michael@0: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: // Scopers help you manage ownership of a pointer, helping you easily manage the
michael@0: // a pointer within a scope, and automatically destroying the pointer at the
michael@0: // end of a scope.  There are two main classes you will use, which correspond
michael@0: // to the operators new/delete and new[]/delete[].
michael@0: //
michael@0: // Example usage (scoped_ptr<T>):
michael@0: //   {
michael@0: //     scoped_ptr<Foo> foo(new Foo("wee"));
michael@0: //   }  // foo goes out of scope, releasing the pointer with it.
michael@0: //
michael@0: //   {
michael@0: //     scoped_ptr<Foo> foo;          // No pointer managed.
michael@0: //     foo.reset(new Foo("wee"));    // Now a pointer is managed.
michael@0: //     foo.reset(new Foo("wee2"));   // Foo("wee") was destroyed.
michael@0: //     foo.reset(new Foo("wee3"));   // Foo("wee2") was destroyed.
michael@0: //     foo->Method();                // Foo::Method() called.
michael@0: //     foo.get()->Method();          // Foo::Method() called.
michael@0: //     SomeFunc(foo.release());      // SomeFunc takes ownership, foo no longer
michael@0: //                                   // manages a pointer.
michael@0: //     foo.reset(new Foo("wee4"));   // foo manages a pointer again.
michael@0: //     foo.reset();                  // Foo("wee4") destroyed, foo no longer
michael@0: //                                   // manages a pointer.
michael@0: //   }  // foo wasn't managing a pointer, so nothing was destroyed.
michael@0: //
michael@0: // Example usage (scoped_ptr<T[]>):
michael@0: //   {
michael@0: //     scoped_ptr<Foo[]> foo(new Foo[100]);
michael@0: //     foo.get()->Method();  // Foo::Method on the 0th element.
michael@0: //     foo[10].Method();     // Foo::Method on the 10th element.
michael@0: //   }
michael@0: //
michael@0: // These scopers also implement part of the functionality of C++11 unique_ptr
michael@0: // in that they are "movable but not copyable."  You can use the scopers in
michael@0: // the parameter and return types of functions to signify ownership transfer
michael@0: // in to and out of a function.  When calling a function that has a scoper
michael@0: // as the argument type, it must be called with the result of an analogous
michael@0: // scoper's Pass() function or another function that generates a temporary;
michael@0: // passing by copy will NOT work.  Here is an example using scoped_ptr:
michael@0: //
michael@0: //   void TakesOwnership(scoped_ptr<Foo> arg) {
michael@0: //     // Do something with arg
michael@0: //   }
michael@0: //   scoped_ptr<Foo> CreateFoo() {
michael@0: //     // No need for calling Pass() because we are constructing a temporary
michael@0: //     // for the return value.
michael@0: //     return scoped_ptr<Foo>(new Foo("new"));
michael@0: //   }
michael@0: //   scoped_ptr<Foo> PassThru(scoped_ptr<Foo> arg) {
michael@0: //     return arg.Pass();
michael@0: //   }
michael@0: //
michael@0: //   {
michael@0: //     scoped_ptr<Foo> ptr(new Foo("yay"));  // ptr manages Foo("yay").
michael@0: //     TakesOwnership(ptr.Pass());           // ptr no longer owns Foo("yay").
michael@0: //     scoped_ptr<Foo> ptr2 = CreateFoo();   // ptr2 owns the return Foo.
michael@0: //     scoped_ptr<Foo> ptr3 =                // ptr3 now owns what was in ptr2.
michael@0: //         PassThru(ptr2.Pass());            // ptr2 is correspondingly NULL.
michael@0: //   }
michael@0: //
michael@0: // Notice that if you do not call Pass() when returning from PassThru(), or
michael@0: // when invoking TakesOwnership(), the code will not compile because scopers
michael@0: // are not copyable; they only implement move semantics which require calling
michael@0: // the Pass() function to signify a destructive transfer of state. CreateFoo()
michael@0: // is different though because we are constructing a temporary on the return
michael@0: // line and thus can avoid needing to call Pass().
