text: /*
   * Copyright (C) 2008 Google 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.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``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 COMPUTER, INC. OR
   * 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 THIRD_PARTY_BLINK_RENDERER_PLATFORM_LINK_HASH_H_
  #define THIRD_PARTY_BLINK_RENDERER_PLATFORM_LINK_HASH_H_
  
  #include "third_party/blink/renderer/platform/platform_export.h"
  #include "third_party/blink/renderer/platform/wtf/allocator.h"
  #include "third_party/blink/renderer/platform/wtf/forward.h"
  #include "third_party/blink/renderer/platform/wtf/text/string_hash.h"
  
  namespace blink {
  
  class KURL;
  
  typedef uint64_t LinkHash;
  
  // Use the low 32-bits of the 64-bit LinkHash as the key for HashSets.
  struct LinkHashHash {
    STATIC_ONLY(LinkHashHash);
    static unsigned GetHash(LinkHash key) { return static_cast<unsigned>(key); }
    static bool Equal(LinkHash a, LinkHash b) { return a == b; }
    static const bool safe_to_compare_to_empty_or_deleted = true;
  
    // See AlreadyHashed::avoidDeletedValue.
    static unsigned AvoidDeletedValue(LinkHash hash64) {
      DCHECK(hash64);
      unsigned hash = static_cast<unsigned>(hash64);
      unsigned new_hash = hash | (!(hash + 1) << 31);
      DCHECK(new_hash);
      DCHECK_NE(new_hash, 0xFFFFFFFF);
      return new_hash;
    }
  };
  
  // Resolves the potentially relative URL "attributeURL" relative to the given
  // base URL, and returns the hash of the string that will be used for visited
  // link coloring. It will return the special value of 0 if attributeURL does not
  // look like a relative URL.
  PLATFORM_EXPORT LinkHash VisitedLinkHash(const KURL& base,
                                           const AtomicString& attribute_url);
  
  }  // namespace blink
  
  #endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_LINK_HASH_H_
  