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Diffstat (limited to 'base/memory/scoped_ptr.h')
| -rw-r--r-- | base/memory/scoped_ptr.h | 450 |
1 files changed, 450 insertions, 0 deletions
diff --git a/base/memory/scoped_ptr.h b/base/memory/scoped_ptr.h new file mode 100644 index 0000000..5c3e931 --- /dev/null +++ b/base/memory/scoped_ptr.h @@ -0,0 +1,450 @@ +// 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. + +#ifndef I18N_PHONENUMBERS_BASE_MEMORY_SCOPED_PTR_H_ +#define I18N_PHONENUMBERS_BASE_MEMORY_SCOPED_PTR_H_ + +#if defined(I18N_PHONENUMBERS_USE_BOOST) + +#include <boost/scoped_ptr.hpp> +using boost::scoped_ptr; + +#else // !I18N_PHONENUMBERS_USE_BOOST + +// This is an implementation designed to match the anticipated future TR2 +// implementation of the scoped_ptr class and scoped_ptr_malloc (deprecated). + +#include <assert.h> +#include <stddef.h> +#include <stdlib.h> + +#include <algorithm> // For std::swap(). + +#include "phonenumbers/base/basictypes.h" +#include "phonenumbers/base/template_util.h" + +namespace i18n { +namespace phonenumbers { + +// 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 scoped_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 COMPILE_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) }; + COMPILE_ASSERT((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 scoped_ptr<int[10]>. + COMPILE_ASSERT(sizeof(T) == -1, do_not_use_array_with_size_as_type); +}; + +// 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); + } +}; + +// Minimal implementation of the core logic of scoped_ptr, suitable for +// reuse in both scoped_ptr and its specializations. +template <class T, class D> +class scoped_ptr_impl { + public: + explicit scoped_ptr_impl(T* p) : data_(p) { } + + // Initializer for deleters that have data parameters. + scoped_ptr_impl(T* p, const D& d) : data_(p, d) {} + + // Templated constructor that destructively takes the value from another + // scoped_ptr_impl. + template <typename U, typename V> + scoped_ptr_impl(scoped_ptr_impl<U, V>* other) + : data_(other->release(), other->get_deleter()) { + // We do not support move-only deleters. We could modify our move + // emulation to have base::subtle::move() and base::subtle::forward() + // functions that are imperfect emulations of their C++11 equivalents, + // but until there's a requirement, just assume deleters are copyable. + } + + template <typename U, typename V> + void TakeState(scoped_ptr_impl<U, V>* other) { + // See comment in templated constructor above regarding lack of support + // for move-only deleters. + reset(other->release()); + get_deleter() = other->get_deleter(); + } + + ~scoped_ptr_impl() { + if (data_.ptr != NULL) { + // Not using get_deleter() saves one function call in non-optimized + // builds. + static_cast<D&>(data_)(data_.ptr); + } + } + + void reset(T* p) { + // This is a self-reset, which is no longer allowed: http://crbug.com/162971 + if (p != NULL && p == data_.ptr) + abort(); + + // Note that running data_.ptr = p can lead to undefined behavior if + // get_deleter()(get()) deletes this. In order to pevent this, reset() + // should update the stored pointer before deleting its old value. + // + // However, changing reset() to use that behavior may cause current code to + // break in unexpected ways. If the destruction of the owned object + // dereferences the scoped_ptr when it is destroyed by a call to reset(), + // then it will incorrectly dispatch calls to |p| rather than the original + // value of |data_.ptr|. + // + // During the transition period, set the stored pointer to NULL while + // deleting the object. Eventually, this safety check will be removed to + // prevent the scenario initially described from occuring and + // http://crbug.com/176091 can be closed. + T* old = data_.ptr; + data_.ptr = NULL; + if (old != NULL) + static_cast<D&>(data_)(old); + data_.ptr = p; + } + + T* get() const { return data_.ptr; } + + D& get_deleter() { return data_; } + const D& get_deleter() const { return data_; } + + void swap(scoped_ptr_impl& p2) { + // Standard swap idiom: 'using std::swap' ensures that std::swap is + // present in the overload set, but we call swap unqualified so that + // any more-specific overloads can be used, if available. + using std::swap; + swap(static_cast<D&>(data_), static_cast<D&>(p2.data_)); + swap(data_.ptr, p2.data_.ptr); + } + + T* release() { + T* old_ptr = data_.ptr; + data_.ptr = NULL; + return old_ptr; + } + + private: + // Needed to allow type-converting constructor. + template <typename U, typename V> friend class scoped_ptr_impl; + + // 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(T* ptr_in) : ptr(ptr_in) {} + Data(T* ptr_in, const D& other) : D(other), ptr(ptr_in) {} + T* ptr; + }; + + Data data_; + + DISALLOW_COPY_AND_ASSIGN(scoped_ptr_impl); +}; + +// A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T> +// automatically deletes the pointer it holds (if any). +// That is, scoped_ptr<T> owns the T object that it points to. +// Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object. +// Also like T*, scoped_ptr<T> is thread-compatible, and once you +// dereference it, you get the thread safety guarantees of T. +// +// The size of scoped_ptr is small. On most compilers, when using the +// DefaultDeleter, sizeof(scoped_ptr<T>) == sizeof(T*). Custom deleters will +// increase the size proportional to whatever state they need to have. See +// comments inside scoped_ptr_impl<> for details. +// +// Current implementation targets having a strict subset of C++11's +// unique_ptr<> features. Known deficiencies include not supporting move-only +// deleteres, function pointers as deleters, and deleters with reference +// types. +template <class T, class D = DefaultDeleter<T> > +class scoped_ptr { + public: + // The element and deleter types. + typedef T element_type; + typedef D deleter_type; + + // Constructor. Defaults to initializing with NULL. + scoped_ptr() : impl_(NULL) { } + + // Constructor. Takes ownership of p. + explicit scoped_ptr(element_type* p) : impl_(p) { } + + // Constructor. Allows initialization of a stateful deleter. + scoped_ptr(element_type* p, const D& d) : impl_(p, d) { } + + // Constructor. Allows construction from a scoped_ptr rvalue for a + // convertible type and deleter. + // + // IMPLEMENTATION NOTE: C++11 unique_ptr<> keeps this constructor distinct + // from the normal move constructor. By C++11 20.7.1.2.1.21, this constructor + // has different post-conditions if D is a reference type. Since this + // implementation does not support deleters with reference type, + // we do not need a separate move constructor allowing us to avoid one + // use of SFINAE. You only need to care about this if you modify the + // implementation of scoped_ptr. + template <typename U, typename V> + scoped_ptr(scoped_ptr<U, V> other) : impl_(&other.impl_) { + COMPILE_ASSERT(!is_array<U>::value, U_cannot_be_an_array); + } + + // operator=. Allows assignment from a scoped_ptr rvalue for a convertible + // type and deleter. + // + // IMPLEMENTATION NOTE: C++11 unique_ptr<> keeps this operator= distinct from + // the normal move assignment operator. By C++11 20.7.1.2.3.4, this templated + // form has different requirements on for move-only Deleters. Since this + // implementation does not support move-only Deleters, we do not need a + // separate move assignment operator allowing us to avoid one use of SFINAE. + // You only need to care about this if you modify the implementation of + // scoped_ptr. + template <typename U, typename V> + scoped_ptr& operator=(scoped_ptr<U, V> rhs) { + COMPILE_ASSERT(!is_array<U>::value, U_cannot_be_an_array); + impl_.TakeState(&rhs.impl_); + return *this; + } + + // Reset. Deletes the currently owned object, if any. + // Then takes ownership of a new object, if given. + void reset(element_type* p = NULL) { impl_.reset(p); } + + // Accessors to get the owned object. + // operator* and operator-> will assert() if there is no current object. + element_type& operator*() const { + assert(impl_.get() != NULL); + return *impl_.get(); + } + element_type* operator->() const { + assert(impl_.get() != NULL); + return impl_.get(); + } + element_type* get() const { return impl_.get(); } + + // Access to the deleter. + deleter_type& get_deleter() { return impl_.get_deleter(); } + const deleter_type& get_deleter() const { return impl_.get_deleter(); } + + // Allow scoped_ptr<element_type> to be used in boolean expressions, but not + // implicitly convertible to a real bool (which is dangerous). + private: + typedef scoped_ptr_impl<element_type, deleter_type> scoped_ptr::*Testable; + + public: + operator Testable() const { return impl_.get() ? &scoped_ptr::impl_ : NULL; } + + // Comparison operators. + // These return whether two scoped_ptr refer to the same object, not just to + // two different but equal objects. + bool operator==(const element_type* p) const { return impl_.get() == p; } + bool operator!