michael@0: //
michael@0: // Pass() properly handles upcast in assignment, i.e. you can assign
michael@0: // scoped_ptr<Child> to scoped_ptr<Parent>:
michael@0: //
michael@0: //   scoped_ptr<Foo> foo(new Foo());
michael@0: //   scoped_ptr<FooParent> parent = foo.Pass();
michael@0: //
michael@0: // PassAs<>() should be used to upcast return value in return statement:
michael@0: //
michael@0: //   scoped_ptr<Foo> CreateFoo() {
michael@0: //     scoped_ptr<FooChild> result(new FooChild());
michael@0: //     return result.PassAs<Foo>();
michael@0: //   }
michael@0: //
michael@0: // Note that PassAs<>() is implemented only for scoped_ptr<T>, but not for
michael@0: // scoped_ptr<T[]>. This is because casting array pointers may not be safe.
michael@0: 
michael@0: #ifndef BASE_MEMORY_SCOPED_PTR_H_
michael@0: #define BASE_MEMORY_SCOPED_PTR_H_
michael@0: 
michael@0: // This is an implementation designed to match the anticipated future TR2
michael@0: // implementation of the scoped_ptr class and scoped_ptr_malloc (deprecated).
michael@0: 
michael@0: #include <assert.h>
michael@0: #include <stddef.h>
michael@0: #include <stdlib.h>
michael@0: 
michael@0: #include <algorithm>  // For std::swap().
michael@0: 
michael@0: #include "base/basictypes.h"
michael@0: #include "base/compiler_specific.h"
michael@0: #include "base/move.h"
michael@0: #include "base/template_util.h"
michael@0: 
michael@0: namespace base {
michael@0: 
michael@0: namespace subtle {
michael@0: class RefCountedBase;
michael@0: class RefCountedThreadSafeBase;
michael@0: }  // namespace subtle
michael@0: 
michael@0: // Function object which deletes its parameter, which must be a pointer.
michael@0: // If C is an array type, invokes 'delete[]' on the parameter; otherwise,
michael@0: // invokes 'delete'. The default deleter for scoped_ptr<T>.
michael@0: template <class T>
michael@0: struct DefaultDeleter {
michael@0:   DefaultDeleter() {}
michael@0:   template <typename U> DefaultDeleter(const DefaultDeleter<U>& other) {
michael@0:     // IMPLEMENTATION NOTE: C++11 20.7.1.1.2p2 only provides this constructor
michael@0:     // if U* is implicitly convertible to T* and U is not an array type.
michael@0:     //
michael@0:     // Correct implementation should use SFINAE to disable this
michael@0:     // constructor. However, since there are no other 1-argument constructors,
michael@0:     // using a COMPILE_ASSERT() based on is_convertible<> and requiring
michael@0:     // complete types is simpler and will cause compile failures for equivalent
michael@0:     // misuses.
michael@0:     //
michael@0:     // Note, the is_convertible<U*, T*> check also ensures that U is not an
michael@0:     // array. T is guaranteed to be a non-array, so any U* where U is an array
michael@0:     // cannot convert to T*.
michael@0:     enum { T_must_be_complete = sizeof(T) };
michael@0:     enum { U_must_be_complete = sizeof(U) };
michael@0:     COMPILE_ASSERT((base::is_convertible<U*, T*>::value),
michael@0:                    U_ptr_must_implicitly_convert_to_T_ptr);
michael@0:   }
michael@0:   inline void operator()(T* ptr) const {
michael@0:     enum { type_must_be_complete = sizeof(T) };
michael@0:     delete ptr;
michael@0:   }
michael@0: };
michael@0: 
michael@0: // Specialization of DefaultDeleter for array types.
michael@0: template <class T>
michael@0: struct DefaultDeleter<T[]> {
michael@0:   inline void operator()(T* ptr) const {
michael@0:     enum { type_must_be_complete = sizeof(T) };
michael@0:     delete[] ptr;
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   // Disable this operator for any U != T because it is undefined to execute
michael@0:   // an array delete when the static type of the array mismatches the dynamic
michael@0:   // type.
michael@0:   //
michael@0:   // References:
michael@0:   //   C++98 [expr.delete]p3
michael@0:   //   http://cplusplus.github.com/LWG/lwg-defects.html#938
michael@0:   template <typename U> void operator()(U* array) const;
michael@0: };
michael@0: 
michael@0: template <class T, int n>
michael@0: struct DefaultDeleter<T[n]> {
michael@0:   // Never allow someone to declare something like scoped_ptr<int[10]>.
