// Copyright 2013 Google Inc. 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 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. // This is a copy of breakpad's standalone scoped_ptr, which has been // renamed to nonstd::unique_ptr, and from which more complicated classes // have been removed. The reset() method has also been tweaked to more // closely match c++11, and an implicit conversion to bool has been added. // Scopers help you manage ownership of a pointer, helping you easily manage the // a pointer within a scope, and automatically destroying the pointer at the // end of a scope. // // A unique_ptr<T> is like a T*, except that the destructor of unique_ptr<T> // automatically deletes the pointer it holds (if any). // That is, unique_ptr<T> owns the T object that it points to. // Like a T*, a unique_ptr<T> may hold either NULL or a pointer to a T object. // Also like T*, unique_ptr<T> is thread-compatible, and once you // dereference it, you get the thread safety guarantees of T. // // Example usage (unique_ptr): // { // unique_ptr<Foo> foo(new Foo("wee")); // } // foo goes out of scope, releasing the pointer with it. // // { // unique_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. // // The size of a unique_ptr is small: sizeof(unique_ptr<C>) == sizeof(C*) #ifndef NONSTD_UNIQUE_PTR_H_ #define NONSTD_UNIQUE_PTR_H_ // This is an implementation designed to match the anticipated future C++11 // implementation of the unique_ptr class. #include <assert.h> #include <stddef.h> #include <stdlib.h> #include <ostream> #include "template_util.h" namespace nonstd { // Replacement for move, but doesn't allow things that are already // rvalue references. template <class T> T&& move(T& t) { return static_cast<T&&>(t); } // Function object which deletes its parameter, which must be a pointer. // If C is an array type, invokes 'delete[]' on the parameter; otherwise, // invokes 'delete'. The default deleter for unique_ptr<T>. template <class T> struct DefaultDeleter { DefaultDeleter() {} template <typename U> DefaultDeleter(const DefaultDeleter<U>& other) { // IMPLEMENTATION NOTE: C++11 20.7.1.1.2p2 only provides this constructor // if U* is implicitly convertible to T* and U is not an array type. // // Correct implementation should use SFINAE to disable this // constructor. However, since there are no other 1-argument constructors, // using a static_assert() based on is_convertible<> and requiring // complete types is simpler and will cause compile failures for equivalent // misuses. // // Note, the is_convertible<U*, T*> check also ensures that U is not an // array. T is guaranteed to be a non-array, so any U* where U is an array // cannot convert to T*. enum { T_must_be_complete = sizeof(T) }; enum { U_must_be_complete = sizeof(U) }; static_assert((pdfium::base::is_convertible<U*, T*>::value), "U_ptr_must_implicitly_convert_to_T_ptr"); } inline void operator()(T* ptr) const { enum { type_must_be_complete = sizeof(T) }; delete ptr; } }; // Specialization of DefaultDeleter for array types. template <class T> struct DefaultDeleter<T[]> { inline void operator()(T* ptr) const { enum { type_must_be_complete = sizeof(T) }; delete[] ptr; } private: // Disable this operator for any U != T because it is undefined to execute // an array delete when the static type of the array mismatches the dynamic // type. // // References: // C++98 [expr.delete]p3 // http://cplusplus.github.com/LWG/lwg-defects.html#938 template <typename U> void operator()(U* array) const; }; template <class T, int n> struct DefaultDeleter<T[n]> { // Never allow someone to declare something like unique_ptr<int[10]>. static_assert(sizeof(T) == -1, "do_not_use_array_with_size_as_type"); }; namespace internal { // Common implementation for both pointers to elements and pointers to // arrays. These are differentiated below based on the need to invoke // delete vs. delete[] as appropriate. template <class C, class D> class unique_ptr_base { public: // The element type typedef C element_type; explicit unique_ptr_base(C* p) : data_(p) {} // Initializer for deleters that have data parameters. unique_ptr_base(C* p, const D& d) : data_(p, d) {} // Move constructor. unique_ptr_base(unique_ptr_base<C, D>&& that) : data_(that.release(), that.get_deleter()) {} ~unique_ptr_base() { enum { type_must_be_complete = sizeof(C) }; if (data_.ptr != nullptr) { // Not using get_deleter() saves one function call in non-optimized // builds. static_cast<D&>(data_)(data_.ptr); } } void reset(C* p = nullptr) { C* old = data_.ptr; data_.ptr = p; if (old != nullptr) static_cast<D&>(data_)(old); } C* get() const { return data_.ptr; } D& get_deleter() { return data_; } const D& get_deleter() const { return data_; } // Comparison operators. // These return whether two unique_ptr refer to the same object, not just to // two different but equal objects. bool operator==(C* p) const { return data_.ptr == p; } bool operator!=(C* p) const { return data_.ptr != p; } // Swap two unique pointers. void swap(unique_ptr_base& p2) { Data tmp = data_; data_ = p2.data_; p2.data_ = tmp; } // Release a pointer. // The return value is the current pointer held by this object. // If this object holds a NULL pointer, the return value is NULL. // After this operation, this object will hold a NULL pointer, // and will not own the object any more. C* release() { C* ptr = data_.ptr; data_.ptr = nullptr; return ptr; } // Allow promotion to bool for conditional statements. explicit operator bool() const { return data_.ptr != nullptr; } protected: // Use the empty base class optimization to allow us to have a D // member, while avoiding any space overhead for it when D is an // empty class. See e.g. http://www.cantrip.org/emptyopt.html for a good // discussion of this technique. struct Data : public D { explicit Data(C* ptr_in) : ptr(ptr_in) {} Data(C* ptr_in, const D& other) : D(other), ptr(ptr_in) {} C* ptr; }; Data