[Fix] Update key generation for adding handlers

Receiver/Sources/Receiver.swift

@@ -68,7 +68,8 @@ public class Receiver<Wave> {
 
     private let values = Atomic<[Wave]>([])
     private let strategy: Strategy
-    private let handlers = Atomic<[Int:Handler]>([:])
+    private let handlers = Atomic<[UInt64:Handler]>([:])
+    private var nextKey: UInt64 = 0
 
     private init(strategy: Strategy) {
         self.strategy = strategy
@@ -105,12 +106,12 @@ public class Receiver<Wave> {
     ///             a new value is sent.
     /// - returns: A reference to a disposable
     @discardableResult public func listen(to handle: @escaping (Wave) -> Void) -> Disposable {
-        var _key: Int!
-        handlers.apply { _handlers in
-            _key = (_handlers.keys.map { $0.hashValue }.max() ?? -1) + 1
-            _handlers[_key] = handle
-        }
-
+        var _key: UInt64!
+            handlers.apply { _handlers in
+                _key = nextKey
+                _handlers[_key] = handle
+                nextKey = nextKey &+ 1
+            }
         switch strategy {
         case .cold:
             broadcast(elements: Int.max)

ReceiverTests/ReceiverTests+Performance.swift

@@ -18,4 +18,37 @@ class ReceiverTests_Performance: XCTestCase {
             }
         }
     }
+
+    func test_listen_and_dispose_performance() {
+        self.measure {
+            let numberOfListeners = 10000
+            var numberOfDisposes = 0
+            let (transmitter, receiver) = Receiver<Int>.make()
+            var called = 0
+            var disposables = [Disposable]()
+
+            for i in 1...numberOfListeners {
+
+                let disposable = receiver.listen { wave in
+                    XCTAssertTrue(wave == 1)
+                    called = called + 1
+                }
+
+                disposables.append(disposable)
+
+                if i % 3 == 0 && disposables.count > 0 {
+                    let d = disposables.remove(at: Int.random(in: 0..<disposables.count))
+                    d.dispose()
+                    numberOfDisposes += 1
+                }
+            }
+
+            transmitter.broadcast(1)
+            XCTAssertEqual(called, numberOfListeners-numberOfDisposes)
+
+            transmitter.broadcast(1)
+            XCTAssertEqual(called, (numberOfListeners-numberOfDisposes)*2)
+        }
+    }
+
 }