=(const element_type* p) const { return impl_.get() != p; } + + // Swap two scoped pointers. + void swap(scoped_ptr& p2) { + impl_.swap(p2.impl_); + } + + // 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. + element_type* release() { + return impl_.release(); + } + + private: + // Needed to reach into |impl_| in the constructor. + template <typename U, typename V> friend class scoped_ptr; + scoped_ptr_impl<element_type, deleter_type> impl_; + + // Forbid comparison of scoped_ptr types. If U != T, it totally + // doesn't make sense, and if U == T, it still doesn't make sense + // because you should never have the same object owned by two different + // scoped_ptrs. + template <class U> bool operator==(scoped_ptr<U> const& p2) const; + template <class U> bool operator!=(scoped_ptr<U> const& p2) const; +}; + +template <class T, class D> +class scoped_ptr<T[], D> { + public: + // The element and deleter types. + typedef T element_type; + typedef D deleter_type; + + // Constructor. Defaults to initializing with NULL. + scoped_ptr() : impl_(NULL) { } + + // 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 NULL, because NULL is an integral expression, not a + // pointer to T. Use the no-argument version instead of explicitly + // passing NULL. + // - 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 implicit_cast<const T*>(). + // However, because of the first bullet in this comment, users MUST + // NOT use implicit_cast<Base*>() to upcast the static type of the array. + explicit scoped_ptr(element_type* array) : impl_(array) { } + + // Reset. Deletes the currently owned array, if any. + // Then takes ownership of a new object, if given. + void reset(element_type* array = NULL) { impl_.reset(array); } + + // Accessors to get the owned array. + element_type& operator[](size_t i) const { + assert(impl_.get() != NULL); + return impl_.get()[i]; + } + element_type* get() const { return impl_.get(); } + + // Access to the deleter. + deleter_type& get_deleter() { return impl_.get_deleter(); } + const deleter_type& get_deleter() const { return impl_.get_deleter(); } + + // Allow scoped_ptr<element_type> to be used in boolean expressions, but not + // implicitly convertible to a real bool (which is dangerous). + private: + typedef scoped_ptr_impl<element_type, deleter_type> scoped_ptr::*Testable; + + public: + operator Testable() const { return impl_.get() ? &scoped_ptr::impl_ : NULL; } + + // Comparison operators. + // These return whether two scoped_ptr refer to the same object, not just to + // two different but equal objects. + bool operator==(element_type* array) const { return impl_.get() == array; } + bool operator!=(element_type* array) const { return impl_.get() != array; } + + // Swap two scoped pointers. + void swap(scoped_ptr& p2) { + impl_.swap(p2.impl_); + } + + // 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. + element_type* release() { + return impl_.release(); + } + + private: + // Force element_type to be a complete type. + enum { type_must_be_complete = sizeof(element_type) }; + + // Actually hold the data. + scoped_ptr_impl<element_type, deleter_type> impl_; + + // 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 scoped_ptr(U* array); + explicit scoped_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); + + // Forbid comparison of scoped_ptr types. If U != T, it totally + // doesn't make sense, and if U == T, it still doesn't make sense + // because you should never have the same object owned by two different + // scoped_ptrs. + template <class U> bool operator==(scoped_ptr<U> const& p2) const; + template <class U> bool operator!=(scoped_ptr<U> const& p2) const; +}; + +// Free functions +template <class T, class D> +void swap(scoped_ptr<T, D>& p1, scoped_ptr<T, D>& p2) { + p1.swap(p2); +} + +template <class T, class D> +bool operator==(T* p1, const scoped_ptr<T, D>& p2) { + return p1 == p2.get(); +} + +template <class T, class D> +bool operator!=(T* p1, const scoped_ptr<T, D>& p2) { + return p1 != p2.get(); +} + +// 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); +} + +} // namespace phonenumbers +} // namespace i18n + +#endif // !I18N_PHONENUMBERS_USE_BOOST +#endif // I18N_PHONENUMBERS_BASE_MEMORY_SCOPED_PTR_H_ |