| /* |
| * Copyright (C) 2005, 2006, 2007, 2008, 2011, 2012 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_HashTraits_h |
| #define WTF_HashTraits_h |
| |
| #include <wtf/HashFunctions.h> |
| #include <wtf/StdLibExtras.h> |
| #include <wtf/TypeTraits.h> |
| #include <utility> |
| #include <limits> |
| |
| namespace WTF { |
| |
| class String; |
| |
| template<typename T> class OwnPtr; |
| template<typename T> class PassOwnPtr; |
| |
| template<typename T> struct HashTraits; |
| |
| template<bool isInteger, typename T> struct GenericHashTraitsBase; |
| |
| template<typename T> struct GenericHashTraitsBase<false, T> { |
| // The emptyValueIsZero flag is used to optimize allocation of empty hash tables with zeroed memory. |
| static const bool emptyValueIsZero = false; |
| |
| // The hasIsEmptyValueFunction flag allows the hash table to automatically generate code to check |
| // for the empty value when it can be done with the equality operator, but allows custom functions |
| // for cases like String that need them. |
| static const bool hasIsEmptyValueFunction = false; |
| |
| // The needsDestruction flag is used to optimize destruction and rehashing. |
| static const bool needsDestruction = true; |
| |
| // The starting table size. Can be overridden when we know beforehand that |
| // a hash table will have at least N entries. |
| static const int minimumTableSize = 8; |
| }; |
| |
| // Default integer traits disallow both 0 and -1 as keys (max value instead of -1 for unsigned). |
| template<typename T> struct GenericHashTraitsBase<true, T> : GenericHashTraitsBase<false, T> { |
| static const bool emptyValueIsZero = true; |
| static const bool needsDestruction = false; |
| static void constructDeletedValue(T& slot) { slot = static_cast<T>(-1); } |
| static bool isDeletedValue(T value) { return value == static_cast<T>(-1); } |
| }; |
| |
| template<typename T> struct GenericHashTraits : GenericHashTraitsBase<IsInteger<T>::value, T> { |
| typedef T TraitType; |
| typedef T EmptyValueType; |
| |
| static T emptyValue() { return T(); } |
| |
| // Type for functions that take ownership, such as add. |
| // The store function either not be called or called once to store something passed in. |
| // The value passed to the store function will be either PassInType or PassInType&. |
| typedef const T& PassInType; |
| static void store(const T& value, T& storage) { storage = value; } |
| |
| // Type for return value of functions that transfer ownership, such as take. |
| typedef T PassOutType; |
| static PassOutType passOut(const T& value) { return value; } |
| |
| // Type for return value of functions that do not transfer ownership, such as get. |
| // FIXME: We could change this type to const T& for better performance if we figured out |
| // a way to handle the return value from emptyValue, which is a temporary. |
| typedef T PeekType; |
| static PeekType peek(const T& value) { return value; } |
| }; |
| |
| template<typename T> struct HashTraits : GenericHashTraits<T> { }; |
| |
| template<typename T> struct FloatHashTraits : GenericHashTraits<T> { |
| static const bool needsDestruction = false; |
| static T emptyValue() { return std::numeric_limits<T>::infinity(); } |
| static void constructDeletedValue(T& slot) { slot = -std::numeric_limits<T>::infinity(); } |
| static bool isDeletedValue(T value) { return value == -std::numeric_limits<T>::infinity(); } |
| }; |
| |
| template<> struct HashTraits<float> : FloatHashTraits<float> { }; |
| template<> struct HashTraits<double> : FloatHashTraits<double> { }; |
