// LexicalHandler.java - optional handler for lexical parse events.
// Public Domain: no warranty.
// $Id: LexicalHandler.java,v 1.1 2001/05/20 03:12:57 curcuru 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, and it is not part of the core SAX2
 * distribution.</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/properties/lexical-handler".
 * 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 1.0
 * @author David Megginson, 
 *         <a href="mailto:sax@megginson.com">sax@megginson.com</a>
 * @version 1.0
 * @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>This method is intended to report the beginning of the
     * DOCTYPE declaration; if the document has no DOCTYPE declaration,
     * this method will not be invoked.</p>
     *
     * <p>All declarations reported through 
     * {@link org.xml.sax.DTDHandler DTDHandler} or
     * {@link org.xml.sax.ext.DeclHandler DeclHandler} events must appear
     * between the startDTD and {@link #endDTD endDTD} events.
     * Declarations are assumed to belong to the internal DTD subset
     * unless they appear between {@link #startEntity startEntity}
     * and {@link #endEntity endEntity} events.  Comments and
     * processing instructions from the DTD should also be reported
     * between the startDTD and endDTD events, in their original 
     * order of (logical) occurrence; they are not required to
     * appear in their correct locations relative to DTDHandler
     * or DeclHandler events, however.</p>
     *
     * <p>Note that the start/endDTD events will appear within
     * the start/endDocument events from ContentHandler and
     * before the first 
     * {@link org.xml.sax.ContentHandler#startElement 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.
     *
     * <p>This method is intended to report the end of the
     * DOCTYPE declaration; if the document has no DOCTYPE declaration,
     * this method will not be invoked.</p>
     *
     * @exception SAXException The application may raise an exception.
     * @see #startDTD
     */
    public abstract void endDTD ()
	throws SAXException;


    /**
     * Report the beginning of some internal and external XML entities.
     *
     * <p>The reporting of parameter entities (including
     * the external DTD subset) is optional, and SAX2 drivers that
     * support LexicalHandler may not support it; you can use the
     * <code
     * >http://xml.org/sax/features/lexical-handler/parameter-entities</code>
     * feature to query or control the reporting of parameter entities.</p>
     *
     * <p>General entities are reported with their regular names,
     * parameter entities have '%' prepended to their names, and 
     * the external DTD subset has the pseudo-entity name "[dtd]".</p>
     *
     * <p>When a SAX2 driver is providing these events, all other 
     * events must be properly nested within start/end entity 
     * events.  There is no additional requirement that events from 
     * {@link org.xml.sax.ext.DeclHandler DeclHandler} or
     * {@link org.xml.sax.DTDHandler DTDHandler} be properly ordered.</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>
     *
     * <p>Because of the streaming event model that SAX uses, some
     * entity boundaries cannot be reported under any 
     * circumstances:</p>
     *
     * <ul>
     * <li>general entities within attribute values</li>
     * <li>parameter entities within declarations</li>
     * </ul>
     *
     * <p>These will be silently expanded, with no indication of where
     * the original entity boundaries were.</p>
     *
     * <p>Note also that the boundaries of character references (which
     * are not really entities anyway) are not reported.</p>
     *
     * <p>All start/endEntity events must be properly nested.
     *
     * @param name The name of the entity.  If it is a parameter
     *        entity, the name will begin with '%', and if it is the
     *        external DTD subset, it will be "[dtd]".
     * @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; this event is intended only to report
     * the boundary.</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).  Comments in the DTD must be properly
     * nested inside start/endDTD and start/endEntity events (if
     * used).</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
