third_party/WebKit/Source/platform/LinkHash.h

   1 /*
   2  * Copyright (C) 2008 Google Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef LinkHash_h
  27 #define LinkHash_h
  28
  29 #include "platform/PlatformExport.h"
  30 #include "wtf/Forward.h"
  31 #include "wtf/text/StringHash.h"
  32
  33 namespace blink {
  34
  35 class KURL;
  36
  37 typedef uint64_t LinkHash;
  38
  39 // Use the low 32-bits of the 64-bit LinkHash as the key for HashSets.
  40 struct LinkHashHash {
  41     static unsigned hash(LinkHash key) { return static_cast<unsigned>(key); }
  42     static bool equal(LinkHash a, LinkHash b) { return a == b; }
  43     static const bool safeToCompareToEmptyOrDeleted = true;
  44
  45     // See AlreadyHashed::avoidDeletedValue.
  46     static unsigned avoidDeletedValue(LinkHash hash64)
  47     {
  48         ASSERT(hash64);
  49         unsigned hash = static_cast<unsigned>(hash64);
  50         unsigned newHash = hash | (!(hash + 1) << 31);
  51         ASSERT(newHash);
  52         ASSERT(newHash != 0xFFFFFFFF);
  53         return newHash;
  54     }
  55 };
  56
  57 // Resolves the potentially relative URL "attributeURL" relative to the given
  58 // base URL, and returns the hash of the string that will be used for visited
  59 // link coloring. It will return the special value of 0 if attributeURL does not
  60 // look like a relative URL.
  61 PLATFORM_EXPORT LinkHash visitedLinkHash(const KURL& base, const AtomicString& attributeURL);
  62
  63 } // namespace blink
  64
  65 #endif // LinkHash_h