/*
 * Copyright (c) 1999-2000 by David Brownell.  All Rights Reserved.
 *
 * This program is open source software; you may use, copy, modify, and
 * redistribute it under the terms of the LICENSE with which it was
 * originally distributed.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * LICENSE for more details.
 */

//
// Copyright (c) 1997, 1998 by Microstar Software Ltd.
// From Microstar's README (the entire original license):
//
// AElfred is free for both commercial and non-commercial use and
// redistribution, provided that Microstar's copyright and disclaimer are
// retained intact.  You are free to modify AElfred for your own use and
// to redistribute AElfred with your modifications, provided that the
// modifications are clearly documented.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// merchantability or fitness for a particular purpose.  Please use it AT
// YOUR OWN RISK.
//


package org.dom4j.io.aelfred;

import java.io.BufferedInputStream;
import java.io.CharConversionException;
import java.io.EOFException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.Reader;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;

import org.xml.sax.SAXException;


// $Id: XmlParser.java,v 1.4 2002/02/01 10:55:25 jstrachan Exp $

/**
 * Parse XML documents and return parse events through call-backs.
 * Use the <code>SAXDriver</code> class as your entry point, as the
 * internal parser interfaces are subject to change.
 *
 * @author Written by David Megginson &lt;dmeggins@microstar.com&gt;
 *      (version 1.2a with bugfixes)
 * @author Updated by David Brownell &lt;david-b@pacbell.net&gt;
 * @version $Date: 2002/02/01 10:55:25 $
 * @see SAXDriver
 */
final class XmlParser
{
    //
    // Use special cheats that speed up the code by
    // avoiding per-character readCh () method calls.
    //
    private final static boolean USE_CHEATS = true;


    //////////////////////////////////////////////////////////////////////
    // Constructors.
    ////////////////////////////////////////////////////////////////////////


    /**
     * Construct a new parser with no associated handler.
     * @see #setHandler
     * @see #parse
     */
    // package private
    XmlParser ()
    {
            cleanupVariables ();
    }


    /**
     * Set the handler that will receive parsing events.
     * @param handler The handler to receive callback events.
     * @see #parse
     */
    // package private
    void setHandler (SAXDriver handler)
    {
            this.handler = handler;
    }


    /**
     * Parse an XML document from the character stream, byte stream, or URI
     * that you provide (in that order of preference).  Any URI that you
     * supply will become the base URI for resolving relative URI, and may
     * be used to acquire a reader or byte stream.
     *
     * <p>You may parse more than one document, but that must be done
     * sequentially.  Only one thread at a time may use this parser.
     *
     * @param systemId The URI of the document; should never be null,
     *  but may be so iff a reader <em>or</em> a stream is provided.
     * @param publicId The public identifier of the document, or null.
     * @param reader A character stream; must be null if stream isn't.
     * @param stream A byte input stream; must be null if reader isn't.
     * @param encoding The suggested encoding, or null if unknown.
     * @exception java.lang.Exception Basically SAXException or IOException
     */
    // package private 
    void doParse (
        String          systemId,
        String          publicId,
        Reader          reader,
        InputStream     stream,
        String          encoding
    ) throws Exception
    {
        if (handler == null)
            throw new IllegalStateException ("no callback handler");

        basePublicId = publicId;
        baseURI = systemId;
        baseReader = reader;
        baseInputStream = stream;

        initializeVariables ();

        // predeclare the built-in entities here (replacement texts)
        // we don't need to intern(), since we're guaranteed literals
        // are always (globally) interned.
        setInternalEntity ("amp", "&#38;");
        setInternalEntity ("lt", "&#60;");
        setInternalEntity ("gt", "&#62;");
        setInternalEntity ("apos", "&#39;");
        setInternalEntity ("quot", "&#34;");

        handler.startDocument ();

        pushURL ("[document]", basePublicId, baseURI,
                baseReader, baseInputStream, encoding);

        try {
            parseDocument ();
            handler.endDocument ();
        } finally {
            if (baseReader != null)
                try { baseReader.close ();
                } catch (IOException e) { /* ignore */ }
            if (baseInputStream != null)
                try { baseInputStream.close ();
                } catch (IOException e) { /* ignore */ }
            if (is != null)
                try { is.close ();
                } catch (IOException e) { /* ignore */ }
            if (reader != null)
                try {
                    reader.close ();
                } catch (IOException e) { /* ignore */
                }
            cleanupVariables ();
        }
    }


    ////////////////////////////////////////////////////////////////////////
    // Constants.
    ////////////////////////////////////////////////////////////////////////

    //
    // Constants for element content type.
    //

    /**
     * Constant: an element has not been declared.
     * @see #getElementContentType
     */
    public final static int CONTENT_UNDECLARED = 0;

    /**
     * Constant: the element has a content model of ANY.
     * @see #getElementContentType
     */
    public final static int CONTENT_ANY = 1;

    /**
     * Constant: the element has declared content of EMPTY.
     * @see #getElementContentType
     */
    public final static int CONTENT_EMPTY = 2;

    /**
     * Constant: the element has mixed content.
     * @see #getElementContentType
     */
    public final static int CONTENT_MIXED = 3;

    /**
     * Constant: the element has element content.
     * @see #getElementContentType
     */
    public final static int CONTENT_ELEMENTS = 4;


    //
    // Constants for the entity type.
    //

    /**
     * Constant: the entity has not been declared.
     * @see #getEntityType
     */
    public final static int ENTITY_UNDECLARED = 0;

    /**
     * Constant: the entity is internal.
     * @see #getEntityType
     */
    public final static int ENTITY_INTERNAL = 1;

    /**
     * Constant: the entity is external, non-XML data.
     * @see #getEntityType
     */
    public final static int ENTITY_NDATA = 2;

    /**
     * Constant: the entity is external XML data.
     * @see #getEntityType
     */
    public final static int ENTITY_TEXT = 3;


    //
    // Constants for attribute type.
    //

    /**
     * Constant: the attribute has not been declared for this element type.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_UNDECLARED = 0;

    /**
     * Constant: the attribute value is a string value.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_CDATA = 1;

    /**
     * Constant: the attribute value is a unique identifier.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_ID = 2;

    /**
     * Constant: the attribute value is a reference to a unique identifier.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_IDREF = 3;

    /**
     * Constant: the attribute value is a list of ID references.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_IDREFS = 4;

    /**
     * Constant: the attribute value is the name of an entity.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_ENTITY = 5;

    /**
     * Constant: the attribute value is a list of entity names.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_ENTITIES = 6;

    /**
     * Constant: the attribute value is a name token.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_NMTOKEN = 7;

    /**
     * Constant: the attribute value is a list of name tokens.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_NMTOKENS = 8;

    /**
     * Constant: the attribute value is a token from an enumeration.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_ENUMERATED = 9;

    /**
     * Constant: the attribute is the name of a notation.
     * @see #getAttributeType
     */
    public final static int ATTRIBUTE_NOTATION = 10;


    //
    // When the class is loaded, populate the hash table of
    // attribute types.
    //

    /**
     * Hash table of attribute types.
     */
    private static HashMap attributeTypeHash;
    static {
        attributeTypeHash = new HashMap (13);
        attributeTypeHash.put ("CDATA", new Integer (ATTRIBUTE_CDATA));
        attributeTypeHash.put ("ID", new Integer (ATTRIBUTE_ID));
        attributeTypeHash.put ("IDREF", new Integer (ATTRIBUTE_IDREF));
        attributeTypeHash.put ("IDREFS", new Integer (ATTRIBUTE_IDREFS));
        attributeTypeHash.put ("ENTITY", new Integer (ATTRIBUTE_ENTITY));
        attributeTypeHash.put ("ENTITIES", new Integer (ATTRIBUTE_ENTITIES));
        attributeTypeHash.put ("NMTOKEN", new Integer (ATTRIBUTE_NMTOKEN));
        attributeTypeHash.put ("NMTOKENS", new Integer (ATTRIBUTE_NMTOKENS));
        attributeTypeHash.put ("NOTATION", new Integer (ATTRIBUTE_NOTATION));
    }


    //
    // Constants for supported encodings.  "external" is just a flag.
    //
    private final static int ENCODING_EXTERNAL = 0;
    private final static int ENCODING_UTF_8 = 1;
    private final static int ENCODING_ISO_8859_1 = 2;
    private final static int ENCODING_UCS_2_12 = 3;
    private final static int ENCODING_UCS_2_21 = 4;
    private final static int ENCODING_UCS_4_1234 = 5;
    private final static int ENCODING_UCS_4_4321 = 6;
    private final static int ENCODING_UCS_4_2143 = 7;
    private final static int ENCODING_UCS_4_3412 = 8;
    private final static int ENCODING_ASCII = 9;


    //
    // Constants for attribute default value.
    //

    /**
     * Constant: the attribute is not declared.
     * @see #getAttributeDefaultValueType
     */
    public final static int ATTRIBUTE_DEFAULT_UNDECLARED = 30;

    /**
     * Constant: the attribute has a literal default value specified.
     * @see #getAttributeDefaultValueType
     * @see #getAttributeDefaultValue
     */
    public final static int ATTRIBUTE_DEFAULT_SPECIFIED = 31;

    /**
     * Constant: the attribute was declared #IMPLIED.
     * @see #getAttributeDefaultValueType
     */
    public final static int ATTRIBUTE_DEFAULT_IMPLIED = 32;

    /**
     * Constant: the attribute was declared #REQUIRED.
     * @see #getAttributeDefaultValueType
     */
    public final static int ATTRIBUTE_DEFAULT_REQUIRED = 33;

    /**
     * Constant: the attribute was declared #FIXED.
     * @see #getAttributeDefaultValueType
     * @see #getAttributeDefaultValue
     */
    public final static int ATTRIBUTE_DEFAULT_FIXED = 34;


    //
    // Constants for input.
    //
    private final static int INPUT_NONE = 0;
    private final static int INPUT_INTERNAL = 1;
    private final static int INPUT_EXTERNAL = 2;
    private final static int INPUT_STREAM = 3;
    private final static int INPUT_BUFFER = 4;
    private final static int INPUT_READER = 5;


    //
    // Flags for reading literals.
    //
        // expand general entity refs (attribute values in dtd and content)
    private final static int LIT_ENTITY_REF = 2;
        // normalize this value (whitespace etc) (attributes, public ids)
    private final static int LIT_NORMALIZE = 4;
        // literal is an attribute value 
    private final static int LIT_ATTRIBUTE = 8;
        // don't expand parameter entities
    private final static int LIT_DISABLE_PE = 16;
        // don't expand [or parse] character refs
    private final static int LIT_DISABLE_CREF = 32;
        // don't parse general entity refs
    private final static int LIT_DISABLE_EREF = 64;
        // don't expand general entities, but make sure we _could_
    private final static int LIT_ENTITY_CHECK = 128;


    //
    // Flags affecting PE handling in DTDs (if expandPE is true).
    // PEs expand with space padding, except inside literals.
    //
    private final static int CONTEXT_NORMAL = 0;
    private final static int CONTEXT_LITERAL = 1;


    //////////////////////////////////////////////////////////////////////
    // Error reporting.
    //////////////////////////////////////////////////////////////////////


    /**
     * Report an error.
     * @param message The error message.
     * @param textFound The text that caused the error (or null).
     * @see SAXDriver#error
     * @see #line
     */
    private void error (String message, String textFound, String textExpected)
    throws SAXException
    {
        if (textFound != null) {
            message = message + " (found \"" + textFound + "\")";
        }
        if (textExpected != null) {
            message = message + " (expected \"" + textExpected + "\")";
        }
        String uri = null;

        if (externalEntity != null) {
            uri = externalEntity.getURL ().toString ();
        }
        handler.error (message, uri, line, column);

        // "can't happen"
        throw new SAXException (message);
    }


    /**
     * Report a serious error.
     * @param message The error message.
     * @param textFound The text that caused the error (or null).
     */
    private void error (String message, char textFound, String textExpected)
    throws SAXException
    {
        error (message, new Character (textFound).toString (), textExpected);
    }

    /** Report typical case fatal errors. */
    private void error (String message)
    throws SAXException
    {
        error (message, null, null);
    }


    //////////////////////////////////////////////////////////////////////
    // Major syntactic productions.
    //////////////////////////////////////////////////////////////////////


    /**
     * Parse an XML document.
     * <pre>
     * [1] document ::= prolog element Misc*
     * </pre>
     * <p>This is the top-level parsing function for a single XML
     * document.  As a minimum, a well-formed document must have
     * a document element, and a valid document must have a prolog
     * (one with doctype) as well.
     */
    private void parseDocument ()
    throws Exception
    {
        char c;
        try {                                       // added by MHK
            parseProlog ();
            require ('<');
            parseElement ();
        } catch (EOFException ee) {                 // added by MHK
            error("premature end of file", "[EOF]", null);
        }
        
        try {
            parseMisc ();   //skip all white, PIs, and comments
            c = readCh ();    //if this doesn't throw an exception...
            error ("unexpected characters after document end", c, null);
        } catch (EOFException e) {
            return;
        }
    }


    /**
     * Skip a comment.
     * <pre>
     * [15] Comment ::= '&lt;!--' ((Char - '-') | ('-' (Char - '-')))* "-->"
     * </pre>
     * <p> (The <code>&lt;!--</code> has already been read.)
     */
    private void parseComment ()
    throws Exception
    {
        char c;
        boolean saved = expandPE;

        expandPE = false;
        parseUntil ("--");
        require ('>');
        expandPE = saved;
        handler.comment (dataBuffer, 0, dataBufferPos);
        dataBufferPos = 0;
    }


    /**
     * Parse a processing instruction and do a call-back.
     * <pre>
     * [16] PI ::= '&lt;?' PITarget
     *          (S (Char* - (Char* '?&gt;' Char*)))?
     *          '?&gt;'
     * [17] PITarget ::= Name - ( ('X'|'x') ('M'|m') ('L'|l') )
     * </pre>
     * <p> (The <code>&lt;?</code> has already been read.)
     */
    private void parsePI ()
    throws SAXException, IOException
    {
        String name;
        boolean saved = expandPE;

        expandPE = false;
        name = readNmtoken (true);
        if ("xml".equalsIgnoreCase (name))
            error ("Illegal processing instruction target", name, null);
        if (!tryRead ("?>")) {
            requireWhitespace ();
            parseUntil ("?>");
        }
        expandPE = saved;
        handler.processingInstruction (name, dataBufferToString ());
    }


    /**
     * Parse a CDATA section.
     * <pre>
     * [18] CDSect ::= CDStart CData CDEnd
     * [19] CDStart ::= '&lt;![CDATA['
     * [20] CData ::= (Char* - (Char* ']]&gt;' Char*))
     * [21] CDEnd ::= ']]&gt;'
     * </pre>
     * <p> (The '&lt;![CDATA[' has already been read.)
     */
    private void parseCDSect ()
    throws Exception
    {
        parseUntil ("]]>");
        dataBufferFlush ();
    }


    /**
     * Parse the prolog of an XML document.
     * <pre>
     * [22] prolog ::= XMLDecl? Misc* (Doctypedecl Misc*)?
     * </pre>
     * <p>There are a couple of tricks here.  First, it is necessary to
     * declare the XML default attributes after the DTD (if present)
     * has been read. [??]  Second, it is not possible to expand general
     * references in attribute value literals until after the entire
     * DTD (if present) has been parsed.
     * <p>We do not look for the XML declaration here, because it was
     * handled by pushURL ().
     * @see pushURL
     */
    private void parseProlog ()
    throws Exception
    {
        parseMisc ();

        if (tryRead ("<!DOCTYPE")) {
            parseDoctypedecl ();
            parseMisc ();
        }
    }


