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/HashTableDeletedValueType.h" 26 #include "wtf/StdLibExtras.h" 27 #include "wtf/TypeTraits.h" 28 #include <utility> 29 #include <limits> 30 31 namespace WTF { 32 33 class String; 34 35 template<typename T> class OwnPtr; 36 template<typename T> class PassOwnPtr; 37 38 template<typename T> struct HashTraits; 39 40 template<bool isInteger, typename T> struct GenericHashTraitsBase; 41 42 template<typename T> struct GenericHashTraitsBase<false, T> { 43 // The emptyValueIsZero flag is used to optimize allocation of empty hash tables with zeroed memory. 44 static const bool emptyValueIsZero = false; 45 46 // The hasIsEmptyValueFunction flag allows the hash table to automatically generate code to check 47 // for the empty value when it can be done with the equality operator, but allows custom functions 48 // for cases like String that need them. 49 static const bool hasIsEmptyValueFunction = false; 50 51 // The needsDestruction flag is used to optimize destruction and rehashing. 52 static const bool needsDestruction = true; 53 54 // The starting table size. Can be overridden when we know beforehand that 55 // a hash table will have at least N entries. 56 #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR) 57 static const unsigned minimumTableSize = 1; 58 #else 59 static const unsigned minimumTableSize = 8; 60 #endif 61 }; 62 63 // Default integer traits disallow both 0 and -1 as keys (max value instead of -1 for unsigned). 64 template<typename T> struct GenericHashTraitsBase<true, T> : GenericHashTraitsBase<false, T> { 65 static const bool emptyValueIsZero = true; 66 static const bool needsDestruction = false; 67 static void constructDeletedValue(T& slot) { slot = static_cast<T>(-1); } 68 static bool isDeletedValue(T value) { return value == static_cast<T>(-1); } 69 }; 70 71 template<typename T> struct GenericHashTraits : GenericHashTraitsBase<IsInteger<T>::value, T> { 72 typedef T TraitType; 73 typedef T EmptyValueType; 74 75 static T emptyValue() { return T(); } 76 77 // Type for functions that take ownership, such as add. 78 // The store function either not be called or called once to store something passed in. 79 // The value passed to the store function will be either PassInType or PassInType&. 80 typedef const T& PassInType; 81 static void store(const T& value, T& storage) { storage = value; } 82 83 // Type for return value of functions that transfer ownership, such as take. 84 typedef T PassOutType; 85 static PassOutType passOut(const T& value) { return value; } 86 static T& passOut(T& value) { return value; } // Overloaded to avoid copying of non-temporary values. 87 88 // Type for return value of functions that do not transfer ownership, such as get. 89 // FIXME: We could change this type to const T& for better performance if we figured out 90 // a way to handle the return value from emptyValue, which is a temporary. 91 typedef T PeekType; 92 static PeekType peek(const T& value) { return value; } 93 static T& peek(T& value) { return value; } // Overloaded to avoid copying of non-temporary values. 94 }; 95 96 template<typename T> struct HashTraits : GenericHashTraits<T> { }; 97 98 template<typename T> struct FloatHashTraits : GenericHashTraits<T> { 99 static const bool needsDestruction = false; 100 static T emptyValue() { return std::numeric_limits<T>::infinity(); } 101 static void constructDeletedValue(T& slot) { slot = -std::numeric_limits<T>::infinity(); } 102 static bool isDeletedValue(T value) { return value == -std::numeric_limits<T>::infinity(); } 103 }; 104 105 template<> struct HashTraits<float> : FloatHashTraits<float> { }; 106 template<> struct HashTraits<double> : FloatHashTraits<double> { }; 107 108 // Default unsigned traits disallow both 0 and max as keys -- use these traits to allow zero and disallow max - 1. 