text: // Copyright (c) 2012 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 NATIVE_CLIENT_SRC_INCLUDE_REF_COUNTED_H_
  #define NATIVE_CLIENT_SRC_INCLUDE_REF_COUNTED_H_
  
  #include "native_client/src/shared/platform/nacl_sync_checked.h"
  
  namespace nacl {
  
  namespace subtle {
  
  class RefCountedBase {
   public:
    static bool ImplementsThreadSafeReferenceCounting() { return true; }
  
    bool HasOneRef() const {
      nacl::ScopedNaClMutexLock ml(&mu_);
      return (ref_count_ == 1);
    }
  
   protected:
    RefCountedBase() : ref_count_(0) {
      NaClXMutexCtor(&mu_);
    }
    ~RefCountedBase() {
      NaClMutexDtor(&mu_);
    }
  
    void AddRef() const {
      nacl::ScopedNaClMutexLock ml(&mu_);
      ++ref_count_;
    }
  
    // Returns true if the object should self-delete.
    bool Release() const {
      nacl::ScopedNaClMutexLock ml(&mu_);
      bool should_delete = (--ref_count_ == 0);
      return should_delete;
    }
  
   private:
    mutable int ref_count_;
    mutable struct NaClMutex mu_;
  
    RefCountedBase(const RefCountedBase&);
    void operator=(const RefCountedBase&);
  };
  
  }  // namespace subtle
  
  //
  // A base class for reference counted classes.  Otherwise, known as a cheap
  // knock-off of WebKit's RefCounted<T> class.  To use this guy just extend your
  // class from it like so:
  //
  //   class MyFoo : public nacl::RefCounted<MyFoo> {
  //    ...
  //    private:
  //     friend class nacl::RefCounted<MyFoo>;
  //     ~MyFoo();
  //   };
  //
  // You should always make your destructor private, to avoid any code deleting
  // the object accidently while there are references to it.
  template <class T>
  class RefCounted : public subtle::RefCountedBase {
   public:
    RefCounted() { }
    ~RefCounted() { }
  
    void AddRef() const {
      subtle::RefCountedBase::AddRef();
    }
  
    void Release() const {
      if (subtle::RefCountedBase::Release()) {
        delete static_cast<const T*>(this);
      }
    }
  
   private:
    RefCounted(const RefCounted<T>&);
    void operator=(const RefCounted<T>&);
  };
  
  //
  // A wrapper for some piece of data so we can place other things in
  // scoped_refptrs<>.
  //
  template<typename T>
  class RefCountedData : public nacl::RefCounted< nacl::RefCountedData<T> > {
   public:
    RefCountedData() : data() {}
    RefCountedData(const T& in_value) : data(in_value) {}
  
    T data;
  };
  
  }  // namespace nacl
  
  //
  // A smart pointer class for reference counted objects.  Use this class instead
  // of calling AddRef and Release manually on a reference counted object to
  // avoid common memory leaks caused by forgetting to Release an object
  // reference.  Sample usage:
  //
  //   class MyFoo : public RefCounted<MyFoo> {
  //    ...
  //   };
  //
  //   void some_function() {
  //     scoped_refptr<MyFoo> foo = new MyFoo();
  //     foo->Method(param);
  //     // |foo| is released when this function returns
  //   }
  //
  //   void some_other_function() {
  //     scoped_refptr<MyFoo> foo = new MyFoo();
  //     ...
  //     foo = NULL;  // explicitly releases |foo|
  //     ...
  //     if (foo)
  //       foo->Method(param);
  //   }
  //
  // The above examples show how scoped_refptr<T> acts like a pointer to T.
  // Given two scoped_refptr<T> classes, it is also possible to exchange
  // references between the two objects, like so:
  //
  //   {
  //     scoped_refptr<MyFoo> a = new MyFoo();
  //     scoped_refptr<MyFoo> b;
  //
  //     b.swap(a);
  //     // now, |b| references the MyFoo object, and |a| references NULL.
  //   }
  //
  // To make both |a| and |b| in the above example reference the same MyFoo
  // object, simply use the assignment operator:
  //
  //   {
  //     scoped_refptr<MyFoo> a = new MyFoo();
  //     scoped_refptr<MyFoo> b;
  //
  //     b = a;
  //     // now, |a| and |b| each own a reference to the same MyFoo object.
  //   }
  //
  template <class T>
  class scoped_refptr {
   public:
    scoped_refptr() : ptr_((T*)0) {
    }
  
    scoped_refptr(T* p) : ptr_(p) {
      if (ptr_)
        ptr_->AddRef();
    }
  
    scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
      if (ptr_)
        ptr_->AddRef();
    }
  
    template <typename U>
    scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
      if (ptr_)
        ptr_->AddRef();
    }
  
    ~scoped_refptr() {
      if (ptr_)
        ptr_->Release();
    }
  
    T* get() const { return ptr_; }
    operator T*() const { return ptr_; }
    T* operator->() const { return ptr_; }
  
    // Release a pointer.
    // The return value is the current pointer held by this object.
    // If this object holds a NULL pointer, the return value is NULL.
    // After this operation, this object will hold a NULL pointer,
    // and will not own the object any more.
    T* release() {
      T* retVal = ptr_;
      ptr_ = (void*)0;
      return retVal;
    }
  
    scoped_refptr<T>& operator=(T* p) {
      // AddRef first so that self assignment should work
      if (p)
        p->AddRef();
      if (ptr_ )
        ptr_ ->Release();
      ptr_ = p;
      return *this;
    }
  
    scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
      return *this = r.ptr_;
    }
  
    template <typename U>
    scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
      return *this = r.get();
    }
  
    void swap(T** pp) {
      T* p = ptr_;
      ptr_ = *pp;
      *pp = p;
    }
  
    void swap(scoped_refptr<T>& r) {
      swap(&r.ptr_);
    }
  
   protected:
    T* ptr_;
  };
  
  // Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
  // having to retype all the template arguments
  template <typename T>
  scoped_refptr<T> make_scoped_refptr(T* t) {
    return scoped_refptr<T>(t);
  }
  
  #endif  // NATIVE_CLIENT_SRC_INCLUDE_REF_COUNTED_H_
  