    /**
     * Parse the XML declaration.
     * <pre>
     * [23] XMLDecl ::= '&lt;?xml' VersionInfo EncodingDecl? SDDecl? S? '?&gt;'
     * [24] VersionInfo ::= S 'version' Eq
     *          ("'" VersionNum "'" | '"' VersionNum '"' )
     * [26] VersionNum ::= ([a-zA-Z0-9_.:] | '-')*
     * [32] SDDecl ::= S 'standalone' Eq
     *          ( "'"" ('yes' | 'no') "'"" | '"' ("yes" | "no") '"' )
     * [80] EncodingDecl ::= S 'encoding' Eq
     *          ( "'" EncName "'" | "'" EncName "'" )
     * [81] EncName ::= [A-Za-z] ([A-Za-z0-9._] | '-')*
     * </pre>
     * <p> (The <code>&lt;?xml</code> and whitespace have already been read.)
     * @return the encoding in the declaration, uppercased; or null
     * @see #parseTextDecl
     * @see #setupDecoding
     */
    private String parseXMLDecl (boolean ignoreEncoding)
    throws SAXException, IOException
    {
        String  version;
        String  encodingName = null;
        String  standalone = null;
        boolean white;
        int     flags = LIT_DISABLE_CREF | LIT_DISABLE_PE | LIT_DISABLE_EREF;

        // Read the version.
        require ("version");
        parseEq ();
        version = readLiteral (flags);
        if (!version.equals ("1.0")) {
            error ("unsupported XML version", version, "1.0");
        }

        // Try reading an encoding declaration.
        white = tryWhitespace ();
        if (tryRead ("encoding")) {
            if (!white)
                error ("whitespace required before 'encoding='");
            parseEq ();
            encodingName = readLiteral (flags);
            if (!ignoreEncoding)
                setupDecoding (encodingName);
        }

        // Try reading a standalone declaration
        if (encodingName != null)
            white = tryWhitespace ();
        if (tryRead ("standalone")) {
            if (!white)
                error ("whitespace required before 'standalone='");
            parseEq ();
            standalone = readLiteral (flags);
            if (! ("yes".equals (standalone) || "no".equals (standalone)))
                error ("standalone flag must be 'yes' or 'no'");
        }

        skipWhitespace ();
        require ("?>");

        return encodingName;
    }


    /**
     * Parse a text declaration.
     * <pre>
     * [79] TextDecl ::= '&lt;?xml' VersionInfo? EncodingDecl S? '?&gt;'
     * [80] EncodingDecl ::= S 'encoding' Eq
     *          ( '"' EncName '"' | "'" EncName "'" )
     * [81] EncName ::= [A-Za-z] ([A-Za-z0-9._] | '-')*
     * </pre>
     * <p> (The <code>&lt;?xml</code>' and whitespace have already been read.)
     * @return the encoding in the declaration, uppercased; or null
     * @see #parseXMLDecl
     * @see #setupDecoding
     */
    private String parseTextDecl (boolean ignoreEncoding)
    throws SAXException, IOException
    {
        String  encodingName = null;
        int     flags = LIT_DISABLE_CREF | LIT_DISABLE_PE | LIT_DISABLE_EREF;

        // Read an optional version.
        if (tryRead ("version")) {
            String version;
            parseEq ();
            version = readLiteral (flags);
            if (!version.equals ("1.0")) {
                error ("unsupported XML version", version, "1.0");
            }
            requireWhitespace ();
        }


        // Read the encoding.
        require ("encoding");
        parseEq ();
        encodingName = readLiteral (flags);
        if (!ignoreEncoding)
            setupDecoding (encodingName);

        skipWhitespace ();
        require ("?>");

        return encodingName;
    }


    /**
     * Sets up internal state so that we can decode an entity using the
     * specified encoding.  This is used when we start to read an entity
     * and we have been given knowledge of its encoding before we start to
     * read any data (e.g. from a SAX input source or from a MIME type).
     *
     * <p> It is also used after autodetection, at which point only very
     * limited adjustments to the encoding may be used (switching between
     * related builtin decoders).
     *
     * @param encodingName The name of the encoding specified by the user.
     * @exception IOException if the encoding isn't supported either
     *  internally to this parser, or by the hosting JVM.
     * @see #parseXMLDecl
     * @see #parseTextDecl
     */
    private void setupDecoding (String encodingName)
    throws SAXException, IOException
    {
        encodingName = encodingName.toUpperCase ();

        // ENCODING_EXTERNAL indicates an encoding that wasn't
        // autodetected ... we can use builtin decoders, or
        // ones from the JVM (InputStreamReader).

        // Otherwise we can only tweak what was autodetected, and
        // only for single byte (ASCII derived) builtin encodings.

        // ASCII-derived encodings
        if (encoding == ENCODING_UTF_8 || encoding == ENCODING_EXTERNAL) {
            if (encodingName.equals ("ISO-8859-1")
                    || encodingName.equals ("8859_1")
                    || encodingName.equals ("ISO8859_1")
              ) {
                encoding = ENCODING_ISO_8859_1;
                return;
            } else if (encodingName.equals ("US-ASCII")
                        || encodingName.equals ("ASCII")) {
                encoding = ENCODING_ASCII;
                return;
            } else if (encodingName.equals ("UTF-8")
                        || encodingName.equals ("UTF8")) {
                encoding = ENCODING_UTF_8;
                return;
            } else if (encoding != ENCODING_EXTERNAL) {
                // fatal error
                error ("unsupported ASCII-derived encoding",
                       encodingName,
                       "UTF-8, US-ASCII, or ISO-8859-1");
            }
            // else fallthrough ...
            // it's ASCII-ish and something other than a builtin
        }

        // Unicode and such
        if (encoding == ENCODING_UCS_2_12 || encoding == ENCODING_UCS_2_21) {
            if (!(encodingName.equals ("ISO-10646-UCS-2")
                    || encodingName.equals ("UTF-16")
                    || encodingName.equals ("UTF-16BE")
                    || encodingName.equals ("UTF-16LE")))
                error ("unsupported Unicode encoding",
                       encodingName,
                       "UTF-16");
            return;
        }

        // four byte encodings
        if (encoding == ENCODING_UCS_4_1234
                || encoding == ENCODING_UCS_4_4321
                || encoding == ENCODING_UCS_4_2143
                || encoding == ENCODING_UCS_4_3412) {
            if (!encodingName.equals ("ISO-10646-UCS-4"))
                error ("unsupported 32-bit encoding",
                       encodingName,
                       "ISO-10646-UCS-4");
            return;
        }

        // assert encoding == ENCODING_EXTERNAL
        // if (encoding != ENCODING_EXTERNAL)
        //     throw new RuntimeException ("encoding = " + encoding);

        if (encodingName.equals ("UTF-16BE")) {
            encoding = ENCODING_UCS_2_12;
            return;
        }
        if (encodingName.equals ("UTF-16LE")) {
            encoding = ENCODING_UCS_2_21;
            return;
        }

        // We couldn't use the builtin decoders at all.  But we can try to
        // create a reader, since we haven't messed up buffering.  Tweak
        // the encoding name if necessary.

        if (encodingName.equals ("UTF-16")
                || encodingName.equals ("ISO-10646-UCS-2"))
            encodingName = "Unicode";
        // Ignoring all the EBCDIC aliases here

        reader = new InputStreamReader (is, encodingName);
        sourceType = INPUT_READER;
        is = null;
    }


    /**
     * Parse miscellaneous markup outside the document element and DOCTYPE
     * declaration.
     * <pre>
     * [27] Misc ::= Comment | PI | S
     * </pre>
     */
    private void parseMisc ()
    throws Exception
    {
        while (true) {
            skipWhitespace ();
            if (tryRead ("<?")) {
                parsePI ();
            } else if (tryRead ("<!--")) {
                parseComment ();
            } else {
                return;
            }
        }
    }


    /**
     * Parse a document type declaration.
     * <pre>
     * [28] doctypedecl ::= '&lt;!DOCTYPE' S Name (S ExternalID)? S?
     *          ('[' (markupdecl | PEReference | S)* ']' S?)? '&gt;'
     * </pre>
     * <p> (The <code>&lt;!DOCTYPE</code> has already been read.)
     */
    private void parseDoctypedecl ()
    throws Exception
    {
        char c;
        String doctypeName, ids[];

        // Read the document type name.
        requireWhitespace ();
        doctypeName = readNmtoken (true);

        // Read the External subset's IDs
        skipWhitespace ();
        ids = readExternalIds (false);

        // report (a) declaration of name, (b) lexical info (ids)
        handler.doctypeDecl (doctypeName, ids [0], ids [1]);

        // Internal subset is parsed first, if present
        skipWhitespace ();
        if (tryRead ('[')) {

            // loop until the subset ends
            while (true) {
                expandPE = true;
                skipWhitespace ();
                expandPE = false;
                if (tryRead (']')) {
                    break;              // end of subset
                } else {
                    // WFC, PEs in internal subset (only between decls)
                    peIsError = expandPE = true;
                    parseMarkupdecl ();
                    peIsError = expandPE = false;
                }
            }
        }

        // Read the external subset, if any
        if (ids [1] != null) {
            pushURL ("[external subset]", ids [0], ids [1], null, null, null);

            // Loop until we end up back at '>'
            while (true) {
                expandPE = true;
                skipWhitespace ();
                expandPE = false;
                if (tryRead ('>')) {
                    break;
                } else {
                    expandPE = true;
                    parseMarkupdecl ();
                    expandPE = false;
                }
            }
        } else {
            // No external subset.
            skipWhitespace ();
            require ('>');
        }

        // done dtd
        handler.endDoctype ();
        expandPE = false;
    }


    /**
     * Parse a markup declaration in the internal or external DTD subset.
     * <pre>
     * [29] markupdecl ::= elementdecl | Attlistdecl | EntityDecl
     *          | NotationDecl | PI | Comment
     * [30] extSubsetDecl ::= (markupdecl | conditionalSect
     *          | PEReference | S) *
     * </pre>
     * <p> Reading toplevel PE references is handled as a lexical issue
     * by the caller, as is whitespace.
     */
    private void parseMarkupdecl ()
    throws Exception
    {
        if (tryRead ("<!ELEMENT")) {
            parseElementdecl ();
        } else if (tryRead ("<!ATTLIST")) {
            parseAttlistDecl ();
        } else if (tryRead ("<!ENTITY")) {
            parseEntityDecl ();
        } else if (tryRead ("<!NOTATION")) {
            parseNotationDecl ();
        } else if (tryRead ("<?")) {
            parsePI ();
        } else if (tryRead ("<!--")) {
            parseComment ();
        } else if (tryRead ("<![")) {
            if (inputStack.size () > 0)
                parseConditionalSect ();
            else
                error ("conditional sections illegal in internal subset");
        } else {
            error ("expected markup declaration");
        }
    }


    /**
     * Parse an element, with its tags.
     * <pre>
     * [39] element ::= EmptyElementTag | STag content ETag
     * [40] STag ::= '&lt;' Name (S Attribute)* S? '&gt;'
     * [44] EmptyElementTag ::= '&lt;' Name (S Attribute)* S? '/&gt;'
     * </pre>
     * <p> (The '&lt;' has already been read.)
     * <p>NOTE: this method actually chains onto parseContent (), if necessary,
     * and parseContent () will take care of calling parseETag ().
     */
    private void parseElement ()
    throws Exception
    {
        String  gi;
        char    c;
        int     oldElementContent = currentElementContent;
        String  oldElement = currentElement;
        Object  element [];

        // This is the (global) counter for the
        // array of specified attributes.
        tagAttributePos = 0;

        // Read the element type name.
        gi = readNmtoken (true);

        // Determine the current content type.
        currentElement = gi;
        element = (Object []) elementInfo.get (gi);
        currentElementContent = getContentType (element, CONTENT_ANY);

        // Read the attributes, if any.
        // After this loop, "c" is the closing delimiter.
        boolean white = tryWhitespace ();
        c = readCh ();
        while (c != '/' && c != '>') {
            unread (c);
            if (!white)
                error ("need whitespace between attributes");
            parseAttribute (gi);
            white = tryWhitespace ();
            c = readCh ();
        }

        // Supply any defaulted attributes.
        Iterator atts = declaredAttributes (element);
        if (atts != null) {
            String aname;
loop:
            while (atts.hasNext ()) {
                aname = (String) atts.next ();
                // See if it was specified.
                for (int i = 0; i < tagAttributePos; i++) {
                    if (tagAttributes [i] == aname) {
                        continue loop;
                    }
                }
                // I guess not...
                handler.attribute (aname,
                                   getAttributeExpandedValue (gi, aname),
                                   false);
            }
        }

        // Figure out if this is a start tag
        // or an empty element, and dispatch an
        // event accordingly.
        switch (c) {
        case '>':
            handler.startElement (gi);
            parseContent ();
            break;
        case '/':
            require ('>');
            handler.startElement (gi);
            handler.endElement (gi);
            break;
        }

        // Restore the previous state.
        currentElement = oldElement;
        currentElementContent = oldElementContent;
    }


    /**
     * Parse an attribute assignment.
     * <pre>
     * [41] Attribute ::= Name Eq AttValue
     * </pre>
     * @param name The name of the attribute's element.
     * @see SAXDriver#attribute
     */
    private void parseAttribute (String name)
    throws Exception
    {
        String aname;
        int type;
        String value;
        int flags = LIT_ATTRIBUTE |  LIT_ENTITY_REF;

        // Read the attribute name.
        aname = readNmtoken (true);
        type = getAttributeType (name, aname);

        // Parse '='
        parseEq ();

        // Read the value, normalizing whitespace
        // unless it is CDATA.
        if (type == ATTRIBUTE_CDATA || type == ATTRIBUTE_UNDECLARED) {
            value = readLiteral (flags);
        } else {
            value = readLiteral (flags | LIT_NORMALIZE);
        }

        // WFC: no duplicate attributes
        for (int i = 0; i < tagAttributePos; i++)
            if (aname.equals (tagAttributes [i]))
                error ("duplicate attribute", aname, null);

        // Inform the handler about the
        // attribute.
        handler.attribute (aname, value, true);
        dataBufferPos = 0;

        // Note that the attribute has been
        // specified.
        if (tagAttributePos == tagAttributes.length) {
            String newAttrib[] = new String [tagAttributes.length * 2];
            System.arraycopy (tagAttributes, 0, newAttrib, 0, tagAttributePos);
            tagAttributes = newAttrib;
        }
        tagAttributes [tagAttributePos++] = aname;
    }


    /**
     * Parse an equals sign surrounded by optional whitespace.
     * <pre>
     * [25] Eq ::= S? '=' S?
     * </pre>
     */
    private void parseEq ()
    throws SAXException, IOException
    {
        skipWhitespace ();
        require ('=');
        skipWhitespace ();
    }


    /**
     * Parse an end tag.
     * <pre>
     * [42] ETag ::= '</' Name S? '>'
     * </pre>
     * <p>NOTE: parseContent () chains to here, we already read the
     * "&lt;/".
     */
    private void parseETag ()
    throws Exception
    {
        require (currentElement);
        skipWhitespace ();
        require ('>');
        handler.endElement (currentElement);
        // not re-reporting any SAXException re bogus end tags,
        // even though that diagnostic might be clearer ...
    }


    /**
     * Parse the content of an element.
     * <pre>
     * [43] content ::= (element | CharData | Reference
     *          | CDSect | PI | Comment)*
     * [67] Reference ::= EntityRef | CharRef
     * </pre>
     * <p> NOTE: consumes ETtag.
     */
    private void parseContent ()
    throws Exception
    {
        String data;
        char c;

        while (true) {
            switch (currentElementContent) {
                case CONTENT_ANY:
                case CONTENT_MIXED:
                case CONTENT_UNDECLARED:    // this line added by MHK 24 May 2000
                case CONTENT_EMPTY:         // this line added by MHK 8 Sept 2000
                        parseCharData ();
                        break;
                case CONTENT_ELEMENTS:
                        parseWhitespace ();
                        break;
            }

