incrementalsaxsource_filter.java

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/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999,2000 The Apache Software Foundation.  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.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xerces" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written 
 *    permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
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 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, International
 * Business Machines, Inc., http://www.apache.org.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.apache.xml.dtm.ref;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXNotSupportedException;
import org.xml.sax.ext.LexicalHandler;
import org.xml.sax.ContentHandler;
import org.xml.sax.DTDHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.Locator;
import org.xml.sax.Attributes;
import org.xml.sax.XMLReader;
import java.io.IOException;
import org.apache.xml.dtm.ref.IncrementalSAXSource;

import org.apache.xalan.res.XSLTErrorResources;
import org.apache.xalan.res.XSLMessages;

/** <p>IncrementalSAXSource_Filter implements IncrementalSAXSource, using a
 * standard SAX2 event source as its input and parcelling out those
 * events gradually in reponse to deliverMoreNodes() requests.  Output from the
 * filter will be passed along to a SAX handler registered as our
 * listener, but those callbacks will pass through a counting stage
 * which periodically yields control back to the controller coroutine.
 * </p>
 *
 * <p>%REVIEW%: This filter is not currenly intended to be reusable
 * for parsing additional streams/documents. We may want to consider
 * making it resettable at some point in the future. But it's a 
 * small object, so that'd be mostly a convenience issue; the cost
 * of allocating each time is trivial compared to the cost of processing
 * any nontrival stream.</p>
 *
 * <p>For a brief usage example, see the unit-test main() method.</p>
 *
 * <p>This is a simplification of the old CoroutineSAXParser, focusing
 * specifically on filtering. The resulting controller protocol is _far_
 * simpler and less error-prone; the only controller operation is deliverMoreNodes(),
 * and the only requirement is that deliverMoreNodes(false) be called if you want to
 * discard the rest of the stream and the previous deliverMoreNodes() didn't return
 * false.
 * */
public class IncrementalSAXSource_Filter
implements IncrementalSAXSource, ContentHandler, DTDHandler, LexicalHandler, ErrorHandler, Runnable
{
  boolean DEBUG=false; //Internal status report

  //
  // Data
  //
  private CoroutineManager fCoroutineManager = null;
  private int fControllerCoroutineID = -1;
  private int fSourceCoroutineID = -1;

  private ContentHandler clientContentHandler=null; // %REVIEW% support multiple?
  private LexicalHandler clientLexicalHandler=null; // %REVIEW% support multiple?
  private DTDHandler clientDTDHandler=null; // %REVIEW% support multiple?
  private ErrorHandler clientErrorHandler=null; // %REVIEW% support multiple?
  private int eventcounter;
  private int frequency=5;

  // Flag indicating that no more events should be delivered -- either
  // because input stream ran to completion (endDocument), or because
  // the user requested an early stop via deliverMoreNodes(false).
  private boolean fNoMoreEvents=false;

  // Support for startParse()
  private XMLReader fXMLReader=null;
  private InputSource fXMLReaderInputSource=null;

  //
  // Constructors
  //

  public IncrementalSAXSource_Filter() {
    this.init( new CoroutineManager(), -1, -1);
  }
  
  /** Create a IncrementalSAXSource_Filter which is not yet bound to a specific
   * SAX event source.
   * */
  public IncrementalSAXSource_Filter(CoroutineManager co, int controllerCoroutineID)
  {
    this.init( co, controllerCoroutineID, -1 );
  }

  //
  // Factories
  //
  static public IncrementalSAXSource createIncrementalSAXSource(CoroutineManager co, int controllerCoroutineID) {
    return new IncrementalSAXSource_Filter(co, controllerCoroutineID);
  }

  //
  // Public methods
  //

  public void init( CoroutineManager co, int controllerCoroutineID,
                    int sourceCoroutineID)
  {
    if(co==null)
      co = new CoroutineManager();
    fCoroutineManager = co;
    fControllerCoroutineID = co.co_joinCoroutineSet(controllerCoroutineID);
    fSourceCoroutineID = co.co_joinCoroutineSet(sourceCoroutineID);
    if (fControllerCoroutineID == -1 || fSourceCoroutineID == -1)
      throw new RuntimeException(XSLMessages.createMessage(XSLTErrorResources.ER_COJOINROUTINESET_FAILED, null)); //"co_joinCoroutineSet() failed");

    fNoMoreEvents=false;
    eventcounter=frequency;
  }
    
  /** Bind our input streams to an XMLReader.
   *
   * Just a convenience routine; obviously you can explicitly register
   * this as a listener with the same effect.
   * */
  public void setXMLReader(XMLReader eventsource)
  {
    fXMLReader=eventsource;
    eventsource.setContentHandler(this);
    eventsource.setDTDHandler(this);
    eventsource.setErrorHandler(this); // to report fatal errors in filtering mode

    // Not supported by all SAX2 filters:
    try 
    {
      eventsource.
        setProperty("http://xml.org/sax/properties/lexical-handler",
                    this);
    }
    catch(SAXNotRecognizedException e)
    {
      // Nothing we can do about it
    }
    catch(SAXNotSupportedException e)
    {
      // Nothing we can do about it
    }

