Request: added error callback.

src/Request/Request.cpp

@@ -57,6 +57,11 @@ void Request<T>::set_resolver(Resolver resolver) {
   function_ = std::async(std::launch::async, std::bind(resolver, this));
 }
 
+template <class T>
+void Request<T>::set_error_callback(ErrorCallback f) {
+  error_callback_ = f;
+}
+
 template <class T>
 void Request<T>::finish() {
   std::shared_future<T> future = function_;
@@ -108,7 +113,9 @@ bool Request<T>::reauthorize() {
 }
 
 template <class T>
-void Request<T>::error(int, const std::string&) {}
+void Request<T>::error(int code, const std::string& desc) {
+  if (error_callback_) error_callback_(code, desc);
+}
 
 template <class T>
 std::string Request<T>::error_string(int code, const std::string& desc) const {

src/Request/Request.h

@@ -43,10 +43,12 @@ class Request : public IRequest<ReturnValue> {
  public:
   using ProgressFunction = std::function<void(uint32_t, uint32_t)>;
   using Resolver = std::function<ReturnValue(Request*)>;
+  using ErrorCallback = std::function<void(int, const std::string&)>;
 
   Request(std::shared_ptr<CloudProvider>);
 
   void set_resolver(Resolver);
+  void set_error_callback(ErrorCallback);
 
   void finish();
   void cancel();
@@ -60,7 +62,6 @@ class Request : public IRequest<ReturnValue> {
            std::ostream* error, ProgressFunction download = nullptr,
            ProgressFunction upload = nullptr);
 
- protected:
   std::shared_ptr<CloudProvider> provider() const { return provider_; }
   virtual void error(int code, const std::string& description);
   std::string error_string(int code, const std::string& desc) const;
@@ -77,6 +78,7 @@ class Request : public IRequest<ReturnValue> {
   std::shared_ptr<CloudProvider> provider_;
   std::atomic_bool is_cancelled_;
   std::shared_future<ReturnValue> function_;
+  ErrorCallback error_callback_;
 };
 
 }  // namespace cloudstorage