mirror of
https://github.com/classilla/tenfourfox.git
synced 2024-08-17 00:29:04 +00:00
220 lines
5.7 KiB
C++
220 lines
5.7 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/. */
|
|
|
|
/* A class holding a pair of objects that tries to conserve storage space. */
|
|
|
|
#ifndef mozilla_Pair_h
|
|
#define mozilla_Pair_h
|
|
|
|
#include "mozilla/Attributes.h"
|
|
#include "mozilla/Move.h"
|
|
#include "mozilla/TypeTraits.h"
|
|
|
|
namespace mozilla {
|
|
|
|
namespace detail {
|
|
|
|
enum StorageType { AsBase, AsMember };
|
|
|
|
// Optimize storage using the Empty Base Optimization -- that empty base classes
|
|
// don't take up space -- to optimize size when one or the other class is
|
|
// stateless and can be used as a base class.
|
|
//
|
|
// The extra conditions on storage for B are necessary so that PairHelper won't
|
|
// ambiguously inherit from either A or B, such that one or the other base class
|
|
// would be inaccessible.
|
|
template<typename A, typename B,
|
|
detail::StorageType =
|
|
IsEmpty<A>::value ? detail::AsBase : detail::AsMember,
|
|
detail::StorageType =
|
|
IsEmpty<B>::value && !IsBaseOf<A, B>::value && !IsBaseOf<B, A>::value
|
|
? detail::AsBase
|
|
: detail::AsMember>
|
|
struct PairHelper;
|
|
|
|
template<typename A, typename B>
|
|
struct PairHelper<A, B, AsMember, AsMember>
|
|
{
|
|
protected:
|
|
template<typename AArg, typename BArg>
|
|
PairHelper(AArg&& aA, BArg&& aB)
|
|
: mFirstA(Forward<AArg>(aA)),
|
|
mSecondB(Forward<BArg>(aB))
|
|
{}
|
|
|
|
A& first() { return mFirstA; }
|
|
const A& first() const { return mFirstA; }
|
|
B& second() { return mSecondB; }
|
|
const B& second() const { return mSecondB; }
|
|
|
|
void swap(PairHelper& aOther)
|
|
{
|
|
Swap(mFirstA, aOther.mFirstA);
|
|
Swap(mSecondB, aOther.mSecondB);
|
|
}
|
|
|
|
private:
|
|
A mFirstA;
|
|
B mSecondB;
|
|
};
|
|
|
|
template<typename A, typename B>
|
|
struct PairHelper<A, B, AsMember, AsBase> : private B
|
|
{
|
|
protected:
|
|
template<typename AArg, typename BArg>
|
|
PairHelper(AArg&& aA, BArg&& aB)
|
|
: B(Forward<BArg>(aB)),
|
|
mFirstA(Forward<AArg>(aA))
|
|
{}
|
|
|
|
A& first() { return mFirstA; }
|
|
const A& first() const { return mFirstA; }
|
|
B& second() { return *this; }
|
|
const B& second() const { return *this; }
|
|
|
|
void swap(PairHelper& aOther)
|
|
{
|
|
Swap(mFirstA, aOther.mFirstA);
|
|
Swap(static_cast<B&>(*this), static_cast<B&>(aOther));
|
|
}
|
|
|
|
private:
|
|
A mFirstA;
|
|
};
|
|
|
|
template<typename A, typename B>
|
|
struct PairHelper<A, B, AsBase, AsMember> : private A
|
|
{
|
|
protected:
|
|
template<typename AArg, typename BArg>
|
|
PairHelper(AArg&& aA, BArg&& aB)
|
|
: A(Forward<AArg>(aA)),
|
|
mSecondB(Forward<BArg>(aB))
|
|
{}
|
|
|
|
A& first() { return *this; }
|
|
const A& first() const { return *this; }
|
|
B& second() { return mSecondB; }
|
|
const B& second() const { return mSecondB; }
|
|
|
|
void swap(PairHelper& aOther)
|
|
{
|
|
Swap(static_cast<A&>(*this), static_cast<A&>(aOther));
|
|
Swap(mSecondB, aOther.mSecondB);
|
|
}
|
|
|
|
private:
|
|
B mSecondB;
|
|
};
|
|
|
|
template<typename A, typename B>
|
|
struct PairHelper<A, B, AsBase, AsBase> : private A, private B
|
|
{
|
|
protected:
|
|
template<typename AArg, typename BArg>
|
|
PairHelper(AArg&& aA, BArg&& aB)
|
|
: A(Forward<AArg>(aA)),
|
|
B(Forward<BArg>(aB))
|
|
{}
|
|
|
|
A& first() { return static_cast<A&>(*this); }
|
|
const A& first() const { return static_cast<A&>(*this); }
|
|
B& second() { return static_cast<B&>(*this); }
|
|
const B& second() const { return static_cast<B&>(*this); }
|
|
|
|
void swap(PairHelper& aOther)
|
|
{
|
|
Swap(static_cast<A&>(*this), static_cast<A&>(aOther));
|
|
Swap(static_cast<B&>(*this), static_cast<B&>(aOther));
|
|
}
|
|
};
|
|
|
|
} // namespace detail
|
|
|
|
/**
|
|
* Pair is the logical concatenation of an instance of A with an instance B.
