[GitHub] [pulsar] BewareMyPower commented on a change in pull request #12586: [C++] Fix request timeout for GetLastMessageId doesn't work

[GitBox <gi...@apache.org>]

BewareMyPower commented on a change in pull request #12586:
URL: https://github.com/apache/pulsar/pull/12586#discussion_r741562539



##########
File path: pulsar-client-cpp/lib/Future.h
##########
@@ -31,121 +32,138 @@ typedef std::unique_lock<std::mutex> Lock;
 namespace pulsar {
 
 template <typename Result, typename Type>
-struct InternalState {
-    std::mutex mutex;
-    std::condition_variable condition;
-    Result result;
-    Type value;
-    bool complete;
-
-    std::list<typename std::function<void(Result, const Type&)> > listeners;
-};
-
-template <typename Result, typename Type>
-class Future {
+class InternalState {
    public:
-    typedef std::function<void(Result, const Type&)> ListenerCallback;
+    using ListenerCallback = std::function<void(Result, const Type&)>;
 
-    Future& addListener(ListenerCallback callback) {
-        InternalState<Result, Type>* state = state_.get();
-        Lock lock(state->mutex);
+    // There's a bug about the defaulted default constructor for GCC < 4.9.1, so we cannot use
+    // `InternalState() = default` here.
+    InternalState() {}
+    InternalState(const InternalState&) = delete;
+    InternalState& operator=(const InternalState&) = delete;
 
-        if (state->complete) {
+    static Result defaultResult() {
+        static Result result;
+        return result;
+    }
+
+    static Type defaultValue() {
+        static Type value;
+        return value;
+    }
+
+    bool completed() const noexcept { return completed_; }
+
+    void addListener(const ListenerCallback& callback) {
+        Lock lock(mutex_);
+        if (completed_) {
+            const auto result = result_;
+            const auto value = value_;
             lock.unlock();
-            callback(state->result, state->value);
+            callback(result, value);
         } else {
-            state->listeners.push_back(callback);
+            listeners_.emplace_back(callback);
         }
+    }
 
-        return *this;
+    Result wait(Type& value) {
+        Lock lock(mutex_);
+        while (!completed_) {
+            condition_.wait(lock);
+        }
+        value = value_;
+        return result_;
     }
 
-    Result get(Type& result) {
-        InternalState<Result, Type>* state = state_.get();
-        Lock lock(state->mutex);
+    bool complete(const Type& value) {
+        if (completed_) {

Review comment:
       Yes, it's right.




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