1b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// Copyright 2014 The Chromium Authors. All rights reserved. 2b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// Use of this source code is governed by a BSD-style license that can be 3b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// found in the LICENSE file. 4b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 5b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat#ifndef BASE_SCOPED_GENERIC_H_ 6b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat#define BASE_SCOPED_GENERIC_H_ 7b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 8b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat#include <stdlib.h> 9b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 10b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat#include <algorithm> 11b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 12b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat#include "base/compiler_specific.h" 130d205d712abd16eeed2f5d5b1052a367d23a223fAlex Vakulenko#include "base/macros.h" 14b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 15b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Eratnamespace base { 16b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 173a83cddbf6d8fe9c9d70d01e008ff8e86a823cb6Jay Civelli// This class acts like unique_ptr with a custom deleter (although is slightly 18b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// less fancy in some of the more escoteric respects) except that it keeps a 19b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// copy of the object rather than a pointer, and we require that the contained 20b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// object has some kind of "invalid" value. 21b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// 22b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// Defining a scoper based on this class allows you to get a scoper for 23b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// non-pointer types without having to write custom code for set, reset, and 24b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// move, etc. and get almost identical semantics that people are used to from 253a83cddbf6d8fe9c9d70d01e008ff8e86a823cb6Jay Civelli// unique_ptr. 26b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// 27b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// It is intended that you will typedef this class with an appropriate deleter 28b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// to implement clean up tasks for objects that act like pointers from a 29b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// resource management standpoint but aren't, such as file descriptors and 303a83cddbf6d8fe9c9d70d01e008ff8e86a823cb6Jay Civelli// various types of operating system handles. Using unique_ptr for these 31b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// things requires that you keep a pointer to the handle valid for the lifetime 32b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// of the scoper (which is easy to mess up). 33b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// 34b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// For an object to be able to be put into a ScopedGeneric, it must support 35b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// standard copyable semantics and have a specific "invalid" value. The traits 36b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// must define a free function and also the invalid value to assign for 37b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// default-constructed and released objects. 38b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// 39b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// struct FooScopedTraits { 40b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// // It's assumed that this is a fast inline function with little-to-no 41b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// // penalty for duplicate calls. This must be a static function even 42b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// // for stateful traits. 43b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// static int InvalidValue() { 44b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// return 0; 45b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// } 46b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// 47b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// // This free function will not be called if f == InvalidValue()! 48b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// static void Free(int f) { 49b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// ::FreeFoo(f); 50b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// } 51b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// }; 52b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// 53b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat// typedef ScopedGeneric<int, FooScopedTraits> ScopedFoo; 54b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erattemplate<typename T, typename Traits> 55b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Eratclass ScopedGeneric { 56b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat private: 57b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // This must be first since it's used inline below. 58b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // 59b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Use the empty base class optimization to allow us to have a D 60b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // member, while avoiding any space overhead for it when D is an 61b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // empty class. See e.g. http://www.cantrip.org/emptyopt.html for a good 62b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // discussion of this technique. 63b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat struct Data : public Traits { 64b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat explicit Data(const T& in) : generic(in) {} 65b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat Data(const T& in, const Traits& other) : Traits(other), generic(in) {} 66b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat T generic; 67b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat }; 68b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 69b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat public: 70b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat typedef T element_type; 71b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat typedef Traits traits_type; 72b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 73b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat ScopedGeneric() : data_(traits_type::InvalidValue()) {} 74b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 75b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Constructor. Takes responsibility for freeing the resource associated with 76b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // the object T. 77b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat explicit ScopedGeneric(const element_type& value) : data_(value) {} 78b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 79b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Constructor. Allows initialization of a stateful traits object. 80b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat ScopedGeneric(const element_type& value, const traits_type& traits) 81b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat : data_(value, traits) { 82b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 83b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 84b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Move constructor. Allows initialization from a ScopedGeneric rvalue. 85b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat ScopedGeneric(ScopedGeneric<T, Traits>&& rvalue) 86b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat : data_(rvalue.release(), rvalue.get_traits()) { 87b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 88b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 89b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat ~ScopedGeneric() { 90b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat FreeIfNecessary(); 91b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 92b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 93b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // operator=. Allows assignment from a ScopedGeneric rvalue. 