third_party/WebKit/Source/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
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef AtomicStringHash_h
#define AtomicStringHash_h

#include "wtf/HashTraits.h"
#include "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<AtomicString> : SimpleClassHashTraits<AtomicString> {
  // Unlike other types, we can return a const reference for AtomicString's
  // empty value (nullAtom).
  typedef const AtomicString& PeekOutType;

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

  static const bool hasIsEmptyValueFunction = true;
  static bool isEmptyValue(const AtomicString& value) { return value.isNull(); }
};

}  // namespace WTF

using WTF::AtomicStringHash;

#endif