sky/engine/wtf/text/AtomicStringHash.h

/*
 * Copyright (C) 2008 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 */

#ifndef SKY_ENGINE_WTF_TEXT_ATOMICSTRINGHASH_H_
#define SKY_ENGINE_WTF_TEXT_ATOMICSTRINGHASH_H_

#include "sky/engine/wtf/HashTraits.h"
#include "sky/engine/wtf/text/AtomicString.h"

namespace WTF {

    struct AtomicStringHash {
        static unsigned hash(const AtomicString& key)
        {
            return key.impl()->existingHash();
        }

        static bool equal(const AtomicString& a, const AtomicString& b)
        {
            return a == b;
        }

        static const bool safeToCompareToEmptyOrDeleted = false;
    };

    // AtomicStringHash is the default hash for AtomicString
    template<> struct HashTraits<WTF::AtomicString> : GenericHashTraits<WTF::AtomicString> {
        // Unlike other types, we can return a const reference for AtomicString's empty value (nullAtom).
        typedef const WTF::AtomicString& PeekOutType;

        static const WTF::AtomicString& emptyValue() { return nullAtom; }
        static PeekOutType peek(const WTF::AtomicString& value) { return value; }

        static const bool emptyValueIsZero = true;
        static void constructDeletedValue(WTF::AtomicString& slot, bool) { new (NotNull, &slot) WTF::AtomicString(HashTableDeletedValue); }
        static bool isDeletedValue(const WTF::AtomicString& slot) { return slot.isHashTableDeletedValue(); }
    };

}

using WTF::AtomicStringHash;

#endif  // SKY_ENGINE_WTF_TEXT_ATOMICSTRINGHASH_H_