            // Handle delimiters
            c = readCh ();
            switch (c) {

            case '&':                   // Found "&"

                c = readCh ();
                if (c == '#') {
                    parseCharRef ();
                } else {
                    unread (c);
                    parseEntityRef (true);
                }
                break;

            case '<':                   // Found "<"
                dataBufferFlush ();
                c = readCh ();
                switch (c) {
                  case '!':                     // Found "<!"
                    c = readCh ();
                    switch (c) {
                      case '-':                 // Found "<!-"
                                require ('-');
                                parseComment ();
                                break;
                      case '[':                 // Found "<!["
                                require ("CDATA[");
                                handler.startCDATA ();
                                inCDATA = true;
                                parseCDSect ();
                                inCDATA = false;
                                handler.endCDATA ();
                                break;
                      default:
                                error ("expected comment or CDATA section", c, null);
                                break;
                    }
                    break;

                  case '?':             // Found "<?"
                    parsePI ();
                    break;

                  case '/':             // Found "</"
                    parseETag ();
                    return;

                  default:              // Found "<" followed by something else
                    unread (c);
                    parseElement ();
                    break;
                }
                }
            }
    }


    /**
     * Parse an element type declaration.
     * <pre>
     * [45] elementdecl ::= '&lt;!ELEMENT' S Name S contentspec S? '&gt;'
     * </pre>
     * <p> NOTE: the '&lt;!ELEMENT' has already been read.
     */
    private void parseElementdecl ()
    throws Exception
    {
        String name;

        requireWhitespace ();
        // Read the element type name.
        name = readNmtoken (true);

        requireWhitespace ();
        // Read the content model.
        parseContentspec (name);

        skipWhitespace ();
        require ('>');
    }


    /**
     * Content specification.
     * <pre>
     * [46] contentspec ::= 'EMPTY' | 'ANY' | Mixed | elements
     * </pre>
     */
    private void parseContentspec (String name)
    throws Exception
    {
        if (tryRead ("EMPTY")) {
            setElement (name, CONTENT_EMPTY, null, null);
            return;
        } else if (tryRead ("ANY")) {
            setElement (name, CONTENT_ANY, null, null);
            return;
        } else {
            require ('(');
            dataBufferAppend ('(');
            skipWhitespace ();
            if (tryRead ("#PCDATA")) {
                dataBufferAppend ("#PCDATA");
                parseMixed ();
                setElement (name, CONTENT_MIXED, dataBufferToString (), null);
            } else {
                parseElements ();
                setElement (name, CONTENT_ELEMENTS,
                        dataBufferToString (), null);
            }
        }
    }


    /**
     * Parse an element-content model.
     * <pre>
     * [47] elements ::= (choice | seq) ('?' | '*' | '+')?
     * [49] choice ::= '(' S? cp (S? '|' S? cp)+ S? ')'
     * [50] seq ::= '(' S? cp (S? ',' S? cp)* S? ')'
     * </pre>
     *
     * <p> NOTE: the opening '(' and S have already been read.
     */
    private void parseElements ()
    throws Exception
    {
        char c;
        char sep;

        // Parse the first content particle
        skipWhitespace ();
        parseCp ();

        // Check for end or for a separator.
        skipWhitespace ();
        c = readCh ();
        switch (c) {
        case ')':
            dataBufferAppend (')');
            c = readCh ();
            switch (c) {
            case '*':
            case '+':
            case '?':
                dataBufferAppend (c);
                break;
            default:
                unread (c);
            }
            return;
        case ',':                       // Register the separator.
        case '|':
            sep = c;
            dataBufferAppend (c);
            break;
        default:
            error ("bad separator in content model", c, null);
            return;
        }

        // Parse the rest of the content model.
        while (true) {
            skipWhitespace ();
            parseCp ();
            skipWhitespace ();
            c = readCh ();
            if (c == ')') {
                dataBufferAppend (')');
                break;
            } else if (c != sep) {
                error ("bad separator in content model", c, null);
                return;
            } else {
                dataBufferAppend (c);
            }
        }

        // Check for the occurrence indicator.
        c = readCh ();
        switch (c) {
        case '?':
        case '*':
        case '+':
            dataBufferAppend (c);
            return;
        default:
            unread (c);
            return;
        }
    }


    /**
     * Parse a content particle.
     * <pre>
     * [48] cp ::= (Name | choice | seq) ('?' | '*' | '+')?
     * </pre>
     */
    private void parseCp ()
    throws Exception
    {
        char c;

        if (tryRead ('(')) {
            dataBufferAppend ('(');
            parseElements ();
        } else {
            dataBufferAppend (readNmtoken (true));
            c = readCh ();
            switch (c) {
            case '?':
            case '*':
            case '+':
                dataBufferAppend (c);
                break;
            default:
                unread (c);
                break;
            }
        }
    }


    /**
     * Parse mixed content.
     * <pre>
     * [51] Mixed ::= '(' S? ( '#PCDATA' (S? '|' S? Name)*) S? ')*'
     *        | '(' S? ('#PCDATA') S? ')'
     * </pre>
     */
    private void parseMixed ()
    throws Exception
    {
        char c;

        // Check for PCDATA alone.
        skipWhitespace ();
        if (tryRead (')')) {
            dataBufferAppend (")*");
            tryRead ('*');
            return;
        }

        // Parse mixed content.
        skipWhitespace ();
        while (!tryRead (")*")) {
            require ('|');
            dataBufferAppend ('|');
            skipWhitespace ();
            dataBufferAppend (readNmtoken (true));
            skipWhitespace ();
        }
        dataBufferAppend (")*");
    }


    /**
     * Parse an attribute list declaration.
     * <pre>
     * [52] AttlistDecl ::= '&lt;!ATTLIST' S Name AttDef* S? '&gt;'
     * </pre>
     * <p>NOTE: the '&lt;!ATTLIST' has already been read.
     */
    private void parseAttlistDecl ()
    throws Exception
    {
        String elementName;

        requireWhitespace ();
        elementName = readNmtoken (true);
        boolean white = tryWhitespace ();
        while (!tryRead ('>')) {
            if (!white)
                error ("whitespace required before attribute definition");
            parseAttDef (elementName);
            white = tryWhitespace ();
        }
    }


    /**
     * Parse a single attribute definition.
     * <pre>
     * [53] AttDef ::= S Name S AttType S DefaultDecl
     * </pre>
     */
    private void parseAttDef (String elementName)
    throws Exception
    {
      String name;
      int type;
      String myEnum = null;
    
      // Read the attribute name.
      name = readNmtoken (true);
    
      // Read the attribute type.
      requireWhitespace ();
      type = readAttType ();
    
      // Get the string of enumerated values
      // if necessary.
      if (type == ATTRIBUTE_ENUMERATED || type == ATTRIBUTE_NOTATION) {
          myEnum = dataBufferToString ();
      }
    
      // Read the default value.
      requireWhitespace ();
      parseDefault (elementName, name, type, myEnum);
    }


    /**
     * Parse the attribute type.
     * <pre>
     * [54] AttType ::= StringType | TokenizedType | EnumeratedType
     * [55] StringType ::= 'CDATA'
     * [56] TokenizedType ::= 'ID' | 'IDREF' | 'IDREFS' | 'ENTITY'
     *          | 'ENTITIES' | 'NMTOKEN' | 'NMTOKENS'
     * [57] EnumeratedType ::= NotationType | Enumeration
     * </pre>
     */
    private int readAttType ()
    throws Exception
    {
      String typeString;
      Integer type;
    
      if (tryRead ('(')) {
          parseEnumeration (false);
          return ATTRIBUTE_ENUMERATED;
      } else {
          typeString = readNmtoken (true);
          if (typeString.equals ("NOTATION")) {
        parseNotationType ();
          }
          type = (Integer) attributeTypeHash.get (typeString);
          if (type == null) {
        error ("illegal attribute type", typeString, null);
        return ATTRIBUTE_UNDECLARED;
          } else {
        return type.intValue ();
          }
      }
    }


    /**
     * Parse an enumeration.
     * <pre>
     * [59] Enumeration ::= '(' S? Nmtoken (S? '|' S? Nmtoken)* S? ')'
     * </pre>
     * <p>NOTE: the '(' has already been read.
     */
    private void parseEnumeration (boolean isNames)
    throws Exception
    {
        char c;

        dataBufferAppend ('(');

        // Read the first token.
        skipWhitespace ();
        dataBufferAppend (readNmtoken (isNames));
        // Read the remaining tokens.
        skipWhitespace ();
        while (!tryRead (')')) {
            require ('|');
            dataBufferAppend ('|');
            skipWhitespace ();
            dataBufferAppend (readNmtoken (isNames));
            skipWhitespace ();
        }
        dataBufferAppend (')');
    }


    /**
     * Parse a notation type for an attribute.
     * <pre>
     * [58] NotationType ::= 'NOTATION' S '(' S? NameNtoks
     *          (S? '|' S? name)* S? ')'
     * </pre>
     * <p>NOTE: the 'NOTATION' has already been read
     */
    private void parseNotationType ()
    throws Exception
    {
        requireWhitespace ();
        require ('(');

        parseEnumeration (true);
    }


    /**
     * Parse the default value for an attribute.
     * <pre>
     * [60] DefaultDecl ::= '#REQUIRED' | '#IMPLIED'
     *          | (('#FIXED' S)? AttValue)
     * </pre>
     */
    private void parseDefault (
        String elementName,
        String name,
        int type,
        String myEnum
    ) throws Exception
    {
        int     valueType = ATTRIBUTE_DEFAULT_SPECIFIED;
        String  value = null;
        int     flags = LIT_ATTRIBUTE | LIT_DISABLE_CREF | LIT_ENTITY_CHECK;

        // Note: char refs not checked here, and input not normalized,
        // since it's done correctly later when we actually expand any
        // entity refs.  We ought to report char ref syntax errors now,
        // but don't.  Cost: unused defaults mean unreported WF errs.
        
        // LIT_ATTRIBUTE forces '<' checks now (ASAP) and turns whitespace
        // chars to spaces (doesn't matter when that's done if it doesn't
        // interfere with char refs expanding to whitespace).

        if (tryRead ('#')) {
            if (tryRead ("FIXED")) {
                valueType = ATTRIBUTE_DEFAULT_FIXED;
                requireWhitespace ();
                value = readLiteral (flags);
            } else if (tryRead ("REQUIRED")) {
                valueType = ATTRIBUTE_DEFAULT_REQUIRED;
            } else if (tryRead ("IMPLIED")) {
                valueType = ATTRIBUTE_DEFAULT_IMPLIED;
            } else {
                error ("illegal keyword for attribute default value");
            }
        } else
            value = readLiteral (flags);
        setAttribute (elementName, name, type, myEnum, value, valueType);
    }


    /**
     * Parse a conditional section.
     * <pre>
     * [61] conditionalSect ::= includeSect || ignoreSect
     * [62] includeSect ::= '&lt;![' S? 'INCLUDE' S? '['
     *          extSubsetDecl ']]&gt;'
     * [63] ignoreSect ::= '&lt;![' S? 'IGNORE' S? '['
     *          ignoreSectContents* ']]&gt;'
     * [64] ignoreSectContents ::= Ignore
     *          ('&lt;![' ignoreSectContents* ']]&gt;' Ignore )*
     * [65] Ignore ::= Char* - (Char* ( '&lt;![' | ']]&gt;') Char* )
     * </pre>
     * <p> NOTE: the '&gt;![' has already been read.
     */
    private void parseConditionalSect ()
    throws Exception
    {
        skipWhitespace ();
        if (tryRead ("INCLUDE")) {
            skipWhitespace ();
            require ('[');
            skipWhitespace ();
            while (!tryRead ("]]>")) {
                parseMarkupdecl ();
                skipWhitespace ();
            }
        } else if (tryRead ("IGNORE")) {
            skipWhitespace ();
            require ('[');
            int nesting = 1;
            char c;
            expandPE = false;
            for (int nest = 1; nest > 0;) {
                c = readCh ();
                switch (c) {
                case '<':
                    if (tryRead ("![")) {
                        nest++;
                    }
                case ']':
                    if (tryRead ("]>")) {
                        nest--;
                    }
                }
            }
            expandPE = true;
        } else {
            error ("conditional section must begin with INCLUDE or IGNORE");
        }
    }


    /**
     * Read and interpret a character reference.
     * <pre>
     * [66] CharRef ::= '&#' [0-9]+ ';' | '&#x' [0-9a-fA-F]+ ';'
     * </pre>
     * <p>NOTE: the '&#' has already been read.
     */
    private void parseCharRef ()
    throws SAXException, IOException
    {
        int value = 0;
        char c;

        if (tryRead ('x')) {
loop1:
            while (true) {
                c = readCh ();
                switch (c) {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                case 'a':
                case 'A':
                case 'b':
                case 'B':
                case 'c':
                case 'C':
                case 'd':
                case 'D':
                case 'e':
                case 'E':
                case 'f':
                case 'F':
                    value *= 16;
                    value += Integer.parseInt (new Character (c).toString (),
                                    16);
                    break;
                case ';':
                    break loop1;
                default:
                    error ("illegal character in character reference", c, null);
                    break loop1;
                }
            }
        } else {
loop2:
            while (true) {
                c = readCh ();
                switch (c) {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                    value *= 10;
                    value += Integer.parseInt (new Character (c).toString (),
                                    10);
                    break;
                case ';':
                    break loop2;
                default:
                    error ("illegal character in character reference", c, null);
                    break loop2;
                }
            }
        }

        // check for character refs being legal XML
        if ((value < 0x0020
                && ! (value == '\n' || value == '\t' || value == '\r'))
                || (value >= 0xD800 && value <= 0xDFFF)
                || value == 0xFFFE || value == 0xFFFF
                || value > 0x0010ffff)
            error ("illegal XML character reference U+"
                    + Integer.toHexString (value));

        // Check for surrogates: 00000000 0000xxxx yyyyyyyy zzzzzzzz
        //  (1101|10xx|xxyy|yyyy + 1101|11yy|zzzz|zzzz:
        if (value <= 0x0000ffff) {
            // no surrogates needed
            dataBufferAppend ((char) value);
        } else if (value <= 0x0010ffff) {
            value -= 0x10000;
            // > 16 bits, surrogate needed
            dataBufferAppend ((char) (0xd800 | (value >> 10)));
            dataBufferAppend ((char) (0xdc00 | (value & 0x0003ff)));
        } else {
            // too big for surrogate
            error ("character reference " + value + " is too large for UTF-16",
                   new Integer (value).toString (), null);
        }
    }


    /**
     * Parse and expand an entity reference.
     * <pre>
     * [68] EntityRef ::= '&' Name ';'
     * </pre>
     * <p>NOTE: the '&amp;' has already been read.
     * @param externalAllowed External entities are allowed here.
     */
    private void parseEntityRef (boolean externalAllowed)
    throws SAXException, IOException
    {
        String name;

        name = readNmtoken (true);
        require (';');
        switch (getEntityType (name)) {
        case ENTITY_UNDECLARED:
            error ("reference to undeclared entity", name, null);
            break;
        case ENTITY_INTERNAL:
            pushString (name, getEntityValue (name));
            break;
        case ENTITY_TEXT:
            if (externalAllowed) {
                pushURL (name, getEntityPublicId (name),
                         getEntitySystemId (name),
                         null, null, null);
            } else {
                error ("reference to external entity in attribute value.",
                        name, null);
            }
            break;
        case ENTITY_NDATA:
            if (externalAllowed) {
                error ("unparsed entity reference in content", name, null);
            } else {
                error ("reference to external entity in attribute value.",
                        name, null);
            }
            break;
        }
    }


