mirror of
https://github.com/classilla/tenfourfox.git
synced 2024-09-10 11:54:40 +00:00
652 lines
21 KiB
C
652 lines
21 KiB
C
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
||
|
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
|
||
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
||
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
||
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
||
|
|
||
|
/* Smart pointer managing sole ownership of a resource. */
|
||
|
|
||
|
#ifndef mozilla_UniquePtr_h
|
||
|
#define mozilla_UniquePtr_h
|
||
|
|
||
|
#include "mozilla/Assertions.h"
|
||
|
#include "mozilla/Attributes.h"
|
||
|
#include "mozilla/Compiler.h"
|
||
|
#include "mozilla/Move.h"
|
||
|
#include "mozilla/Pair.h"
|
||
|
#include "mozilla/TypeTraits.h"
|
||
|
|
||
|
namespace mozilla {
|
||
|
|
||
|
template<typename T> class DefaultDelete;
|
||
|
template<typename T, class D = DefaultDelete<T>> class UniquePtr;
|
||
|
|
||
|
} // namespace mozilla
|
||
|
|
||
|
namespace mozilla {
|
||
|
|
||
|
/**
|
||
|
* UniquePtr is a smart pointer that wholly owns a resource. Ownership may be
|
||
|
* transferred out of a UniquePtr through explicit action, but otherwise the
|
||
|
* resource is destroyed when the UniquePtr is destroyed.
|
||
|
*
|
||
|
* UniquePtr is similar to C++98's std::auto_ptr, but it improves upon auto_ptr
|
||
|
* in one crucial way: it's impossible to copy a UniquePtr. Copying an auto_ptr
|
||
|
* obviously *can't* copy ownership of its singly-owned resource. So what
|
||
|
* happens if you try to copy one? Bizarrely, ownership is implicitly
|
||
|
* *transferred*, preserving single ownership but breaking code that assumes a
|
||
|
* copy of an object is identical to the original. (This is why auto_ptr is
|
||
|
* prohibited in STL containers.)
|
||
|
*
|
||
|
* UniquePtr solves this problem by being *movable* rather than copyable.
|
||
|
* Instead of passing a |UniquePtr u| directly to the constructor or assignment
|
||
|
* operator, you pass |Move(u)|. In doing so you indicate that you're *moving*
|
||
|
* ownership out of |u|, into the target of the construction/assignment. After
|
||
|
* the transfer completes, |u| contains |nullptr| and may be safely destroyed.
|
||
|
* This preserves single ownership but also allows UniquePtr to be moved by
|
||
|
* algorithms that have been made move-safe. (Note: if |u| is instead a
|
||
|
* temporary expression, don't use |Move()|: just pass the expression, because
|
||
|
* it's already move-ready. For more information see Move.h.)
|
||
|
*
|
||
|
* UniquePtr is also better than std::auto_ptr in that the deletion operation is
|
||
|
* customizable. An optional second template parameter specifies a class that
|
||
|
* (through its operator()(T*)) implements the desired deletion policy. If no
|
||
|
* policy is specified, mozilla::DefaultDelete<T> is used -- which will either
|
||
|
* |delete| or |delete[]| the resource, depending whether the resource is an
|
||
|
* array. Custom deletion policies ideally should be empty classes (no member
|
||
|
* fields, no member fields in base classes, no virtual methods/inheritance),
|
||
|
* because then UniquePtr can be just as efficient as a raw pointer.
