2 * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved
3 * Copyright (C) Research In Motion Limited 2009. All rights reserved.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Library General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Library General Public License for more details.
15 * You should have received a copy of the GNU Library General Public License
16 * along with this library; see the file COPYING.LIB. If not, write to
17 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
18 * Boston, MA 02110-1301, USA.
25 #include "AtomicString.h"
26 #include "WTFString.h"
27 #include <wtf/Forward.h>
28 #include <wtf/HashTraits.h>
29 #include <wtf/StringHasher.h>
30 #include <wtf/unicode/Unicode.h>
34 // The hash() functions on StringHash and CaseFoldingHash do not support
35 // null strings. get(), contains(), and add() on HashMap<String,..., StringHash>
36 // cause a null-pointer dereference when passed null strings.
38 // FIXME: We should really figure out a way to put the computeHash function that's
39 // currently a member function of StringImpl into this file so we can be a little
40 // closer to having all the nearly-identical hash functions in one place.
43 static unsigned hash(StringImpl* key) { return key->hash(); }
44 static bool equal(const StringImpl* a, const StringImpl* b)
51 unsigned aLength = a->length();
52 unsigned bLength = b->length();
53 if (aLength != bLength)
56 // FIXME: perhaps we should have a more abstract macro that indicates when
57 // going 4 bytes at a time is unsafe
58 #if CPU(ARM) || CPU(SH4) || CPU(MIPS) || CPU(SPARC)
59 const UChar* aChars = a->characters();
60 const UChar* bChars = b->characters();
61 for (unsigned i = 0; i != aLength; ++i) {
62 if (*aChars++ != *bChars++)
67 /* Do it 4-bytes-at-a-time on architectures where it's safe */
68 const uint32_t* aChars = reinterpret_cast<const uint32_t*>(a->characters());
69 const uint32_t* bChars = reinterpret_cast<const uint32_t*>(b->characters());
71 unsigned halfLength = aLength >> 1;
72 for (unsigned i = 0; i != halfLength; ++i)
73 if (*aChars++ != *bChars++)
76 if (aLength & 1 && *reinterpret_cast<const uint16_t*>(aChars) != *reinterpret_cast<const uint16_t*>(bChars))
83 static unsigned hash(const RefPtr<StringImpl>& key) { return key->hash(); }
84 static bool equal(const RefPtr<StringImpl>& a, const RefPtr<StringImpl>& b)
86 return equal(a.get(), b.get());
89 static unsigned hash(const String& key) { return key.impl()->hash(); }
90 static bool equal(const String& a, const String& b)
92 return equal(a.impl(), b.impl());
95 static const bool safeToCompareToEmptyOrDeleted = false;
98 class CaseFoldingHash {
100 template<typename T> static inline UChar foldCase(T ch)
102 return WTF::Unicode::foldCase(ch);
105 static unsigned hash(const UChar* data, unsigned length)
107 return StringHasher::computeHash<UChar, foldCase<UChar> >(data, length);
110 static unsigned hash(StringImpl* str)
112 return hash(str->characters(), str->length());
115 static unsigned hash(const char* data, unsigned length)
117 return StringHasher::computeHash<char, foldCase<char> >(data, length);
120 static bool equal(const StringImpl* a, const StringImpl* b)
126 unsigned length = a->length();
127 if (length != b->length())
129 return WTF::Unicode::umemcasecmp(a->characters(), b->characters(), length) == 0;
132 static unsigned hash(const RefPtr<StringImpl>& key)
134 return hash(key.get());
137 static bool equal(const RefPtr<StringImpl>& a, const RefPtr<StringImpl>& b)
139 return equal(a.get(), b.get());
142 static unsigned hash(const String& key)
144 return hash(key.impl());
146 static unsigned hash(const AtomicString& key)
148 return hash(key.impl());
150 static bool equal(const String& a, const String& b)
152 return equal(a.impl(), b.impl());
154 static bool equal(const AtomicString& a, const AtomicString& b)
156 return (a == b) || equal(a.impl(), b.impl());
159 static const bool safeToCompareToEmptyOrDeleted = false;
162 // This hash can be used in cases where the key is a hash of a string, but we don't
163 // want to store the string. It's not really specific to string hashing, but all our
164 // current uses of it are for strings.
165 struct AlreadyHashed : IntHash<unsigned> {
166 static unsigned hash(unsigned key) { return key; }
168 // To use a hash value as a key for a hash table, we need to eliminate the
169 // "deleted" value, which is negative one. That could be done by changing
170 // the string hash function to never generate negative one, but this works
171 // and is still relatively efficient.
172 static unsigned avoidDeletedValue(unsigned hash)
175 unsigned newHash = hash | (!(hash + 1) << 31);
177 ASSERT(newHash != 0xFFFFFFFF);
184 using WTF::StringHash;
185 using WTF::CaseFoldingHash;
186 using WTF::AlreadyHashed;