cef/include/internal/cef_ptr.h

// Copyright (c) 2014 Marshall A. Greenblatt. All rights reserved.
//
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// modification, are permitted provided that the following conditions are
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#ifndef CEF_INCLUDE_INTERNAL_CEF_PTR_H_
#define CEF_INCLUDE_INTERNAL_CEF_PTR_H_
#pragma once

#include <memory>

#include "include/base/cef_build.h"
#include "include/base/cef_ref_counted.h"

///
/// Smart pointer implementation that is an alias of scoped_refptr from
/// include/base/cef_ref_counted.h.
///
/// 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:
///
/// <pre>
///   class MyFoo : public CefBaseRefCounted {
///     ...
///   };
///
///   void some_function() {
///     // The MyFoo object that |foo| represents starts with a single
///     // reference.
///     CefRefPtr&lt;MyFoo&gt; foo = new MyFoo();
///     foo-&gt;Method(param);
///     // |foo| is released when this function returns
///   }
///
///   void some_other_function() {
///     CefRefPtr&lt;MyFoo&gt; foo = new MyFoo();
///     ...
///     foo = NULL;  /// explicitly releases |foo|
///     ...
///     if (foo)
///       foo-&gt;Method(param);
///   }
/// </pre>
///
/// The above examples show how CefRefPtr&lt;T&gt; acts like a pointer to T.
/// Given two CefRefPtr&lt;T&gt; classes, it is also possible to exchange
/// references between the two objects, like so:
///
/// <pre>
///   {
///     CefRefPtr&lt;MyFoo&gt; a = new MyFoo();
///     CefRefPtr&lt;MyFoo&gt; b;
///
///     b.swap(a);
///     // now, |b| references the MyFoo object, and |a| references NULL.
///   }
/// </pre>
///
/// To make both |a| and |b| in the above example reference the same MyFoo
/// object, simply use the assignment operator:
///
/// <pre>
///   {
///     CefRefPtr&lt;MyFoo&gt; a = new MyFoo();
///     CefRefPtr&lt;MyFoo&gt; b;
///
///     b = a;
///     // now, |a| and |b| each own a reference to the same MyFoo object.
///     // the reference count of the underlying MyFoo object will be 2.
///   }
/// </pre>
///
/// Reference counted objects can also be passed as function parameters and
/// used as function return values:
///
/// <pre>
///   void some_func_with_param(CefRefPtr&lt;MyFoo&gt; param) {
///     // A reference is added to the MyFoo object that |param| represents
///     // during the scope of some_func_with_param() and released when
///     // some_func_with_param() goes out of scope.
///   }
///
///   CefRefPtr&lt;MyFoo&gt; some_func_with_retval() {
///     // The MyFoo object that |foox| represents starts with a single
///     // reference.
///     CefRefPtr&lt;MyFoo&gt; foox = new MyFoo();
///
///     // Creating the return value adds an additional reference.
///     return foox;
///
///     // When some_func_with_retval() goes out of scope the original |foox|
///     // reference is released.
///   }
///
///   void and_another_function() {
///     CefRefPtr&lt;MyFoo&gt; foo = new MyFoo();
///
///     // pass |foo| as a parameter.
///     some_function(foo);
///
///     CefRefPtr&lt;MyFoo&gt; foo2 = some_func_with_retval();
///     // Now, since we kept a reference to the some_func_with_retval() return
///     // value, |foo2| is the only class pointing to the MyFoo object created
///     in some_func_with_retval(), and it has a reference count of 1.
///
///     some_func_with_retval();
///     // Now, since we didn't keep a reference to the some_func_with_retval()
///     // return value, the MyFoo object created in some_func_with_retval()
///     // will automatically be released.
///   }
/// </pre>
///
/// And in standard containers:
///
/// <pre>
///   {
///     // Create a vector that holds MyFoo objects.
///     std::vector&lt;CefRefPtr&lt;MyFoo&gt; &gt; MyFooVec;
///
///     // The MyFoo object that |foo| represents starts with a single
///     // reference.
///     CefRefPtr&lt;MyFoo&gt; foo = new MyFoo();
///
///     // When the MyFoo object is added to |MyFooVec| the reference count
///     // is increased to 2.
///     MyFooVec.push_back(foo);
///   }
/// </pre>
///
template <class T>
using CefRefPtr = scoped_refptr<T>;

///
/// A CefOwnPtr<T> is like a T*, except that the destructor of CefOwnPtr<T>
/// automatically deletes the pointer it holds (if any). That is, CefOwnPtr<T>
/// owns the T object that it points to. Like a T*, a CefOwnPtr<T> may hold
/// either NULL or a pointer to a T object. Also like T*, CefOwnPtr<T> is
/// thread-compatible, and once you dereference it, you get the thread safety
/// guarantees of T.
///
template <class T, class D = std::default_delete<T>>
using CefOwnPtr = std::unique_ptr<T, D>;

///
/// A CefRawPtr<T> is the same as T*
///
template <class T>
using CefRawPtr = T*;

#endif  // CEF_INCLUDE_INTERNAL_CEF_PTR_H_