|
||
|
*
|
||
|
* Use of UniquePtr proceeds like so:
|
||
|
*
|
||
|
* UniquePtr<int> g1; // initializes to nullptr
|
||
|
* g1.reset(new int); // switch resources using reset()
|
||
|
* g1 = nullptr; // clears g1, deletes the int
|
||
|
*
|
||
|
* UniquePtr<int> g2(new int); // owns that int
|
||
|
* int* p = g2.release(); // g2 leaks its int -- still requires deletion
|
||
|
* delete p; // now freed
|
||
|
*
|
||
|
* struct S { int x; S(int x) : x(x) {} };
|
||
|
* UniquePtr<S> g3, g4(new S(5));
|
||
|
* g3 = Move(g4); // g3 owns the S, g4 cleared
|
||
|
* S* p = g3.get(); // g3 still owns |p|
|
||
|
* assert(g3->x == 5); // operator-> works (if .get() != nullptr)
|
||
|
* assert((*g3).x == 5); // also operator* (again, if not cleared)
|
||
|
* Swap(g3, g4); // g4 now owns the S, g3 cleared
|
||
|
* g3.swap(g4); // g3 now owns the S, g4 cleared
|
||
|
* UniquePtr<S> g5(Move(g3)); // g5 owns the S, g3 cleared
|
||
|
* g5.reset(); // deletes the S, g5 cleared
|
||
|
*
|
||
|
* struct FreePolicy { void operator()(void* p) { free(p); } };
|
||
|
* UniquePtr<int, FreePolicy> g6(static_cast<int*>(malloc(sizeof(int))));
|
||
|
* int* ptr = g6.get();
|
||
|
* g6 = nullptr; // calls free(ptr)
|
||
|
*
|
||
|
* Now, carefully note a few things you *can't* do:
|
||
|
*
|
||
|
* UniquePtr<int> b1;
|
||
|
* b1 = new int; // BAD: can only assign another UniquePtr
|
||
|
* int* ptr = b1; // BAD: no auto-conversion to pointer, use get()
|
||
|
*
|
||
|
* UniquePtr<int> b2(b1); // BAD: can't copy a UniquePtr
|
||
|
* UniquePtr<int> b3 = b1; // BAD: can't copy-assign a UniquePtr
|
||
|
*
|
||
|
* (Note that changing a UniquePtr to store a direct |new| expression is
|
||
|
* permitted, but usually you should use MakeUnique, defined at the end of this
|
||
|
* header.)
|
||
|
*
|
||
|
* A few miscellaneous notes:
|
||
|
*
|
||
|
* UniquePtr, when not instantiated for an array type, can be move-constructed
|
||
|
* and move-assigned, not only from itself but from "derived" UniquePtr<U, E>
|
||
|
* instantiations where U converts to T and E converts to D. If you want to use
|
||
|
* this, you're going to have to specify a deletion policy for both UniquePtr
|
||
|
* instantations, and T pretty much has to have a virtual destructor. In other
|
||
|
* words, this doesn't work:
|
||
|
*
|
||
|
* struct Base { virtual ~Base() {} };
|
||
|
* struct Derived : Base {};
|
||
|
*
|
||
|
* UniquePtr<Base> b1;
|
||
|
* // BAD: DefaultDelete<Base> and DefaultDelete<Derived> don't interconvert
|
||
|
* UniquePtr<Derived> d1(Move(b));
|
||
|
*
|
||
|
* UniquePtr<Base> b2;
|
||
|
* UniquePtr<Derived, DefaultDelete<Base>> d2(Move(b2)); // okay
|
||
|
*
|
||
|
* UniquePtr is specialized for array types. Specializing with an array type
|
||
|
* creates a smart-pointer version of that array -- not a pointer to such an
|
||
|
* array.
|
||
|
*
|
||
|
* UniquePtr<int[]> arr(new int[5]);
|
||
|
* arr[0] = 4;
|
||
|
*
|
||
|
* What else is different? Deletion of course uses |delete[]|. An operator[]
|
||
|
* is provided. Functionality that doesn't make sense for arrays is removed.
|
||
|
* The constructors and mutating methods only accept array pointers (not T*, U*
|
||
|
* that converts to T*, or UniquePtr<U[]> or UniquePtr<U>) or |nullptr|.