    /**
     * Parse and expand a parameter entity reference.
     * <pre>
     * [69] PEReference ::= '%' Name ';'
     * </pre>
     * <p>NOTE: the '%' has already been read.
     */
    private void parsePEReference ()
    throws SAXException, IOException
    {
        String name;

        name = "%" + readNmtoken (true);
        require (';');
        switch (getEntityType (name)) {
        case ENTITY_UNDECLARED:
            // this is a validity problem, not a WFC violation ... but
            // we should disable handling of all subsequent declarations
            // unless this is a standalone document
            // warn ("reference to undeclared parameter entity", name, null);

            break;
        case ENTITY_INTERNAL:
            if (inLiteral)
                pushString (name, getEntityValue (name));
            else
                pushString (name, " " + getEntityValue (name) + ' ');
            break;
        case ENTITY_TEXT:
            if (!inLiteral)
                pushString (null, " ");
            pushURL (name, getEntityPublicId (name),
                     getEntitySystemId (name),
                     null, null, null);
            if (!inLiteral)
                pushString (null, " ");
            break;
        }
    }

    /**
     * Parse an entity declaration.
     * <pre>
     * [70] EntityDecl ::= GEDecl | PEDecl
     * [71] GEDecl ::= '&lt;!ENTITY' S Name S EntityDef S? '&gt;'
     * [72] PEDecl ::= '&lt;!ENTITY' S '%' S Name S PEDef S? '&gt;'
     * [73] EntityDef ::= EntityValue | (ExternalID NDataDecl?)
     * [74] PEDef ::= EntityValue | ExternalID
     * [75] ExternalID ::= 'SYSTEM' S SystemLiteral
     *             | 'PUBLIC' S PubidLiteral S SystemLiteral
     * [76] NDataDecl ::= S 'NDATA' S Name
     * </pre>
     * <p>NOTE: the '&lt;!ENTITY' has already been read.
     */
    private void parseEntityDecl ()
    throws Exception
    {
        char c;
        boolean peFlag = false;
        String name, value, notationName, ids[];

        // Check for a parameter entity.
        expandPE = false;
        requireWhitespace ();
        if (tryRead ('%')) {
            peFlag = true;
            requireWhitespace ();
        }
        expandPE = true;

        // Read the entity name, and prepend
        // '%' if necessary.
        name = readNmtoken (true);
        if (peFlag) {
            name = "%" + name;
        }

        // Read the entity value.
        requireWhitespace ();
        c = readCh ();
        unread (c);
        if (c == '"' || c == '\'') {
            // Internal entity ... replacement text has expanded refs
            // to characters and PEs, but not to general entities
            value = readLiteral (0);
            setInternalEntity (name, value);
        } else {
            // Read the external IDs
            ids = readExternalIds (false);
            if (ids [1] == null) {
                error ("system identifer missing", name, null);
            }

            // Check for NDATA declaration.
            boolean white = tryWhitespace ();
            if (!peFlag && tryRead ("NDATA")) {
                if (!white)
                    error ("whitespace required before NDATA");
                requireWhitespace ();
                notationName = readNmtoken (true);
                setExternalDataEntity (name, ids [0], ids [1], notationName);
            } else {
                setExternalTextEntity (name, ids [0], ids [1]);
            }
        }

        // Finish the declaration.
        skipWhitespace ();
        require ('>');
    }


    /**
     * Parse a notation declaration.
     * <pre>
     * [82] NotationDecl ::= '&lt;!NOTATION' S Name S
     *          (ExternalID | PublicID) S? '&gt;'
     * [83] PublicID ::= 'PUBLIC' S PubidLiteral
     * </pre>
     * <P>NOTE: the '&lt;!NOTATION' has already been read.
     */
    private void parseNotationDecl ()
    throws Exception
    {
        String nname, ids[];


        requireWhitespace ();
        nname = readNmtoken (true);

        requireWhitespace ();

        // Read the external identifiers.
        ids = readExternalIds (true);
        if (ids [0] == null && ids [1] == null) {
            error ("external identifer missing", nname, null);
        }

        // Register the notation.
        setNotation (nname, ids [0], ids [1]);

        skipWhitespace ();
        require ('>');
    }


    /**
     * Parse character data.
     * <pre>
     * [14] CharData ::= [^&lt;&amp;]* - ([^&lt;&amp;]* ']]&gt;' [^&lt;&amp;]*)
     * </pre>
     */
    private void parseCharData ()
    throws Exception
    {
        char c;

        // Start with a little cheat -- in most
        // cases, the entire sequence of
        // character data will already be in
        // the readBuffer; if not, fall through to
        // the normal approach.
        if (USE_CHEATS) {
            int lineAugment = 0;
            int columnAugment = 0;

loop:
            for (int i = readBufferPos; i < readBufferLength; i++) {
                switch (c = readBuffer [i]) {
                case '\n':
                    lineAugment++;
                    columnAugment = 0;
                    break;
                case '&':
                case '<':
                    int start = readBufferPos;
                    columnAugment++;
                    readBufferPos = i;
                    if (lineAugment > 0) {
                        line += lineAugment;
                        column = columnAugment;
                    } else {
                        column += columnAugment;
                    }
                    dataBufferAppend (readBuffer, start, i - start);
                    return;
                case ']':
                    // XXX missing two end-of-buffer cases
                    if ((i + 2) < readBufferLength) {
                        if (readBuffer [i + 1] == ']'
                                && readBuffer [i + 2] == '>') {
                            error ("character data may not contain ']]>'");
                        }
                    }
                    columnAugment++;
                    break;
                default:
                    if (c < 0x0020 || c > 0xFFFD)
                        error ("illegal XML character U+"
                                + Integer.toHexString (c));
                    // FALLTHROUGH
                case '\r':
                case '\t':
                    columnAugment++;
                }
            }
        }

        // OK, the cheat didn't work; start over
        // and do it by the book.
        while (true) {
            c = readCh ();
            switch (c) {
            case '<':
            case '&':
                unread (c);
                return;
            // XXX "]]>" precluded ...
            default:
                dataBufferAppend (c);
                break;
            }
        }
    }


    //////////////////////////////////////////////////////////////////////
    // High-level reading and scanning methods.
    //////////////////////////////////////////////////////////////////////

    /**
     * Require whitespace characters.
     */
    private void requireWhitespace ()
    throws SAXException, IOException
    {
        char c = readCh ();
        if (isWhitespace (c)) {
            skipWhitespace ();
        } else {
            error ("whitespace required", c, null);
        }
    }


    /**
     * Parse whitespace characters, and leave them in the data buffer.
     */
    private void parseWhitespace ()
    throws Exception
    {
        char c = readCh ();
        while (isWhitespace (c)) {
            dataBufferAppend (c);
            c = readCh ();
        }
        unread (c);
    }


    /**
     * Skip whitespace characters.
     * <pre>
     * [3] S ::= (#x20 | #x9 | #xd | #xa)+
     * </pre>
     */
    private void skipWhitespace ()
    throws SAXException, IOException
    {
        // Start with a little cheat.  Most of
        // the time, the white space will fall
        // within the current read buffer; if
        // not, then fall through.
        if (USE_CHEATS) {
            int lineAugment = 0;
            int columnAugment = 0;

loop:
            for (int i = readBufferPos; i < readBufferLength; i++) {
                switch (readBuffer [i]) {
                case ' ':
                case '\t':
                case '\r':
                    columnAugment++;
                    break;
                case '\n':
                    lineAugment++;
                    columnAugment = 0;
                    break;
                case '%':
                    if (expandPE)
                        break loop;
                    // else fall through...
                default:
                    readBufferPos = i;
                    if (lineAugment > 0) {
                        line += lineAugment;
                        column = columnAugment;
                    } else {
                        column += columnAugment;
                    }
                    return;
                }
            }
        }

        // OK, do it by the book.
        char c = readCh ();
        while (isWhitespace (c)) {
            c = readCh ();
        }
        unread (c);
    }


    /**
     * Read a name or (when parsing an enumeration) name token.
     * <pre>
     * [5] Name ::= (Letter | '_' | ':') (NameChar)*
     * [7] Nmtoken ::= (NameChar)+
     * </pre>
     */
    private String readNmtoken (boolean isName)
    throws SAXException, IOException
    {
        char c;

        if (USE_CHEATS) {
loop:
            for (int i = readBufferPos; i < readBufferLength; i++) {
                c = readBuffer [i];
                switch (c) {
                  case '%':
                    if (expandPE)
                        break loop;
                    // else fall through...

                    // What may legitimately come AFTER a name/nmtoken?
                  case '<': case '>': case '&':
                  case ',': case '|': case '*': case '+': case '?':
                  case ')':
                  case '=':
                  case '\'': case '"':
                  case '[':
                  case ' ': case '\t': case '\r': case '\n':
                  case ';':
                  case '/':
                    int start = readBufferPos;
                    if (i == start)
                        error ("name expected", readBuffer [i], null);
                    readBufferPos = i;
                    return intern (readBuffer, start, i - start);

                  default:
                    // punt on exact tests from Appendix A; approximate
                    // them using the Unicode ID start/part rules
                    if (i == readBufferPos && isName) {
                        if (!Character.isUnicodeIdentifierStart (c)
                                && c != ':' && c != '_')
                            error ("Not a name start character, U+"
                                  + Integer.toHexString (c));
                    } else if (!Character.isUnicodeIdentifierPart (c)
                            && c != '-' && c != ':' && c != '_' && c != '.'
                            && !isExtender (c))
                        error ("Not a name character, U+"
                                + Integer.toHexString (c));
                }
            }
        }

        nameBufferPos = 0;

        // Read the first character.
loop:
        while (true) {
            c = readCh ();
            switch (c) {
            case '%':
            case '<': case '>': case '&':
            case ',': case '|': case '*': case '+': case '?':
            case ')':
            case '=':
            case '\'': case '"':
            case '[':
            case ' ': case '\t': case '\n': case '\r':
            case ';':
            case '/':
                unread (c);
                if (nameBufferPos == 0) {
                    error ("name expected");
                }
                // punt on exact tests from Appendix A, but approximate them
                if (isName
                        && !Character.isUnicodeIdentifierStart (
                                nameBuffer [0])
                        && ":_".indexOf (nameBuffer [0]) == -1)
                    error ("Not a name start character, U+"
                              + Integer.toHexString (nameBuffer [0]));
                String s = intern (nameBuffer, 0, nameBufferPos);
                nameBufferPos = 0;
                return s;
            default:
                // punt on exact tests from Appendix A, but approximate them

                if ((nameBufferPos != 0 || !isName)
                        && !Character.isUnicodeIdentifierPart (c)
                        && ":-_.".indexOf (c) == -1
                        && !isExtender (c))
                    error ("Not a name character, U+"
                            + Integer.toHexString (c));
                if (nameBufferPos >= nameBuffer.length)
                    nameBuffer =
                        (char[]) extendArray (nameBuffer,
                                    nameBuffer.length, nameBufferPos);
                nameBuffer [nameBufferPos++] = c;
            }
        }
    }

    private static boolean isExtender (char c)
    {
        // [88] Extender ::= ...
        return c == 0x00b7 || c == 0x02d0 || c == 0x02d1 || c == 0x0387
               || c == 0x0640 || c == 0x0e46 || c == 0x0ec6 || c == 0x3005
               || (c >= 0x3031 && c <= 0x3035)
               || (c >= 0x309d && c <= 0x309e)
               || (c >= 0x30fc && c <= 0x30fe);
    }


    /**
     * Read a literal.  With matching single or double quotes as
     * delimiters (and not embedded!) this is used to parse:
     * <pre>
     *  [9] EntityValue ::= ... ([^%&amp;] | PEReference | Reference)* ...
     *  [10] AttValue ::= ... ([^<&] | Reference)* ...
     *  [11] SystemLiteral ::= ... (URLchar - "'")* ...
     *  [12] PubidLiteral ::= ... (PubidChar - "'")* ...
     * </pre>
     * as well as the quoted strings in XML and text declarations
     * (for version, encoding, and standalone) which have their
     * own constraints.
     */
    private String readLiteral (int flags)
    throws SAXException, IOException
    {
        char    delim, c;
        int     startLine = line;
        boolean saved = expandPE;

        // Find the first delimiter.
        delim = readCh ();
        if (delim != '"' && delim != '\'' && delim != (char) 0) {
            error ("expected '\"' or \"'\"", delim, null);
            return null;
        }
        inLiteral = true;
        if ((flags & LIT_DISABLE_PE) != 0)
            expandPE = false;

        // Each level of input source has its own buffer; remember
        // ours, so we won't read the ending delimiter from any
        // other input source, regardless of entity processing.
        char ourBuf [] = readBuffer;

        // Read the literal.
        try {
            c = readCh ();
loop:
            while (! (c == delim && readBuffer == ourBuf)) {
                switch (c) {
                    // Can't escape this normalization for attributes
                case '\n':
                case '\r':
                case '\t':
                    if ((flags & LIT_ATTRIBUTE) != 0)
                        c = ' ';
                    break;
                case '&':
                    c = readCh ();
                    // Char refs are expanded immediately, except for
                    // all the cases where it's deferred.
                    if (c == '#') {
                        if ((flags & LIT_DISABLE_CREF) != 0) {
                            dataBufferAppend ('&');
                            dataBufferAppend ('#');
                            continue;
                        }
                        parseCharRef ();

                    // It looks like an entity ref ...
                    } else {
                        unread (c);
                        // Expand it?
                        if ((flags & LIT_ENTITY_REF) > 0) {
                            parseEntityRef (false);

                        // Is it just data?
                        } else if ((flags & LIT_DISABLE_EREF) != 0) {
                            dataBufferAppend ('&');

                        // OK, it will be an entity ref -- expanded later.
                        } else {
                            String name = readNmtoken (true);
                            require (';');
                            if ((flags & LIT_ENTITY_CHECK) != 0
                                    && getEntityType (name) ==
                                            ENTITY_UNDECLARED) {
                                error ("General entity '" + name
                                    + "' must be declared before use");
                            }
                            dataBufferAppend ('&');
                            dataBufferAppend (name);
                            dataBufferAppend (';');
                        }
                    }
                    c = readCh ();
                    continue loop;

                case '<':
                    // and why?  Perhaps so "&foo;" expands the same
                    // inside and outside an attribute?
                    if ((flags & LIT_ATTRIBUTE) != 0)
                        error ("attribute values may not contain '<'");
                    break;

                // We don't worry about case '%' and PE refs, readCh does.

                default:
                    break;
                }
                dataBufferAppend (c);
                c = readCh ();
            }
        } catch (EOFException e) {
            error ("end of input while looking for delimiter (started on line "
                   + startLine + ')', null, new Character (delim).toString ());
        }
        inLiteral = false;
        expandPE = saved;

        // Normalise whitespace if necessary.
        if ((flags & LIT_NORMALIZE) > 0) {
            dataBufferNormalize ();
        }

