xpathmatcher.java

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/*
 * Copyright 2001, 2002,2004,2005 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xerces.internal.impl.xs.identity;

import com.sun.org.apache.xerces.internal.impl.Constants;
import com.sun.org.apache.xerces.internal.impl.xpath.XPath;
import com.sun.org.apache.xerces.internal.util.IntStack;
import com.sun.org.apache.xerces.internal.xni.QName;
import com.sun.org.apache.xerces.internal.xni.XMLAttributes;
import com.sun.org.apache.xerces.internal.xs.AttributePSVI;
import com.sun.org.apache.xerces.internal.xs.ShortList;
import com.sun.org.apache.xerces.internal.xs.XSTypeDefinition;
import org.xml.sax.SAXException;


/**
 * XPath matcher.
 *
 * @xerces.internal 
 *
 * @author Andy Clark, IBM
 *
 * @version $Id: XPathMatcher.java,v 1.2.6.1 2005/09/08 09:02:30 sunithareddy Exp $
 */
public class XPathMatcher {

    //
    // Constants
    //

    // debugging

    /** Compile to true to debug everything. */
    protected static final boolean DEBUG_ALL = false;

    /** Compile to true to debug method callbacks. */
    protected static final boolean DEBUG_METHODS = false || DEBUG_ALL;

    /** Compile to true to debug important method callbacks. */
    protected static final boolean DEBUG_METHODS2 = false || DEBUG_METHODS || DEBUG_ALL;

    /** Compile to true to debug the <em>really</em> important methods. */
    protected static final boolean DEBUG_METHODS3 = false || DEBUG_METHODS || DEBUG_ALL;

    /** Compile to true to debug match. */
    protected static final boolean DEBUG_MATCH = false || DEBUG_ALL;

    /** Compile to true to debug step index stack. */
    protected static final boolean DEBUG_STACK = false || DEBUG_ALL;

    /** Don't touch this value unless you add more debug constants. */
    protected static final boolean DEBUG_ANY = DEBUG_METHODS ||
                                               DEBUG_METHODS2 ||
                                               DEBUG_METHODS3 ||
                                               DEBUG_MATCH ||
                                               DEBUG_STACK;

    // constants describing whether a match was made,
    // and if so how.  
    // matched any way
    protected static final int MATCHED = 1;
    // matched on the attribute axis
    protected static final int MATCHED_ATTRIBUTE = 3;
    // matched on the descendant-or-self axixs
    protected static final int MATCHED_DESCENDANT = 5;
    // matched some previous (ancestor) node on the descendant-or-self-axis, but not this node
    protected static final int MATCHED_DESCENDANT_PREVIOUS = 13;

    //
    // Data
    //

    /** XPath location path. */
    private XPath.LocationPath[] fLocationPaths;

    /** True if XPath has been matched. */
    private int[] fMatched;

    /** The matching string. */
    protected Object fMatchedString;

    /** Integer stack of step indexes. */
    private IntStack[] fStepIndexes;

    /** Current step. */
    private int[] fCurrentStep;

    /**
     * No match depth. The value of this field will be zero while
     * matching is successful for the given xpath expression.
     */
    private int [] fNoMatchDepth;
    
    final QName fQName = new QName();


    //
    // Constructors
    //

    /**
     * Constructs an XPath matcher that implements a document fragment
     * handler.
     *
     * @param xpath   The xpath.
     */
    public XPathMatcher(XPath xpath) {
        fLocationPaths = xpath.getLocationPaths();
        fStepIndexes = new IntStack[fLocationPaths.length];
        for(int i=0; i<fStepIndexes.length; i++) fStepIndexes[i] = new IntStack();
        fCurrentStep = new int[fLocationPaths.length];
        fNoMatchDepth = new int[fLocationPaths.length];
        fMatched = new int[fLocationPaths.length];        
    } // <init>(XPath)