|
||
|
*
|
||
|
* It's perfectly okay to return a UniquePtr from a method to assure the related
|
||
|
* resource is properly deleted. You'll need to use |Move()| when returning a
|
||
|
* local UniquePtr. Otherwise you can return |nullptr|, or you can return
|
||
|
* |UniquePtr(ptr)|.
|
||
|
*
|
||
|
* UniquePtr will commonly be a member of a class, with lifetime equivalent to
|
||
|
* that of that class. If you want to expose the related resource, you could
|
||
|
* expose a raw pointer via |get()|, but ownership of a raw pointer is
|
||
|
* inherently unclear. So it's better to expose a |const UniquePtr&| instead.
|
||
|
* This prohibits mutation but still allows use of |get()| when needed (but
|
||
|
* operator-> is preferred). Of course, you can only use this smart pointer as
|
||
|
* long as the enclosing class instance remains live -- no different than if you
|
||
|
* exposed the |get()| raw pointer.
|
||
|
*
|
||
|
* To pass a UniquePtr-managed resource as a pointer, use a |const UniquePtr&|
|
||
|
* argument. To specify an inout parameter (where the method may or may not
|
||
|
* take ownership of the resource, or reset it), or to specify an out parameter
|
||
|
* (where simply returning a |UniquePtr| isn't possible), use a |UniquePtr&|
|
||
|
* argument. To unconditionally transfer ownership of a UniquePtr
|
||
|
* into a method, use a |UniquePtr| argument. To conditionally transfer
|
||
|
* ownership of a resource into a method, should the method want it, use a
|
||
|
* |UniquePtr&&| argument.
|
||
|
*/
|
||
|
template<typename T, class D>
|
||
|
class UniquePtr
|
||
|
{
|
||
|
public:
|
||
|
typedef T* Pointer;
|
||
|
typedef T ElementType;
|
||
|
typedef D DeleterType;
|
||
|
|
||
|
private:
|
||
|
Pair<Pointer, DeleterType> mTuple;
|
||
|
|
||
|
Pointer& ptr() { return mTuple.first(); }
|
||
|
const Pointer& ptr() const { return mTuple.first(); }
|
||
|
|
||
|
DeleterType& del() { return mTuple.second(); }
|
||
|
const DeleterType& del() const { return mTuple.second(); }
|
||
|
|
||
|
public:
|
||
|
/**
|
||
|
* Construct a UniquePtr containing |nullptr|.
|
||
|
*/
|
||
|
MOZ_CONSTEXPR UniquePtr()
|
||
|
: mTuple(static_cast<Pointer>(nullptr), DeleterType())
|
||
|
{
|
||
|
static_assert(!IsPointer<D>::value, "must provide a deleter instance");
|
||
|
static_assert(!IsReference<D>::value, "must provide a deleter instance");
|
||
|
}
|
||
|
|
||
|
/**
|
||
|
* Construct a UniquePtr containing |aPtr|.
|
||
|
*/
|
||
|
explicit UniquePtr(Pointer aPtr)
|
||
|
: mTuple(aPtr, DeleterType())
|
||
|
{
|
||
|
static_assert(!IsPointer<D>::value, "must provide a deleter instance");
|
||
|
static_assert(!IsReference<D>::value, "must provide a deleter instance");
|
||
|
}
|
||
|
|
||
|
UniquePtr(Pointer aPtr,
|
||
|
typename Conditional<IsReference<D>::value,
|
||
|
D,
|
||
|
const D&>::Type aD1)
|
||
|
: mTuple(aPtr, aD1)
|
||
|
{}
|
||
|
|
||
|
// If you encounter an error with MSVC10 about RemoveReference below, along
|
||
|
// the lines that "more than one partial specialization matches the template
|
||
|
// argument list": don't use UniquePtr<T, reference to function>! Ideally
|
||
|
// you should make deletion use the same function every time, using a
|
||
|
// deleter policy:
|
||
|
//
|
||
|
// // BAD, won't compile with MSVC10, deleter doesn't need to be a
|
||
|
// // variable at all
|
||
|
// typedef void (&FreeSignature)(void*);
|
||
|
// UniquePtr<int, FreeSignature> ptr((int*) malloc(sizeof(int)), free);
|
||
|
//
|
||
|
// // GOOD, compiles with MSVC10, deletion behavior statically known and
|
||
|
// // optimizable
|
||
|
// struct DeleteByFreeing
|
||
|
// {
|
||
|
// void operator()(void* aPtr) { free(aPtr); }
|
||
|
// };
|
||
|
//
|
||
|
// If deletion really, truly, must be a variable: you might be able to work
|
||
|
// around this with a deleter class that contains the function reference.
