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jeremybenn |
/* Selector.java -- A CSS selector
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Copyright (C) 2006 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.javax.swing.text.html.css;
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import gnu.java.lang.CPStringBuilder;
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import java.util.List;
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import java.util.Map;
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import java.util.StringTokenizer;
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/**
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* A CSS selector. This provides methods to interpret a selector and
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* query matches with an actual HTML element tree.
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*/
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public class Selector
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{
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/**
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* The actual selector. The selector tokens are stored backwards, that
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* is the last token first. This makes matching easier.
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*/
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private String[] selector;
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private String[] elements;
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private String[] ids;
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private String[] classes;
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/**
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* The specificity of the selector.
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*/
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private int specificity;
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/**
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* An implicit selector has true here. This is the case for CSS rules that
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* are attached to HTML elements directly via style="<CSS rule>".
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*/
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private boolean implicit;
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/**
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* Creates a new Selector instance for the specified selector string.
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*
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* @param sel the selector
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*/
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public Selector(String sel)
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{
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StringTokenizer selectorTokens = new StringTokenizer(sel, " ");
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selector = new String[selectorTokens.countTokens()];
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for (int i = selector.length - 1; selectorTokens.hasMoreTokens(); i--)
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{
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selector[i] = selectorTokens.nextToken();
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}
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calculateSpecificity();
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}
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/**
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* Determines if this selector matches the element path specified in the
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* arguments. The arguments hold the element names as well as class
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* and id attibutes of the HTML element to be queried. The first item
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* in the array is the deepest element and the last on the highest up (for
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* instance, the html tag).
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*
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* @param tags
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*
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* @return <code>true</code> when this selector matches the element path,
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* <code>false</code> otherwise
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*/
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public boolean matches(String[] tags, List<Map<String,String>> attributes)
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{
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// TODO: This implements class, id and descendent matching. These are
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// the most commonly used selector matchers in CSS together with HTML.
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// However, the CSS spec defines a couple of more sophisticated matches
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// which should be implemented.
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// http://www.w3.org/TR/CSS21/selector.html
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// All parts of the selector must match at some point.
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boolean match = false;
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int numTags = tags.length;
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int numSel = selector.length;
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if (numSel <= numTags)
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{
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match = true;
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int tagIndex = 0;
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for (int j = 0; j < numSel && match; j++)
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{
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boolean tagMatch = false;
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for (; tagIndex < numTags && tagMatch == false; tagIndex++)
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{
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Object pathClass = attributes.get(tagIndex).get("class");
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// Try pseudo class too.
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Object pseudoClass = attributes.get(tagIndex).get("_pseudo");
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Object dynClass = attributes.get(tagIndex).get("_dynamic");
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Object pathId = attributes.get(tagIndex).get("id");
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String tag = elements[j];
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String clazz = classes[j];
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String id = ids[j];
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tagMatch = tag.equals("") || tag.equals("*")
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|| tag.equals(tags[tagIndex]);
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tagMatch = tagMatch && (clazz.equals("*")
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|| clazz.equals(dynClass)
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|| clazz.equals(pseudoClass)
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|| clazz.equals(pathClass));
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tagMatch = tagMatch && (id.equals("*")
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|| id.equals(pathId));
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// For the last element in the selector we must not look
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// further.
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if (j == 0)
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break;
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}
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// If we don't come out here with a matching tag, then we're
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// not matching at all.
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match = tagMatch;
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}
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}
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return match;
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}
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/**
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* Returns the specificity of the selector. This is calculated according
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* to:
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* http://www.w3.org/TR/CSS21/cascade.html#specificity
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*
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* @return the specificity of the selector
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*/
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public int getSpecificity()
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{
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return specificity;
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}
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/**
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* Returns a string representation of the selector. This tries to reconstruct
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* the original selector as closely as possible.
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*
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* @return a string representation of the selector
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*/
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public String toString()
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{
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CPStringBuilder b = new CPStringBuilder();
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for (int i = selector.length - 1; i >= 0; i--)
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{
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b.append(selector[i]);
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if (i > 0)
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b.append(' ');
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}
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return b.toString();
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}
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/**
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* Calculates the specificity of the selector. This is calculated according
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* to:
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* http://www.w3.org/TR/CSS21/cascade.html#specificity
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*/
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private void calculateSpecificity()
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{
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int a = implicit ? 1 : 0;
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int b = 0;
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int c = 0;
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int d = 0;
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int numSel = selector.length;
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elements = new String[numSel];
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ids = new String[numSel];
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classes = new String[numSel];
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for (int i = 0; i < numSel; i++)
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{
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String sel = selector[i];
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int clazzIndex = sel.indexOf('.');
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// Try pseudo class too.
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if (clazzIndex == -1)
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clazzIndex = sel.indexOf(':');
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int idIndex = sel.indexOf('#');
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String clazz;
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if (clazzIndex == -1)
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{
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clazz = "*";
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clazzIndex = sel.length();
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}
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else
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{
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c++;
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clazz = sel.substring(clazzIndex + 1,
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idIndex > 0 ? Math.min(idIndex, sel.length())
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: sel.length());
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}
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String id;
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if (idIndex == -1)
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{
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id = "*";
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idIndex = sel.length();
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}
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else
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{
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b++;
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id = sel.substring(idIndex + 1,
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clazzIndex > 0 ? Math.min(clazzIndex, sel.length())
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: sel.length());
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}
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String tag = sel.substring(0,
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Math.min(Math.min(clazzIndex, idIndex),
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sel.length()));
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if (! tag.equals("") && ! tag.equals("*"))
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d++;
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elements[i] = tag;
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ids[i] = id;
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classes[i] = clazz;
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}
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// An order of 20 should be enough for everybody.
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specificity = a * 20 ^ 3 + b * 20 ^ 2 + c * 20 + d;
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}
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}
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