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/*
* Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#ifndef WTF_VectorTraits_h
#define WTF_VectorTraits_h
#include "wtf/RefPtr.h"
#include "wtf/TypeTraits.h"
#include <memory>
#include <type_traits>
#include <utility>
namespace WTF {
template <typename T>
struct VectorTraitsBase {
static const bool needsDestruction = !IsTriviallyDestructible<T>::value;
static const bool canInitializeWithMemset =
IsTriviallyDefaultConstructible<T>::value;
// true iff memset(slot, 0, size) constructs an unused slot value that is
// valid for Oilpan to trace and if the value needs destruction, its
// destructor can be invoked over. The zero'ed value representing an unused
// slot in the vector's backing storage; it does not have to be equal to
// what its constructor(s) would create, only be valid for those two uses.
static const bool canClearUnusedSlotsWithMemset =
IsTriviallyDefaultConstructible<T>::value;
static const bool canMoveWithMemcpy = IsTriviallyMoveAssignable<T>::value;
static const bool canCopyWithMemcpy = IsTriviallyCopyAssignable<T>::value;
static const bool canFillWithMemset =
IsTriviallyDefaultConstructible<T>::value && (sizeof(T) == sizeof(char));
static const bool canCompareWithMemcmp =
std::is_scalar<T>::value; // Types without padding.
// Supports swapping elements using regular std::swap semantics.
static const bool canSwapUsingCopyOrMove = true;
template <typename U = void>
struct IsTraceableInCollection {
static const bool value = IsTraceable<T>::value;
};
// We don't support weak handling in vectors.
static const WeakHandlingFlag weakHandlingFlag = NoWeakHandlingInCollections;
};
template <typename T>
struct VectorTraits : VectorTraitsBase<T> {};
// Classes marked with SimpleVectorTraits will use memmov, memcpy, memcmp
// instead of constructors, copy operators, etc for initialization, move and
// comparison.
template <typename T>
struct SimpleClassVectorTraits : VectorTraitsBase<T> {
static const bool canInitializeWithMemset = true;
static const bool canClearUnusedSlotsWithMemset = true;
static const bool canMoveWithMemcpy = true;
static const bool canCompareWithMemcmp = true;
};
// We know std::unique_ptr and RefPtr are simple enough that initializing to 0
// and moving with memcpy (and then not destructing the original) will totally
// work.
template <typename P>
struct VectorTraits<RefPtr<P>> : SimpleClassVectorTraits<RefPtr<P>> {};
template <typename P>
struct VectorTraits<std::unique_ptr<P>>
: SimpleClassVectorTraits<std::unique_ptr<P>> {
// std::unique_ptr -> std::unique_ptr has a very particular structure that
// tricks the normal type traits into thinking that the class is "trivially
// copyable".
static const bool canCopyWithMemcpy = false;
};
static_assert(VectorTraits<RefPtr<int>>::canInitializeWithMemset,
"inefficient RefPtr Vector");
static_assert(VectorTraits<RefPtr<int>>::canMoveWithMemcpy,
"inefficient RefPtr Vector");
static_assert(VectorTraits<RefPtr<int>>::canCompareWithMemcmp,
"inefficient RefPtr Vector");
static_assert(VectorTraits<std::unique_ptr<int>>::canInitializeWithMemset,
"inefficient std::unique_ptr Vector");
static_assert(VectorTraits<std::unique_ptr<int>>::canMoveWithMemcpy,
"inefficient std::unique_ptr Vector");
static_assert(VectorTraits<std::unique_ptr<int>>::canCompareWithMemcmp,
"inefficient std::unique_ptr Vector");
template <typename First, typename Second>
struct VectorTraits<std::pair<First, Second>> {
typedef VectorTraits<First> FirstTraits;
typedef VectorTraits<Second> SecondTraits;
static const bool needsDestruction =
FirstTraits::needsDestruction || SecondTraits::needsDestruction;
static const bool canInitializeWithMemset =
FirstTraits::canInitializeWithMemset &&
SecondTraits::canInitializeWithMemset;
static const bool canMoveWithMemcpy =
FirstTraits::canMoveWithMemcpy && SecondTraits::canMoveWithMemcpy;
static const bool canCopyWithMemcpy =
FirstTraits::canCopyWithMemcpy && SecondTraits::canCopyWithMemcpy;
static const bool canFillWithMemset = false;
static const bool canCompareWithMemcmp =
FirstTraits::canCompareWithMemcmp && SecondTraits::canCompareWithMemcmp;
static const bool canClearUnusedSlotsWithMemset =
FirstTraits::canClearUnusedSlotsWithMemset &&
SecondTraits::canClearUnusedSlotsWithMemset;
// Supports swapping elements using regular std::swap semantics.
static const bool canSwapUsingCopyOrMove = true;
template <typename U = void>
struct IsTraceableInCollection {
static const bool value =
IsTraceableInCollectionTrait<FirstTraits>::value ||
IsTraceableInCollectionTrait<SecondTraits>::value;
};
// We don't support weak handling in vectors.
static const WeakHandlingFlag weakHandlingFlag = NoWeakHandlingInCollections;
};
} // namespace WTF
#define WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(ClassName) \
namespace WTF { \
static_assert(!IsTriviallyDefaultConstructible<ClassName>::value || \
!IsTriviallyMoveAssignable<ClassName>::value || \
!std::is_scalar<ClassName>::value, \
"macro not needed"); \
template <> \
struct VectorTraits<ClassName> : SimpleClassVectorTraits<ClassName> {}; \
}
#define WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(ClassName) \
namespace WTF { \
static_assert(!IsTriviallyDefaultConstructible<ClassName>::value || \
!IsTriviallyMoveAssignable<ClassName>::value, \
"macro not needed"); \
template <> \
struct VectorTraits<ClassName> : VectorTraitsBase<ClassName> { \
static const bool canInitializeWithMemset = true; \
static const bool canClearUnusedSlotsWithMemset = true; \
static const bool canMoveWithMemcpy = true; \
}; \
}
#define WTF_ALLOW_INIT_WITH_MEM_FUNCTIONS(ClassName) \
namespace WTF { \
static_assert(!IsTriviallyDefaultConstructible<ClassName>::value, \
"macro not needed"); \
template <> \
struct VectorTraits<ClassName> : VectorTraitsBase<ClassName> { \
static const bool canInitializeWithMemset = true; \
static const bool canClearUnusedSlotsWithMemset = true; \
}; \
}
#define WTF_ALLOW_CLEAR_UNUSED_SLOTS_WITH_MEM_FUNCTIONS(ClassName) \
namespace WTF { \
static_assert(!IsTriviallyDefaultConstructible<ClassName>::value, \
"macro not needed"); \
template <> \
struct VectorTraits<ClassName> : VectorTraitsBase<ClassName> { \
static const bool canClearUnusedSlotsWithMemset = true; \
}; \
}
using WTF::VectorTraits;
using WTF::SimpleClassVectorTraits;
#endif // WTF_VectorTraits_h
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