109 template<typename T> struct UnsignedWithZeroKeyHashTraits : GenericHashTraits<T> { 110 static const bool emptyValueIsZero = false; 111 static const bool needsDestruction = false; 112 static T emptyValue() { return std::numeric_limits<T>::max(); } 113 static void constructDeletedValue(T& slot) { slot = std::numeric_limits<T>::max() - 1; } 114 static bool isDeletedValue(T value) { return value == std::numeric_limits<T>::max() - 1; } 115 }; 116 117 template<typename P> struct HashTraits<P*> : GenericHashTraits<P*> { 118 static const bool emptyValueIsZero = true; 119 static const bool needsDestruction = false; 120 static void constructDeletedValue(P*& slot) { slot = reinterpret_cast<P*>(-1); } 121 static bool isDeletedValue(P* value) { return value == reinterpret_cast<P*>(-1); } 122 }; 123 124 template<typename T> struct SimpleClassHashTraits : GenericHashTraits<T> { 125 static const bool emptyValueIsZero = true; 126 static void constructDeletedValue(T& slot) { new (NotNull, &slot) T(HashTableDeletedValue); } 127 static bool isDeletedValue(const T& value) { return value.isHashTableDeletedValue(); } 128 }; 129 130 template<typename P> struct HashTraits<OwnPtr<P> > : SimpleClassHashTraits<OwnPtr<P> > { 131 typedef std::nullptr_t EmptyValueType; 132 133 static EmptyValueType emptyValue() { return nullptr; } 134 135 typedef PassOwnPtr<P> PassInType; 136 static void store(PassOwnPtr<P> value, OwnPtr<P>& storage) { storage = value; } 137 138 typedef PassOwnPtr<P> PassOutType; 139 static PassOwnPtr<P> passOut(OwnPtr<P>& value) { return value.release(); } 140 static PassOwnPtr<P> passOut(std::nullptr_t) { return nullptr; } 141 142 typedef typename OwnPtr<P>::PtrType PeekType; 143 static PeekType peek(const OwnPtr<P>& value) { return value.get(); } 144 static PeekType peek(std::nullptr_t) { return 0; } 145 }; 146 147 template<typename P> struct HashTraits<RefPtr<P> > : SimpleClassHashTraits<RefPtr<P> > { 148 static P* emptyValue() { return 0; } 149 150 typedef PassRefPtr<P> PassInType; 151 static void store(PassRefPtr<P> value, RefPtr<P>& storage) { storage = value; } 152 153 typedef PassRefPtr<P> PassOutType; 154 static PassRefPtr<P> passOut(RefPtr<P>& value) { return value.release(); } 155 static PassRefPtr<P> passOut(P* value) { return value; } 156 157 typedef P* PeekType; 158 static PeekType peek(const RefPtr<P>& value) { return value.get(); } 159 static PeekType peek(P* value) { return value; } 160 }; 161 162 template<> struct HashTraits<String> : SimpleClassHashTraits<String> { 163 static const bool hasIsEmptyValueFunction = true; 164 static bool isEmptyValue(const String&); 165 }; 166 167 // This struct template is an implementation detail of the isHashTraitsEmptyValue function, 168 // which selects either the emptyValue function or the isEmptyValue function to check for empty values. 169 template<typename Traits, bool hasEmptyValueFunction> struct HashTraitsEmptyValueChecker; 170 template<typename Traits> struct HashTraitsEmptyValueChecker<Traits, true> { 171 template<typename T> static bool isEmptyValue(const T& value) { return Traits::isEmptyValue(value); } 172 }; 173 template<typename Traits> struct HashTraitsEmptyValueChecker<Traits, false> { 174 template<typename T> static bool isEmptyValue(const T& value) { return value == Traits::emptyValue(); } 175 }; 176 template<typename Traits, typename T> inline bool isHashTraitsEmptyValue(const T& value) 177 { 178 return