        // Return the value.
        return dataBufferToString ();
    }


    /**
     * Try reading external identifiers.
     * A system identifier is not required for notations.
     * @param inNotation Are we in a notation?
     * @return A two-member String array containing the identifiers.
     */
    private String[] readExternalIds (boolean inNotation)
    throws Exception
    {
        char    c;
        String  ids[] = new String [2];
        int     flags = LIT_DISABLE_CREF | LIT_DISABLE_PE | LIT_DISABLE_EREF;

        if (tryRead ("PUBLIC")) {
            requireWhitespace ();
            ids [0] = readLiteral (LIT_NORMALIZE | flags);
            if (inNotation) {
                skipWhitespace ();
                c = readCh ();
                unread (c);
                if (c == '"' || c == '\'') {
                    ids [1] = readLiteral (flags);
                }
            } else {
                requireWhitespace ();
                ids [1] = readLiteral (flags);
            }

            for (int i = 0; i < ids [0].length (); i++) {
                c = ids [0].charAt (i);
                if (c >= 'a' && c <= 'z')
                    continue;
                if (c >= 'A' && c <= 'Z')
                    continue;
                if (" \r\n0123456789-' ()+,./:=?;!*#@$_%".indexOf (c) != -1)
                    continue;
                error ("illegal PUBLIC id character U+"
                        + Integer.toHexString (c));
            }
        } else if (tryRead ("SYSTEM")) {
            requireWhitespace ();
            ids [1] = readLiteral (flags);
        }

        // XXX should normalize system IDs as follows:
        // - Convert to UTF-8
        // - Map reserved and non-ASCII characters to %HH

        return ids;
    }


    /**
     * Test if a character is whitespace.
     * <pre>
     * [3] S ::= (#x20 | #x9 | #xd | #xa)+
     * </pre>
     * @param c The character to test.
     * @return true if the character is whitespace.
     */
    private final boolean isWhitespace (char c)
    {
        if (c > 0x20)
            return false;
        if (c == 0x20 || c == 0x0a || c == 0x09 || c == 0x0d)
            return true;
        return false;   // illegal ...
    }


    //////////////////////////////////////////////////////////////////////
    // Utility routines.
    //////////////////////////////////////////////////////////////////////


    /**
     * Add a character to the data buffer.
     */
    private void dataBufferAppend (char c)
    {
        // Expand buffer if necessary.
        if (dataBufferPos >= dataBuffer.length)
            dataBuffer =
                (char[]) extendArray (dataBuffer,
                        dataBuffer.length, dataBufferPos);
        dataBuffer [dataBufferPos++] = c;
    }


    /**
     * Add a string to the data buffer.
     */
    private void dataBufferAppend (String s)
    {
        dataBufferAppend (s.toCharArray (), 0, s.length ());
    }


    /**
     * Append (part of) a character array to the data buffer.
     */
    private void dataBufferAppend (char ch[], int start, int length)
    {
        dataBuffer = (char[])
                extendArray (dataBuffer, dataBuffer.length,
                                    dataBufferPos + length);

        System.arraycopy (ch, start, dataBuffer, dataBufferPos, length);
        dataBufferPos += length;
    }


    /**
     * Normalise whitespace in the data buffer.
     */
    private void dataBufferNormalize ()
    {
        int i = 0;
        int j = 0;
        int end = dataBufferPos;

        // Skip whitespace at the start.
        while (j < end && isWhitespace (dataBuffer [j])) {
            j++;
        }

        // Skip whitespace at the end.
        while (end > j && isWhitespace (dataBuffer [end - 1])) {
            end --;
        }

        // Start copying to the left.
        while (j < end) {

            char c = dataBuffer [j++];

            // Normalise all other whitespace to
            // a single space.
            if (isWhitespace (c)) {
                while (j < end && isWhitespace (dataBuffer [j++])) {}

                dataBuffer [i++] = ' ';
                dataBuffer [i++] = dataBuffer [j - 1];
            } else {
                dataBuffer [i++] = c;
            }
        }

        // The new length is <= the old one.
        dataBufferPos = i;
    }


    /**
     * Convert the data buffer to a string.
     */
    private String dataBufferToString ()
    {
        String s = new String (dataBuffer, 0, dataBufferPos);
        dataBufferPos = 0;
        return s;
    }


    /**
     * Flush the contents of the data buffer to the handler, as
     * appropriate, and reset the buffer for new input.
     */
    private void dataBufferFlush ()
    throws SAXException
    {
        if (currentElementContent == CONTENT_ELEMENTS
                && dataBufferPos > 0
                && !inCDATA
                ) {
            // We can't just trust the buffer to be whitespace, there
            // are cases when it isn't
            for (int i = 0; i < dataBufferPos; i++) {
                if (!isWhitespace (dataBuffer [i])) {
                    handler.charData (dataBuffer, 0, dataBufferPos);
                    dataBufferPos = 0;
                }
            }
            if (dataBufferPos > 0) {
                handler.ignorableWhitespace (dataBuffer, 0, dataBufferPos);
                dataBufferPos = 0;
            }
        } else if (dataBufferPos > 0) {
            handler.charData (dataBuffer, 0, dataBufferPos);
            dataBufferPos = 0;
        }
    }


    /**
     * Require a string to appear, or throw an exception.
     * <p><em>Precondition:</em> Entity expansion is not required.
     * <p><em>Precondition:</em> data buffer has no characters that
     * will get sent to the application.
     */
    private void require (String delim)
    throws SAXException, IOException
    {
        int     length = delim.length ();
        char    ch [];
                
        if (length < dataBuffer.length) {
            ch = dataBuffer;
            delim.getChars (0, length, ch, 0);
        } else
            ch = delim.toCharArray ();

        if (USE_CHEATS
                && length <= (readBufferLength - readBufferPos)) {
            int offset = readBufferPos;

            for (int i = 0; i < length; i++, offset++)
                if (ch [i] != readBuffer [offset])
                    error ("required string", null, delim);
            readBufferPos = offset;
            
        } else {
            for (int i = 0; i < length; i++)
                require (ch [i]);
        }
    }


    /**
     * Require a character to appear, or throw an exception.
     */
    private void require (char delim)
    throws SAXException, IOException
    {
        char c = readCh ();

        if (c != delim) {
            error ("required character", c, new Character (delim).toString ());
        }
    }


    /**
     * Create an interned string from a character array.
     * &AElig;lfred uses this method to create an interned version
     * of all names and name tokens, so that it can test equality
     * with <code>==</code> instead of <code>String.equals ()</code>.
     *
     * <p>This is much more efficient than constructing a non-interned
     * string first, and then interning it.
     *
     * @param ch an array of characters for building the string.
     * @param start the starting position in the array.
     * @param length the number of characters to place in the string.
     * @return an interned string.
     * @see #intern (String)
     * @see java.lang.String#intern
     */
    public String intern (char ch[], int start, int length)
    {
        int     index = 0;
        int     hash = 0;
        Object  bucket [];

        // Generate a hash code.
        for (int i = start; i < start + length; i++)
            hash = 31 * hash + ch [i];
        hash = (hash & 0x7fffffff) % SYMBOL_TABLE_LENGTH;

        // Get the bucket -- consists of {array,String} pairs
        if ((bucket = symbolTable [hash]) == null) {
            // first string in this bucket
            bucket = new Object [8];

        // Search for a matching tuple, and
        // return the string if we find one.
        } else {
            while (index < bucket.length) {
                char chFound [] = (char []) bucket [index];

                // Stop when we hit a null index.
                if (chFound == null)
                    break;

                // If they're the same length, check for a match.
                if (chFound.length == length) {
                    for (int i = 0; i < chFound.length; i++) {
                        // continue search on failure
                        if (ch [start + i] != chFound [i]) {
                            break;
                        } else if (i == length - 1) {
                            // That's it, we have a match!
                            return (String) bucket [index + 1];
                        }
                    }
                }
                index += 2;
            }
            // Not found -- we'll have to add it.

            // Do we have to grow the bucket?
            bucket = (Object []) extendArray (bucket, bucket.length, index);
        }
        symbolTable [hash] = bucket;

        // OK, add it to the end of the bucket -- "local" interning.
        // Intern "globally" to let applications share interning benefits.
        String s = new String (ch, start, length).intern ();
        bucket [index] = s.toCharArray ();
        bucket [index + 1] = s;
        return s;
    }


    /**
     * Ensure the capacity of an array, allocating a new one if
     * necessary.  Usually called only a handful of times.
     */
    private Object extendArray (Object array, int currentSize, int requiredSize)
    {
        if (requiredSize < currentSize) {
            return array;
        } else {
            Object newArray = null;
            int newSize = currentSize * 2;

            if (newSize <= requiredSize)
                newSize = requiredSize + 1;

            if (array instanceof char[])
                newArray = new char [newSize];
            else if (array instanceof Object[])
                newArray = new Object [newSize];
            else
                throw new RuntimeException ();

            System.arraycopy (array, 0, newArray, 0, currentSize);
            return newArray;
        }
    }


    //////////////////////////////////////////////////////////////////////
    // XML query routines.
    //////////////////////////////////////////////////////////////////////


    //
    // Elements
    //

    /**
     * Get the declared elements for an XML document.
     * <p>The results will be valid only after the DTD (if any) has been
     * parsed.
     * @return An enumeration of all element types declared for this
     *   document (as Strings).
     * @see #getElementContentType
     * @see #getElementContentModel
     */
    public Iterator declaredElements ()
    {
        return elementInfo.keySet().iterator();
    }


    /**
     * Look up the content type of an element.
     * @param element element info vector
     * @param defaultType value for null vector
     * @return An integer constant representing the content type.
     * @see #CONTENT_UNDECLARED
     * @see #CONTENT_ANY
     * @see #CONTENT_EMPTY
     * @see #CONTENT_MIXED
     * @see #CONTENT_ELEMENTS
     */
    private int getContentType (Object element [], int defaultType)
    {
        if (element == null)
            return defaultType;
        else
            return ((Integer) element [0]).intValue ();
    }


    /**
     * Look up the content type of an element.
     * @param name The element type name.
     * @return An integer constant representing the content type.
     * @see #getElementContentModel
     * @see #CONTENT_UNDECLARED
     * @see #CONTENT_ANY
     * @see #CONTENT_EMPTY
     * @see #CONTENT_MIXED
     * @see #CONTENT_ELEMENTS
     */
    public int getElementContentType (String name)
    {
        Object element [] = (Object []) elementInfo.get (name);
        return getContentType (element, CONTENT_UNDECLARED);
    }


    /**
     * Look up the content model of an element.
     * <p>The result will always be null unless the content type is
     * CONTENT_ELEMENTS or CONTENT_MIXED.
     * @param name The element type name.
     * @return The normalised content model, as a string.
     * @see #getElementContentType
     */
    public String getElementContentModel (String name)
    {
        Object element[] = (Object[]) elementInfo.get (name);
        if (element == null) {
            return null;
        } else {
            return (String) element [1];
        }
    }


    /**
     * Register an element.
     * Array format:
     *  element type
     *  attribute hash table
     */
    private void setElement (String name, int contentType,
                      String contentModel, HashMap attributes)
    throws Exception
    {
        Object element[];

        // Try looking up the element
        element = (Object[]) elementInfo.get (name);

        // Make a new one if necessary.
        if (element == null) {
            element = new Object [3];
            element [0] = new Integer (CONTENT_UNDECLARED);
            element [1] = null;
            element [2] = null;
        } else if (contentType != CONTENT_UNDECLARED
                && ((Integer) element [0]).intValue () != CONTENT_UNDECLARED
                ) {
            // warn ("multiple declarations for element type", name, null);
            return;
        }

        // Insert the content type, if any.
        if (contentType != CONTENT_UNDECLARED) {
            element [0] = new Integer (contentType);
        }

        // Insert the content model, if any.
        if (contentModel != null) {
            element [1] = contentModel;
        }

        // Insert the attributes, if any.
        if (attributes != null) {
            element [2] = attributes;
        }

        // Save the element info.
        elementInfo.put (name, element);
    }


    /**
     * Look up the attribute hash table for an element.
     * The hash table is the second item in the element array.
     */
    private HashMap getElementAttributes (String name)
    {
        Object element[] = (Object[]) elementInfo.get (name);
        if (element == null) {
            return null;
        } else {
            return (HashMap) element [2];
        }
    }



    //
    // Attributes
    //

    /**
     * Get the declared attributes for an element type.
     * @param elname The name of the element type.
     * @return An Iterator of all the attributes declared for
     *   a specific element type.  The results will be valid only
     *   after the DTD (if any) has been parsed.
     * @see #getAttributeType
     * @see #getAttributeIterator
     * @see #getAttributeDefaultValueType
     * @see #getAttributeDefaultValue
     * @see #getAttributeExpandedValue
     */
    private Iterator declaredAttributes (Object element [])
    {
        HashMap attlist;

        if (element == null)
            return null;
        if ((attlist = (HashMap) element [2]) == null)
            return null;
        return attlist.keySet().iterator();
    }

    /**
     * Get the declared attributes for an element type.
     * @param elname The name of the element type.
     * @return An Iterator of all the attributes declared for
     *   a specific element type.  The results will be valid only
     *   after the DTD (if any) has been parsed.
     * @see #getAttributeType
     * @see #getAttributeIterator
     * @see #getAttributeDefaultValueType
     * @see #getAttributeDefaultValue
     * @see #getAttributeExpandedValue
     */
    public Iterator declaredAttributes (String elname)
    {
        return declaredAttributes ((Object []) elementInfo.get (elname));
    }


    /**
     * Retrieve the declared type of an attribute.
     * @param name The name of the associated element.
     * @param aname The name of the attribute.
     * @return An integer constant representing the attribute type.
     * @see #ATTRIBUTE_UNDECLARED
     * @see #ATTRIBUTE_CDATA
     * @see #ATTRIBUTE_ID
     * @see #ATTRIBUTE_IDREF
     * @see #ATTRIBUTE_IDREFS
     * @see #ATTRIBUTE_ENTITY
     * @see #ATTRIBUTE_ENTITIES
     * @see #ATTRIBUTE_NMTOKEN
     * @see #ATTRIBUTE_NMTOKENS
     * @see #ATTRIBUTE_ENUMERATED
     * @see #ATTRIBUTE_NOTATION
     */
    public int getAttributeType (String name, String aname)
    {
        Object attribute[] = getAttribute (name, aname);
        if (attribute == null) {
            return ATTRIBUTE_UNDECLARED;
        } else {
            return ((Integer) attribute [0]).intValue ();
        }
    }


    /**
     * Retrieve the allowed values for an enumerated attribute type.
     * @param name The name of the associated element.
     * @param aname The name of the attribute.
     * @return A string containing the token list.
     * @see #ATTRIBUTE_ENUMERATED
     * @see #ATTRIBUTE_NOTATION
     */
    public String getAttributeIterator (String name, String aname)
    {
        Object attribute[] = getAttribute (name, aname);
        if (attribute == null) {
            return null;
        } else {
            return (String) attribute [3];
        }
    }


    /**
     * Retrieve the default value of a declared attribute.
     * @param name The name of the associated element.
     * @param aname The name of the attribute.
     * @return The default value, or null if the attribute was
     *   #IMPLIED or simply undeclared and unspecified.
     * @see #getAttributeExpandedValue
     */
    public String getAttributeDefaultValue (String name, String aname)
    {
        Object attribute[] = getAttribute (name, aname);
        if (attribute == null) {
            return null;
        } else {
            return (String) attribute [1];
        }
    }


    /**
     * Retrieve the expanded value of a declared attribute.
     * <p>General entities will be expanded (once).
     * @param name The name of the associated element.
     * @param aname The name of the attribute.
     * @return The expanded default value, or null if the attribute was
     *   #IMPLIED or simply undeclared
     * @see #getAttributeDefaultValue
     */
    public String getAttributeExpandedValue (String name, String aname)
    throws Exception
    {
        Object attribute[] = getAttribute (name, aname);

        if (attribute == null) {
            return null;
        } else if (attribute [4] == null && attribute [1] != null) {
            // we MUST use the same buf for both quotes else the literal
            // can't be properly terminated
            char buf [] = new char [1];
            int flags = LIT_ENTITY_REF | LIT_ATTRIBUTE;
            int type = getAttributeType (name, aname);

            if (type != ATTRIBUTE_CDATA && type != ATTRIBUTE_UNDECLARED)
                flags |= LIT_NORMALIZE;
            buf [0] = '"';
            pushCharArray (null, buf, 0, 1);
            pushString (null, (String) attribute [1]);
            pushCharArray (null, buf, 0, 1);
            attribute [4] = readLiteral (flags);
        }
        return (String) attribute [4];
    }


