Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

1 files changed, 137 insertions, 0 deletions

diff --git a/Source/WebKit2/Shared/VisitedLinkTable.cpp b/Source/WebKit2/Shared/VisitedLinkTable.cpp
new file mode 100644
index 000000000..09b7cc8f4
--- /dev/null
+++ b/Source/WebKit2/Shared/VisitedLinkTable.cpp
@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2010 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. 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 INC. 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.
+ */
+
+#include "config.h"
+#include "VisitedLinkTable.h"
+
+#include "SharedMemory.h"
+
+using namespace WebCore;
+
+namespace WebKit {
+
+VisitedLinkTable::VisitedLinkTable()
+    : m_tableSize(0)
+    , m_table(0)
+{
+}
+
+VisitedLinkTable::~VisitedLinkTable()
+{
+}
+
+static inline bool isPowerOf2(unsigned v)
+{
+    // Taken from http://www.cs.utk.edu/~vose/c-stuff/bithacks.html
+    
+    return !(v & (v - 1)) && v;
+}
+
+void VisitedLinkTable::setSharedMemory(PassRefPtr<SharedMemory> sharedMemory)
+{
+    m_sharedMemory = sharedMemory;
+    
+    ASSERT(m_sharedMemory);
+    ASSERT(!(m_sharedMemory->size() % sizeof(LinkHash)));
+
+    m_table = static_cast<LinkHash*>(m_sharedMemory->data());
+    m_tableSize = m_sharedMemory->size() / sizeof(LinkHash);
+    ASSERT(isPowerOf2(m_tableSize));
+    
+    m_tableSizeMask = m_tableSize - 1;
+}
+
+static inline unsigned doubleHash(unsigned key)
+{
+    key = ~key + (key >> 23);
+    key ^= (key << 12);
+    key ^= (key >> 7);
+    key ^= (key << 2);
+    key ^= (key >> 20);
+    return key;
+}
+    
+bool VisitedLinkTable::addLinkHash(LinkHash linkHash)
+{
+    ASSERT(m_sharedMemory);
+
+    int k = 0;
+    LinkHash* table = m_table;
+    int sizeMask = m_tableSizeMask;
+    unsigned h = static_cast<unsigned>(linkHash);
+    int i = h & sizeMask;
+  
+    LinkHash* entry;
+    while (1) {
+        entry = table + i;
+
+        // Check if this bucket is empty.
+        if (!*entry)
+            break;
+
+        // Check if the same link hash is in the table already.
+        if (*entry == linkHash)
+            return false;
+
+        if (!k)
+            k = 1 | doubleHash(h);
+        i = (i + k) & sizeMask;
+    }
+
+    *entry = linkHash;
+    return true;
+}
+
+bool VisitedLinkTable::isLinkVisited(LinkHash linkHash) const
+{
+    if (!m_sharedMemory)
+        return false;
+
+    int k = 0;
+    LinkHash* table = m_table;
+    int sizeMask = m_tableSizeMask;
+    unsigned h = static_cast<unsigned>(linkHash);
+    int i = h & sizeMask;
+    
+    LinkHash* entry;
+    while (1) {
+        entry = table + i;
+
+        // Check if we've reached the end of the table.
+        if (!*entry)
+            break;
+        
+        if (*entry == linkHash)
+            return true;
+        
+        if (!k)
+            k = 1 | doubleHash(h);
+        i = (i + k) & sizeMask;
+    }
+
+    return false;
+}
+
+} // namespace WebKit