michael@0:   COMPILE_ASSERT(sizeof(T) == -1, do_not_use_array_with_size_as_type);
michael@0: };
michael@0: 
michael@0: // Function object which invokes 'free' on its parameter, which must be
michael@0: // a pointer. Can be used to store malloc-allocated pointers in scoped_ptr:
michael@0: //
michael@0: // scoped_ptr<int, base::FreeDeleter> foo_ptr(
michael@0: //     static_cast<int*>(malloc(sizeof(int))));
michael@0: struct FreeDeleter {
michael@0:   inline void operator()(void* ptr) const {
michael@0:     free(ptr);
michael@0:   }
michael@0: };
michael@0: 
michael@0: namespace internal {
michael@0: 
michael@0: template <typename T> struct IsNotRefCounted {
michael@0:   enum {
michael@0:     value = !base::is_convertible<T*, base::subtle::RefCountedBase*>::value &&
michael@0:         !base::is_convertible<T*, base::subtle::RefCountedThreadSafeBase*>::
michael@0:             value
michael@0:   };
michael@0: };
michael@0: 
michael@0: // Minimal implementation of the core logic of scoped_ptr, suitable for
michael@0: // reuse in both scoped_ptr and its specializations.
michael@0: template <class T, class D>
michael@0: class scoped_ptr_impl {
michael@0:  public:
michael@0:   explicit scoped_ptr_impl(T* p) : data_(p) { }
michael@0: 
michael@0:   // Initializer for deleters that have data parameters.
michael@0:   scoped_ptr_impl(T* p, const D& d) : data_(p, d) {}
michael@0: 
michael@0:   // Templated constructor that destructively takes the value from another
michael@0:   // scoped_ptr_impl.
michael@0:   template <typename U, typename V>
michael@0:   scoped_ptr_impl(scoped_ptr_impl<U, V>* other)
michael@0:       : data_(other->release(), other->get_deleter()) {
michael@0:     // We do not support move-only deleters.  We could modify our move
michael@0:     // emulation to have base::subtle::move() and base::subtle::forward()
michael@0:     // functions that are imperfect emulations of their C++11 equivalents,
michael@0:     // but until there's a requirement, just assume deleters are copyable.
michael@0:   }
michael@0: 
michael@0:   template <typename U, typename V>
michael@0:   void TakeState(scoped_ptr_impl<U, V>* other) {
michael@0:     // See comment in templated constructor above regarding lack of support
michael@0:     // for move-only deleters.
michael@0:     reset(other->release());
michael@0:     get_deleter() = other->get_deleter();
michael@0:   }
michael@0: 
michael@0:   ~scoped_ptr_impl() {
michael@0:     if (data_.ptr != NULL) {
michael@0:       // Not using get_deleter() saves one function call in non-optimized
michael@0:       // builds.
michael@0:       static_cast<D&>(data_)(data_.ptr);
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   void reset(T* p) {
michael@0:     // This is a self-reset, which is no longer allowed: http://crbug.com/162971
michael@0:     if (p != NULL && p == data_.ptr)
michael@0:       abort();
michael@0: 
michael@0:     // Note that running data_.ptr = p can lead to undefined behavior if
michael@0:     // get_deleter()(get()) deletes this. In order to pevent this, reset()
michael@0:     // should update the stored pointer before deleting its old value.
michael@0:     //
michael@0:     // However, changing reset() to use that behavior may cause current code to
michael@0:     // break in unexpected ways. If the destruction of the owned object
michael@0:     // dereferences the scoped_ptr when it is destroyed by a call to reset(),
michael@0:     // then it will incorrectly dispatch calls to |p| rather than the original
michael@0:     // value of |data_.ptr|.
michael@0:     //
michael@0:     // During the transition period, set the stored pointer to NULL while
michael@0:     // deleting the object. Eventually, this safety check will be removed to
michael@0:     // prevent the scenario initially described from occuring and
michael@0:     // http://crbug.com/176091 can be closed.
michael@0:     T* old = data_.ptr;
michael@0:     data_.ptr = NULL;
michael@0:     if (old != NULL)
michael@0:       static_cast<D&>(data_)(old);
michael@0:     data_.ptr = p;
michael@0:   }
michael@0: 
michael@0:   T* get() const { return data_.ptr; }
michael@0: 
michael@0:   D& get_deleter() { return data_; }
michael@0:   const D& get_deleter() const { return data_; }
michael@0: 
michael@0:   void swap(scoped_ptr_impl& p2) {
michael@0:     // Standard swap idiom: 'using std::swap' ensures that std::swap is
michael@0:     // present in the overload set, but we call swap unqualified so that
michael@0:     // any more-specific overloads can be used, if available.