    /**
     * Retrieve the default value type of a declared attribute.
     * @see #ATTRIBUTE_DEFAULT_SPECIFIED
     * @see #ATTRIBUTE_DEFAULT_IMPLIED
     * @see #ATTRIBUTE_DEFAULT_REQUIRED
     * @see #ATTRIBUTE_DEFAULT_FIXED
     */
    public int getAttributeDefaultValueType (String name, String aname)
    {
        Object attribute[] = getAttribute (name, aname);
        if (attribute == null) {
            return ATTRIBUTE_DEFAULT_UNDECLARED;
        } else {
            return ((Integer) attribute [2]).intValue ();
        }
    }


    /**
     * Register an attribute declaration for later retrieval.
     * Format:
     * - String type
     * - String default value
     * - int value type
     */
    private void setAttribute (String elName, String name, int type,
                        String myEnum,
                        String value, int valueType)
    throws Exception
    {
        HashMap attlist;
        Object attribute[];

        // Create a new hashtable if necessary.
        attlist = getElementAttributes (elName);
        if (attlist == null) {
            attlist = new HashMap ();
        }

        // ignore multiple attribute declarations!
        if (attlist.get (name) != null) {
            return;
        } else {
            attribute = new Object [5];
            attribute [0] = new Integer (type);
            attribute [1] = value;
            attribute [2] = new Integer (valueType);
            attribute [3] = myEnum;
            attribute [4] = null;
            attlist.put (name, attribute);

            // Use CONTENT_UNDECLARED to avoid overwriting
            // existing element declaration.
            setElement (elName, CONTENT_UNDECLARED, null, attlist);
        }
    }


    /**
     * Retrieve the three-member array representing an
     * attribute declaration.
     */
    private Object[] getAttribute (String elName, String name)
    {
        HashMap attlist;
        Object attribute[];

        attlist = getElementAttributes (elName);
        if (attlist == null) {
            return null;
        }

        attribute = (Object[]) attlist.get (name);
        return attribute;
    }


    //
    // Entities
    //

    /**
     * Get declared entities.
     * @return An Iterator of all the entities declared for
     *   this XML document.  The results will be valid only
     *   after the DTD (if any) has been parsed.
     * @see #getEntityType
     * @see #getEntityPublicId
     * @see #getEntitySystemId
     * @see #getEntityValue
     * @see #getEntityNotationName
     */
    public Iterator declaredEntities ()
    {
        return entityInfo.keySet().iterator();
    }


    /**
     * Find the type of an entity.
     * @returns An integer constant representing the entity type.
     * @see #ENTITY_UNDECLARED
     * @see #ENTITY_INTERNAL
     * @see #ENTITY_NDATA
     * @see #ENTITY_TEXT
     */
    public int getEntityType (String ename)
    {
        Object entity[] = (Object[]) entityInfo.get (ename);
        if (entity == null) {
            return ENTITY_UNDECLARED;
        } else {
            return ((Integer) entity [0]).intValue ();
        }
    }


    /**
     * Return an external entity's public identifier, if any.
     * @param ename The name of the external entity.
     * @return The entity's system identifier, or null if the
     *   entity was not declared, if it is not an
     *   external entity, or if no public identifier was
     *   provided.
     * @see #getEntityType
     */
    public String getEntityPublicId (String ename)
    {
        Object entity[] = (Object[]) entityInfo.get (ename);
        if (entity == null) {
            return null;
        } else {
            return (String) entity [1];
        }
    }


    /**
     * Return an external entity's system identifier.
     * @param ename The name of the external entity.
     * @return The entity's system identifier, or null if the
     *   entity was not declared, or if it is not an
     *   external entity.
     * @see #getEntityType
     */
    public String getEntitySystemId (String ename)
    {
        Object entity[] = (Object[]) entityInfo.get (ename);
        if (entity == null) {
            return null;
        } else {
            return (String) entity [2];
        }
    }


    /**
     * Return the value of an internal entity.
     * @param ename The name of the internal entity.
     * @return The entity's value, or null if the entity was
     *   not declared, or if it is not an internal entity.
     * @see #getEntityType
     */
    public String getEntityValue (String ename)
    {
        Object entity[] = (Object[]) entityInfo.get (ename);
        if (entity == null) {
            return null;
        } else {
            return (String) entity [3];
        }
    }


    /**
     * Get the notation name associated with an NDATA entity.
     * @param ename The NDATA entity name.
     * @return The associated notation name, or null if the
     *   entity was not declared, or if it is not an
     *   NDATA entity.
     * @see #getEntityType
     */
    public String getEntityNotationName (String eName)
    {
        Object entity[] = (Object[]) entityInfo.get (eName);
        if (entity == null) {
            return null;
        } else {
            return (String) entity [4];
        }
    }


    /**
     * Register an entity declaration for later retrieval.
     */
    private void setInternalEntity (String eName, String value)
    {
        setEntity (eName, ENTITY_INTERNAL, null, null, value, null);
    }


    /**
     * Register an external data entity.
     */
    private void setExternalDataEntity (String eName, String pubid,
                                 String sysid, String nName)
    {
        setEntity (eName, ENTITY_NDATA, pubid, sysid, null, nName);
    }


    /**
     * Register an external text entity.
     */
    private void setExternalTextEntity (String eName,
                    String pubid, String sysid)
    {
        setEntity (eName, ENTITY_TEXT, pubid, sysid, null, null);
    }


    /**
     * Register an entity declaration for later retrieval.
     */
    private void setEntity (String eName, int eClass,
                     String pubid, String sysid,
                     String value, String nName)
    {
        Object entity[];

        if (entityInfo.get (eName) == null) {
            entity = new Object [5];
            entity [0] = new Integer (eClass);
            entity [1] = pubid;
            entity [2] = sysid;
            entity [3] = value;
            entity [4] = nName;

            entityInfo.put (eName, entity);
        }
    }


    //
    // Notations.
    //

    /**
     * Get declared notations.
     * @return An Iterator of all the notations declared for
     *   this XML document.  The results will be valid only
     *   after the DTD (if any) has been parsed.
     * @see #getNotationPublicId
     * @see #getNotationSystemId
     */
    public Iterator declaredNotations ()
    {
        return notationInfo.keySet().iterator();
    }


    /**
     * Look up the public identifier for a notation.
     * You will normally use this method to look up a notation
     * that was provided as an attribute value or for an NDATA entity.
     * @param nname The name of the notation.
     * @return A string containing the public identifier, or null
     *   if none was provided or if no such notation was
     *   declared.
     * @see #getNotationSystemId
     */
    public String getNotationPublicId (String nname)
    {
        Object notation[] = (Object[]) notationInfo.get (nname);
        if (notation == null) {
            return null;
        } else {
            return (String) notation [0];
        }
    }


    /**
     * Look up the system identifier for a notation.
     * You will normally use this method to look up a notation
     * that was provided as an attribute value or for an NDATA entity.
     * @param nname The name of the notation.
     * @return A string containing the system identifier, or null
     *   if no such notation was declared.
     * @see #getNotationPublicId
     */
    public String getNotationSystemId (String nname)
    {
        Object notation[] = (Object[]) notationInfo.get (nname);
        if (notation == null) {
            return null;
        } else {
            return (String) notation [1];
        }
    }


    /**
     * Register a notation declaration for later retrieval.
     * Format:
     * - public id
     * - system id
     */
    private void setNotation (String nname, String pubid, String sysid)
    throws Exception
    {
        Object notation[];

        if (notationInfo.get (nname) == null) {
            notation = new Object [2];
            notation [0] = pubid;
            notation [1] = sysid;
            notationInfo.put (nname, notation);
        } else {
            // VC: Unique Notation Name
            // (it's not fatal)
        }
    }


    //
    // Location.
    //


    /**
     * Return the current line number.
     */
    public int getLineNumber ()
    {
        return line;
    }


    /**
     * Return the current column number.
     */
    public int getColumnNumber ()
    {
        return column;
    }


    //////////////////////////////////////////////////////////////////////
    // High-level I/O.
    //////////////////////////////////////////////////////////////////////


    /**
     * Read a single character from the readBuffer.
     * <p>The readDataChunk () method maintains the buffer.
     * <p>If we hit the end of an entity, try to pop the stack and
     * keep going.
     * <p> (This approach doesn't really enforce XML's rules about
     * entity boundaries, but this is not currently a validating
     * parser).
     * <p>This routine also attempts to keep track of the current
     * position in external entities, but it's not entirely accurate.
     * @return The next available input character.
     * @see #unread (char)
     * @see #unread (String)
     * @see #readDataChunk
     * @see #readBuffer
     * @see #line
     * @return The next character from the current input source.
     */
    private char readCh ()
    throws SAXException, IOException
    {
        char c;

        // As long as there's nothing in the
        // read buffer, try reading more data
        // (for an external entity) or popping
        // the entity stack (for either).
        while (readBufferPos >= readBufferLength) {
            switch (sourceType) {
            case INPUT_READER:
            case INPUT_EXTERNAL:
            case INPUT_STREAM:
                readDataChunk ();
                while (readBufferLength < 1) {
                    popInput ();
                    if (readBufferLength < 1) {
                        readDataChunk ();
                    }
                }
                break;

            default:

                popInput ();
                break;
            }
        }

        c = readBuffer [readBufferPos++];

        if (c == '\n') {
            line++;
            column = 0;
        } else {
            if (c == '<')
                /* favorite return to parseContent () .. NOP */ ;
            else if ((c < 0x0020 && (c != '\t') && (c != '\r')) || c > 0xFFFD)
                error ("illegal XML character U+"
                        + Integer.toHexString (c));

            // If we're in the DTD and in a context where PEs get expanded,
            // do so ... 1/14/2000 errata identify those contexts.  There
            // are also spots in the internal subset where PE refs are fatal
            // errors, hence yet another flag.
            else if (c == '%' && expandPE) {
                if (peIsError)
                    error ("PE reference within decl in internal subset.");
                parsePEReference ();
                return readCh ();
            }
            column++;
        }

        return c;
    }


    /**
     * Push a single character back onto the current input stream.
     * <p>This method usually pushes the character back onto
     * the readBuffer, while the unread (String) method treats the
     * string as a new internal entity.
     * <p>I don't think that this would ever be called with 
     * readBufferPos = 0, because the methods always reads a character
     * before unreading it, but just in case, I've added a boundary
     * condition.
     * @param c The character to push back.
     * @see #readCh
     * @see #unread (String)
     * @see #unread (char[])
     * @see #readBuffer
     */
    private void unread (char c)
    throws SAXException
    {
        // Normal condition.
        if (c == '\n') {
            line--;
            column = -1;
        }
        if (readBufferPos > 0) {
            readBuffer [--readBufferPos] = c;
        } else {
            pushString (null, new Character (c).toString ());
        }
    }


    /**
     * Push a char array back onto the current input stream.
     * <p>NOTE: you must <em>never</em> push back characters that you
     * haven't actually read: use pushString () instead.
     * @see #readCh
     * @see #unread (char)
     * @see #unread (String)
     * @see #readBuffer
     * @see #pushString
     */
    private void unread (char ch[], int length)
    throws SAXException
    {
        for (int i = 0; i < length; i++) {
            if (ch [i] == '\n') {
                line--;
                column = -1;
            }
        }
        if (length < readBufferPos) {
            readBufferPos -= length;
        } else {
            pushCharArray (null, ch, 0, length);
            sourceType = INPUT_BUFFER;
        }
    }


    /**
     * Push a new external input source.
     * The source will be some kind of parsed entity, such as a PE
     * (including the external DTD subset) or content for the body.
     * <p>TODO: Right now, this method always attempts to autodetect
     * the encoding; in the future, it should allow the caller to 
     * request an encoding explicitly, and it should also look at the
     * headers with an HTTP connection.
     * @param url The java.net.URL object for the entity.
     * @see SAXDriver#resolveEntity
     * @see #pushString
     * @see #sourceType
     * @see #pushInput
     * @see #detectEncoding
     * @see #sourceType
     * @see #readBuffer
     */
    private void pushURL (
        String          ename,
        String          publicId,
        String          systemId,
        Reader          reader,
        InputStream     stream,
        String          encoding
    ) throws SAXException, IOException
    {
        URL     url;
        boolean ignoreEncoding = false;

        // Push the existing status.
        pushInput (ename);

        // Create a new read buffer.
        // (Note the four-character margin)
        readBuffer = new char [READ_BUFFER_MAX + 4];
        readBufferPos = 0;
        readBufferLength = 0;
        readBufferOverflow = -1;
        is = null;
        line = 1;

        currentByteCount = 0;

        // Make any system ID (URI/URL) absolute.  There's one case
        // where it may be null:  parser was invoked without providing
        // one, e.g. since the XML data came from a memory buffer.

        if (systemId != null && externalEntity != null) {
            systemId = new URL (externalEntity.getURL (), systemId).toString ();
        } else if (baseURI != null) {
            systemId = new URL (new URL (baseURI), systemId).toString ();
            // throws IOException if couldn't create new URL
        }

        // See if the application wants to
        // redirect the system ID and/or
        // supply its own character stream.
        if (reader == null && stream == null && systemId != null) {
            Object input = handler.resolveEntity (publicId, systemId);
            if (input != null) {
                if (input instanceof String) {
                    systemId = (String) input;
                } else if (input instanceof InputStream) {
                    stream = (InputStream) input;
                } else if (input instanceof Reader) {
                    reader = (Reader) input;
                }
            }
        }

        // Start the entity.
        if (systemId != null) {
            handler.startExternalEntity (systemId);
        } else {
            handler.startExternalEntity ("[unidentified data stream]");
        }

        // If there's an explicit character stream, just
        // ignore encoding declarations.
        if (reader != null) {
            sourceType = INPUT_READER;
            this.reader = reader;
            tryEncodingDecl (true);
            return;
        }
        
        // Else we handle the conversion, and need to ensure
        // it's done right.
        if (stream != null) {
            sourceType = INPUT_STREAM;
            is = stream;
            url = null;
        } else {
            // We have to open our own stream to the URL.

