1/* 2 * Copyright (C) 2005, 2006, 2007, 2008, 2011, 2012 Apple Inc. All rights reserved. 3 * 4 * This library is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU Library General Public 6 * License as published by the Free Software Foundation; either 7 * version 2 of the License, or (at your option) any later version. 8 * 9 * This library is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * Library General Public License for more details. 13 * 14 * You should have received a copy of the GNU Library General Public License 15 * along with this library; see the file COPYING.LIB. If not, write to 16 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 17 * Boston, MA 02110-1301, USA. 18 * 19 */ 20 21#ifndef WTF_HashTraits_h 22#define WTF_HashTraits_h 23 24#include <wtf/HashFunctions.h> 25#include <wtf/StdLibExtras.h> 26#include <utility> 27#include <limits> 28 29namespace WTF { 30 31class String; 32 33template<typename T> class OwnPtr; 34template<typename T> class PassOwnPtr; 35 36template<typename T> struct HashTraits; 37 38template<bool isInteger, typename T> struct GenericHashTraitsBase; 39 40template<typename T> struct GenericHashTraitsBase<false, T> { 41 // The emptyValueIsZero flag is used to optimize allocation of empty hash tables with zeroed memory. 42 static const bool emptyValueIsZero = false; 43 44 // The hasIsEmptyValueFunction flag allows the hash table to automatically generate code to check 45 // for the empty value when it can be done with the equality operator, but allows custom functions 46 // for cases like String that need them. 47 static const bool hasIsEmptyValueFunction = false; 48 49 // The starting table size. Can be overridden when we know beforehand that 50 // a hash table will have at least N entries. 51 static const int minimumTableSize = 8; 52}; 53 54// Default integer traits disallow both 0 and -1 as keys (max value instead of -1 for unsigned). 55template<typename T> struct GenericHashTraitsBase<true, T> : GenericHashTraitsBase<false, T> { 56 static const bool emptyValueIsZero = true; 57 static void constructDeletedValue(T& slot) { slot = static_cast<T>(-1); } 58 static bool isDeletedValue(T value) { return value == static_cast<T>(-1); } 59}; 60 61template<typename T> struct GenericHashTraits : GenericHashTraitsBase<std::is_integral<T>::value, T> { 62 typedef T TraitType; 63 typedef T EmptyValueType; 64 65 static T emptyValue() { return T(); } 66 67 // Type for return value of functions that do not transfer ownership, such as get. 68 typedef T PeekType; 69 static PeekType peek(const T& value) { return value; } 70 static T& peek(T& value) { return value; } // Overloaded to avoid copying of non-temporary values. 71}; 72 73template<typename T> struct HashTraits : GenericHashTraits<T> { }; 74 75template<typename T> struct FloatHashTraits : GenericHashTraits<T> { 76 static T emptyValue() { return std::numeric_limits<T>::infinity(); } 77 static void constructDeletedValue(T& slot) { slot = -std::numeric_limits<T>::infinity(); } 78 static bool isDeletedValue(T value) { return value == -std::numeric_limits<T>::infinity(); } 79}; 80 81template<> struct HashTraits<float> : FloatHashTraits<float> { }; 82template<> struct HashTraits<double> : FloatHashTraits<double> { }; 83 84// Default unsigned traits disallow both 0 and max as keys -- use these traits to allow zero and disallow max - 1. 