/*

 * 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