() {
+            // `self.delegates` is only modified if the token is found.
+            if let Some(i) = old_delegates
+                .iter()
+                .position(|old_delegate| old_delegate.to_token() == token)
+            {
+                let new_list = Arc::from_iter(
+                    old_delegates[..i]
+                        .iter()
+                        .chain(old_delegates[i + 1..].iter())
+                        .cloned(),
+                );
+
+                old_list = guard.replace(new_list);
+            }
+        }
+        drop(guard);
+        drop(old_list); // drop the old delegates _after_ releasing lock
+    }
+
+    /// Clears the event, removing all delegates.
+    pub fn clear(&self) {
+        let mut guard = self.delegates.write().unwrap();
+        let old_list = guard.take();
+        drop(guard);
+        drop(old_list); // drop the old delegates _after_ releasing lock
+    }
+
+    /// Invokes all of the event object's registered delegates with the provided callback.
+    pub fn call<F: FnMut(&T) -> Result<()>>(&self, mut callback: F) {
+        let delegates = {
+            let guard = self.delegates.read().unwrap();
+            if let Some(delegates) = guard.as_ref() {
+                delegates.clone()
+            } else {
+                // No delegates to call.
+                return;
+            }
+            // <-- lock is released here
+        };
+
+        for delegate in delegates.iter() {
+            if let Err(error) = delegate.call(&mut callback) {
+                const RPC_E_SERVER_UNAVAILABLE: HRESULT = HRESULT(-2147023174); // HRESULT_FROM_WIN32(RPC_S_SERVER_UNAVAILABLE)
+                if matches!(
+                    error.code(),
+                    imp::RPC_E_DISCONNECTED | imp::JSCRIPT_E_CANTEXECUTE | RPC_E_SERVER_UNAVAILABLE
+                ) {
+                    self.remove(delegate.to_token());
+                }
+            }
+        }
+    }
+}
+
+/// Holds either a direct or indirect reference to a delegate. A direct reference is typically
+/// agile while an indirect reference is an agile wrapper.
+#[derive(Clone)]
+enum Delegate<T> {
+    Direct(T),
+    Indirect(AgileReference<T>),
+}
+
+impl<T: Interface> Delegate<T> {
+    /// Creates a new `Delegate<T>`, containing a suitable reference to the specified delegate.
+    fn new(delegate: &T) -> Result<Self> {
+        if delegate.cast::<imp::IAgileObject>().is_ok() {
+            Ok(Self::Direct(delegate.clone()))
+        } else {
+            Ok(Self::Indirect(AgileReference::new(delegate)?))
+        }
+    }
+
+    /// Returns an encoded token to identify the delegate.
+    fn to_token(&self) -> i64 {
+        unsafe {
+            match self {
+                Self::Direct(delegate) => imp::EncodePointer(transmute_copy(delegate)) as i64,
+                Self::Indirect(delegate) => imp::EncodePointer(transmute_copy(delegate)) as i64,
+            }
+        }
+    }
+
+    /// Invokes the delegates with the provided callback.
+    fn call<F: FnMut(&T) -> Result<()>>(&self, mut callback: F) -> Result<()> {
+        match self {
+            Self::Direct(delegate) => callback(delegate),
+            Self::Indirect(delegate) => callback(&delegate.resolve()?),
+        }
+    }
+}