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diff --git a/WebCore/css/CSSNthSelector.cpp b/WebCore/css/CSSNthSelector.cpp
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+/*
+ * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.
+ * Copyright (C) 2008 David Smith (catfish.man@gmail.com)
+ *
+ * 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.
+ */
+
+#include "config.h"
+#include "CSSNthSelector.h"
+
+namespace WebCore {
+
+// a helper function for parsing nth-arguments
+bool CSSNthSelector::parseNth()
+{
+    if (m_parsedNth)
+        return true;
+    
+    const String& m_ar = m_argument;
+    
+    if (m_ar.isEmpty())
+        return false;
+    
+    m_parsedNth = true;
+    m_a = 0;
+    m_b = 0;
+    if (m_ar == "odd") {
+        m_a = 2;
+        m_b = 1;
+    } else if (m_ar == "even") {
+        m_a = 2;
+        m_b = 0;
+    } else {
+        int n = m_ar.find('n');
+        if (n != -1) {
+            if (m_ar[0] == '-') {
+                if (n == 1)
+                    m_a = -1; // -n == -1n
+                else
+                    m_a = m_ar.substring(0, n).toInt();
+            } else if (!n)
+                m_a = 1; // n == 1n
+            else
+                m_a = m_ar.substring(0, n).toInt();
+            
+            int p = m_ar.find('+', n);
+            if (p != -1)
+                m_b = m_ar.substring(p + 1, m_ar.length() - p - 1).toInt();
+            else {
+                p = m_ar.find('-', n);
+                m_b = -m_ar.substring(p + 1, m_ar.length() - p - 1).toInt();
+            }
+        } else
+            m_b = m_ar.toInt();
+    }
+    return true;
+}
+
+// a helper function for checking nth-arguments
+bool CSSNthSelector::matchNth(int count)
+{
+    if (!m_a)
+        return count == m_b;
+    else if (m_a > 0) {
+        if (count < m_b)
+            return false;
+        return (count - m_b) % m_a == 0;
+    } else {
+        if (count > m_b)
+            return false;
+        return (m_b - count) % (-m_a) == 0;
+    }
+}
+
+} // namespace WebCore