a slight shortcut when no event is being requested

glessard · glessard · commit d445787bdfd1 · 2019-05-24T22:06:57.000-06:00
diff --git a/Sources/ReactiveStreams/stream-post.swift b/Sources/ReactiveStreams/stream-post.swift
@@ -101,11 +101,14 @@ open class PostBox<Value>: EventStream<Value>
     }
 #endif
 
+    let requested = self.requested
+    if requested <= 0 && CAtomicsLoad(last, .relaxed) == nil { return }
+
     // try to dequeue the next event
     let head = Node(storage: CAtomicsLoad(self.head, .acquire))
     let next = CAtomicsLoad(head.next, .acquire)
 
-    if requested <= 0 && next != CAtomicsLoad(last, .relaxed) { return }
+    if requested <= 0 && CAtomicsLoad(last, .relaxed) != next { return }
 
     if let next = next
     {

Original file line number	Diff line number	Diff line change
`@@ -101,11 +101,14 @@ open class PostBox<Value>: EventStream<Value>`
`101`	`101`	`}`
`102`	`102`	`#endif`
`103`	`103`
	`104`	`+ let requested = self.requested`
	`105`	`+ if requested <= 0 && CAtomicsLoad(last, .relaxed) == nil { return }`
	`106`	`+`
`104`	`107`	`// try to dequeue the next event`
`105`	`108`	`let head = Node(storage: CAtomicsLoad(self.head, .acquire))`
`106`	`109`	`let next = CAtomicsLoad(head.next, .acquire)`
`107`	`110`
`108`		`- if requested <= 0 && next != CAtomicsLoad(last, .relaxed) { return }`
	`111`	`+ if requested <= 0 && CAtomicsLoad(last, .relaxed) != next { return }`
`109`	`112`
`110`	`113`	`if let next = next`
`111`	`114`	`{`