|
||
|
// But this workaround is untried and untested, because variable deletion
|
||
|
// behavior really isn't something you should use.
|
||
|
UniquePtr(Pointer aPtr,
|
||
|
typename RemoveReference<D>::Type&& aD2)
|
||
|
: mTuple(aPtr, Move(aD2))
|
||
|
{
|
||
|
static_assert(!IsReference<D>::value,
|
||
|
"rvalue deleter can't be stored by reference");
|
||
|
}
|
||
|
|
||
|
UniquePtr(UniquePtr&& aOther)
|
||
|
: mTuple(aOther.release(), Forward<DeleterType>(aOther.getDeleter()))
|
||
|
{}
|
||
|
|
||
|
MOZ_IMPLICIT
|
||
|
UniquePtr(decltype(nullptr))
|
||
|
: mTuple(nullptr, DeleterType())
|
||
|
{
|
||
|
static_assert(!IsPointer<D>::value, "must provide a deleter instance");
|
||
|
static_assert(!IsReference<D>::value, "must provide a deleter instance");
|
||
|
}
|
||
|
|
||
|
template<typename U, class E>
|
||
|
MOZ_IMPLICIT
|
||
|
UniquePtr(UniquePtr<U, E>&& aOther,
|
||
|
typename EnableIf<IsConvertible<typename UniquePtr<U, E>::Pointer,
|
||
|
Pointer>::value &&
|
||
|
!IsArray<U>::value &&
|
||
|
(IsReference<D>::value
|
||
|
? IsSame<D, E>::value
|
||
|
: IsConvertible<E, D>::value),
|
||
|
int>::Type aDummy = 0)
|
||
|
: mTuple(aOther.release(), Forward<E>(aOther.getDeleter()))
|
||
|
{
|
||
|
}
|
||
|
|
||
|
~UniquePtr() { reset(nullptr); }
|
||
|
|
||
|
UniquePtr& operator=(UniquePtr&& aOther)
|
||
|
{
|
||
|
reset(aOther.release());
|
||
|
getDeleter() = Forward<DeleterType>(aOther.getDeleter());
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
template<typename U, typename E>
|
||
|
UniquePtr& operator=(UniquePtr<U, E>&& aOther)
|
||
|
{
|
||
|
static_assert(IsConvertible<typename UniquePtr<U, E>::Pointer,
|
||
|
Pointer>::value,
|
||
|
"incompatible UniquePtr pointees");
|
||
|
static_assert(!IsArray<U>::value,
|
||
|
"can't assign from UniquePtr holding an array");
|
||
|
|
||
|
reset(aOther.release());
|
||
|
getDeleter() = Forward<E>(aOther.getDeleter());
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
UniquePtr& operator=(decltype(nullptr))
|
||
|
{
|
||
|
reset(nullptr);
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
T& operator*() const { return *get(); }
|
||
|
Pointer operator->() const
|
||
|
{
|
||
|
MOZ_ASSERT(get(), "dereferencing a UniquePtr containing nullptr");
|
||
|
return get();
|
||
|
}
|
||
|
|
||
|
explicit operator bool() const { return get() != nullptr; }
|
||
|
|
||
|
Pointer get() const { return ptr(); }
|
||
|
|
||
|
DeleterType& getDeleter() { return del(); }
|
||
|
const DeleterType& getDeleter() const { return del(); }
|
||
|
|
||
|
Pointer release()
|
||
|
{
|
||
|
Pointer p = ptr();
|
||
|
ptr() = nullptr;
|
||
|
return p;
|
||
|
}
|
||
|
|
||
|
void reset(Pointer aPtr = Pointer())
|
||
|
{
|
||
|
Pointer old = ptr();
|
||
|
ptr() = aPtr;
|
||
|
if (old != nullptr) {
|
||
|
getDeleter()(old);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
void swap(UniquePtr& aOther)
|
||
|
{
|
||
|
mTuple.swap(aOther.mTuple);
|
||
|
}
|
||
|
|
||
|
UniquePtr(const UniquePtr& aOther) = delete; // construct using Move()!
