// LexicalHandler.java - optional handler for lexical parse events.
// Public Domain: no warranty.
// $Id: LexicalHandler.java,v 1.4 2000/02/25 14:55:59 david Exp $

package org.xml.sax.ext;

import org.xml.sax.SAXException;

/**
 * SAX2 extension handler for lexical events.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * </blockquote>
 *
 * <p>This is an optional extension handler for SAX2 to provide
 * lexical information about an XML document, such as comments
 * and CDATA section boundaries; XML readers are not required to 
 * support this handler.</p>
 *
 * <p>The events in the lexical handler apply to the entire document,
 * not just to the document element, and all lexical handler events
 * must appear between the content handler's startDocument and
 * endDocument events.</p>
 *
 * <p>To set the LexicalHandler for an XML reader, use the
 * {@link org.xml.sax.XMLReader#setProperty setProperty} method
 * with the propertyId "http://xml.org/sax/handlers/LexicalHandler".
 * If the reader does not support lexical events, it will throw a
 * {@link org.xml.sax.SAXNotRecognizedException SAXNotRecognizedException}
 * or a
 * {@link org.xml.sax.SAXNotSupportedException SAXNotSupportedException}
 * when you attempt to register the handler.</p>
 *
 * @since SAX 2.0
 * @author David Megginson, 
 *         <a href="mailto:sax@megginson.com">sax@megginson.com</a>
 * @version 2.0beta
 * @see org.xml.sax.XMLReader#setProperty
 * @see org.xml.sax.SAXNotRecognizedException
 * @see org.xml.sax.SAXNotSupportedException
 */
public interface LexicalHandler
{

    /**
     * Report the start of DTD declarations, if any.
     *
     * <p>Any declarations are assumed to be in the internal subset
     * unless otherwise indicated by a {@link #startEntity startEntity}
     * event.</p>
     *
     * <p>Note that the start/endDTD events will appear within
     * the start/endDocument events from ContentHandler and
     * before the first startElement event.</p>
     *
     * @param name The document type name.
     * @param publicId The declared public identifier for the
     *        external DTD subset, or null if none was declared.
     * @param systemId The declared system identifier for the
     *        external DTD subset, or null if none was declared.
     * @exception SAXException The application may raise an
     *            exception.
     * @see #endDTD
     * @see #startEntity
     */
    public abstract void startDTD (String name, String publicId,
				   String systemId)
	throws SAXException;


    /**
     * Report the end of DTD declarations.
     *
     * @exception SAXException The application may raise an exception.
     * @see #startDTD
     */
    public abstract void endDTD ()
	throws SAXException;


    /**
     * Report the beginning of an entity in content.
     *
     * <p><strong>NOTE:</entity> entity references in attribute
     * values -- and the start and end of the document entity --
     * are never reported.</p>
     *
     * <p>The start and end of the external DTD subset are reported
     * using the pseudo-name "[dtd]".  All other events must be
     * properly nested within start/end entity events.</p>
     *
     * <p>Note that skipped entities will be reported through the
     * {@link org.xml.sax.ContentHandler#skippedEntity skippedEntity}
     * event, which is part of the ContentHandler interface.</p>
     *
     * @param name The name of the entity.  If it is a parameter
     *        entity, the name will begin with '%'.
     * @exception SAXException The application may raise an exception.
     * @see #endEntity
     * @see org.xml.sax.ext.DeclHandler#internalEntityDecl
     * @see org.xml.sax.ext.DeclHandler#externalEntityDecl
     */
    public abstract void startEntity (String name)
	throws SAXException;


    /**
     * Report the end of an entity.
     *
     * @param name The name of the entity that is ending.
     * @exception SAXException The application may raise an exception.
     * @see #startEntity
     */
    public abstract void endEntity (String name)
	throws SAXException;


    /**
     * Report the start of a CDATA section.
     *
     * <p>The contents of the CDATA section will be reported through
     * the regular {@link org.xml.sax.ContentHandler#characters
     * characters} event.</p>
     *
     * @exception SAXException The application may raise an exception.
     * @see #endCDATA
     */
    public abstract void startCDATA ()
	throws SAXException;


    /**
     * Report the end of a CDATA section.
     *
     * @exception SAXException The application may raise an exception.
     * @see #startCDATA
     */
    public abstract void endCDATA ()
	throws SAXException;


    /**
     * Report an XML comment anywhere in the document.
     *
     * <p>This callback will be used for comments inside or outside the
     * document element, including comments in the external DTD
     * subset (if read).</p>
     *
     * @param ch An array holding the characters in the comment.
     * @param start The starting position in the array.
     * @param length The number of characters to use from the array.
     * @exception SAXException The application may raise an exception.
     */
    public abstract void comment (char ch[], int start, int length)
	throws SAXException;

}

// end of LexicalHandler.java