Mojo: request/response bindings

mojo/public/bindings/lib/shared_data.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_BINDINGS_LIB_SHARED_DATA_H_
 #define MOJO_PUBLIC_BINDINGS_LIB_SHARED_DATA_H_
 
 namespace mojo {
 namespace internal {
 
 // Used to allocate an instance of T that can be shared via reference counting.
 template <typename T>
 class SharedData {
  public:
   ~SharedData() {
     holder_->Release();
   }
 
+  SharedData() : holder_(new Holder()) {
+  }
+
   explicit SharedData(const T& value) : holder_(new Holder(value)) {
   }
 
   SharedData(const SharedData<T>& other) : holder_(other.holder_) {
     holder_->Retain();
   }
 
   SharedData<T>& operator=(const SharedData<T>& other) {
     if (other.holder_ == holder_)
       return *this;
     holder_->Release();
     holder_ = other.holder_;
     holder_->Retain();
   }
 
+  void reset() {
+    holder_->Release();
+    holder_ = new Holder();
+  }
+
+  void reset(const T& value) {
+    holder_->Release();
+    holder_ = new Holder(value);
+  }
+
   void set_value(const T& value) {
     holder_->value = value;
   }
+  T* mutable_value() {
+    return &holder_->value;
+  }
   const T& value() const {
     return holder_->value;
   }
 
  private:
-  SharedData();  // NOT IMPLEMENTED
-
   class Holder {
    public:
     Holder() : value(), ref_count_(1) {
     }
     Holder(const T& value) : value(value), ref_count_(1) {
     }
 
     void Retain() { ++ref_count_; }
     void Release() { if (--ref_count_ == 0) delete this; }
 
     T value;
 
    private:
     int ref_count_;
     MOJO_DISALLOW_COPY_AND_ASSIGN(Holder);
   };
 
   Holder* holder_;
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_BINDINGS_LIB_SHARED_DATA_H_