|
||
|
void operator=(const UniquePtr& aOther) = delete; // assign using Move()!
|
||
|
};
|
||
|
|
||
|
// In case you didn't read the comment by the main definition (you should!): the
|
||
|
// UniquePtr<T[]> specialization exists to manage array pointers. It deletes
|
||
|
// such pointers using delete[], it will reject construction and modification
|
||
|
// attempts using U* or U[]. Otherwise it works like the normal UniquePtr.
|
||
|
template<typename T, class D>
|
||
|
class UniquePtr<T[], D>
|
||
|
{
|
||
|
public:
|
||
|
typedef T* Pointer;
|
||
|
typedef T ElementType;
|
||
|
typedef D DeleterType;
|
||
|
|
||
|
private:
|
||
|
Pair<Pointer, DeleterType> mTuple;
|
||
|
|
||
|
public:
|
||
|
/**
|
||
|
* Construct a UniquePtr containing nullptr.
|
||
|
*/
|
||
|
MOZ_CONSTEXPR UniquePtr()
|
||
|
: mTuple(static_cast<Pointer>(nullptr), DeleterType())
|
||
|
{
|
||
|
static_assert(!IsPointer<D>::value, "must provide a deleter instance");
|
||
|
static_assert(!IsReference<D>::value, "must provide a deleter instance");
|
||
|
}
|
||
|
|
||
|
/**
|
||
|
* Construct a UniquePtr containing |aPtr|.
|
||
|
*/
|
||
|
explicit UniquePtr(Pointer aPtr)
|
||
|
: mTuple(aPtr, DeleterType())
|
||
|
{
|
||
|
static_assert(!IsPointer<D>::value, "must provide a deleter instance");
|
||
|
static_assert(!IsReference<D>::value, "must provide a deleter instance");
|
||
|
}
|
||
|
|
||
|
// delete[] knows how to handle *only* an array of a single class type. For
|
||
|
// delete[] to work correctly, it must know the size of each element, the
|
||
|
// fields and base classes of each element requiring destruction, and so on.
|
||
|
// So forbid all overloads which would end up invoking delete[] on a pointer
|
||
|
// of the wrong type.
|
||
|
template<typename U>
|
||
|
UniquePtr(U&& aU,
|
||
|
typename EnableIf<IsPointer<U>::value &&
|
||
|
IsConvertible<U, Pointer>::value,
|
||
|
int>::Type aDummy = 0)
|
||
|
= delete;
|
||
|
|
||
|
UniquePtr(Pointer aPtr,
|
||
|
typename Conditional<IsReference<D>::value,
|
||
|
D,
|
||
|
const D&>::Type aD1)
|
||
|
: mTuple(aPtr, aD1)
|
||
|
{}
|
||
|
|
||
|
// If you encounter an error with MSVC10 about RemoveReference below, along
|
||
|
// the lines that "more than one partial specialization matches the template
|
||
|
// argument list": don't use UniquePtr<T[], reference to function>! See the
|
||
|
// comment by this constructor in the non-T[] specialization above.
