smart-pointer.h.svn-base

Google浏览器V8内核代码

// Copyright 2008 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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#ifndef V8_SMART_POINTER_H_
#define V8_SMART_POINTER_H_

namespace v8 { namespace internal {


// A 'scoped array pointer' that calls DeleteArray on its pointer when the
// destructor is called.
template<typename T>
class SmartPointer {
 public:

  // Default constructor. Construct an empty scoped pointer.
  inline SmartPointer() : p(NULL) {}


  // Construct a scoped pointer from a plain one.
  explicit inline SmartPointer(T* pointer) : p(pointer) {}


  // Copy constructor removes the pointer from the original to avoid double
  // freeing.
  inline SmartPointer(const SmartPointer<T>& rhs) : p(rhs.p) {
    const_cast<SmartPointer<T>&>(rhs).p = NULL;
  }


  // When the destructor of the scoped pointer is executed the plain pointer
  // is deleted using DeleteArray.  This implies that you must allocate with
  // NewArray.
  inline ~SmartPointer() { if (p) DeleteArray(p); }


  // You can get the underlying pointer out with the * operator.
  inline T* operator*() { return p; }


  // You can use [n] to index as if it was a plain pointer
  inline T& operator[](size_t i) {
    return p[i];
  }

  // We don't have implicit conversion to a T* since that hinders migration:
  // You would not be able to change a method from returning a T* to
  // returning an SmartPointer<T> and then get errors wherever it is used.


  // If you want to take out the plain pointer and don't want it automatically
  // deleted then call Detach().  Afterwards, the smart pointer is empty
  // (NULL).
  inline T* Detach() {
    T* temp = p;
    p = NULL;
    return temp;
  }


  // Assignment requires an empty (NULL) SmartPointer as the receiver.  Like
  // the copy constructor it removes the pointer in the original to avoid
  // double freeing.
  inline SmartPointer& operator=(const SmartPointer<T>& rhs) {
    ASSERT(p == NULL);
    T* tmp = rhs.p;  // swap to handle self-assignment
    const_cast<SmartPointer<T>&>(rhs).p = NULL;
    p = tmp;
    return *this;
  }


 private:
  T* p;
};

} }  // namespace v8::internal

#endif  // V8_SMART_POINTER_H_