michael@0:     using std::swap;
michael@0:     swap(static_cast<D&>(data_), static_cast<D&>(p2.data_));
michael@0:     swap(data_.ptr, p2.data_.ptr);
michael@0:   }
michael@0: 
michael@0:   T* release() {
michael@0:     T* old_ptr = data_.ptr;
michael@0:     data_.ptr = NULL;
michael@0:     return old_ptr;
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   // Needed to allow type-converting constructor.
michael@0:   template <typename U, typename V> friend class scoped_ptr_impl;
michael@0: 
michael@0:   // Use the empty base class optimization to allow us to have a D
michael@0:   // member, while avoiding any space overhead for it when D is an
michael@0:   // empty class.  See e.g. http://www.cantrip.org/emptyopt.html for a good
michael@0:   // discussion of this technique.
michael@0:   struct Data : public D {
michael@0:     explicit Data(T* ptr_in) : ptr(ptr_in) {}
michael@0:     Data(T* ptr_in, const D& other) : D(other), ptr(ptr_in) {}
michael@0:     T* ptr;
michael@0:   };
michael@0: 
michael@0:   Data data_;
michael@0: 
michael@0:   DISALLOW_COPY_AND_ASSIGN(scoped_ptr_impl);
michael@0: };
michael@0: 
michael@0: }  // namespace internal
michael@0: 
michael@0: }  // namespace base
michael@0: 
michael@0: // A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T>
michael@0: // automatically deletes the pointer it holds (if any).
michael@0: // That is, scoped_ptr<T> owns the T object that it points to.
michael@0: // Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object.
michael@0: // Also like T*, scoped_ptr<T> is thread-compatible, and once you
michael@0: // dereference it, you get the thread safety guarantees of T.
michael@0: //
michael@0: // The size of scoped_ptr is small. On most compilers, when using the
michael@0: // DefaultDeleter, sizeof(scoped_ptr<T>) == sizeof(T*). Custom deleters will
michael@0: // increase the size proportional to whatever state they need to have. See
michael@0: // comments inside scoped_ptr_impl<> for details.
michael@0: //
michael@0: // Current implementation targets having a strict subset of  C++11's
michael@0: // unique_ptr<> features. Known deficiencies include not supporting move-only
michael@0: // deleteres, function pointers as deleters, and deleters with reference
michael@0: // types.
michael@0: template <class T, class D = base::DefaultDeleter<T> >
michael@0: class scoped_ptr {
michael@0:   MOVE_ONLY_TYPE_FOR_CPP_03(scoped_ptr, RValue)
michael@0: 
michael@0:   COMPILE_ASSERT(base::internal::IsNotRefCounted<T>::value,
michael@0:                  T_is_refcounted_type_and_needs_scoped_refptr);
michael@0: 
michael@0:  public:
michael@0:   // The element and deleter types.
michael@0:   typedef T element_type;
michael@0:   typedef D deleter_type;
michael@0: 
michael@0:   // Constructor.  Defaults to initializing with NULL.
michael@0:   scoped_ptr() : impl_(NULL) { }
michael@0: 
michael@0:   // Constructor.  Takes ownership of p.
michael@0:   explicit scoped_ptr(element_type* p) : impl_(p) { }
michael@0: 
michael@0:   // Constructor.  Allows initialization of a stateful deleter.
michael@0:   scoped_ptr(element_type* p, const D& d) : impl_(p, d) { }
michael@0: 
michael@0:   // Constructor.  Allows construction from a scoped_ptr rvalue for a
michael@0:   // convertible type and deleter.
michael@0:   //
michael@0:   // IMPLEMENTATION NOTE: C++11 unique_ptr<> keeps this constructor distinct
michael@0:   // from the normal move constructor. By C++11 20.7.1.2.1.21, this constructor
michael@0:   // has different post-conditions if D is a reference type. Since this
michael@0:   // implementation does not support deleters with reference type,
michael@0:   // we do not need a separate move constructor allowing us to avoid one
michael@0:   // use of SFINAE. You only need to care about this if you modify the
michael@0:   // implementation of scoped_ptr.
michael@0:   template <typename U, typename V>
michael@0:   scoped_ptr(scoped_ptr<U, V> other) : impl_(&other.impl_) {
michael@0:     COMPILE_ASSERT(!base::is_array<U>::value, U_cannot_be_an_array);
michael@0:   }
michael@0: 
michael@0:   // Constructor.  Move constructor for C++03 move emulation of this type.
