text: // Copyright (c) 2006-2009 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 BASE_SCOPED_PTR_H__
  #define BASE_SCOPED_PTR_H__
  
  //  This is an implementation designed to match the anticipated future TR2
  //  implementation of the scoped_ptr class, and its closely-related brethren,
  //  scoped_array, scoped_ptr_malloc, and make_scoped_ptr.
  //
  //  See http://wiki/Main/ScopedPointerInterface for the spec that drove this
  //  file.
  
  #include <assert.h>
  #include <stdlib.h>
  #include <cstddef>
  
  #ifdef OS_EMBEDDED_QNX
  // NOTE(akirmse):
  // The C++ standard says that <stdlib.h> declares both ::foo and std::foo
  // But this isn't done in QNX version 6.3.2 200709062316.
  using std::free;
  using std::malloc;
  using std::realloc;
  #endif
  
  template <class C> class scoped_ptr;
  template <class C, class Free> class scoped_ptr_malloc;
  template <class C> class scoped_array;
  
  template <class C>
  scoped_ptr<C> make_scoped_ptr(C *);
  
  // A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T>
  // automatically deletes the pointer it holds (if any).
  // That is, scoped_ptr<T> owns the T object that it points to.
  // Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object.
  // Also like T*, scoped_ptr<T> is thread-compatible, and once you
  // dereference it, you get the threadsafety guarantees of T.
  //
  // The size of a scoped_ptr is small:
  // sizeof(scoped_ptr<C>) == sizeof(C*)
  template <class C>
  class scoped_ptr {
   public:
  
    // The element type
    typedef C element_type;
  
    // Constructor.  Defaults to intializing with NULL.
    // There is no way to create an uninitialized scoped_ptr.
    // The input parameter must be allocated with new.
    explicit scoped_ptr(C* p = NULL) : ptr_(p) { }
  
    // Destructor.  If there is a C object, delete it.
    // We don't need to test ptr_ == NULL because C++ does that for us.
    ~scoped_ptr() {
      enum { type_must_be_complete = sizeof(C) };
      delete ptr_;
    }
  
    // Reset.  Deletes the current owned object, if any.
    // Then takes ownership of a new object, if given.
    // this->reset(this->get()) works.
    void reset(C* p = NULL) {
      if (p != ptr_) {
        enum { type_must_be_complete = sizeof(C) };
        delete ptr_;
        ptr_ = p;
      }
    }
  
    // Accessors to get the owned object.
    // operator* and operator-> will assert() if there is no current object.
    C& operator*() const {
      assert(ptr_ != NULL);
      return *ptr_;
    }
    C* operator->() const  {
      assert(ptr_ != NULL);
      return ptr_;
    }
    C* get() const { return ptr_; }
  
    // Comparison operators.
    // These return whether a scoped_ptr and a raw pointer refer to
    // the same object, not just to two different but equal objects.
    bool operator==(const C* p) const { return ptr_ == p; }
    bool operator!=(const C* p) const { return ptr_ != p; }
  
    // Swap two scoped pointers.
    void swap(scoped_ptr& p2) {
      C* tmp = ptr_;
      ptr_ = p2.ptr_;
      p2.ptr_ = tmp;
    }
  
    // 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.
    C* release() {
      C* retVal = ptr_;
      ptr_ = NULL;
      return retVal;
    }
  
   private:
    C* ptr_;
  
    // google3 friend class that can access copy ctor (although if it actually
    // calls a copy ctor, there will be a problem) see below
    friend scoped_ptr<C> make_scoped_ptr<C>(C *p);
  
    // Forbid comparison of scoped_ptr types.  If C2 != C, it totally doesn't
    // make sense, and if C2 == C, it still doesn't make sense because you should
    // never have the same object owned by two different scoped_ptrs.
    template <class C2> bool operator==(scoped_ptr<C2> const& p2) const;
    template <class C2> bool operator!=(scoped_ptr<C2> const& p2) const;
  
    // Disallow evil constructors
    scoped_ptr(const scoped_ptr&);
    void operator=(const scoped_ptr&);
  };
  