            // Set the new status
            sourceType = INPUT_EXTERNAL;
            url = new URL (systemId);

            externalEntity = url.openConnection ();
            externalEntity.connect ();
            is = externalEntity.getInputStream ();
        }

        // If we get to here, there must be
        // an InputStream available.
        if (!is.markSupported ()) {
            is = new BufferedInputStream (is);
        }

        // Get any external encoding label.
        if (encoding == null && externalEntity != null) {
            // External labels can be untrustworthy; filesystems in
            // particular often have the wrong default for content
            // that wasn't locally originated.  Those we autodetect.
            if (!"file".equals (externalEntity.getURL ().getProtocol ())) {
                int temp;

                // application/xml;charset=something;otherAttr=...
                // ... with many variants on 'something'
                encoding = externalEntity.getContentType ();

                // MHK code (fix for Saxon 5.5.1/007): protect against encoding==null
                if (encoding==null) {
                    temp = -1;
                } else {
                    temp = encoding.indexOf ("charset");
                }

                // RFC 2376 sez MIME text defaults to ASCII, but since the
                // JDK will create a MIME type out of thin air, we always
                // autodetect when there's no explicit charset attribute.
                if (temp < 0)
                    encoding = null;    // autodetect
                else {
                    temp = encoding.indexOf ('=', temp + 7);
                    encoding = encoding.substring (temp);
                    if ((temp = encoding.indexOf (';')) > 0)
                        encoding = encoding.substring (0, temp);

                    // attributes can have comment fields (RFC 822)
                    if ((temp = encoding.indexOf ('(')) > 0)
                        encoding = encoding.substring (0, temp);
                    // ... and values may be quoted
                    if ((temp = encoding.indexOf ('"')) > 0)
                        encoding = encoding.substring (temp + 1,
                                encoding.indexOf ('"', temp + 2));
                    encoding.trim ();
                }
            }
        }

        // if we got an external encoding label, use it ...
        if (encoding != null) {
            this.encoding = ENCODING_EXTERNAL;
            setupDecoding (encoding);
            ignoreEncoding = true;
        
        // ... else autodetect
        } else {
            detectEncoding ();
            ignoreEncoding = false;
        }

        // Read any XML or text declaration.
        tryEncodingDecl (ignoreEncoding);
    }


    /**
     * Check for an encoding declaration.  This is the second part of the
     * XML encoding autodetection algorithm, relying on detectEncoding to
     * get to the point that this part can read any encoding declaration
     * in the document (using only US-ASCII characters).
     *
     * <p> Because this part starts to fill parser buffers with this data,
     * it's tricky to to a reader so that Java's built-in decoders can be
     * used for the character encodings that aren't built in to this parser
     * (such as EUC-JP, KOI8-R, Big5, etc).
     *
     * @return any encoding in the declaration, uppercased; or null
     * @see detectEncoding
     */
    private String tryEncodingDecl (boolean ignoreEncoding)
    throws SAXException, IOException
    {
        // Read the XML/text declaration.
        if (tryRead ("<?xml")) {
            dataBufferFlush ();
            if (tryWhitespace ()) {
                if (inputStack.size () > 0) {
                    return parseTextDecl (ignoreEncoding);
                } else {
                    return parseXMLDecl (ignoreEncoding);
                }
            } else {
                unread ("xml".toCharArray (), 3);
                parsePI ();
            }
        }
        return null;
    }


    /**
     * Attempt to detect the encoding of an entity.
     * <p>The trick here (as suggested in the XML standard) is that
     * any entity not in UTF-8, or in UCS-2 with a byte-order mark, 
     * <b>must</b> begin with an XML declaration or an encoding
     * declaration; we simply have to look for "&lt;?xml" in various
     * encodings.
     * <p>This method has no way to distinguish among 8-bit encodings.
     * Instead, it sets up for UTF-8, then (possibly) revises its assumption
     * later in setupDecoding ().  Any ASCII-derived 8-bit encoding
     * should work, but most will be rejected later by setupDecoding ().
     * <p>I don't currently detect EBCDIC, since I'm concerned that it
     * could also be a valid UTF-8 sequence; I'll have to do more checking
     * later.
     * @see #tryEncoding (byte[], byte, byte, byte, byte)
     * @see #tryEncoding (byte[], byte, byte)
     * @see #setupDecoding
     * @see #read8bitEncodingDeclaration
     */
    private void detectEncoding ()
    throws SAXException, IOException
    {
        byte signature[] = new byte [4];

        // Read the first four bytes for
        // autodetection.
        is.mark (4);
        is.read (signature);
        is.reset ();

        //
        // FIRST:  four byte encodings (who uses these?)
        //
        if (tryEncoding (signature, (byte) 0x00, (byte) 0x00,
                          (byte) 0x00, (byte) 0x3c)) {
            // UCS-4 must begin with "<?xml"
            // 0x00 0x00 0x00 0x3c: UCS-4, big-endian (1234)
            encoding = ENCODING_UCS_4_1234;

        } else if (tryEncoding (signature, (byte) 0x3c, (byte) 0x00,
                                 (byte) 0x00, (byte) 0x00)) {
            // 0x3c 0x00 0x00 0x00: UCS-4, little-endian (4321)
            encoding = ENCODING_UCS_4_4321;

        } else if (tryEncoding (signature, (byte) 0x00, (byte) 0x00,
                                 (byte) 0x3c, (byte) 0x00)) {
            // 0x00 0x00 0x3c 0x00: UCS-4, unusual (2143)
            encoding = ENCODING_UCS_4_2143;

        } else if (tryEncoding (signature, (byte) 0x00, (byte) 0x3c,
                                 (byte) 0x00, (byte) 0x00)) {
            // 0x00 0x3c 0x00 0x00: UCS-4, unusual (3421)
            encoding = ENCODING_UCS_4_3412;

            // 00 00 fe ff UCS_4_1234 (with BOM)
            // ff fe 00 00 UCS_4_4321 (with BOM)
        }

        //
        // SECOND:  two byte encodings
        // note ... with 1/14/2000 errata the XML spec identifies some
        // more "broken UTF-16" autodetection cases, with no XML decl,
        // which we don't handle here (that's legal too).
        //
        else if (tryEncoding (signature, (byte) 0xfe, (byte) 0xff)) {
            // UCS-2 with a byte-order marker. (UTF-16)
            // 0xfe 0xff: UCS-2, big-endian (12)
            encoding = ENCODING_UCS_2_12;
            is.read (); is.read ();

        } else if (tryEncoding (signature, (byte) 0xff, (byte) 0xfe)) {
            // UCS-2 with a byte-order marker. (UTF-16)
            // 0xff 0xfe: UCS-2, little-endian (21)
            encoding = ENCODING_UCS_2_21;
            is.read (); is.read ();

        } else if (tryEncoding (signature, (byte) 0x00, (byte) 0x3c,
                                 (byte) 0x00, (byte) 0x3f)) {
            // UTF-16-BE (otherwise, malformed UTF-16)
            // 0x00 0x3c 0x00 0x3f: UCS-2, big-endian, no byte-order mark
            encoding = ENCODING_UCS_2_12;
            error ("no byte-order mark for UCS-2 entity");

        } else if (tryEncoding (signature, (byte) 0x3c, (byte) 0x00,
                                 (byte) 0x3f, (byte) 0x00)) {
            // UTF-16-LE (otherwise, malformed UTF-16)
            // 0x3c 0x00 0x3f 0x00: UCS-2, little-endian, no byte-order mark
            encoding = ENCODING_UCS_2_21;
            error ("no byte-order mark for UCS-2 entity");
        }

        //
        // THIRD:  ASCII-derived encodings, fixed and variable lengths
        //
        else if (tryEncoding (signature, (byte) 0x3c, (byte) 0x3f,
                               (byte) 0x78, (byte) 0x6d)) {
            // ASCII derived
            // 0x3c 0x3f 0x78 0x6d: UTF-8 or other 8-bit markup (read ENCODING)
            encoding = ENCODING_UTF_8;
            read8bitEncodingDeclaration ();

        } else {
            // 4c 6f a7 94 ... we don't understand EBCDIC flavors
            // ... but we COULD at least kick in some fixed code page

            // (default) UTF-8 without encoding/XML declaration
            encoding = ENCODING_UTF_8;
        }
    }


    /**
     * Check for a four-byte signature.
     * <p>Utility routine for detectEncoding ().
     * <p>Always looks for some part of "<?XML" in a specific encoding.
     * @param sig The first four bytes read.
     * @param b1 The first byte of the signature
     * @param b2 The second byte of the signature
     * @param b3 The third byte of the signature
     * @param b4 The fourth byte of the signature
     * @see #detectEncoding
     */
    private static boolean tryEncoding (
        byte sig[], byte b1, byte b2, byte b3, byte b4)
    {
        return (sig [0] == b1 && sig [1] == b2
                && sig [2] == b3 && sig [3] == b4);
    }


    /**
     * Check for a two-byte signature.
     * <p>Looks for a UCS-2 byte-order mark.
     * <p>Utility routine for detectEncoding ().
     * @param sig The first four bytes read.
     * @param b1 The first byte of the signature
     * @param b2 The second byte of the signature
     * @see #detectEncoding
     */
    private static boolean tryEncoding (byte sig[], byte b1, byte b2)
    {
        return ((sig [0] == b1) && (sig [1] == b2));
    }


    /**
     * This method pushes a string back onto input.
     * <p>It is useful either as the expansion of an internal entity, 
     * or for backtracking during the parse.
     * <p>Call pushCharArray () to do the actual work.
     * @param s The string to push back onto input.
     * @see #pushCharArray
     */
    private void pushString (String ename, String s)
    throws SAXException
    {
        char ch[] = s.toCharArray ();
        pushCharArray (ename, ch, 0, ch.length);
    }


    /**
     * Push a new internal input source.
     * <p>This method is useful for expanding an internal entity,
     * or for unreading a string of characters.  It creates a new
     * readBuffer containing the characters in the array, instead
     * of characters converted from an input byte stream.
     * @param ch The char array to push.
     * @see #pushString
     * @see #pushURL
     * @see #readBuffer
     * @see #sourceType
     * @see #pushInput
     */
    private void pushCharArray (String ename, char ch[], int start, int length)
    throws SAXException
    {
        // Push the existing status
        pushInput (ename);
        sourceType = INPUT_INTERNAL;
        readBuffer = ch;
        readBufferPos = start;
        readBufferLength = length;
        readBufferOverflow = -1;
    }


    /**
     * Save the current input source onto the stack.
     * <p>This method saves all of the global variables associated with
     * the current input source, so that they can be restored when a new
     * input source has finished.  It also tests for entity recursion.
     * <p>The method saves the following global variables onto a stack
     * using a fixed-length array:
     * <ol>
     * <li>sourceType
     * <li>externalEntity
     * <li>readBuffer
     * <li>readBufferPos
     * <li>readBufferLength
     * <li>line
     * <li>encoding
     * </ol>
     * @param ename The name of the entity (if any) causing the new input.
     * @see #popInput
     * @see #sourceType
     * @see #externalEntity
     * @see #readBuffer
     * @see #readBufferPos
     * @see #readBufferLength
     * @see #line
     * @see #encoding
     */
    private void pushInput (String ename)
    throws SAXException
    {
        Object input[] = new Object [12];

        // Check for entity recursion.
        if (ename != null) {
            Iterator entities = entityStack.iterator ();
            while (entities.hasNext ()) {
                String e = (String) entities.next ();
                if (e == ename) {
                    error ("recursive reference to entity", ename, null);
                }
            }
        }
        entityStack.add (ename);

        // Don't bother if there is no current input.
        if (sourceType == INPUT_NONE) {
            return;
        }

        // Set up a snapshot of the current
        // input source.
        input [0] = new Integer (sourceType);
        input [1] = externalEntity;
        input [2] = readBuffer;
        input [3] = new Integer (readBufferPos);
        input [4] = new Integer (readBufferLength);
        input [5] = new Integer (line);
        input [6] = new Integer (encoding);
        input [7] = new Integer (readBufferOverflow);
        input [8] = is;
        input [9] = new Integer (currentByteCount);
        input [10] = new Integer (column);
        input [11] = reader;

        // Push it onto the stack.
        inputStack.add (input);
    }


    /**
     * Restore a previous input source.
     * <p>This method restores all of the global variables associated with
     * the current input source.
     * @exception java.io.EOFException
     *    If there are no more entries on the input stack.
     * @see #pushInput
     * @see #sourceType
     * @see #externalEntity
     * @see #readBuffer
     * @see #readBufferPos
     * @see #readBufferLength
     * @see #line
     * @see #encoding
     */
    private void popInput ()
    throws SAXException, IOException
    {
        Object input[];


        switch (sourceType) {

        case INPUT_EXTERNAL:
            if (externalEntity != null) {
                handler.endExternalEntity (
                        externalEntity.getURL ().toString ());
            }
            break;
        case INPUT_STREAM:
            if (baseURI != null) {
                handler.endExternalEntity (baseURI);
            }
            is.close ();
            break;
        case INPUT_READER:
            if (baseURI != null) {
                handler.endExternalEntity (baseURI);
            }
            reader.close ();
            break;
        }

        // Throw an EOFException if there
        // is nothing else to pop.
        if (inputStack.isEmpty ()) {
            throw new EOFException ("no more input");
        } else {
            String s;
            input = (Object[]) inputStack.remove ( inputStack.size() - 1 );
            s = (String) entityStack.remove ( entityStack.size() - 1 );
        }

        sourceType = ((Integer) input [0]).intValue ();
        externalEntity = (URLConnection) input [1];
        readBuffer = (char[]) input [2];
        readBufferPos = ((Integer) input [3]).intValue ();
        readBufferLength = ((Integer) input [4]).intValue ();
        line = ((Integer) input [5]).intValue ();
        encoding = ((Integer) input [6]).intValue ();
        readBufferOverflow = ((Integer) input [7]).intValue ();
        is = (InputStream) input [8];
        currentByteCount = ((Integer) input [9]).intValue ();
        column = ((Integer) input [10]).intValue ();
        reader = (Reader) input [11];
    }


    /**
     * Return true if we can read the expected character.
     * <p>Note that the character will be removed from the input stream
     * on success, but will be put back on failure.  Do not attempt to
     * read the character again if the method succeeds.
     * @param delim The character that should appear next.  For a
     *        insensitive match, you must supply this in upper-case.
     * @return true if the character was successfully read, or false if
     *   it was not.
     * @see #tryRead (String)
     */
    private boolean tryRead (char delim)
    throws SAXException, IOException
    {
        char c;

        // Read the character
        c = readCh ();

        // Test for a match, and push the character
        // back if the match fails.
        if (c == delim) {
            return true;
        } else {
            unread (c);
            return false;
        }
    }


    /**
     * Return true if we can read the expected string.
     * <p>This is simply a convenience method.
     * <p>Note that the string will be removed from the input stream
     * on success, but will be put back on failure.  Do not attempt to
     * read the string again if the method succeeds.
     * <p>This method will push back a character rather than an
     * array whenever possible (probably the majority of cases).
     * <p><b>NOTE:</b> This method currently has a hard-coded limit
     * of 100 characters for the delimiter.
     * @param delim The string that should appear next.
     * @return true if the string was successfully read, or false if
     *   it was not.
     * @see #tryRead (char)
     */
    private boolean tryRead (String delim)
    throws SAXException, IOException
    {
        char ch[] = delim.toCharArray ();
        char c;

        // Compare the input, character-
        // by character.

        for (int i = 0; i < ch.length; i++) {
            c = readCh ();
            if (c != ch [i]) {
                unread (c);
                if (i != 0) {
                    unread (ch, i);
                }
                return false;
            }
        }
        return true;
    }



    /**
     * Return true if we can read some whitespace.
     * <p>This is simply a convenience method.
     * <p>This method will push back a character rather than an
     * array whenever possible (probably the majority of cases).
     * @return true if whitespace was found.
     */
    private boolean tryWhitespace ()
    throws SAXException, IOException
    {
        char c;
        c = readCh ();
        if (isWhitespace (c)) {
            skipWhitespace ();
            return true;
        } else {
            unread (c);
            return false;
        }
    }


    /**
     * Read all data until we find the specified string.
     * This is useful for scanning CDATA sections and PIs.
     * <p>This is inefficient right now, since it calls tryRead ()
     * for every character.
     * @param delim The string delimiter
     * @see #tryRead (String, boolean)
     * @see #readCh
     */
    private void parseUntil (String delim)
    throws SAXException, IOException
    {
        char c;
        int startLine = line;

        try {
            while (!tryRead (delim)) {
                c = readCh ();
                dataBufferAppend (c);
            }
        } catch (EOFException e) {
            error ("end of input while looking for delimiter "
                + "(started on line " + startLine
                + ')', null, delim);
        }
    }