michael@0:   scoped_ptr(RValue rvalue) : impl_(&rvalue.object->impl_) { }
michael@0: 
michael@0:   // operator=.  Allows assignment from a scoped_ptr rvalue for a convertible
michael@0:   // type and deleter.
michael@0:   //
michael@0:   // IMPLEMENTATION NOTE: C++11 unique_ptr<> keeps this operator= distinct from
michael@0:   // the normal move assignment operator. By C++11 20.7.1.2.3.4, this templated
michael@0:   // form has different requirements on for move-only Deleters. Since this
michael@0:   // implementation does not support move-only Deleters, we do not need a
michael@0:   // separate move assignment operator allowing us to avoid one use of SFINAE.
michael@0:   // You only need to care about this if you modify the implementation of
michael@0:   // scoped_ptr.
michael@0:   template <typename U, typename V>
michael@0:   scoped_ptr& operator=(scoped_ptr<U, V> rhs) {
michael@0:     COMPILE_ASSERT(!base::is_array<U>::value, U_cannot_be_an_array);
michael@0:     impl_.TakeState(&rhs.impl_);
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0:   // Reset.  Deletes the currently owned object, if any.
michael@0:   // Then takes ownership of a new object, if given.
michael@0:   void reset(element_type* p = NULL) { impl_.reset(p); }
michael@0: 
michael@0:   // Accessors to get the owned object.
michael@0:   // operator* and operator-> will assert() if there is no current object.
michael@0:   element_type& operator*() const {
michael@0:     assert(impl_.get() != NULL);
michael@0:     return *impl_.get();
michael@0:   }
michael@0:   element_type* operator->() const  {
michael@0:     assert(impl_.get() != NULL);
michael@0:     return impl_.get();
michael@0:   }
michael@0:   element_type* get() const { return impl_.get(); }
michael@0: 
michael@0:   // Access to the deleter.
michael@0:   deleter_type& get_deleter() { return impl_.get_deleter(); }
michael@0:   const deleter_type& get_deleter() const { return impl_.get_deleter(); }
michael@0: 
michael@0:   // Allow scoped_ptr<element_type> to be used in boolean expressions, but not
michael@0:   // implicitly convertible to a real bool (which is dangerous).
michael@0:   //
michael@0:   // Note that this trick is only safe when the == and != operators
michael@0:   // are declared explicitly, as otherwise "scoped_ptr1 ==
michael@0:   // scoped_ptr2" will compile but do the wrong thing (i.e., convert
michael@0:   // to Testable and then do the comparison).
michael@0:  private:
michael@0:   typedef base::internal::scoped_ptr_impl<element_type, deleter_type>
michael@0:       scoped_ptr::*Testable;
michael@0: 
michael@0:  public:
michael@0:   operator Testable() const { return impl_.get() ? &scoped_ptr::impl_ : NULL; }
michael@0: 
michael@0:   // Comparison operators.
michael@0:   // These return whether two scoped_ptr refer to the same object, not just to
michael@0:   // two different but equal objects.
michael@0:   bool operator==(const element_type* p) const { return impl_.get() == p; }
michael@0:   bool operator!=(const element_type* p) const { return impl_.get() != p; }
michael@0: 
michael@0:   // Swap two scoped pointers.
michael@0:   void swap(scoped_ptr& p2) {
michael@0:     impl_.swap(p2.impl_);
michael@0:   }
michael@0: 
michael@0:   // Release a pointer.
michael@0:   // The return value is the current pointer held by this object.
michael@0:   // If this object holds a NULL pointer, the return value is NULL.
michael@0:   // After this operation, this object will hold a NULL pointer,
michael@0:   // and will not own the object any more.
michael@0:   element_type* release() WARN_UNUSED_RESULT {
michael@0:     return impl_.release();
michael@0:   }
michael@0: 
michael@0:   // C++98 doesn't support functions templates with default parameters which
michael@0:   // makes it hard to write a PassAs() that understands converting the deleter
michael@0:   // while preserving simple calling semantics.
michael@0:   //
michael@0:   // Until there is a use case for PassAs() with custom deleters, just ignore
michael@0:   // the custom deleter.
michael@0:   template <typename PassAsType>
michael@0:   scoped_ptr<PassAsType> PassAs() {
michael@0:     return scoped_ptr<PassAsType>(Pass());
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   // Needed to reach into |impl_| in the constructor.
