summaryrefslogtreecommitdiff
path: root/Source/JavaScriptCore/wtf/StringHasher.h
diff options
context:
space:
mode:
authorSimon Hausmann <simon.hausmann@nokia.com>2012-05-07 11:21:11 +0200
committerSimon Hausmann <simon.hausmann@nokia.com>2012-05-07 11:21:11 +0200
commit2cf6c8816a73e0132bd8fa3b509d62d7c51b6e47 (patch)
tree988e8c5b116dd0466244ae2fe5af8ee9be926d76 /Source/JavaScriptCore/wtf/StringHasher.h
parentdd91e772430dc294e3bf478c119ef8d43c0a3358 (diff)
downloadqtwebkit-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.h185
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