Merge pull request #40 from glessard/consolidate

consolidate notifications and waiter deallocations

Author: glessard

Source/deferred/waiter.swift

@@ -11,38 +11,55 @@ import Outcome
 
 struct Waiter<T>
 {
-  private let queue: DispatchQueue?
-  private let handler: (Outcome<T>) -> Void
+  fileprivate let queue: DispatchQueue?
+  fileprivate let handler: (Outcome<T>) -> Void
   var next: UnsafeMutablePointer<Waiter<T>>? = nil
 
   init(_ queue: DispatchQueue?, _ handler: @escaping (Outcome<T>) -> Void)
   {
     self.queue = queue
     self.handler = handler
   }
-
-  fileprivate func notify(_ queue: DispatchQueue, _ value: Outcome<T>)
-  {
-    let q = self.queue ?? queue
-    q.async { [handler = self.handler] in handler(value) }
-  }
 }
 
 func notifyWaiters<T>(_ queue: DispatchQueue, _ tail: UnsafeMutablePointer<Waiter<T>>?, _ value: Outcome<T>)
 {
-  var head = reverseList(tail)
+  let (normal, custom) = reverseAndSplitList(tail)
+
+  queue.async {
+    var head = normal
+    while let current = head
+    {
+      head = current.pointee.next
+
+      assert(current.pointee.queue == nil)
+      current.pointee.handler(value)
+
+      current.deinitialize(count: 1)
+#if swift(>=4.1)
+      current.deallocate()
+#else
+      current.deallocate(capacity: 1)
+#endif
+    }
+  }
+
+  var head = custom
   while let current = head
   {
     head = current.pointee.next
 
-    current.pointee.notify(queue, value)
+    assert(current.pointee.queue != nil)
+    current.pointee.queue!.async {
+      current.pointee.handler(value)
 
-    current.deinitialize(count: 1)
+      current.deinitialize(count: 1)
 #if swift(>=4.1)
-    current.deallocate()
+      current.deallocate()
 #else
-    current.deallocate(capacity: 1)
+      current.deallocate(capacity: 1)
 #endif
+    }
   }
 }
 
@@ -62,18 +79,33 @@ func deallocateWaiters<T>(_ tail: UnsafeMutablePointer<Waiter<T>>?)
   }
 }
 
-private func reverseList<T>(_ tail: UnsafeMutablePointer<Waiter<T>>?) -> UnsafeMutablePointer<Waiter<T>>?
+private func reverseAndSplitList<T>(_ tail: UnsafeMutablePointer<Waiter<T>>?) -> (UnsafeMutablePointer<Waiter<T>>?, UnsafeMutablePointer<Waiter<T>>?)
 {
-  if tail?.pointee.next == nil { return tail }
+  if tail?.pointee.next == nil
+  {
+    if tail?.pointee.queue == nil
+    { return (tail, nil) }
+    else
+    { return (nil, tail) }
+  }
 
-  var head: UnsafeMutablePointer<Waiter<T>>? = nil
+  var normal: UnsafeMutablePointer<Waiter<T>>? = nil
+  var custom: UnsafeMutablePointer<Waiter<T>>? = nil
   var current = tail
   while let element = current
   {
     current = element.pointee.next
 
-    element.pointee.next = head
-    head = element
+    if element.pointee.queue == nil
+    {
+      element.pointee.next = normal
+      normal = element
+    }
+    else
+    {
+      element.pointee.next = custom
+      custom = element
+    }
   }
-  return head
+  return (normal, custom)
 }