|
||
|
UniquePtr(Pointer aPtr,
|
||
|
typename RemoveReference<D>::Type&& aD2)
|
||
|
: mTuple(aPtr, Move(aD2))
|
||
|
{
|
||
|
static_assert(!IsReference<D>::value,
|
||
|
"rvalue deleter can't be stored by reference");
|
||
|
}
|
||
|
|
||
|
// Forbidden for the same reasons as stated above.
|
||
|
template<typename U, typename V>
|
||
|
UniquePtr(U&& aU, V&& aV,
|
||
|
typename EnableIf<IsPointer<U>::value &&
|
||
|
IsConvertible<U, Pointer>::value,
|
||
|
int>::Type aDummy = 0)
|
||
|
= delete;
|
||
|
|
||
|
UniquePtr(UniquePtr&& aOther)
|
||
|
: mTuple(aOther.release(), Forward<DeleterType>(aOther.getDeleter()))
|
||
|
{}
|
||
|
|
||
|
MOZ_IMPLICIT
|
||
|
UniquePtr(decltype(nullptr))
|
||
|
: mTuple(nullptr, DeleterType())
|
||
|
{
|
||
|
static_assert(!IsPointer<D>::value, "must provide a deleter instance");
|
||
|
static_assert(!IsReference<D>::value, "must provide a deleter instance");
|
||
|
}
|
||
|
|
||
|
~UniquePtr() { reset(nullptr); }
|
||
|
|
||
|
UniquePtr& operator=(UniquePtr&& aOther)
|
||
|
{
|
||
|
reset(aOther.release());
|
||
|
getDeleter() = Forward<DeleterType>(aOther.getDeleter());
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
UniquePtr& operator=(decltype(nullptr))
|
||
|
{
|
||
|
reset();
|
||
|
return *this;
|
||
|
}
|
||
|
|
||
|
explicit operator bool() const { return get() != nullptr; }
|
||
|
|
||
|
T& operator[](decltype(sizeof(int)) aIndex) const { return get()[aIndex]; }
|
||
|
Pointer get() const { return mTuple.first(); }
|
||
|
|
||
|
DeleterType& getDeleter() { return mTuple.second(); }
|
||
|
const DeleterType& getDeleter() const { return mTuple.second(); }
|
||
|
|
||
|
Pointer release()
|
||
|
{
|
||
|
Pointer p = mTuple.first();
|
||
|
mTuple.first() = nullptr;
|
||
|
return p;
|
||
|
}
|
||
|
|
||
|
void reset(Pointer aPtr = Pointer())
|
||
|
{
|
||
|
Pointer old = mTuple.first();
|
||
|
mTuple.first() = aPtr;
|
||
|
if (old != nullptr) {
|
||
|
mTuple.second()(old);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
void reset(decltype(nullptr))
|
||
|
{
|
||
|
Pointer old = mTuple.first();
|
||
|
mTuple.first() = nullptr;
|
||
|
if (old != nullptr) {
|
||
|
mTuple.second()(old);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
template<typename U>
|
||
|
void reset(U) = delete;
|
||
|
|
||
|
void swap(UniquePtr& aOther) { mTuple.swap(aOther.mTuple); }
|
||
|
|
||
|
UniquePtr(const UniquePtr& aOther) = delete; // construct using Move()!
|
||
|
void operator=(const UniquePtr& aOther) = delete; // assign using Move()!