94b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat ScopedGeneric& operator=(ScopedGeneric<T, Traits>&& rvalue) { 95b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat reset(rvalue.release()); 96b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat return *this; 97b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 98b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 99b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Frees the currently owned object, if any. Then takes ownership of a new 1003a83cddbf6d8fe9c9d70d01e008ff8e86a823cb6Jay Civelli // object, if given. Self-resets are not allowd as on unique_ptr. See 101b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // http://crbug.com/162971 102b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat void reset(const element_type& value = traits_type::InvalidValue()) { 103b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat if (data_.generic != traits_type::InvalidValue() && data_.generic == value) 104b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat abort(); 105b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat FreeIfNecessary(); 106b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat data_.generic = value; 107b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 108b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 109b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat void swap(ScopedGeneric& other) { 110b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Standard swap idiom: 'using std::swap' ensures that std::swap is 111b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // present in the overload set, but we call swap unqualified so that 112b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // any more-specific overloads can be used, if available. 113b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat using std::swap; 114b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat swap(static_cast<Traits&>(data_), static_cast<Traits&>(other.data_)); 115b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat swap(data_.generic, other.data_.generic); 116b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 117b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 118b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Release the object. The return value is the current object held by this 119b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // object. After this operation, this object will hold a null value, and 120b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // will not own the object any more. 121b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat element_type release() WARN_UNUSED_RESULT { 122b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat element_type old_generic = data_.generic; 123b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat data_.generic = traits_type::InvalidValue(); 124b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat return old_generic; 125b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 126b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 127b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat const element_type& get() const { return data_.generic; } 128b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 129b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Returns true if this object doesn't hold the special null value for the 130b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // associated data type. 131b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat bool is_valid() const { return data_.generic != traits_type::InvalidValue(); } 132b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 133b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat bool operator==(const element_type& value) const { 134b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat return data_.generic == value; 135b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 136b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat bool operator!=(const element_type& value) const { 137b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat return data_.generic != value; 138b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 139b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 140b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat Traits& get_traits() { return data_; } 141b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat const Traits& get_traits() const { return data_; } 142b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 143b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat private: 144b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat void FreeIfNecessary() { 145b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat if (data_.generic != traits_type::InvalidValue()) { 146b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat data_.Free(data_.generic); 147b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat data_.generic = traits_type::InvalidValue(); 148b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 149b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat } 150b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 151b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // Forbid comparison. If U != T, it totally doesn't make sense, and if U == 152b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // T, it still doesn't make sense because you should never have the same 153b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat // object owned by two different ScopedGenerics. 154b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat template <typename T2, typename Traits2> bool operator==( 155b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat const ScopedGeneric<T2, Traits2>& p2) const; 156b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat template <typename T2, typename Traits2> bool operator!=( 157b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat const ScopedGeneric<T2, Traits2>& p2) const; 158b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 159b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat Data data_; 1600c4f26a46430b8c503c65f5cae1d2b6876d53e30Luis Hector Chavez 1610c4f26a46430b8c503c65f5cae1d2b6876d53e30Luis Hector Chavez DISALLOW_COPY_AND_ASSIGN(ScopedGeneric); 162b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat}; 163b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 164b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erattemplate<class T, class Traits> 165b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Eratvoid swap(const ScopedGeneric<T, Traits>& a, 166b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat const ScopedGeneric<T, Traits>& b) { 167b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat a.swap(b); 168b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat} 169b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 170b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erattemplate<class T, class Traits> 171b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Eratbool operator==(const T& value, const ScopedGeneric<T, Traits>& scoped) { 172b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat return value == scoped.get(); 173b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat} 174b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 175b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erattemplate<class T, class Traits> 176b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Eratbool operator!=(const T& value, const ScopedGeneric<T, Traits>& scoped) { 177b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat return value != scoped.get(); 178b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat} 179b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 180b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat} // namespace base 181b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat 182b8cf94937c52feb53b55c39e3f82094d27de464cDaniel Erat#endif // BASE_SCOPED_GENERIC_H_ 183