HashTraitsEmptyValueChecker<Traits, Traits::hasIsEmptyValueFunction>::isEmptyValue(value); 179 } 180 181 template<typename FirstTraitsArg, typename SecondTraitsArg> 182 struct PairHashTraits : GenericHashTraits<std::pair<typename FirstTraitsArg::TraitType, typename SecondTraitsArg::TraitType> > { 183 typedef FirstTraitsArg FirstTraits; 184 typedef SecondTraitsArg SecondTraits; 185 typedef std::pair<typename FirstTraits::TraitType, typename SecondTraits::TraitType> TraitType; 186 typedef std::pair<typename FirstTraits::EmptyValueType, typename SecondTraits::EmptyValueType> EmptyValueType; 187 188 static const bool emptyValueIsZero = FirstTraits::emptyValueIsZero && SecondTraits::emptyValueIsZero; 189 static EmptyValueType emptyValue() { return std::make_pair(FirstTraits::emptyValue(), SecondTraits::emptyValue()); } 190 191 static const bool needsDestruction = FirstTraits::needsDestruction || SecondTraits::needsDestruction; 192 193 static const unsigned minimumTableSize = FirstTraits::minimumTableSize; 194 195 static void constructDeletedValue(TraitType& slot) { FirstTraits::constructDeletedValue(slot.first); } 196 static bool isDeletedValue(const TraitType& value) { return FirstTraits::isDeletedValue(value.first); } 197 }; 198 199 template<typename First, typename Second> 200 struct HashTraits<std::pair<First, Second> > : public PairHashTraits<HashTraits<First>, HashTraits<Second> > { }; 201 202 template<typename KeyTypeArg, typename ValueTypeArg> 203 struct KeyValuePair { 204 typedef KeyTypeArg KeyType; 205 206 KeyValuePair() 207 { 208 } 209 210 KeyValuePair(const KeyTypeArg& _key, const ValueTypeArg& _value) 211 : key(_key) 212 , value(_value) 213 { 214 } 215 216 template <typename OtherKeyType, typename OtherValueType> 217 KeyValuePair(const KeyValuePair<OtherKeyType, OtherValueType>& other) 218 : key(other.key) 219 , value(other.value) 220 { 221 } 222 223 KeyTypeArg key; 224 ValueTypeArg value; 225 }; 226 227 template<typename KeyTraitsArg, typename ValueTraitsArg> 228 struct KeyValuePairHashTraits : GenericHashTraits<KeyValuePair<typename KeyTraitsArg::TraitType, typename ValueTraitsArg::TraitType> > { 229 typedef KeyTraitsArg KeyTraits; 230 typedef ValueTraitsArg ValueTraits; 231 typedef KeyValuePair<typename KeyTraits::TraitType, typename ValueTraits::TraitType> TraitType; 232 typedef KeyValuePair<typename KeyTraits::EmptyValueType, typename ValueTraits::EmptyValueType> EmptyValueType; 233 234 static const bool emptyValueIsZero = KeyTraits::emptyValueIsZero && ValueTraits::emptyValueIsZero; 235 static EmptyValueType emptyValue() { return KeyValuePair<typename KeyTraits::EmptyValueType, typename ValueTraits::EmptyValueType>(KeyTraits::emptyValue(), ValueTraits::emptyValue()); } 236 237 static const bool needsDestruction = KeyTraits::needsDestruction || ValueTraits::needsDestruction; 238 239 static const unsigned minimumTableSize = KeyTraits::minimumTableSize; 240 241 static void constructDeletedValue(TraitType& slot) { KeyTraits::constructDeletedValue(slot.key); } 242 static bool isDeletedValue(const TraitType& value) { return KeyTraits::isDeletedValue(value.key); } 243 }; 244 245 template<typename Key, typename Value> 246 struct HashTraits<KeyValuePair<Key, Value> > : public KeyValuePairHashTraits<HashTraits<Key>, HashTraits<Value> > { }; 247 248 template<typename T> 249 struct NullableHashTraits : public HashTraits<T> { 250 static const bool emptyValueIsZero = false; 251 static T emptyValue() { return reinterpret_cast<T>(1); } 252 }; 253 254 } // namespace WTF 255 256 using WTF::HashTraits; 257 using WTF::PairHashTraits; 258 using WTF::NullableHashTraits; 259 using WTF::SimpleClassHashTraits; 260 261 #endif // WTF_HashTraits_h 262