|
||
|
};
|
||
|
|
||
|
/** A default deletion policy using plain old operator delete. */
|
||
|
template<typename T>
|
||
|
class DefaultDelete
|
||
|
{
|
||
|
public:
|
||
|
MOZ_CONSTEXPR DefaultDelete() {}
|
||
|
|
||
|
template<typename U>
|
||
|
MOZ_IMPLICIT DefaultDelete(const DefaultDelete<U>& aOther,
|
||
|
typename EnableIf<mozilla::IsConvertible<U*, T*>::value,
|
||
|
int>::Type aDummy = 0)
|
||
|
{}
|
||
|
|
||
|
void operator()(T* aPtr) const
|
||
|
{
|
||
|
static_assert(sizeof(T) > 0, "T must be complete");
|
||
|
delete aPtr;
|
||
|
}
|
||
|
};
|
||
|
|
||
|
/** A default deletion policy using operator delete[]. */
|
||
|
template<typename T>
|
||
|
class DefaultDelete<T[]>
|
||
|
{
|
||
|
public:
|
||
|
MOZ_CONSTEXPR DefaultDelete() {}
|
||
|
|
||
|
void operator()(T* aPtr) const
|
||
|
{
|
||
|
static_assert(sizeof(T) > 0, "T must be complete");
|
||
|
delete[] aPtr;
|
||
|
}
|
||
|
|
||
|
template<typename U>
|
||
|
void operator()(U* aPtr) const = delete;
|
||
|
};
|
||
|
|
||
|
template<typename T, class D>
|
||
|
void
|
||
|
Swap(UniquePtr<T, D>& aX, UniquePtr<T, D>& aY)
|
||
|
{
|
||
|
aX.swap(aY);
|
||
|
}
|
||
|
|
||
|
template<typename T, class D, typename U, class E>
|
||
|
bool
|
||
|
operator==(const UniquePtr<T, D>& aX, const UniquePtr<U, E>& aY)
|
||
|
{
|
||
|
return aX.get() == aY.get();
|
||
|
}
|
||
|
|
||
|
template<typename T, class D, typename U, class E>
|
||
|
bool
|
||
|
operator!=(const UniquePtr<T, D>& aX, const UniquePtr<U, E>& aY)
|
||
|
{
|
||
|
return aX.get() != aY.get();
|
||
|
}
|
||
|
|
||
|
template<typename T, class D>
|
||
|
bool
|
||
|
operator==(const UniquePtr<T, D>& aX, decltype(nullptr))
|
||
|
{
|
||
|
return !aX;
|
||
|
}
|
||
|
|
||
|
template<typename T, class D>
|
||
|
bool
|
||
|
operator==(decltype(nullptr), const UniquePtr<T, D>& aX)
|
||
|
{
|
||
|
return !aX;
|
||
|
}
|
||
|
|
||
|
template<typename T, class D>
|
||
|
bool
|
||
|
operator!=(const UniquePtr<T, D>& aX, decltype(nullptr))
|
||
|
{
|
||
|
return bool(aX);
|
||
|
}
|
||
|
|
||
|
template<typename T, class D>
|
||
|
bool
|
||
|
operator!=(decltype(nullptr), const UniquePtr<T, D>& aX)
|
||
|
{
|
||
|
return bool(aX);
|
||
|
}
|
||
|
|
||
|
// No operator<, operator>, operator<=, operator>= for now because simplicity.
|
||
|
|
||
|
namespace detail {
|
||
|
|
||
|
template<typename T>
|
||
|
struct UniqueSelector
|
||
|
{
|
||
|
typedef UniquePtr<T> SingleObject;
|
||
|
};
|
||
|
|
||
|
template<typename T>
|
||
|
struct UniqueSelector<T[]>
|
||
|
{
|
||
|
typedef UniquePtr<T[]> UnknownBound;
|
||
|
};
|
||
|
|
||
|
template<typename T, decltype(sizeof(int)) N>
|
||
|
struct UniqueSelector<T[N]>
|
||
|
{
|
||
|
typedef UniquePtr<T[N]> KnownBound;
|
||
|
};
|
||
|
|
||
|
} // namespace detail
|
||
|
|
||
|
/**
|
||
|
* MakeUnique is a helper function for allocating new'd objects and arrays,
|
||
|
* returning a UniquePtr containing the resulting pointer. The semantics of
|
||
|
* MakeUnique<Type>(...) are as follows.
