/*
* Copyright (C) 2006 Apple Computer, Inc.
*
* 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 "AtomicStringImpl.h"
#include "PlatformString.h"
#include <wtf/HashTraits.h>
#include <wtf/unicode/Unicode.h>
namespace WTF {
template<typename T> struct StrHash;
template<> struct StrHash<WebCore::StringImpl*> {
static unsigned hash(const WebCore::StringImpl* key) { return key->hash(); }
static bool equal(const WebCore::StringImpl* a, const WebCore::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;
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;
}
};
template<> struct StrHash<WebCore::AtomicStringImpl*> : public StrHash<WebCore::StringImpl*> { };
template<> struct StrHash<RefPtr<WebCore::StringImpl> > {
static unsigned hash(const RefPtr<WebCore::StringImpl>& key) { return key->hash(); }
static bool equal(const RefPtr<WebCore::StringImpl>& a, const RefPtr<WebCore::StringImpl>& b)
{
return StrHash<WebCore::StringImpl*>::equal(a.get(), b.get());
}
};
template<> struct StrHash<WebCore::String> {
static unsigned hash(const WebCore::String& key) { return key.impl()->hash(); }
static bool equal(const WebCore::String& a, const WebCore::String& b)
{
return StrHash<WebCore::StringImpl*>::equal(a.impl(), b.impl());
}
};
template<typename T> struct CaseInsensitiveHash;
template<> class CaseInsensitiveHash<WebCore::StringImpl*> {
private:
// Golden ratio - arbitrary start value to avoid mapping all 0's to all 0's
static const unsigned PHI = 0x9e3779b9U;
public:
// Paul Hsieh's SuperFastHash
// http://www.azillionmonkeys.com/qed/hash.html
static unsigned hash(const WebCore::StringImpl* str)
{
unsigned l = str->length();
const UChar* s = str->characters();
uint32_t hash = PHI;
uint32_t tmp;
int rem = l & 1;
l >>= 1;
// Main loop
for (; l > 0; l--) {
hash += WTF::Unicode::foldCase(s[0]);
tmp = (WTF::Unicode::foldCase(s[1]) << 11) ^ hash;
hash = (hash << 16) ^ tmp;
s += 2;
hash += hash >> 11;
}
// Handle end case
if (rem) {
hash += WTF::Unicode::foldCase(s[0]);
hash ^= hash << 11;
hash += hash >> 17;
}
// Force "avalanching" of final 127 bits
hash ^= hash << 3;
hash += hash >> 5;
hash ^= hash << 2;
hash += hash >> 15;
hash ^= hash << 10;
// this avoids ever returning a hash code of 0, since that is used to
// signal "hash not computed yet", using a value that is likely to be
// effectively the same as 0 when the low bits are masked
if (hash == 0)
hash = 0x80000000;
return hash;
}
static unsigned hash(const char* str, unsigned length)
{
// This hash is designed to work on 16-bit chunks at a time. But since the normal case
// (above) is to hash UTF-16 characters, we just treat the 8-bit chars as if they
// were 16-bit chunks, which will give matching results.
unsigned l = length;
const char* s = str;
uint32_t hash = PHI;
uint32_t tmp;
int rem = l & 1;
l >>= 1;
// Main loop
for (; l > 0; l--) {
hash += WTF::Unicode::foldCase(s[0]);
tmp = (WTF::Unicode::foldCase(s[1]) << 11) ^ hash;
hash = (hash << 16) ^ tmp;
s += 2;
hash += hash >> 11;
}
// Handle end case
if (rem) {
hash += WTF::Unicode::foldCase(s[0]);
hash ^= hash << 11;
hash += hash >> 17;
}
// Force "avalanching" of final 127 bits
hash ^= hash << 3;
hash += hash >> 5;
hash ^= hash << 2;
hash += hash >> 15;
hash ^= hash << 10;
// this avoids ever returning a hash code of 0, since that is used to
// signal "hash not computed yet", using a value that is likely to be
// effectively the same as 0 when the low bits are masked
if (hash == 0)
hash = 0x80000000;
return hash;
}
static bool equal(const WebCore::StringImpl* a, const WebCore::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;
}
};
template<> struct CaseInsensitiveHash<WebCore::AtomicStringImpl*> : public CaseInsensitiveHash<WebCore::StringImpl*> { };
template<> struct CaseInsensitiveHash<RefPtr<WebCore::StringImpl> > {
static unsigned hash(const RefPtr<WebCore::StringImpl>& key)
{
return CaseInsensitiveHash<WebCore::StringImpl*>::hash(key.get());
}
static bool equal(const RefPtr<WebCore::StringImpl>& a, const RefPtr<WebCore::StringImpl>& b)
{
return CaseInsensitiveHash<WebCore::StringImpl*>::equal(a.get(), b.get());
}
};
template<> struct CaseInsensitiveHash<WebCore::String> {
static unsigned hash(const WebCore::String& key)
{
return CaseInsensitiveHash<WebCore::StringImpl*>::hash(key.impl());
}
static bool equal(const WebCore::String& a, const WebCore::String& b)
{
return CaseInsensitiveHash<WebCore::StringImpl*>::equal(a.impl(), b.impl());
}
};
// store WebCore::String as StringImpl*
template<> struct HashTraits<WebCore::String> : GenericHashTraits<WebCore::String> {
typedef HashTraits<WebCore::StringImpl*>::StorageTraits StorageTraits;
typedef StorageTraits::TraitType StorageType;
static const bool emptyValueIsZero = true;
static const bool needsRef = true;
typedef union {
WebCore::StringImpl* m_p;
StorageType m_s;
} UnionType;
static void ref(const StorageType& s) { ref(reinterpret_cast<const UnionType*>(&s)->m_p); }
static void deref(const StorageType& s) { deref(reinterpret_cast<const UnionType*>(&s)->m_p); }
static void ref(const WebCore::StringImpl* str) { if (str) const_cast<WebCore::StringImpl*>(str)->ref(); }
static void deref(const WebCore::StringImpl* str) { if (str) const_cast<WebCore::StringImpl*>(str)->deref(); }
};
// share code between StringImpl*, RefPtr<StringImpl>, and String
template<> struct HashKeyStorageTraits<StrHash<RefPtr<WebCore::StringImpl> >, HashTraits<RefPtr<WebCore::StringImpl> > > {
typedef StrHash<WebCore::StringImpl*> Hash;
typedef HashTraits<WebCore::StringImpl*> Traits;
};
template<> struct HashKeyStorageTraits<StrHash<WebCore::String>, HashTraits<WebCore::String> > {
typedef StrHash<WebCore::StringImpl*> Hash;
typedef HashTraits<WebCore::StringImpl*> Traits;
};
template<> struct HashKeyStorageTraits<CaseInsensitiveHash<RefPtr<WebCore::StringImpl> >, HashTraits<RefPtr<WebCore::StringImpl> > > {
typedef CaseInsensitiveHash<WebCore::StringImpl*> Hash;
typedef HashTraits<WebCore::StringImpl*> Traits;
};
template<> struct HashKeyStorageTraits<CaseInsensitiveHash<WebCore::String>, HashTraits<WebCore::String> > {
typedef CaseInsensitiveHash<WebCore::StringImpl*> Hash;
typedef HashTraits<WebCore::StringImpl*> Traits;
};
}
using WTF::CaseInsensitiveHash;
#endif