Move base to DEPS

base/memory/scoped_ptr.h

-// 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.
-//   }
-//
-// 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 the result of an analogous
-// scoper's Pass() function or 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 Pass() because we are constructing a temporary
-//     // for the return value.
-//     return scoped_ptr<Foo>(new Foo("new"));
-//   }
-//   scoped_ptr<Foo> PassThru(scoped_ptr<Foo> arg) {
-//     return arg.Pass();
-//   }
-//
-//   {
-//     scoped_ptr<Foo> ptr(new Foo("yay"));  // ptr manages Foo("yay").
-//     TakesOwnership(ptr.Pass());           // 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(ptr2.Pass());            // ptr2 is correspondingly nullptr.
-//   }
-//
-// Notice that if you do not call Pass() 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 Pass() 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 Pass().
-//
-// Pass() 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(foo.Pass());
-
-#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.
-
-#include <assert.h>
-#include <stddef.h>
-#include <stdlib.h>
-
-#include <algorithm>  // For std::swap().
-#include <iosfwd>
-
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "base/move.h"
-#include "base/template_util.h"
-
-namespace base {
-
-namespace subtle {
-class RefCountedBase;
-class RefCountedThreadSafeBase;
-}  // namespace subtle
-
-// 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((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 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);
-  }
-};
-
-namespace internal {
-
-template <typename T> struct IsNotRefCounted {
-  enum {
-    value = !base::is_convertible<T*, base::subtle::RefCountedBase*>::value &&
-        !base::is_convertible<T*, base::subtle::RefCountedThreadSafeBase*>::
-            value
-  };
-};
-
-template <typename T>
-struct ShouldAbortOnSelfReset {
-  template <typename U>
-  static NoType Test(const typename U::AllowSelfReset*);
-
-  template <typename U>
-  static YesType Test(...);
-
-  static const bool value = sizeof(Test<T>(0)) == sizeof(YesType);
-};
-
-// 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 != nullptr) {
-      // 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 for default deleters:
-    // https://crbug.com/162971
-    assert(!ShouldAbortOnSelfReset<D>::value || p == nullptr || p != data_.ptr);
-
-    // Note that running data_.ptr = p can lead to undefined behavior if
-    // get_deleter()(get()) deletes this. In order to prevent 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 nullptr 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 = nullptr;
-    if (old != nullptr)
-      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 = nullptr;
-    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);
-};
-
-}  // namespace internal
-
-}  // namespace base
-
-// 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 nullptr 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 = base::DefaultDeleter<T> >
-class scoped_ptr {
-  MOVE_ONLY_TYPE_WITH_MOVE_CONSTRUCTOR_FOR_CPP_03(scoped_ptr)
-
-  COMPILE_ASSERT(base::internal::IsNotRefCounted<T>::value,
-                 T_is_refcounted_type_and_needs_scoped_refptr);
-
- public:
-  // The element and deleter types.
-  typedef T element_type;
-  typedef D deleter_type;
-
-  // Constructor.  Defaults to initializing with nullptr.
-  scoped_ptr() : impl_(nullptr) {}
-
-  // 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 nullptr.
-  scoped_ptr(decltype(nullptr)) : impl_(nullptr) {}
-
-  // 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(!base::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(!base::is_array<U>::value, U_cannot_be_an_array);
-    impl_.TakeState(&rhs.impl_);
-    return *this;
-  }
-
-  // operator=.  Allows assignment from a nullptr. Deletes the currently owned
-  // object, if any.
-  scoped_ptr& operator=(decltype(nullptr)) {
-    reset();
-    return *this;
-  }
-
-  // Reset.  Deletes the currently owned object, if any.
-  // Then takes ownership of a new object, if given.
-  void reset(element_type* p = nullptr) { 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() != nullptr);
-    return *impl_.get();
-  }
-  element_type* operator->() const  {
-    assert(impl_.get() != nullptr);
-    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).
-  //
-  // Note that this trick is only safe when the == and != operators
-  // are declared explicitly, as otherwise "scoped_ptr1 ==
-  // scoped_ptr2" will compile but do the wrong thing (i.e., convert
-  // to Testable and then do the comparison).
- private:
-  typedef base::internal::scoped_ptr_impl<element_type, deleter_type>
-      scoped_ptr::*Testable;
-
- public:
-  operator Testable() const {
-    return impl_.get() ? &scoped_ptr::impl_ : nullptr;
-  }
-
-  // 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 nullptr, the return value is nullptr. After this operation, this
-  // object will hold a nullptr, and will not own the object any more.
-  element_type* release() WARN_UNUSED_RESULT {
-    return impl_.release();
-  }
-
- private:
-  // Needed to reach into |impl_| in the constructor.
-  template <typename U, typename V> friend class scoped_ptr;
-  base::internal::scoped_ptr_impl<element_type, deleter_type> impl_;
-
-  // Forbidden for API compatibility with std::unique_ptr.
-  explicit scoped_ptr(int disallow_construction_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;
-};
-
-template <class T, class D>
-class scoped_ptr<T[], D> {
-  MOVE_ONLY_TYPE_WITH_MOVE_CONSTRUCTOR_FOR_CPP_03(scoped_ptr)
-
- public:
-  // The element and deleter types.
-  typedef T element_type;
-  typedef D deleter_type;
-
-  // Constructor.  Defaults to initializing with nullptr.
-  scoped_ptr() : impl_(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 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) {}
-
-  // Constructor.  Allows construction from a nullptr.
-  scoped_ptr(decltype(nullptr)) : impl_(nullptr) {}
-
-  // Constructor.  Allows construction from a scoped_ptr rvalue.
-  scoped_ptr(scoped_ptr&& other) : impl_(&other.impl_) {}
-
-  // operator=.  Allows assignment from a scoped_ptr rvalue.
-  scoped_ptr& operator=(scoped_ptr&& rhs) {
-    impl_.TakeState(&rhs.impl_);
-    return *this;
-  }
-
-  // operator=.  Allows assignment from a nullptr. Deletes the currently owned
-  // array, if any.
-  scoped_ptr& operator=(decltype(nullptr)) {
-    reset();
-    return *this;
-  }
-
-  // Reset.  Deletes the currently owned array, if any.
-  // Then takes ownership of a new object, if given.
-  void reset(element_type* array = nullptr) { impl_.reset(array); }
-
-  // Accessors to get the owned array.
-  element_type& operator[](size_t i) const {
-    assert(impl_.get() != nullptr);
-    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 base::internal::scoped_ptr_impl<element_type, deleter_type>
-      scoped_ptr::*Testable;
-
- public:
-  operator Testable() const {
-    return impl_.get() ? &scoped_ptr::impl_ : nullptr;
-  }
-
-  // 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 nullptr, the return value is nullptr. After this operation, this
-  // object will hold a nullptr, and will not own the object any more.
-  element_type* release() WARN_UNUSED_RESULT {
-    return impl_.release();
-  }
-
- private:
-  // Force element_type to be a complete type.
-  enum { type_must_be_complete = sizeof(element_type) };
-
-  // Actually hold the data.
-  base::internal::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);
-}
-
-template <typename T>
-std::ostream& operator<<(std::ostream& out, const scoped_ptr<T>& p) {
-  return out << p.get();
-}
-
-#endif  // BASE_MEMORY_SCOPED_PTR_H_