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author | Simon Hausmann <simon.hausmann@nokia.com> | 2012-05-07 11:21:11 +0200 |
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committer | Simon Hausmann <simon.hausmann@nokia.com> | 2012-05-07 11:21:11 +0200 |
commit | 2cf6c8816a73e0132bd8fa3b509d62d7c51b6e47 (patch) | |
tree | 988e8c5b116dd0466244ae2fe5af8ee9be926d76 /Source/JavaScriptCore/wtf/StringHasher.h | |
parent | dd91e772430dc294e3bf478c119ef8d43c0a3358 (diff) | |
download | qtwebkit-2cf6c8816a73e0132bd8fa3b509d62d7c51b6e47.tar.gz |
Imported WebKit commit 7e538425aa020340619e927792f3d895061fb54b (http://svn.webkit.org/repository/webkit/trunk@116286)
Diffstat (limited to 'Source/JavaScriptCore/wtf/StringHasher.h')
-rw-r--r-- | Source/JavaScriptCore/wtf/StringHasher.h | 185 |
1 files changed, 0 insertions, 185 deletions
diff --git a/Source/JavaScriptCore/wtf/StringHasher.h b/Source/JavaScriptCore/wtf/StringHasher.h deleted file mode 100644 index 714525188..000000000 --- a/Source/JavaScriptCore/wtf/StringHasher.h +++ /dev/null @@ -1,185 +0,0 @@ -/* - * Copyright (C) 2005, 2006, 2008, 2010 Apple Inc. All rights reserved. - * Copyright (C) 2010 Patrick Gansterer <paroga@paroga.com> - * - * 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_StringHasher_h -#define WTF_StringHasher_h - -#include <wtf/unicode/Unicode.h> - -namespace WTF { - -// Golden ratio - arbitrary start value to avoid mapping all 0's to all 0's -static const unsigned stringHashingStartValue = 0x9e3779b9U; - -// Paul Hsieh's SuperFastHash -// http://www.azillionmonkeys.com/qed/hash.html -// char* data is interpreted as latin-encoded (zero extended to 16 bits). - -// NOTE: This class must stay in sync with the create_hash_table script in -// JavaScriptCore and the CodeGeneratorJS.pm script in WebCore. -class StringHasher { -public: - static const unsigned flagCount = 8; // Save 8 bits for StringImpl to use as flags. - - inline StringHasher() - : m_hash(stringHashingStartValue) - , m_hasPendingCharacter(false) - , m_pendingCharacter(0) - { - } - - inline void addCharacters(UChar a, UChar b) - { - ASSERT(!m_hasPendingCharacter); - addCharactersToHash(a, b); - } - - inline void addCharacter(UChar ch) - { - if (m_hasPendingCharacter) { - addCharactersToHash(m_pendingCharacter, ch); - m_hasPendingCharacter = false; - return; - } - - m_pendingCharacter = ch; - m_hasPendingCharacter = true; - } - - inline unsigned hash() const - { - unsigned result = m_hash; - - // Handle end case. - if (m_hasPendingCharacter) { - result += m_pendingCharacter; - result ^= result << 11; - result += result >> 17; - } - - // Force "avalanching" of final 31 bits. - result ^= result << 3; - result += result >> 5; - result ^= result << 2; - result += result >> 15; - result ^= result << 10; - - // Reserving space from the high bits for flags preserves most of the hash's - // value, since hash lookup typically masks out the high bits anyway. - result &= (1u << (sizeof(result) * 8 - flagCount)) - 1; - - // This avoids ever returning a hash code of 0, since that is used to - // signal "hash not computed yet". Setting the high bit maintains - // reasonable fidelity to a hash code of 0 because it is likely to yield - // exactly 0 when hash lookup masks out the high bits. - if (!result) - result = 0x80000000 >> flagCount; - - return result; - } - - template<typename T, UChar Converter(T)> static inline unsigned computeHash(const T* data, unsigned length) - { - StringHasher hasher; - bool rem = length & 1; - length >>= 1; - - while (length--) { - hasher.addCharacters(Converter(data[0]), Converter(data[1])); - data += 2; - } - - if (rem) - hasher.addCharacter(Converter(*data)); - - return hasher.hash(); - } - - template<typename T, UChar Converter(T)> static inline unsigned computeHash(const T* data) - { - StringHasher hasher; - - while (true) { - UChar b0 = Converter(*data++); - if (!b0) - break; - UChar b1 = Converter(*data++); - if (!b1) { - hasher.addCharacter(b0); - break; - } - - hasher.addCharacters(b0, b1); - } - - return hasher.hash(); - } - - template<typename T> static inline unsigned computeHash(const T* data, unsigned length) - { - return computeHash<T, defaultConverter>(data, length); - } - - template<typename T> static inline unsigned computeHash(const T* data) - { - return computeHash<T, defaultConverter>(data); - } - - template<size_t length> static inline unsigned hashMemory(const void* data) - { - COMPILE_ASSERT(!(length % 4), length_must_be_a_multible_of_four); - return computeHash<UChar>(static_cast<const UChar*>(data), length / sizeof(UChar)); - } - - static inline unsigned hashMemory(const void* data, unsigned size) - { - ASSERT(!(size % 2)); - return computeHash<UChar>(static_cast<const UChar*>(data), size / sizeof(UChar)); - } - -private: - static inline UChar defaultConverter(UChar ch) - { - return ch; - } - - static inline UChar defaultConverter(LChar ch) - { - return ch; - } - - inline void addCharactersToHash(UChar a, UChar b) - { - m_hash += a; - unsigned tmp = (b << 11) ^ m_hash; - m_hash = (m_hash << 16) ^ tmp; - m_hash += m_hash >> 11; - } - - unsigned m_hash; - bool m_hasPendingCharacter; - UChar m_pendingCharacter; -}; - -} // namespace WTF - -using WTF::StringHasher; - -#endif // WTF_StringHasher_h |