  // Free functions
  template <class C>
  inline void swap(scoped_ptr<C>& p1, scoped_ptr<C>& p2) {
    p1.swap(p2);
  }
  
  template <class C>
  inline bool operator==(const C* p1, const scoped_ptr<C>& p2) {
    return p1 == p2.get();
  }
  
  template <class C>
  inline bool operator==(const C* p1, const scoped_ptr<const C>& p2) {
    return p1 == p2.get();
  }
  
  template <class C>
  inline bool operator!=(const C* p1, const scoped_ptr<C>& p2) {
    return p1 != p2.get();
  }
  
  template <class C>
  inline bool operator!=(const C* p1, const scoped_ptr<const C>& p2) {
    return p1 != p2.get();
  }
  
  template <class C>
  scoped_ptr<C> make_scoped_ptr(C *p) {
    // This does nothing but to return a scoped_ptr of the type that the passed
    // pointer is of.  (This eliminates the need to specify the name of T when
    // making a scoped_ptr that is used anonymously/temporarily.)  From an
    // access control point of view, we construct an unnamed scoped_ptr here
    // which we return and thus copy-construct.  Hence, we need to have access
    // to scoped_ptr::scoped_ptr(scoped_ptr const &).  However, it is guaranteed
    // that we never actually call the copy constructor, which is a good thing
    // as we would call the temporary's object destructor (and thus delete p)
    // if we actually did copy some object, here.
    return scoped_ptr<C>(p);
  }
  
  // scoped_array<C> is like scoped_ptr<C>, except that the caller must allocate
  // with new [] and the destructor deletes objects with delete [].
  //
  // As with scoped_ptr<C>, a scoped_array<C> either points to an object
  // or is NULL.  A scoped_array<C> owns the object that it points to.
  // scoped_array<T> is thread-compatible, and once you index into it,
  // the returned objects have only the threadsafety guarantees of T.
  //
  // Size: sizeof(scoped_array<C>) == sizeof(C*)
  template <class C>
  class scoped_array {
   public:
  
    // The element type
    typedef C element_type;
  
    // Constructor.  Defaults to intializing with NULL.
    // There is no way to create an uninitialized scoped_array.
    // The input parameter must be allocated with new [].
    explicit scoped_array(C* p = NULL) : array_(p) { }
  
    // Destructor.  If there is a C object, delete it.
    // We don't need to test ptr_ == NULL because C++ does that for us.
    ~scoped_array() {
      enum { type_must_be_complete = sizeof(C) };
      delete[] array_;
    }
  
    // Reset.  Deletes the current owned object, if any.
    // Then takes ownership of a new object, if given.
    // this->reset(this->get()) works.
    void reset(C* p = NULL) {
      if (p != array_) {
        enum { type_must_be_complete = sizeof(C) };
        delete[] array_;
        array_ = p;
      }
    }
  
    // Get one element of the current object.
    // Will assert() if there is no current object, or index i is negative.
    C& operator[](std::ptrdiff_t i) const {
      assert(i >= 0);
      assert(array_ != NULL);
      return array_[i];
    }
  
    // Get a pointer to the zeroth element of the current object.
    // If there is no current object, return NULL.
    C* get() const {
      return array_;
    }
  
    // Comparison operators.
    // These return whether a scoped_array and a raw pointer refer to
    // the same array, not just to two different but equal arrays.
    bool operator==(const C* p) const { return array_ == p; }
    bool operator!=(const C* p) const { return array_ != p; }
  
    // Swap two scoped arrays.
    void swap(scoped_array& p2) {
      C* tmp = array_;
      array_ = p2.array_;
      p2.array_ = tmp;
    }
  
    // Release an array.
    // 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.
    C* release() {
      C* retVal = array_;
      array_ = NULL;
      return retVal;
    }
  
   private:
    C* array_;
  
    // Forbid comparison of different scoped_array types.
    template <class C2> bool operator==(scoped_array<C2> const& p2) const;
    template <class C2> bool operator!=(scoped_array<C2> const& p2) const;
  
    // Disallow evil constructors
    scoped_array(const scoped_array&);
    void operator=(const scoped_array&);
  };
  
  // Free functions
  template <class C>
  inline void swap(scoped_array<C>& p1, scoped_array<C>& p2) {
    p1.swap(p2);
  }
  
  template <class C>
  inline bool operator==(const C* p1, const scoped_array<C>& p2) {
    return p1 == p2.get();
  }
  
  template <class C>
  inline bool operator==(const C* p1, const scoped_array<const C>& p2) {
    return p1 == p2.get();
  }
  
  template <class C>
  inline bool operator!=(const C* p1, const scoped_array<C>& p2) {
    return p1 != p2.get();
  }
  
  template <class C>
  inline bool operator!=(const C* p1, const scoped_array<const C>& p2) {
    return p1 != p2.get();
  }
  