| |
| // Default unsigned traits disallow both 0 and max as keys -- use these traits to allow zero and disallow max - 1. |
| template<typename T> struct UnsignedWithZeroKeyHashTraits : GenericHashTraits<T> { |
| static const bool emptyValueIsZero = false; |
| static const bool needsDestruction = false; |
| static T emptyValue() { return std::numeric_limits<T>::max(); } |
| static void constructDeletedValue(T& slot) { slot = std::numeric_limits<T>::max() - 1; } |
| static bool isDeletedValue(T value) { return value == std::numeric_limits<T>::max() - 1; } |
| }; |
| |
| template<typename P> struct HashTraits<P*> : GenericHashTraits<P*> { |
| static const bool emptyValueIsZero = true; |
| static const bool needsDestruction = false; |
| static void constructDeletedValue(P*& slot) { slot = reinterpret_cast<P*>(-1); } |
| static bool isDeletedValue(P* value) { return value == reinterpret_cast<P*>(-1); } |
| }; |
| |
| template<typename T> struct SimpleClassHashTraits : GenericHashTraits<T> { |
| static const bool emptyValueIsZero = true; |
| static void constructDeletedValue(T& slot) { new (NotNull, &slot) T(HashTableDeletedValue); } |
| static bool isDeletedValue(const T& value) { return value.isHashTableDeletedValue(); } |
| }; |
| |
| template<typename P> struct HashTraits<OwnPtr<P> > : SimpleClassHashTraits<OwnPtr<P> > { |
| typedef std::nullptr_t EmptyValueType; |
| |
| static EmptyValueType emptyValue() { return nullptr; } |
| |
| typedef PassOwnPtr<P> PassInType; |
| static void store(PassOwnPtr<P> value, OwnPtr<P>& storage) { storage = value; } |
| |
| typedef PassOwnPtr<P> PassOutType; |
| static PassOwnPtr<P> passOut(OwnPtr<P>& value) { return value.release(); } |
| static PassOwnPtr<P> passOut(std::nullptr_t) { return nullptr; } |
| |
| typedef typename OwnPtr<P>::PtrType PeekType; |
| static PeekType peek(const OwnPtr<P>& value) { return value.get(); } |
| static PeekType peek(std::nullptr_t) { return 0; } |
| }; |
| |
| template<typename P> struct HashTraits<RefPtr<P> > : SimpleClassHashTraits<RefPtr<P> > { |
| typedef PassRefPtr<P> PassInType; |
| static void store(PassRefPtr<P> value, RefPtr<P>& storage) { storage = value; } |
| |
| // FIXME: We should change PassOutType to PassRefPtr for better performance. |
| // FIXME: We should consider changing PeekType to a raw pointer for better performance, |
| // but then callers won't need to call get; doing so will require updating many call sites. |
| }; |
| |
| template<> struct HashTraits<String> : SimpleClassHashTraits<String> { |
| static const bool hasIsEmptyValueFunction = true; |
| static bool isEmptyValue(const String&); |
| }; |
| |
| // This struct template is an implementation detail of the isHashTraitsEmptyValue function, |
| // which selects either the emptyValue function or the isEmptyValue function to check for empty values. |
| template<typename Traits, bool hasEmptyValueFunction> struct HashTraitsEmptyValueChecker; |
| template<typename Traits> struct HashTraitsEmptyValueChecker<Traits, true> { |
| template<typename T> static bool isEmptyValue(const T& value) { return Traits::isEmptyValue(value); } |
| }; |
| template<typename Traits> struct HashTraitsEmptyValueChecker<Traits, false> { |
| template<typename T> static bool isEmptyValue(const T& value) { return value == Traits::emptyValue(); } |
| }; |
| template<typename Traits, typename T> inline bool isHashTraitsEmptyValue(const T& value) |
| { |
| return HashTraitsEmptyValueChecker<Traits, Traits::hasIsEmptyValueFunction>::isEmptyValue(value); |
