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Diffstat (limited to 'third_party/chromium/base/memory/scoped_ptr.h')
-rw-r--r-- | third_party/chromium/base/memory/scoped_ptr.h | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/third_party/chromium/base/memory/scoped_ptr.h b/third_party/chromium/base/memory/scoped_ptr.h new file mode 100644 index 0000000..2d2c0ec --- /dev/null +++ b/third_party/chromium/base/memory/scoped_ptr.h @@ -0,0 +1,135 @@ +// 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 <stddef.h> +#include <stdlib.h> + +#include <iosfwd> +#include <memory> +#include <type_traits> +#include <utility> + +#include "base/compiler_specific.h" +#include "base/logging.h" +#include "base/macros.h" +#include "base/move.h" +#include "build/build_config.h" + +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_ |