  // This class wraps the c library function free() in a class that can be
  // passed as a template argument to scoped_ptr_malloc below.
  class ScopedPtrMallocFree {
   public:
    inline void operator()(void* x) const {
      free(x);
    }
  };
  
  // scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a
  // second template argument, the functor used to free the object.
  
  template<class C, class FreeProc = ScopedPtrMallocFree>
  class scoped_ptr_malloc {
   public:
  
    // The element type
    typedef C element_type;
  
    // Construction with no arguments sets ptr_ to NULL.
    // There is no way to create an uninitialized scoped_ptr.
    // The input parameter must be allocated with an allocator that matches the
    // Free functor.  For the default Free functor, this is malloc, calloc, or
    // realloc.
    explicit scoped_ptr_malloc(): ptr_(NULL) { }
  
    // Construct with a C*, and provides an error with a D*.
    template<class must_be_C>
    explicit scoped_ptr_malloc(must_be_C* p): ptr_(p) { }
  
    // Construct with a void*, such as you get from malloc.
    explicit scoped_ptr_malloc(void *p): ptr_(static_cast<C*>(p)) { }
  
    // Destructor.  If there is a C object, call the Free functor.
    ~scoped_ptr_malloc() {
      free_(ptr_);
    }
  
    // Reset.  Calls the Free functor on the current owned object, if any.
    // Then takes ownership of a new object, if given.
    // this->reset(this->get()) works.
    void reset(C* p = NULL) {
      if (ptr_ != p) {
        free_(ptr_);
        ptr_ = p;
      }
    }
  
    // Reallocates the existing pointer, and returns 'true' if
    // the reallcation is succesfull.  If the reallocation failed, then
    // the pointer remains in its previous state.
    //
    // Note: this calls realloc() directly, even if an alternate 'free'
    // functor is provided in the template instantiation.
    bool try_realloc(size_t new_size) {
      C* new_ptr = static_cast<C*>(realloc(ptr_, new_size));
      if (new_ptr == NULL) {
        return false;
      }
      ptr_ = new_ptr;
      return true;
    }
  
    // Get the current object.
    // operator* and operator-> will cause an assert() failure if there is
    // no current object.
    C& operator*() const {
      assert(ptr_ != NULL);
      return *ptr_;
    }
  
    C* operator->() const {
      assert(ptr_ != NULL);
      return ptr_;
    }
  
    C* get() const {
      return ptr_;
    }
  
    // Comparison operators.
    // These return whether a scoped_ptr_malloc and a plain pointer refer
    // to the same object, not just to two different but equal objects.
    // For compatibility with the boost-derived implementation, these
    // take non-const arguments.
    bool operator==(C* p) const {
      return ptr_ == p;
    }
  
    bool operator!=(C* p) const {
      return ptr_ != p;
    }
  
    // Swap two scoped pointers.
    void swap(scoped_ptr_malloc & b) {
      C* tmp = b.ptr_;
      b.ptr_ = ptr_;
      ptr_ = tmp;
    }
  
    // 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.
    C* release() {
      C* tmp = ptr_;
      ptr_ = NULL;
      return tmp;
    }
  
   private:
    C* ptr_;
  
    // no reason to use these: each scoped_ptr_malloc should have its own object
    template <class C2, class GP>
    bool operator==(scoped_ptr_malloc<C2, GP> const& p) const;
    template <class C2, class GP>
    bool operator!=(scoped_ptr_malloc<C2, GP> const& p) const;
  
    static FreeProc const free_;
  
    // Disallow evil constructors
    scoped_ptr_malloc(const scoped_ptr_malloc&);
    void operator=(const scoped_ptr_malloc&);
  };
  
  template<class C, class FP>
  FP const scoped_ptr_malloc<C, FP>::free_ = FP();
  
  template<class C, class FP> inline
  void swap(scoped_ptr_malloc<C, FP>& a, scoped_ptr_malloc<C, FP>& b) {
    a.swap(b);
  }
  
  template<class C, class FP> inline
  bool operator==(C* p, const scoped_ptr_malloc<C, FP>& b) {
    return p == b.get();
  }
  
  template<class C, class FP> inline
  bool operator!=(C* p, const scoped_ptr_malloc<C, FP>& b) {
    return p != b.get();
  }
  
  #endif  // BASE_SCOPED_PTR_H__
  