1/*
2 * Copyright (C) 2005, 2006, 2007, 2008 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 "HashFunctions.h"
25#include "TypeTraits.h"
26#include <utility>
27#include <limits>
28
29namespace WTF {
30
31 using std::pair;
32 using std::make_pair;
33
34 template<typename T> struct HashTraits;
35
36 template<bool isInteger, typename T> struct GenericHashTraitsBase;
37
38 template<typename T> struct GenericHashTraitsBase<false, T> {
39 static const bool emptyValueIsZero = false;
40 static const bool needsDestruction = true;
41 };
42
43 // Default integer traits disallow both 0 and -1 as keys (max value instead of -1 for unsigned).
44 template<typename T> struct GenericHashTraitsBase<true, T> {
45 static const bool emptyValueIsZero = true;
46 static const bool needsDestruction = false;
47 static void constructDeletedValue(T& slot) { slot = static_cast<T>(-1); }
48 static bool isDeletedValue(T value) { return value == static_cast<T>(-1); }
49 };
50
51 template<typename T> struct GenericHashTraits : GenericHashTraitsBase<IsInteger<T>::value, T> {
52 typedef T TraitType;
53 static T emptyValue() { return T(); }
54 };
55
56 template<typename T> struct HashTraits : GenericHashTraits<T> { };
57
58 template<typename T> struct FloatHashTraits : GenericHashTraits<T> {
59 static const bool needsDestruction = false;
60 static T emptyValue() { return std::numeric_limits<T>::infinity(); }
61 static void constructDeletedValue(T& slot) { slot = -std::numeric_limits<T>::infinity(); }
62 static bool isDeletedValue(T value) { return value == -std::numeric_limits<T>::infinity(); }
63 };
64
65 template<> struct HashTraits<float> : FloatHashTraits<float> { };
66 template<> struct HashTraits<double> : FloatHashTraits<double> { };
67
68 // Default unsigned traits disallow both 0 and max as keys -- use these traits to allow zero and disallow max - 1.
69 template<typename T> struct UnsignedWithZeroKeyHashTraits : GenericHashTraits<T> {
70 static const bool emptyValueIsZero = false;
71 static const bool needsDestruction = false;
72 static T emptyValue() { return std::numeric_limits<T>::max(); }
73 static void constructDeletedValue(T& slot) { slot = std::numeric_limits<T>::max() - 1; }
74 static bool isDeletedValue(T value) { return value == std::numeric_limits<T>::max() - 1; }
75 };
76
77 template<typename P> struct HashTraits<P*> : GenericHashTraits<P*> {
78 static const bool emptyValueIsZero = true;
79 static const bool needsDestruction = false;
80 static void constructDeletedValue(P*& slot) { slot = reinterpret_cast<P*>(-1); }
81 static bool isDeletedValue(P* value) { return value == reinterpret_cast<P*>(-1); }
82 };
83
84 template<typename P> struct HashTraits<RefPtr<P> > : GenericHashTraits<RefPtr<P> > {
85 static const bool emptyValueIsZero = true;
86 static void constructDeletedValue(RefPtr<P>& slot) { new (&slot) RefPtr<P>(HashTableDeletedValue); }
87 static bool isDeletedValue(const RefPtr<P>& value) { return value.isHashTableDeletedValue(); }
88 };
89
90 // special traits for pairs, helpful for their use in HashMap implementation
91
92 template<typename FirstTraitsArg, typename SecondTraitsArg>
93 struct PairHashTraits : GenericHashTraits<pair<typename FirstTraitsArg::TraitType, typename SecondTraitsArg::TraitType> > {
94 typedef FirstTraitsArg FirstTraits;
95 typedef SecondTraitsArg SecondTraits;
96 typedef pair<typename FirstTraits::TraitType, typename SecondTraits::TraitType> TraitType;
97
98 static const bool emptyValueIsZero = FirstTraits::emptyValueIsZero && SecondTraits::emptyValueIsZero;
99 static TraitType emptyValue() { return make_pair(FirstTraits::emptyValue(), SecondTraits::emptyValue()); }
100
101 static const bool needsDestruction = FirstTraits::needsDestruction || SecondTraits::needsDestruction;
102
103 static void constructDeletedValue(TraitType& slot) { FirstTraits::constructDeletedValue(slot.first); }
104 static bool isDeletedValue(const TraitType& value) { return FirstTraits::isDeletedValue(value.first); }
105 };
106
107 template<typename First, typename Second>
108 struct HashTraits<pair<First, Second> > : public PairHashTraits<HashTraits<First>, HashTraits<Second> > { };
109
110} // namespace WTF
111
112using WTF::HashTraits;
113using WTF::PairHashTraits;
114
115#endif // WTF_HashTraits_h
116

source code of qtscript/src/3rdparty/javascriptcore/JavaScriptCore/wtf/HashTraits.h