|
|
* Space is conserved when possible. Neither A nor B may be a final class.
|
|
*
|
|
* It's typically clearer to have individual A and B member fields. Except if
|
|
* you want the space-conserving qualities of Pair, you're probably better off
|
|
* not using this!
|
|
*
|
|
* No guarantees are provided about the memory layout of A and B, the order of
|
|
* initialization or destruction of A and B, and so on. (This is approximately
|
|
* required to optimize space usage.) The first/second names are merely
|
|
* conceptual!
|
|
*/
|
|
template<typename A, typename B>
|
|
struct Pair
|
|
: private detail::PairHelper<A, B>
|
|
{
|
|
typedef typename detail::PairHelper<A, B> Base;
|
|
|
|
public:
|
|
template<typename AArg, typename BArg>
|
|
Pair(AArg&& aA, BArg&& aB)
|
|
: Base(Forward<AArg>(aA), Forward<BArg>(aB))
|
|
{}
|
|
|
|
Pair(Pair&& aOther)
|
|
: Base(Move(aOther.first()), Move(aOther.second()))
|
|
{ }
|
|
|
|
Pair(const Pair& aOther) = default;
|
|
|
|
Pair& operator=(Pair&& aOther)
|
|
{
|
|
MOZ_ASSERT(this != &aOther, "Self-moves are prohibited");
|
|
|
|
first() = Move(aOther.first());
|
|
second() = Move(aOther.second());
|
|
|
|
return *this;
|
|
}
|
|
|
|
Pair& operator=(const Pair& aOther) = default;
|
|
|
|
/** The A instance. */
|
|
using Base::first;
|
|
/** The B instance. */
|
|
using Base::second;
|
|
|
|
/** Swap this pair with another pair. */
|
|
void swap(Pair& aOther) { Base::swap(aOther); }
|
|
};
|
|
|
|
template<typename A, class B>
|
|
void
|
|
Swap(Pair<A, B>& aX, Pair<A, B>& aY)
|
|
{
|
|
aX.swap(aY);
|
|
}
|
|
|
|
/**
|
|
* MakePair allows you to construct a Pair instance using type inference. A call
|
|
* like this:
|
|
*
|
|
* MakePair(Foo(), Bar())
|
|
*
|
|
* will return a Pair<Foo, Bar>.
|
|
*/
|
|
template<typename A, typename B>
|
|
Pair<typename RemoveCV<typename RemoveReference<A>::Type>::Type,
|
|
typename RemoveCV<typename RemoveReference<B>::Type>::Type>
|
|
MakePair(A&& aA, B&& aB)
|
|
{
|
|
return
|
|
Pair<typename RemoveCV<typename RemoveReference<A>::Type>::Type,
|
|
typename RemoveCV<typename RemoveReference<B>::Type>::Type>(
|
|
Forward<A>(aA),
|
|
Forward<B>(aB));
|
|
}
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif /* mozilla_Pair_h */
|