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// Copyright (c) 2012 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.
// Scopers help you manage ownership of a pointer, helping you easily manage a
// pointer within a scope, and automatically destroying the pointer at the end
// of a scope. There are two main classes you will use, which correspond to the
// operators new/delete and new[]/delete[].
//
// Example usage (scoped_ptr<T>):
// {
// scoped_ptr<Foo> foo(new Foo("wee"));
// } // foo goes out of scope, releasing the pointer with it.
//
// {
// scoped_ptr<Foo> foo; // No pointer managed.
// foo.reset(new Foo("wee")); // Now a pointer is managed.
// foo.reset(new Foo("wee2")); // Foo("wee") was destroyed.
// foo.reset(new Foo("wee3")); // Foo("wee2") was destroyed.
// foo->Method(); // Foo::Method() called.
// foo.get()->Method(); // Foo::Method() called.
// SomeFunc(foo.release()); // SomeFunc takes ownership, foo no longer
// // manages a pointer.
// foo.reset(new Foo("wee4")); // foo manages a pointer again.
// foo.reset(); // Foo("wee4") destroyed, foo no longer
// // manages a pointer.
// } // foo wasn't managing a pointer, so nothing was destroyed.
//
// Example usage (scoped_ptr<T[]>):
// {
// scoped_ptr<Foo[]> foo(new Foo[100]);
// foo.get()->Method(); // Foo::Method on the 0th element.
// foo[10].Method(); // Foo::Method on the 10th element.
// }
//
// Scopers are testable as booleans:
// {
// scoped_ptr<Foo> foo;
// if (!foo)
// foo.reset(new Foo());
// if (foo)
// LOG(INFO) << "This code is reached."
// }
//
// These scopers also implement part of the functionality of C++11 unique_ptr
// in that they are "movable but not copyable." You can use the scopers in
// the parameter and return types of functions to signify ownership transfer
// in to and out of a function. When calling a function that has a scoper
// as the argument type, it must be called with an rvalue of a scoper, which
// can be created by using std::move(), or the result of another function that
// generates a temporary; passing by copy will NOT work. Here is an example
// using scoped_ptr:
//
// void TakesOwnership(scoped_ptr<Foo> arg) {
// // Do something with arg.
// }
// scoped_ptr<Foo> CreateFoo() {
// // No need for calling std::move() for returning a move-only value, or
// // when you already have an rvalue as we do here.
// return scoped_ptr<Foo>(new Foo("new"));
// }
// scoped_ptr<Foo> PassThru(scoped_ptr<Foo> arg) {
// return arg;
// }
//
// {
// scoped_ptr<Foo> ptr(new Foo("yay")); // ptr manages Foo("yay").
// TakesOwnership(std::move(ptr)); // ptr no longer owns Foo("yay").
// scoped_ptr<Foo> ptr2 = CreateFoo(); // ptr2 owns the return Foo.
// scoped_ptr<Foo> ptr3 = // ptr3 now owns what was in ptr2.
// PassThru(std::move(ptr2)); // ptr2 is correspondingly nullptr.
// }
//
// Notice that if you do not call std::move() when returning from PassThru(), or
// when invoking TakesOwnership(), the code will not compile because scopers
// are not copyable; they only implement move semantics which require calling
// the std::move() function to signify a destructive transfer of state.
// CreateFoo() is different though because we are constructing a temporary on
// the return line and thus can avoid needing to call std::move().
//
// The conversion move-constructor properly handles upcast in initialization,
// i.e. you can use a scoped_ptr<Child> to initialize a scoped_ptr<Parent>:
//
// scoped_ptr<Foo> foo(new Foo());
// scoped_ptr<FooParent> parent(std::move(foo));
#ifndef BASE_MEMORY_SCOPED_PTR_H_
#define BASE_MEMORY_SCOPED_PTR_H_
// This is an implementation designed to match the anticipated future TR2
// implementation of the scoped_ptr class.
// TODO(dcheng): Clean up these headers, but there are likely lots of existing
// IWYU violations.
#include <stdlib.h>
#include <memory>
namespace base {
// Function object which invokes 'free' on its parameter, which must be
// a pointer. Can be used to store malloc-allocated pointers in scoped_ptr:
//
// scoped_ptr<int, base::FreeDeleter> foo_ptr(
// static_cast<int*>(malloc(sizeof(int))));
struct FreeDeleter {
inline void operator()(void* ptr) const {
free(ptr);
}
};
} // namespace base
template <typename T, typename D = std::default_delete<T>>
using scoped_ptr = std::unique_ptr<T, D>;
// A function to convert T* into scoped_ptr<T>
// Doing e.g. make_scoped_ptr(new FooBarBaz<type>(arg)) is a shorter notation
// for scoped_ptr<FooBarBaz<type> >(new FooBarBaz<type>(arg))
template <typename T>
scoped_ptr<T> make_scoped_ptr(T* ptr) {
return scoped_ptr<T>(ptr);
}
#endif // BASE_MEMORY_SCOPED_PTR_H_
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