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cld-src/base/scoped_ptr.h  view on Meta::CPAN

// 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_;
  }