michael@0:   template <typename U, typename V> friend class scoped_ptr;
michael@0:   base::internal::scoped_ptr_impl<element_type, deleter_type> impl_;
michael@0: 
michael@0:   // Forbidden for API compatibility with std::unique_ptr.
michael@0:   explicit scoped_ptr(int disallow_construction_from_null);
michael@0: 
michael@0:   // Forbid comparison of scoped_ptr types.  If U != T, it totally
michael@0:   // doesn't make sense, and if U == T, it still doesn't make sense
michael@0:   // because you should never have the same object owned by two different
michael@0:   // scoped_ptrs.
michael@0:   template <class U> bool operator==(scoped_ptr<U> const& p2) const;
michael@0:   template <class U> bool operator!=(scoped_ptr<U> const& p2) const;
michael@0: };
michael@0: 
michael@0: template <class T, class D>
michael@0: class scoped_ptr<T[], D> {
michael@0:   MOVE_ONLY_TYPE_FOR_CPP_03(scoped_ptr, RValue)
michael@0: 
michael@0:  public:
michael@0:   // The element and deleter types.
michael@0:   typedef T element_type;
michael@0:   typedef D deleter_type;
michael@0: 
michael@0:   // Constructor.  Defaults to initializing with NULL.
michael@0:   scoped_ptr() : impl_(NULL) { }
michael@0: 
michael@0:   // Constructor. Stores the given array. Note that the argument's type
michael@0:   // must exactly match T*. In particular:
michael@0:   // - it cannot be a pointer to a type derived from T, because it is
michael@0:   //   inherently unsafe in the general case to access an array through a
michael@0:   //   pointer whose dynamic type does not match its static type (eg., if
michael@0:   //   T and the derived types had different sizes access would be
michael@0:   //   incorrectly calculated). Deletion is also always undefined
michael@0:   //   (C++98 [expr.delete]p3). If you're doing this, fix your code.
michael@0:   // - it cannot be NULL, because NULL is an integral expression, not a
michael@0:   //   pointer to T. Use the no-argument version instead of explicitly
michael@0:   //   passing NULL.
michael@0:   // - it cannot be const-qualified differently from T per unique_ptr spec
michael@0:   //   (http://cplusplus.github.com/LWG/lwg-active.html#2118). Users wanting
michael@0:   //   to work around this may use implicit_cast<const T*>().
michael@0:   //   However, because of the first bullet in this comment, users MUST
michael@0:   //   NOT use implicit_cast<Base*>() to upcast the static type of the array.
michael@0:   explicit scoped_ptr(element_type* array) : impl_(array) { }
michael@0: 
michael@0:   // Constructor.  Move constructor for C++03 move emulation of this type.
michael@0:   scoped_ptr(RValue rvalue) : impl_(&rvalue.object->impl_) { }
michael@0: 
michael@0:   // operator=.  Move operator= for C++03 move emulation of this type.
michael@0:   scoped_ptr& operator=(RValue rhs) {
michael@0:     impl_.TakeState(&rhs.object->impl_);
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0:   // Reset.  Deletes the currently owned array, if any.
michael@0:   // Then takes ownership of a new object, if given.
michael@0:   void reset(element_type* array = NULL) { impl_.reset(array); }
michael@0: 
michael@0:   // Accessors to get the owned array.
michael@0:   element_type& operator[](size_t i) const {
michael@0:     assert(impl_.get() != NULL);
michael@0:     return impl_.get()[i];
michael@0:   }
michael@0:   element_type* get() const { return impl_.get(); }
michael@0: 
michael@0:   // Access to the deleter.
michael@0:   deleter_type& get_deleter() { return impl_.get_deleter(); }
michael@0:   const deleter_type& get_deleter() const { return impl_.get_deleter(); }
michael@0: 
michael@0:   // Allow scoped_ptr<element_type> to be used in boolean expressions, but not
michael@0:   // implicitly convertible to a real bool (which is dangerous).
michael@0:  private:
michael@0:   typedef base::internal::scoped_ptr_impl<element_type, deleter_type>
michael@0:       scoped_ptr::*Testable;
michael@0: 
michael@0:  public:
michael@0:   operator Testable() const { return impl_.get() ? &scoped_ptr::impl_ : NULL; }
michael@0: 
michael@0:   // Comparison operators.
michael@0:   // These return whether two scoped_ptr refer to the same object, not just to
michael@0:   // two different but equal objects.