85template<typename T> struct UnsignedWithZeroKeyHashTraits : GenericHashTraits<T> { 86 static const bool emptyValueIsZero = false; 87 static T emptyValue() { return std::numeric_limits<T>::max(); } 88 static void constructDeletedValue(T& slot) { slot = std::numeric_limits<T>::max() - 1; } 89 static bool isDeletedValue(T value) { return value == std::numeric_limits<T>::max() - 1; } 90}; 91 92template<typename P> struct HashTraits<P*> : GenericHashTraits<P*> { 93 static const bool emptyValueIsZero = true; 94 static void constructDeletedValue(P*& slot) { slot = reinterpret_cast<P*>(-1); } 95 static bool isDeletedValue(P* value) { return value == reinterpret_cast<P*>(-1); } 96}; 97 98template<typename T> struct SimpleClassHashTraits : GenericHashTraits<T> { 99 static const bool emptyValueIsZero = true; 100 static void constructDeletedValue(T& slot) { new (NotNull, &slot) T(HashTableDeletedValue); } 101 static bool isDeletedValue(const T& value) { return value.isHashTableDeletedValue(); } 102}; 103 104template<typename T, typename Deleter> struct HashTraits<std::unique_ptr<T, Deleter>> : SimpleClassHashTraits<std::unique_ptr<T, Deleter>> { 105 typedef std::nullptr_t EmptyValueType; 106 static EmptyValueType emptyValue() { return nullptr; } 107 108 typedef T* PeekType; 109 static T* peek(const std::unique_ptr<T, Deleter>& value) { return value.get(); } 110 static T* peek(std::nullptr_t) { return nullptr; } 111}; 112 113template<typename T> struct HashTraits<OwnPtr<T>> : SimpleClassHashTraits<OwnPtr<T>> { 114 typedef std::nullptr_t EmptyValueType; 115 static EmptyValueType emptyValue() { return nullptr; } 116 117 typedef T* PeekType; 118 static T* peek(const OwnPtr<T>& value) { return value.get(); } 119 static T* peek(std::nullptr_t) { return nullptr; } 120}; 121 122template<typename P> struct HashTraits<RefPtr<P>> : SimpleClassHashTraits<RefPtr<P>> { 123 static P* emptyValue() { return 0; } 124 125 typedef P* PeekType; 126 static PeekType peek(const RefPtr<P>& value) { return value.get(); } 127 static PeekType peek(P* value) { return value; } 128}; 129 130template<> struct HashTraits<String> : SimpleClassHashTraits<String> { 131 static const bool hasIsEmptyValueFunction = true; 132 static bool isEmptyValue(const String&); 133}; 134 135// This struct template is an implementation detail of the isHashTraitsEmptyValue function, 136// which selects either the emptyValue function or the isEmptyValue function to check for empty values. 137template<typename Traits, bool hasEmptyValueFunction> struct HashTraitsEmptyValueChecker; 138template<typename Traits> struct HashTraitsEmptyValueChecker<Traits, true> { 139 template<typename T> static bool isEmptyValue(const T& value) { return Traits::isEmptyValue(value); } 140}; 141template<typename Traits> struct HashTraitsEmptyValueChecker<Traits, false> { 142 template<typename T> static bool isEmptyValue(const T& value) { return value == Traits::emptyValue(); } 143}; 144template<typename Traits, typename T> inline bool isHashTraitsEmptyValue(const T& value) 145{ 146 return HashTraitsEmptyValueChecker<Traits, Traits::hasIsEmptyValueFunction>::isEmptyValue(value); 147} 148 149template<typename FirstTraitsArg, typename SecondTraitsArg> 150struct PairHashTraits : GenericHashTraits<std::pair<typename FirstTraitsArg::TraitType, typename SecondTraitsArg::TraitType>> { 151 typedef FirstTraitsArg FirstTraits; 152 typedef SecondTraitsArg SecondTraits; 153 typedef std::pair<typename FirstTraits::TraitType, typename SecondTraits::TraitType> TraitType; 154 typedef std::pair<typename FirstTraits::EmptyValueType, typename SecondTraits::EmptyValueType> EmptyValueType; 155 156 static const bool emptyValueIsZero = FirstTraits::emptyValueIsZero && SecondTraits::emptyValueIsZero; 157 static EmptyValueType emptyValue() { return std::make_pair(FirstTraits::emptyValue(), SecondTraits::emptyValue()); } 158 159 static const int minimumTableSize = FirstTraits::minimumTableSize; 160 161 static void constructDeletedValue(TraitType& slot) { FirstTraits::constructDeletedValue(slot.first); } 162 static bool isDeletedValue(const TraitType& value) { return FirstTraits::isDeletedValue(value.first); } 163}; 164 165template<typename First, typename Second> 166struct HashTraits<std::pair<First, Second>> : public PairHashTraits<HashTraits<First>, HashTraits<Second>> { }; 167 168template<typename KeyTypeArg, typename ValueTypeArg> 169struct KeyValuePair { 170 typedef KeyTypeArg KeyType; 171 172 KeyValuePair() 173 { 174 } 175 176 template<typename K, typename V> 177 KeyValuePair(K&& key, V&& value) 178 : key(std::forward<K>(key)) 179 , value(std::forward<V>(value)) 180 { 181 } 182 183 template <typename OtherKeyType, typename OtherValueType> 184 KeyValuePair(KeyValuePair<OtherKeyType, OtherValueType>&& other) 185 : key(std::forward<OtherKeyType>(other.key)) 186 , value(std::forward<OtherValueType>(other.value)) 187 { 188 } 189 190 KeyTypeArg key; 191 ValueTypeArg value; 192}; 193 194template<typename KeyTraitsArg, typename ValueTraitsArg> 195struct KeyValuePairHashTraits : GenericHashTraits<KeyValuePair<typename KeyTraitsArg::TraitType, typename ValueTraitsArg::TraitType>> { 196 typedef KeyTraitsArg KeyTraits; 197 typedef ValueTraitsArg ValueTraits; 198 typedef KeyValuePair<typename KeyTraits::TraitType, typename ValueTraits::TraitType> TraitType; 199 typedef KeyValuePair<typename KeyTraits::EmptyValueType, typename ValueTraits::EmptyValueType> EmptyValueType; 200 201 static const bool emptyValueIsZero = KeyTraits::emptyValueIsZero && ValueTraits::emptyValueIsZero; 202 static EmptyValueType emptyValue() { return KeyValuePair<typename KeyTraits::EmptyValueType, typename ValueTraits::EmptyValueType>(KeyTraits::emptyValue(), ValueTraits::emptyValue()); } 203 204 static const int minimumTableSize = KeyTraits::minimumTableSize; 205 206 static void constructDeletedValue(TraitType& slot) { KeyTraits::constructDeletedValue(slot.key); } 207 static bool isDeletedValue(const TraitType& value) { return KeyTraits::isDeletedValue(value.key); } 208}; 209 210template<typename Key, typename Value> 211struct HashTraits<KeyValuePair<Key, Value>> : public KeyValuePairHashTraits<HashTraits<Key>, HashTraits<Value>> { }; 212 213template<typename T> 214struct NullableHashTraits : public HashTraits<T> { 215 static const bool emptyValueIsZero = false; 216 static T emptyValue() { return reinterpret_cast<T>(1); } 217}; 218 219// Useful for classes that want complete control over what is empty and what is deleted, 220// and how to construct both. 221template<typename T> 222struct CustomHashTraits : public GenericHashTraits<T> { 223 static const bool emptyValueIsZero = false; 224 static const bool hasIsEmptyValueFunction = true; 225 226 static void constructDeletedValue(T& slot) 227 { 228 new (NotNull, &slot) T(T::DeletedValue); 229 } 230 231 static bool isDeletedValue(const T& value) 232 { 233 return value.isDeletedValue(); 234 } 235 236 static T emptyValue() 237 { 238 return T(T::EmptyValue); 239 } 240 241 static bool isEmptyValue(const T& value) 242 { 243 return value.isEmptyValue(); 244 } 245}; 246 247} // namespace WTF 248 249using WTF::HashTraits; 250using WTF::PairHashTraits; 251using WTF::NullableHashTraits; 252using WTF::SimpleClassHashTraits; 253 254#endif // WTF_HashTraits_h 255