| } |
| |
| template<typename FirstTraitsArg, typename SecondTraitsArg> |
| struct PairHashTraits : GenericHashTraits<std::pair<typename FirstTraitsArg::TraitType, typename SecondTraitsArg::TraitType> > { |
| typedef FirstTraitsArg FirstTraits; |
| typedef SecondTraitsArg SecondTraits; |
| typedef std::pair<typename FirstTraits::TraitType, typename SecondTraits::TraitType> TraitType; |
| typedef std::pair<typename FirstTraits::EmptyValueType, typename SecondTraits::EmptyValueType> EmptyValueType; |
| |
| static const bool emptyValueIsZero = FirstTraits::emptyValueIsZero && SecondTraits::emptyValueIsZero; |
| static EmptyValueType emptyValue() { return std::make_pair(FirstTraits::emptyValue(), SecondTraits::emptyValue()); } |
| |
| static const bool needsDestruction = FirstTraits::needsDestruction || SecondTraits::needsDestruction; |
| |
| static const int minimumTableSize = FirstTraits::minimumTableSize; |
| |
| static void constructDeletedValue(TraitType& slot) { FirstTraits::constructDeletedValue(slot.first); } |
| static bool isDeletedValue(const TraitType& value) { return FirstTraits::isDeletedValue(value.first); } |
| }; |
| |
| template<typename First, typename Second> |
| struct HashTraits<std::pair<First, Second> > : public PairHashTraits<HashTraits<First>, HashTraits<Second> > { }; |
| |
| template<typename KeyTypeArg, typename ValueTypeArg> |
| struct KeyValuePair { |
| typedef KeyTypeArg KeyType; |
| |
| KeyValuePair() |
| { |
| } |
| |
| KeyValuePair(const KeyTypeArg& key, const ValueTypeArg& value) |
| : key(key) |
| , value(value) |
| { |
| } |
| |
| template <typename OtherKeyType, typename OtherValueType> |
| KeyValuePair(const KeyValuePair<OtherKeyType, OtherValueType>& other) |
| : key(other.key) |
| , value(other.value) |
| { |
| } |
| |
| KeyTypeArg key; |
| ValueTypeArg value; |
| }; |
| |
| template<typename KeyTraitsArg, typename ValueTraitsArg> |
| struct KeyValuePairHashTraits : GenericHashTraits<KeyValuePair<typename KeyTraitsArg::TraitType, typename ValueTraitsArg::TraitType> > { |
| typedef KeyTraitsArg KeyTraits; |
| typedef ValueTraitsArg ValueTraits; |
| typedef KeyValuePair<typename KeyTraits::TraitType, typename ValueTraits::TraitType> TraitType; |
| typedef KeyValuePair<typename KeyTraits::EmptyValueType, typename ValueTraits::EmptyValueType> EmptyValueType; |
| |
| static const bool emptyValueIsZero = KeyTraits::emptyValueIsZero && ValueTraits::emptyValueIsZero; |
| static EmptyValueType emptyValue() { return KeyValuePair<typename KeyTraits::EmptyValueType, typename ValueTraits::EmptyValueType>(KeyTraits::emptyValue(), ValueTraits::emptyValue()); } |
| |
| static const bool needsDestruction = KeyTraits::needsDestruction || ValueTraits::needsDestruction; |
| |
| static const int minimumTableSize = KeyTraits::minimumTableSize; |
| |
| static void constructDeletedValue(TraitType& slot) { KeyTraits::constructDeletedValue(slot.key); } |
| static bool isDeletedValue(const TraitType& value) { return KeyTraits::isDeletedValue(value.key); } |
| }; |
| |
| template<typename Key, typename Value> |
| struct HashTraits<KeyValuePair<Key, Value> > : public KeyValuePairHashTraits<HashTraits<Key>, HashTraits<Value> > { }; |
| |
| template<typename T> |
| struct NullableHashTraits : public HashTraits<T> { |
| static const bool emptyValueIsZero = false; |
| static T emptyValue() { return reinterpret_cast<T>(1); } |
| }; |
| |
| } // namespace WTF |
| |
| using WTF::HashTraits; |
| using WTF::PairHashTraits; |
| using WTF::NullableHashTraits; |
| |
| #endif // WTF_HashTraits_h |