    // Should we also bind as other varieties of handler?
    // (DTDHandler and so on)
  }

  // Register a content handler for us to output to
  public void setContentHandler(ContentHandler handler)
  {
    clientContentHandler=handler;
  }
  // Register a DTD handler for us to output to
  public void setDTDHandler(DTDHandler handler)
  {
    clientDTDHandler=handler;
  }
  // Register a lexical handler for us to output to
  // Not all filters support this...
  // ??? Should we register directly on the filter?
  // NOTE NAME -- subclassing issue in the Xerces version
  public void setLexicalHandler(LexicalHandler handler)
  {
    clientLexicalHandler=handler;
  }
  // Register an error handler for us to output to
  // NOTE NAME -- subclassing issue in the Xerces version
  public void setErrHandler(ErrorHandler handler)
  {
    clientErrorHandler=handler;
  }

  // Set the number of events between resumes of our coroutine
  // Immediately resets number of events before _next_ resume as well.
  public void setReturnFrequency(int events)
  {
    if(events<1) events=1;
    frequency=eventcounter=events;
  }
  
  //
  // ContentHandler methods
  // These  pass the data to our client ContentHandler...
  // but they also count the number of events passing through,
  // and resume our coroutine each time that counter hits zero and
  // is reset.
  //
  // Note that for everything except endDocument and fatalError, we do the count-and-yield
  // BEFORE passing the call along. I'm hoping that this will encourage JIT
  // compilers to realize that these are tail-calls, reducing the expense of
  // the additional layer of data flow.
  //
  // %REVIEW% Glenn suggests that pausing after endElement, endDocument,
  // and characters may be sufficient. I actually may not want to
  // stop after characters, since in our application these wind up being
  // concatenated before they're processed... but that risks huge blocks of
  // text causing greater than usual readahead. (Unlikely? Consider the
  // possibility of a large base-64 block in a SOAP stream.)
  //
  public void characters(char[] ch, int start, int length)
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.characters(ch,start,length);
  }
  public void endDocument() 
       throws org.xml.sax.SAXException
  {
    // EXCEPTION: In this case we need to run the event BEFORE we yield.
    if(clientContentHandler!=null)
      clientContentHandler.endDocument();

    eventcounter=0;     
    co_yield(false);
  }
  public void endElement(java.lang.String namespaceURI, java.lang.String localName,
      java.lang.String qName) 
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.endElement(namespaceURI,localName,qName);
  }
  public void endPrefixMapping(java.lang.String prefix) 
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.endPrefixMapping(prefix);
  }
  public void ignorableWhitespace(char[] ch, int start, int length) 
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.ignorableWhitespace(ch,start,length);
  }
  public void processingInstruction(java.lang.String target, java.lang.String data) 
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.processingInstruction(target,data);
  }
  public void setDocumentLocator(Locator locator) 
  {
    if(--eventcounter<=0)
      {
        // This can cause a hang.  -sb
        // co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.setDocumentLocator(locator);
  }
  public void skippedEntity(java.lang.String name) 
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.skippedEntity(name);
  }
  public void startDocument() 
       throws org.xml.sax.SAXException
  {
    co_entry_pause();

    // Otherwise, begin normal event delivery
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.startDocument();
  }
  public void startElement(java.lang.String namespaceURI, java.lang.String localName,
      java.lang.String qName, Attributes atts) 
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.startElement(namespaceURI, localName, qName, atts);
  }
  public void startPrefixMapping(java.lang.String prefix, java.lang.String uri) 
       throws org.xml.sax.SAXException
  {
    if(--eventcounter<=0)
      {
        co_yield(true);
        eventcounter=frequency;
      }
    if(clientContentHandler!=null)
      clientContentHandler.startPrefixMapping(prefix,uri);
  }

  //
  // LexicalHandler support. Not all SAX2 filters support these events
  // but we may want to pass them through when they exist...
  //
  // %REVIEW% These do NOT currently affect the eventcounter; I'm asserting
  // that they're rare enough that it makes little or no sense to
  // pause after them. As such, it may make more sense for folks who
  // actually want to use them to register directly with the filter.
  // But I want 'em here for now, to remind us to recheck this assertion!
  //
  public void comment(char[] ch, int start, int length) 
       throws org.xml.sax.SAXException
  {
    if(null!=clientLexicalHandler)
      clientLexicalHandler.comment(ch,start,length);
  }
  public void endCDATA() 
       throws org.xml.sax.SAXException
  {
    if(null!=clientLexicalHandler)
      clientLexicalHandler.endCDATA();
  }
  public void endDTD() 
       throws org.xml.sax.SAXException
  {
    if(null!=clientLexicalHandler)
      clientLexicalHandler.endDTD();
  }
  public void endEntity(java.lang.String name) 
       throws org.xml.sax.SAXException
  {
    if(null!=clientLexicalHandler)
      clientLexicalHandler.endEntity(name);
  }
  public void startCDATA() 
       throws org.xml.sax.SAXException
  {
    if(null!=clientLexicalHandler)
      clientLexicalHandler.startCDATA();
  }