data_; }; } // namespace internal // Implementation for ordinary pointers using delete. template <class C, class D = DefaultDeleter<C>> class unique_ptr : public internal::unique_ptr_base<C, D> { public: // Constructor. Defaults to initializing with nullptr. unique_ptr() : internal::unique_ptr_base<C, D>(nullptr) {} // Constructor. Takes ownership of p. explicit unique_ptr(C* p) : internal::unique_ptr_base<C, D>(p) {} // Constructor. Allows initialization of a stateful deleter. unique_ptr(C* p, const D& d) : internal::unique_ptr_base<C, D>(p, d) {} // Constructor. Allows construction from a nullptr. unique_ptr(decltype(nullptr)) : internal::unique_ptr_base<C, D>(nullptr) {} // Move constructor. unique_ptr(unique_ptr&& that) : internal::unique_ptr_base<C, D>(nonstd::move(that)) {} // operator=. Allows assignment from a nullptr. Deletes the currently owned // object, if any. unique_ptr& operator=(decltype(nullptr)) { this->reset(); return *this; } // Move assignment. unique_ptr<C>& operator=(unique_ptr<C>&& that) { this->reset(that.release()); return *this; } // Accessors to get the owned object. // operator* and operator-> will assert() if there is no current object. C& operator*() const { assert(this->data_.ptr != nullptr); return *this->data_.ptr; } C* operator->() const { assert(this->data_.ptr != nullptr); return this->data_.ptr; } // Comparison operators. // These return whether two unique_ptr refer to the same object, not just to // two different but equal objects. bool operator==(const C* p) const { return this->get() == p; } bool operator!=(const C* p) const { return this->get() != p; } private: // Disallow evil constructors. It doesn't make sense to make a copy of // something that's allegedly unique. unique_ptr(const unique_ptr&) = delete; void operator=(const unique_ptr&) = delete; // Forbid comparison of unique_ptr types. If U != C, it totally // doesn't make sense, and if U == C, it still doesn't make sense // because you should never have the same object owned by two different // unique_ptrs. template <class U> bool operator==(unique_ptr<U> const& p2) const; template <class U> bool operator!=(unique_ptr<U> const& p2) const; }; // Specialization for arrays using delete[]. template <class C, class D> class unique_ptr<C[], D> : public internal::unique_ptr_base<C, D> { public: // Constructor. Defaults to initializing with nullptr. unique_ptr() : internal::unique_ptr_base<C, D>(nullptr) {} // Constructor. Stores the given array. Note that the argument's type // must exactly match T*. In particular: // - it cannot be a pointer to a type derived from T, because it is // inherently unsafe in the general case to access an array through a // pointer whose dynamic type does not match its static type (eg., if // T and the derived types had different sizes access would be // incorrectly calculated). Deletion is also always undefined // (C++98 [expr.delete]p3). If you're doing this, fix your code. // - it cannot be const-qualified differently from T per unique_ptr spec // (http://cplusplus.github.com/LWG/lwg-active.html#2118). Users wanting // to work around this may use const_cast<const T*>(). explicit unique_ptr(C* p) : internal::unique_ptr_base<C, D>(p) {} // Constructor. Allows construction from a nullptr. unique_ptr(decltype(nullptr)) : internal::unique_ptr_base<C, D>(nullptr) {} // Move constructor. unique_ptr(unique_ptr&& that) : internal::unique_ptr_base<C, D>(nonstd::move(that)) {} // operator=. Allows assignment from a nullptr. Deletes the currently owned // array, if any. unique_ptr& operator=(decltype(nullptr)) { this->reset(); return *this; } // Move assignment. unique_ptr<C>& operator=(unique_ptr<C>&& that) { this->reset(that.release()); return *this; } // Reset. Deletes the currently owned array, if any. // Then takes ownership of a new object, if given. void reset(C* array = nullptr) { static_cast<internal::unique_ptr_base<C, D>*>(this)->reset(array); } // Support indexing since it is holding array. C& operator[](size_t i) { return this->data_.ptr[i]; } // Comparison operators. // These return whether two unique_ptr refer to the same object, not just to // two different but equal objects. bool operator==(C* array) const { return this->get() == array; } bool operator!=(C* array) const { return this->get() != array; } private: // Disable initialization from any type other than element_type*, by // providing a constructor that matches such an initialization, but is // private and has no definition. This is disabled because it is not safe to // call delete[] on an array whose static type does not match its dynamic // type. template <typename U> explicit unique_ptr(U* array); explicit unique_ptr(int disallow_construction_from_null); // Disable reset() from any type other than element_type*, for the same // reasons as the constructor above. template <typename U> void reset(U* array); void reset(int disallow_reset_from_null); // Disallow evil constructors. It doesn't make sense to make a copy of // something that's allegedly unique. unique_ptr(const unique_ptr&) = delete; void operator=(const unique_ptr&) = delete; // Forbid comparison of unique_ptr types. If U != C, it totally // doesn't make sense, and if U == C, it still doesn't make sense // because you should never have the same object owned by two different // unique_ptrs. template <class U> bool operator==(unique_ptr<U> const& p2) const; template <class U> bool operator!=(unique_ptr<U> const& p2) const; }; // Free functions template <class C> void swap(unique_ptr<C>& p1, unique_ptr<C>& p2) { p1.swap(p2); } template <class C> bool operator==(C* p1, const unique_ptr<C>& p2) { return p1 == p2.get(); } template <class C> bool operator!=(C* p1, const unique_ptr<C>& p2) { return p1 != p2.get(); } template <typename T> std::ostream& operator<<(std::ostream& out, const unique_ptr<T>& p) { return out << p.get(); } } // namespace nonstd #endif // NONSTD_UNIQUE_PTR_H_