    //
    // Public methods
    //

    /** 
     * Returns value of first member of fMatched that
     * is nonzero.  
     */
    public boolean isMatched() {
        // xpath has been matched if any one of the members of the union have matched.
        for (int i=0; i < fLocationPaths.length; i++) 
            if (((fMatched[i] & MATCHED) == MATCHED) 
                    && ((fMatched[i] & MATCHED_DESCENDANT_PREVIOUS) != MATCHED_DESCENDANT_PREVIOUS) 
                    && ((fNoMatchDepth[i] == 0)
                    || ((fMatched[i] & MATCHED_DESCENDANT) == MATCHED_DESCENDANT))) 
                return true;

        return false;
    } // isMatched():int

    //
    // Protected methods
    //

    // a place-holder method; to be overridden by subclasses
    // that care about matching element content.
    protected void handleContent(XSTypeDefinition type, boolean nillable, Object value, short valueType, ShortList itemValueType) { 
    } 

    /**
     * This method is called when the XPath handler matches the
     * XPath expression. Subclasses can override this method to
     * provide default handling upon a match.
     */
    protected void matched(Object actualValue, short valueType, ShortList itemValueType, boolean isNil) {
        if (DEBUG_METHODS3) {
            System.out.println(toString()+"#matched(\""+actualValue+"\")");
        }
    } // matched(String content, XSSimpleType val)

    //
    // ~XMLDocumentFragmentHandler methods
    //

    /**
     * The start of the document fragment.
     */
    public void startDocumentFragment(){
        if (DEBUG_METHODS) {
            System.out.println(toString()+"#startDocumentFragment("+
                               ")");
        }

        // reset state
        fMatchedString = null;
        for(int i = 0; i < fLocationPaths.length; i++) {
            fStepIndexes[i].clear();
            fCurrentStep[i] = 0;
            fNoMatchDepth[i] = 0;
            fMatched[i] = 0;
        }


    } // startDocumentFragment()

    /**
     * The start of an element. If the document specifies the start element
     * by using an empty tag, then the startElement method will immediately
     * be followed by the endElement method, with no intervening methods.
     *
     * @param element    The name of the element.
     * @param attributes The element attributes.
     *
     * @throws SAXException Thrown by handler to signal an error.
     */
    public void startElement(QName element, XMLAttributes attributes){
        if (DEBUG_METHODS2) {
            System.out.println(toString()+"#startElement("+
                               "element={"+element+"},"+
                               "attributes=..."+attributes+
                               ")");                     
        }

        for(int i = 0; i < fLocationPaths.length; i++) {
            // push context
            int startStep = fCurrentStep[i];
            fStepIndexes[i].push(startStep);

            // try next xpath, if not matching
            if ((fMatched[i] & MATCHED_DESCENDANT) == MATCHED || fNoMatchDepth[i] > 0) {
                fNoMatchDepth[i]++;
                continue;
            }
            if((fMatched[i] & MATCHED_DESCENDANT) == MATCHED_DESCENDANT) {
                fMatched[i] = MATCHED_DESCENDANT_PREVIOUS;
            }

            if (DEBUG_STACK) {
                System.out.println(toString()+": "+fStepIndexes[i]);
            }

            // consume self::node() steps
            XPath.Step[] steps = fLocationPaths[i].steps;
            while (fCurrentStep[i] < steps.length &&
                    steps[fCurrentStep[i]].axis.type == XPath.Axis.SELF) {
                if (DEBUG_MATCH) {
                    XPath.Step step = steps[fCurrentStep[i]];
                    System.out.println(toString()+" [SELF] MATCHED!");
                }
                fCurrentStep[i]++;
            }
            if (fCurrentStep[i] == steps.length) {
                if (DEBUG_MATCH) {
                    System.out.println(toString()+" XPath MATCHED!");
                }
                fMatched[i] = MATCHED;
                continue;
            }

            // now if the current step is a descendant step, we let the next
            // step do its thing; if it fails, we reset ourselves
            // to look at this step for next time we're called.
            // so first consume all descendants:
            int descendantStep = fCurrentStep[i];
            while(fCurrentStep[i] < steps.length && steps[fCurrentStep[i]].axis.type == XPath.Axis.DESCENDANT) {
                if (DEBUG_MATCH) {
                    XPath.Step step = steps[fCurrentStep[i]];
                    System.out.println(toString()+" [DESCENDANT] MATCHED!");
                }
                fCurrentStep[i]++;
            }