|
||
|
*
|
||
|
* If Type is an array T[n]:
|
||
|
* Disallowed, deleted, no overload for you!
|
||
|
* If Type is an array T[]:
|
||
|
* MakeUnique<T[]>(size_t) is the only valid overload. The pointer returned
|
||
|
* is as if by |new T[n]()|, which value-initializes each element. (If T
|
||
|
* isn't a class type, this will zero each element. If T is a class type,
|
||
|
* then roughly speaking, each element will be constructed using its default
|
||
|
* constructor. See C++11 [dcl.init]p7 for the full gory details.)
|
||
|
* If Type is non-array T:
|
||
|
* The arguments passed to MakeUnique<T>(...) are forwarded into a
|
||
|
* |new T(...)| call, initializing the T as would happen if executing
|
||
|
* |T(...)|.
|
||
|
*
|
||
|
* There are various benefits to using MakeUnique instead of |new| expressions.
|
||
|
*
|
||
|
* First, MakeUnique eliminates use of |new| from code entirely. If objects are
|
||
|
* only created through UniquePtr, then (assuming all explicit release() calls
|
||
|
* are safe, including transitively, and no type-safety casting funniness)
|
||
|
* correctly maintained ownership of the UniquePtr guarantees no leaks are
|
||
|
* possible. (This pays off best if a class is only ever created through a
|
||
|
* factory method on the class, using a private constructor.)
|
||
|
*
|
||
|
* Second, initializing a UniquePtr using a |new| expression requires repeating
|
||
|
* the name of the new'd type, whereas MakeUnique in concert with the |auto|
|
||
|
* keyword names it only once:
|
||
|
*
|
||
|
* UniquePtr<char> ptr1(new char()); // repetitive
|
||
|
* auto ptr2 = MakeUnique<char>(); // shorter
|
||
|
*
|
||
|
* Of course this assumes the reader understands the operation MakeUnique
|
||
|
* performs. In the long run this is probably a reasonable assumption. In the
|
||
|
* short run you'll have to use your judgment about what readers can be expected
|
||
|
* to know, or to quickly look up.
|
||
|
*
|
||
|
* Third, a call to MakeUnique can be assigned directly to a UniquePtr. In
|
||
|
* contrast you can't assign a pointer into a UniquePtr without using the
|
||
|
* cumbersome reset().
|
||
|
*
|
||
|
* UniquePtr<char> p;
|
||
|
* p = new char; // ERROR
|
||
|
* p.reset(new char); // works, but fugly
|
||
|
* p = MakeUnique<char>(); // preferred
|
||
|
*
|
||
|
* (And third, although not relevant to Mozilla: MakeUnique is exception-safe.
|
||
|
* An exception thrown after |new T| succeeds will leak that memory, unless the
|
||
|
* pointer is assigned to an object that will manage its ownership. UniquePtr
|
||
|
* ably serves this function.)
|
||
|
*/
|
||
|
|
||
|
template<typename T, typename... Args>
|
||
|
typename detail::UniqueSelector<T>::SingleObject
|
||
|
MakeUnique(Args&&... aArgs)
|
||
|
{
|
||
|
return UniquePtr<T>(new T(Forward<Args>(aArgs)...));
|
||
|
}
|
||
|
|
||
|
template<typename T>
|
||
|
typename detail::UniqueSelector<T>::UnknownBound
|
||
|
MakeUnique(decltype(sizeof(int)) aN)
|
||
|
{
|
||
|
typedef typename RemoveExtent<T>::Type ArrayType;
|
||
|
return UniquePtr<T>(new ArrayType[aN]());
|
||
|
}
|
||
|
|
||
|
template<typename T, typename... Args>
|
||
|
typename detail::UniqueSelector<T>::KnownBound
|
||
|
MakeUnique(Args&&... aArgs) = delete;
|
||
|
|
||
|
} // namespace mozilla
|
||
|
|
||
|
#endif /* mozilla_UniquePtr_h */
|