-/*
- * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved
- * Copyright (C) Research In Motion Limited 2009. All rights reserved.
- *
- * 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 StringHash_h
-#define StringHash_h
-
-#include "AtomicString.h"
-#include "WTFString.h"
-#include <wtf/Forward.h>
-#include <wtf/HashTraits.h>
-#include <wtf/StringHasher.h>
-#include <wtf/unicode/Unicode.h>
-
-namespace WTF {
-
- // The hash() functions on StringHash and CaseFoldingHash do not support
- // null strings. get(), contains(), and add() on HashMap<String,..., StringHash>
- // cause a null-pointer dereference when passed null strings.
-
- // FIXME: We should really figure out a way to put the computeHash function that's
- // currently a member function of StringImpl into this file so we can be a little
- // closer to having all the nearly-identical hash functions in one place.
-
- struct StringHash {
- static unsigned hash(StringImpl* key) { return key->hash(); }
- static bool equal(const StringImpl* a, const StringImpl* b)
- {
- if (a == b)
- return true;
- if (!a || !b)
- return false;
-
- unsigned aLength = a->length();
- unsigned bLength = b->length();
- if (aLength != bLength)
- return false;
-
- // FIXME: perhaps we should have a more abstract macro that indicates when
- // going 4 bytes at a time is unsafe
-#if CPU(ARM) || CPU(SH4) || CPU(MIPS)
- const UChar* aChars = a->characters();
- const UChar* bChars = b->characters();
- for (unsigned i = 0; i != aLength; ++i) {
- if (*aChars++ != *bChars++)
- return false;
- }
- return true;
-#else
- /* Do it 4-bytes-at-a-time on architectures where it's safe */
- const uint32_t* aChars = reinterpret_cast<const uint32_t*>(a->characters());
- const uint32_t* bChars = reinterpret_cast<const uint32_t*>(b->characters());
-
- unsigned halfLength = aLength >> 1;
- for (unsigned i = 0; i != halfLength; ++i)
- if (*aChars++ != *bChars++)
- return false;
-
- if (aLength & 1 && *reinterpret_cast<const uint16_t*>(aChars) != *reinterpret_cast<const uint16_t*>(bChars))
- return false;
-
- return true;
-#endif
- }
-
- static unsigned hash(const RefPtr<StringImpl>& key) { return key->hash(); }
- static bool equal(const RefPtr<StringImpl>& a, const RefPtr<StringImpl>& b)
- {
- return equal(a.get(), b.get());
- }
-
- static unsigned hash(const String& key) { return key.impl()->hash(); }
- static bool equal(const String& a, const String& b)
- {
- return equal(a.impl(), b.impl());
- }
-
- static const bool safeToCompareToEmptyOrDeleted = false;
- };
-
- class CaseFoldingHash {
- public:
- template<typename T> static inline UChar foldCase(T ch)
- {
- return WTF::Unicode::foldCase(ch);
- }
-
- static unsigned hash(const UChar* data, unsigned length)
- {
- return StringHasher::computeHash<UChar, foldCase<UChar> >(data, length);
- }
-
- static unsigned hash(StringImpl* str)
- {
- return hash(str->characters(), str->length());
- }
-
- static unsigned hash(const char* data, unsigned length)
- {
- return StringHasher::computeHash<char, foldCase<char> >(data, length);
- }
-
- static bool equal(const StringImpl* a, const StringImpl* b)
- {
- if (a == b)
- return true;
- if (!a || !b)
- return false;
- unsigned length = a->length();
- if (length != b->length())
- return false;
- return WTF::Unicode::umemcasecmp(a->characters(), b->characters(), length) == 0;
- }
-
- static unsigned hash(const RefPtr<StringImpl>& key)
- {
- return hash(key.get());
- }
-
- static bool equal(const RefPtr<StringImpl>& a, const RefPtr<StringImpl>& b)
- {
- return equal(a.get(), b.get());
- }
-
- static unsigned hash(const String& key)
- {
- return hash(key.impl());
- }
- static unsigned hash(const AtomicString& key)
- {
- return hash(key.impl());
- }
- static bool equal(const String& a, const String& b)
- {
- return equal(a.impl(), b.impl());
- }
- static bool equal(const AtomicString& a, const AtomicString& b)
- {
- return (a == b) || equal(a.impl(), b.impl());
- }
-
- static const bool safeToCompareToEmptyOrDeleted = false;
- };
-
- // This hash can be used in cases where the key is a hash of a string, but we don't
- // want to store the string. It's not really specific to string hashing, but all our
- // current uses of it are for strings.
- struct AlreadyHashed : IntHash<unsigned> {
- static unsigned hash(unsigned key) { return key; }
-
- // To use a hash value as a key for a hash table, we need to eliminate the
- // "deleted" value, which is negative one. That could be done by changing
- // the string hash function to never generate negative one, but this works
- // and is still relatively efficient.
- static unsigned avoidDeletedValue(unsigned hash)
- {
- ASSERT(hash);
- unsigned newHash = hash | (!(hash + 1) << 31);
- ASSERT(newHash);
- ASSERT(newHash != 0xFFFFFFFF);
- return newHash;
- }
- };
-
- template<> struct HashTraits<String> : SimpleClassHashTraits<String> { };
-
-}
-
-using WTF::StringHash;
-using WTF::CaseFoldingHash;
-using WTF::AlreadyHashed;
-
-#endif
projects / apple / javascriptcore.git / blobdiff