michael@0:   bool operator==(element_type* array) const { return impl_.get() == array; }
michael@0:   bool operator!=(element_type* array) const { return impl_.get() != array; }
michael@0: 
michael@0:   // Swap two scoped pointers.
michael@0:   void swap(scoped_ptr& p2) {
michael@0:     impl_.swap(p2.impl_);
michael@0:   }
michael@0: 
michael@0:   // Release a pointer.
michael@0:   // The return value is the current pointer held by this object.
michael@0:   // If this object holds a NULL pointer, the return value is NULL.
michael@0:   // After this operation, this object will hold a NULL pointer,
michael@0:   // and will not own the object any more.
michael@0:   element_type* release() WARN_UNUSED_RESULT {
michael@0:     return impl_.release();
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   // Force element_type to be a complete type.
michael@0:   enum { type_must_be_complete = sizeof(element_type) };
michael@0: 
michael@0:   // Actually hold the data.
michael@0:   base::internal::scoped_ptr_impl<element_type, deleter_type> impl_;
michael@0: 
michael@0:   // Disable initialization from any type other than element_type*, by
michael@0:   // providing a constructor that matches such an initialization, but is
michael@0:   // private and has no definition. This is disabled because it is not safe to
michael@0:   // call delete[] on an array whose static type does not match its dynamic
michael@0:   // type.
michael@0:   template <typename U> explicit scoped_ptr(U* array);
michael@0:   explicit scoped_ptr(int disallow_construction_from_null);
michael@0: 
michael@0:   // Disable reset() from any type other than element_type*, for the same
michael@0:   // reasons as the constructor above.
michael@0:   template <typename U> void reset(U* array);
michael@0:   void reset(int disallow_reset_from_null);
michael@0: 
michael@0:   // Forbid comparison of scoped_ptr types.  If U != T, it totally
michael@0:   // doesn't make sense, and if U == T, it still doesn't make sense
michael@0:   // because you should never have the same object owned by two different
michael@0:   // scoped_ptrs.
michael@0:   template <class U> bool operator==(scoped_ptr<U> const& p2) const;
michael@0:   template <class U> bool operator!=(scoped_ptr<U> const& p2) const;
michael@0: };
michael@0: 
michael@0: // Free functions
michael@0: template <class T, class D>
michael@0: void swap(scoped_ptr<T, D>& p1, scoped_ptr<T, D>& p2) {
michael@0:   p1.swap(p2);
michael@0: }
michael@0: 
michael@0: template <class T, class D>
michael@0: bool operator==(T* p1, const scoped_ptr<T, D>& p2) {
michael@0:   return p1 == p2.get();
michael@0: }
michael@0: 
michael@0: template <class T, class D>
michael@0: bool operator!=(T* p1, const scoped_ptr<T, D>& p2) {
michael@0:   return p1 != p2.get();
michael@0: }
michael@0: 
michael@0: // DEPRECATED: Use scoped_ptr<C, base::FreeDeleter> instead.
michael@0: //
michael@0: // scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a
michael@0: // second template argument, the functor used to free the object.
michael@0: 
michael@0: template<class C, class FreeProc = base::FreeDeleter>
michael@0: class scoped_ptr_malloc {
michael@0:   MOVE_ONLY_TYPE_FOR_CPP_03(scoped_ptr_malloc, RValue)
michael@0: 
michael@0:  public:
michael@0: 
michael@0:   // The element type
michael@0:   typedef C element_type;
michael@0: 
michael@0:   // Constructor.  Defaults to initializing with NULL.
michael@0:   // There is no way to create an uninitialized scoped_ptr.
michael@0:   // The input parameter must be allocated with an allocator that matches the
michael@0:   // Free functor.  For the default Free functor, this is malloc, calloc, or
michael@0:   // realloc.
michael@0:   explicit scoped_ptr_malloc(C* p = NULL): ptr_(p) {}
michael@0: 
michael@0:   // Constructor.  Move constructor for C++03 move emulation of this type.
michael@0:   scoped_ptr_malloc(RValue rvalue)
michael@0:       : ptr_(rvalue.object->release()) {
michael@0:   }
michael@0: 
michael@0:   // Destructor.  If there is a C object, call the Free functor.
michael@0:   ~scoped_ptr_malloc() {
michael@0:     reset();
michael@0:   }
michael@0: 
michael@0:   // operator=.  Move operator= for C++03 move emulation of this type.
