cef/include/internal/cef_ptr.h

169 lines
6.0 KiB
C++

// Copyright (c) 2014 Marshall A. Greenblatt. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the name Chromium Embedded
// Framework nor the names of its contributors may be used to endorse
// or promote products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#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.
// <p>
// 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>
// </p>
///
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_