michael@0:   scoped_ptr_malloc& operator=(RValue rhs) {
michael@0:     reset(rhs.object->release());
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0:   // Reset.  Calls the Free functor on the current owned object, if any.
michael@0:   // Then takes ownership of a new object, if given.
michael@0:   // this->reset(this->get()) works.
michael@0:   void reset(C* p = NULL) {
michael@0:     if (ptr_ != p) {
michael@0:       if (ptr_ != NULL) {
michael@0:         FreeProc free_proc;
michael@0:         free_proc(ptr_);
michael@0:       }
michael@0:       ptr_ = p;
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   // Get the current object.
michael@0:   // operator* and operator-> will cause an assert() failure if there is
michael@0:   // no current object.
michael@0:   C& operator*() const {
michael@0:     assert(ptr_ != NULL);
michael@0:     return *ptr_;
michael@0:   }
michael@0: 
michael@0:   C* operator->() const {
michael@0:     assert(ptr_ != NULL);
michael@0:     return ptr_;
michael@0:   }
michael@0: 
michael@0:   C* get() const {
michael@0:     return ptr_;
michael@0:   }
michael@0: 
michael@0:   // Allow scoped_ptr_malloc<C> to be used in boolean expressions, but not
michael@0:   // implicitly convertible to a real bool (which is dangerous).
michael@0:   typedef C* scoped_ptr_malloc::*Testable;
michael@0:   operator Testable() const { return ptr_ ? &scoped_ptr_malloc::ptr_ : NULL; }
michael@0: 
michael@0:   // Comparison operators.
michael@0:   // These return whether a scoped_ptr_malloc and a plain pointer refer
michael@0:   // to the same object, not just to two different but equal objects.
michael@0:   // For compatibility with the boost-derived implementation, these
michael@0:   // take non-const arguments.
michael@0:   bool operator==(C* p) const {
michael@0:     return ptr_ == p;
michael@0:   }
michael@0: 
michael@0:   bool operator!=(C* p) const {
michael@0:     return ptr_ != p;
michael@0:   }
michael@0: 
michael@0:   // Swap two scoped pointers.
michael@0:   void swap(scoped_ptr_malloc & b) {
michael@0:     C* tmp = b.ptr_;
michael@0:     b.ptr_ = ptr_;
michael@0:     ptr_ = tmp;
michael@0:   }
michael@0: 
michael@0:   // Release a pointer.
michael@0:   // The return value is the current pointer held by this object.
michael@0:   // If this object holds a NULL pointer, the return value is NULL.
michael@0:   // After this operation, this object will hold a NULL pointer,
michael@0:   // and will not own the object any more.
michael@0:   C* release() WARN_UNUSED_RESULT {
michael@0:     C* tmp = ptr_;
michael@0:     ptr_ = NULL;
michael@0:     return tmp;
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   C* ptr_;
michael@0: 
michael@0:   // no reason to use these: each scoped_ptr_malloc should have its own object
michael@0:   template <class C2, class GP>
michael@0:   bool operator==(scoped_ptr_malloc<C2, GP> const& p) const;
michael@0:   template <class C2, class GP>
michael@0:   bool operator!=(scoped_ptr_malloc<C2, GP> const& p) const;
michael@0: };
michael@0: 
michael@0: template<class C, class FP> inline
michael@0: void swap(scoped_ptr_malloc<C, FP>& a, scoped_ptr_malloc<C, FP>& b) {
michael@0:   a.swap(b);
michael@0: }
michael@0: 
michael@0: template<class C, class FP> inline
michael@0: bool operator==(C* p, const scoped_ptr_malloc<C, FP>& b) {
michael@0:   return p == b.get();
michael@0: }
michael@0: 
michael@0: template<class C, class FP> inline
michael@0: bool operator!=(C* p, const scoped_ptr_malloc<C, FP>& b) {
michael@0:   return p != b.get();
michael@0: }
michael@0: 
michael@0: // A function to convert T* into scoped_ptr<T>
michael@0: // Doing e.g. make_scoped_ptr(new FooBarBaz<type>(arg)) is a shorter notation
michael@0: // for scoped_ptr<FooBarBaz<type> >(new FooBarBaz<type>(arg))
michael@0: template <typename T>
michael@0: scoped_ptr<T> make_scoped_ptr(T* ptr) {
michael@0:   return scoped_ptr<T>(ptr);
michael@0: }
michael@0: 
michael@0: #endif  // BASE_MEMORY_SCOPED_PTR_H_