    /**
     * Read just the encoding declaration (or XML declaration) at the 
     * start of an external entity.
     * When this method is called, we know that the declaration is
     * present (or appears to be).  We also know that the entity is
     * in some sort of ASCII-derived 8-bit encoding.
     * The idea of this is to let us read what the 8-bit encoding is
     * before we've committed to converting any more of the file; the
     * XML or encoding declaration must be in 7-bit ASCII, so we're
     * safe as long as we don't go past it.
     */
    private void read8bitEncodingDeclaration ()
    throws SAXException, IOException
    {
        int ch;
        readBufferPos = readBufferLength = 0;

        while (true) {
            ch = is.read ();
            readBuffer [readBufferLength++] = (char) ch;
            switch (ch) {
              case (int) '>':
                return;
              case - 1:
                error ("end of file before end of XML or encoding declaration.",
                       null, "?>");
            }
            if (readBuffer.length == readBufferLength)
                error ("unfinished XML or encoding declaration");
        }
    }


    //////////////////////////////////////////////////////////////////////
    // Low-level I/O.
    //////////////////////////////////////////////////////////////////////


    /**
     * Read a chunk of data from an external input source.
     * <p>This is simply a front-end that fills the rawReadBuffer
     * with bytes, then calls the appropriate encoding handler.
     * @see #encoding
     * @see #rawReadBuffer
     * @see #readBuffer
     * @see #filterCR
     * @see #copyUtf8ReadBuffer
     * @see #copyIso8859_1ReadBuffer
     * @see #copyUcs_2ReadBuffer
     * @see #copyUcs_4ReadBuffer
     */
    private void readDataChunk ()
    throws SAXException, IOException
    {
        int count, i, j;

        // See if we have any overflow (filterCR sets for CR at end)
        if (readBufferOverflow > -1) {
            readBuffer [0] = (char) readBufferOverflow;
            readBufferOverflow = -1;
            readBufferPos = 1;
            sawCR = true;
        } else {
            readBufferPos = 0;
            sawCR = false;
        }

        // input from a character stream.
        if (sourceType == INPUT_READER) {
            count = reader.read (readBuffer,
                            readBufferPos, READ_BUFFER_MAX - readBufferPos);
            if (count < 0)
                readBufferLength = readBufferPos;
            else
                readBufferLength = readBufferPos + count;
            if (readBufferLength > 0)
                filterCR (count >= 0);
            sawCR = false;
            return;
        }

        // Read as many bytes as possible into the raw buffer.
        count = is.read (rawReadBuffer, 0, READ_BUFFER_MAX);

        // Dispatch to an encoding-specific reader method to populate
        // the readBuffer.  In most parser speed profiles, these routines
        // show up at the top of the CPU usage chart.
        if (count > 0) {
            switch (encoding) {
              // one byte builtins
              case ENCODING_ASCII:
                copyIso8859_1ReadBuffer (count, (char) 0x0080);
                break;
              case ENCODING_UTF_8:
                copyUtf8ReadBuffer (count);
                break;
              case ENCODING_ISO_8859_1:
                copyIso8859_1ReadBuffer (count, (char) 0);
                break;

              // two byte builtins
              case ENCODING_UCS_2_12:
                copyUcs2ReadBuffer (count, 8, 0);
                break;
              case ENCODING_UCS_2_21:
                copyUcs2ReadBuffer (count, 0, 8);
                break;

              // four byte builtins
              case ENCODING_UCS_4_1234:
                copyUcs4ReadBuffer (count, 24, 16, 8, 0);
                break;
              case ENCODING_UCS_4_4321:
                copyUcs4ReadBuffer (count, 0, 8, 16, 24);
                break;
              case ENCODING_UCS_4_2143:
                copyUcs4ReadBuffer (count, 16, 24, 0, 8);
                break;
              case ENCODING_UCS_4_3412:
                copyUcs4ReadBuffer (count, 8, 0, 24, 16);
                break;
            }
        } else
            readBufferLength = readBufferPos;

        readBufferPos = 0;

        // Filter out all carriage returns if we've seen any
        // (including any saved from a previous read)
        if (sawCR) {
            filterCR (count >= 0);
            sawCR = false;

            // must actively report EOF, lest some CRs get lost.
            if (readBufferLength == 0 && count >= 0)
                readDataChunk ();
        }

        if (count > 0)
            currentByteCount += count;
    }


    /**
     * Filter carriage returns in the read buffer.
     * CRLF becomes LF; CR becomes LF.
     * @param moreData true iff more data might come from the same source
     * @see #readDataChunk
     * @see #readBuffer
     * @see #readBufferOverflow
     */
    private void filterCR (boolean moreData)
    {
        int i, j;

        readBufferOverflow = -1;

loop:
        for (i = j = readBufferPos; j < readBufferLength; i++, j++) {
            switch (readBuffer [j]) {
            case '\r':
                if (j == readBufferLength - 1) {
                    if (moreData) {
                        readBufferOverflow = '\r';
                        readBufferLength--;
                    } else      // CR at end of buffer
                        readBuffer [i++] = '\n';
                    break loop;
                } else if (readBuffer [j + 1] == '\n') {
                    j++;
                }
                readBuffer [i] = '\n';
                break;

            case '\n':
            default:
                readBuffer [i] = readBuffer [j];
                break;
            }
        }
        readBufferLength = i;
    }

    /**
     * Convert a buffer of UTF-8-encoded bytes into UTF-16 characters.
     * <p>When readDataChunk () calls this method, the raw bytes are in 
     * rawReadBuffer, and the final characters will appear in 
     * readBuffer.
     * @param count The number of bytes to convert.
     * @see #readDataChunk
     * @see #rawReadBuffer
     * @see #readBuffer
     * @see #getNextUtf8Byte
     */
    private void copyUtf8ReadBuffer (int count)
    throws SAXException, IOException
    {
        int     i = 0;
        int     j = readBufferPos;
        int     b1;
        char    c = 0;

        /*
        // check once, so the runtime won't (if it's smart enough)
        if (count < 0 || count > rawReadBuffer.length)
            throw new ArrayIndexOutOfBoundsException (Integer.toString (count));
        */

        while (i < count) {
            b1 = rawReadBuffer [i++];

            // Determine whether we are dealing
            // with a one-, two-, three-, or four-
            // byte sequence.
            if (b1 < 0) {
                if ((b1 & 0xe0) == 0xc0) {
                    // 2-byte sequence: 00000yyyyyxxxxxx = 110yyyyy 10xxxxxx
                    c = (char) (((b1 & 0x1f) << 6)
                                | getNextUtf8Byte (i++, count));
                } else if ((b1 & 0xf0) == 0xe0) {
                    // 3-byte sequence:
                    // zzzzyyyyyyxxxxxx = 1110zzzz 10yyyyyy 10xxxxxx
                    // most CJKV characters
                    c = (char) (((b1 & 0x0f) << 12) |
                                   (getNextUtf8Byte (i++, count) << 6) |
                                   getNextUtf8Byte (i++, count));
                } else if ((b1 & 0xf8) == 0xf0) {
                    // 4-byte sequence: 11101110wwwwzzzzyy + 110111yyyyxxxxxx
                    //     = 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
                    // (uuuuu = wwww + 1)
                    // "Surrogate Pairs" ... from the "Astral Planes"
                    int iso646 = b1 & 07;
                    iso646 = (iso646 << 6) + getNextUtf8Byte (i++, count);
                    iso646 = (iso646 << 6) + getNextUtf8Byte (i++, count);
                    iso646 = (iso646 << 6) + getNextUtf8Byte (i++, count);

                    if (iso646 <= 0xffff) {
                        c = (char) iso646;
                    } else {
                        if (iso646 > 0x0010ffff)
                            encodingError (
                                "UTF-8 value out of range for Unicode",
                                iso646, 0);
                        iso646 -= 0x010000;
                        readBuffer [j++] = (char) (0xd800 | (iso646 >> 10));
                        readBuffer [j++] = (char) (0xdc00 | (iso646 & 0x03ff));
                        continue;
                    }
                } else {
                    // The five and six byte encodings aren't supported;
                    // they exceed the Unicode (and XML) range.
                    encodingError (
                            "unsupported five or six byte UTF-8 sequence",
                            0xff & b1, i);
                    // NOTREACHED
                    c = 0;
                }
            } else {
                // 1-byte sequence: 000000000xxxxxxx = 0xxxxxxx
                // (US-ASCII character, "common" case, one branch to here)
                c = (char) b1;
            }
            readBuffer [j++] = c;
            if (c == '\r')
                sawCR = true;
        }
        // How many characters have we read?
        readBufferLength = j;
    }


    /**
     * Return the next byte value in a UTF-8 sequence.
     * If it is not possible to get a byte from the current
     * entity, throw an exception.
     * @param pos The current position in the rawReadBuffer.
     * @param count The number of bytes in the rawReadBuffer
     * @return The significant six bits of a non-initial byte in
     *   a UTF-8 sequence.
     * @exception EOFException If the sequence is incomplete.
     */
    private int getNextUtf8Byte (int pos, int count)
    throws SAXException, IOException
    {
        int val;

        // Take a character from the buffer
        // or from the actual input stream.
        if (pos < count) {
            val = rawReadBuffer [pos];
        } else {
            val = is.read ();
            if (val == -1) {
                encodingError ("unfinished multi-byte UTF-8 sequence at EOF",
                        -1, pos);
            }
        }

        // Check for the correct bits at the start.
        if ((val & 0xc0) != 0x80) {
            encodingError ("bad continuation of multi-byte UTF-8 sequence",
                    val, pos + 1);
        }

        // Return the significant bits.
        return (val & 0x3f);
    }


    /**
     * Convert a buffer of US-ASCII or ISO-8859-1-encoded bytes into
     * UTF-16 characters.
     *
     * <p>When readDataChunk () calls this method, the raw bytes are in 
     * rawReadBuffer, and the final characters will appear in 
     * readBuffer.
     *
     * @param count The number of bytes to convert.
     * @param mask For ASCII conversion, 0x7f; else, 0xff.
     * @see #readDataChunk
     * @see #rawReadBuffer
     * @see #readBuffer
     */
    private void copyIso8859_1ReadBuffer (int count, char mask)
    throws IOException
    {
        int i, j;
        for (i = 0, j = readBufferPos; i < count; i++, j++) {
            char c = (char) (rawReadBuffer [i] & 0xff);
            if ((c & mask) != 0)
                throw new CharConversionException ("non-ASCII character U+"
                                                    + Integer.toHexString (c));
            readBuffer [j] = c;
            if (c == '\r') {
                sawCR = true;
            }
        }
        readBufferLength = j;
    }


    /**
     * Convert a buffer of UCS-2-encoded bytes into UTF-16 characters
     * (as used in Java string manipulation).
     *
     * <p>When readDataChunk () calls this method, the raw bytes are in 
     * rawReadBuffer, and the final characters will appear in 
     * readBuffer.
     * @param count The number of bytes to convert.
     * @param shift1 The number of bits to shift byte 1.
     * @param shift2 The number of bits to shift byte 2
     * @see #readDataChunk
     * @see #rawReadBuffer
     * @see #readBuffer
     */
    private void copyUcs2ReadBuffer (int count, int shift1, int shift2)
    throws SAXException
    {
        int j = readBufferPos;

        if (count > 0 && (count % 2) != 0) {
            encodingError ("odd number of bytes in UCS-2 encoding", -1, count);
        }
        // The loops are faster with less internal brancing; hence two
        if (shift1 == 0) {      // "UTF-16-LE"
            for (int i = 0; i < count; i += 2) {
                char c = (char) (rawReadBuffer [i + 1] << 8);
                c |= 0xff & rawReadBuffer [i];
                readBuffer [j++] = c;
                if (c == '\r')
                    sawCR = true;
            }
        } else {        // "UTF-16-BE"
            for (int i = 0; i < count; i += 2) {
                char c = (char) (rawReadBuffer [i] << 8);
                c |= 0xff & rawReadBuffer [i + 1];
                readBuffer [j++] = c;
                if (c == '\r')
                    sawCR = true;
            }
        }
        readBufferLength = j;
    }


    /**
     * Convert a buffer of UCS-4-encoded bytes into UTF-16 characters.
     *
     * <p>When readDataChunk () calls this method, the raw bytes are in 
     * rawReadBuffer, and the final characters will appear in 
     * readBuffer.
     * <p>Java has Unicode chars, and this routine uses surrogate pairs
     * for ISO-10646 values between 0x00010000 and 0x000fffff.  An
     * exception is thrown if the ISO-10646 character has no Unicode
     * representation.
     *
     * @param count The number of bytes to convert.
     * @param shift1 The number of bits to shift byte 1.
     * @param shift2 The number of bits to shift byte 2
     * @param shift3 The number of bits to shift byte 2
     * @param shift4 The number of bits to shift byte 2
     * @see #readDataChunk
     * @see #rawReadBuffer
     * @see #readBuffer
     */
    private void copyUcs4ReadBuffer (int count, int shift1, int shift2,
                              int shift3, int shift4)
    throws SAXException
    {
        int j = readBufferPos;
        int value;

        if (count > 0 && (count % 4) != 0) {
            encodingError (
                    "number of bytes in UCS-4 encoding not divisible by 4",
                    -1, count);
        }
        for (int i = 0; i < count; i += 4) {
            value = (((rawReadBuffer [i] & 0xff) << shift1) |
                      ((rawReadBuffer [i + 1] & 0xff) << shift2) |
                      ((rawReadBuffer [i + 2] & 0xff) << shift3) |
                      ((rawReadBuffer [i + 3] & 0xff) << shift4));
            if (value < 0x0000ffff) {
                readBuffer [j++] = (char) value;
                if (value == (int) '\r') {
                    sawCR = true;
                }
            } else if (value < 0x0010ffff) {
                value -= 0x010000;
                readBuffer [j++] = (char) (0xd8 | ((value >> 10) & 0x03ff));
                readBuffer [j++] = (char) (0xdc | (value & 0x03ff));
            } else {
                encodingError ("UCS-4 value out of range for Unicode",
                               value, i);
            }
        }
        readBufferLength = j;
    }


    /**
     * Report a character encoding error.
     */
    private void encodingError (String message, int value, int offset)
    throws SAXException
    {
        String uri;

        if (value != -1) {
            message = message + " (character code: 0x" +
                      Integer.toHexString (value) + ')';
        }
        if (externalEntity != null) {
            uri = externalEntity.getURL ().toString ();
        } else {
            uri = baseURI;
        }
        handler.error (message, uri, -1, offset + currentByteCount);
    }


    //////////////////////////////////////////////////////////////////////
    // Local Variables.
    //////////////////////////////////////////////////////////////////////

    /**
     * Re-initialize the variables for each parse.
     */
    private void initializeVariables ()
    {
        // First line
        line = 1;
        column = 0;

        // Set up the buffers for data and names
        dataBufferPos = 0;
        dataBuffer = new char [DATA_BUFFER_INITIAL];
        nameBufferPos = 0;
        nameBuffer = new char [NAME_BUFFER_INITIAL];

        // Set up the DTD hash tables
        elementInfo = new HashMap ();
        entityInfo = new HashMap ();
        notationInfo = new HashMap ();

        // Set up the variables for the current
        // element context.
        currentElement = null;
        currentElementContent = CONTENT_UNDECLARED;

        // Set up the input variables
        sourceType = INPUT_NONE;
        inputStack = new ArrayList ();
        entityStack = new ArrayList ();
        externalEntity = null;
        tagAttributePos = 0;
        tagAttributes = new String [100];
        rawReadBuffer = new byte [READ_BUFFER_MAX];
        readBufferOverflow = -1;

        inLiteral = false;
        expandPE = false;
        peIsError = false;

        inCDATA = false;

        symbolTable = new Object [SYMBOL_TABLE_LENGTH][];
    }


    /**
     * Clean up after the parse to allow some garbage collection.
     */
    private void cleanupVariables ()
    {
        dataBuffer = null;
        nameBuffer = null;

        elementInfo = null;
        entityInfo = null;
        notationInfo = null;

        currentElement = null;

        inputStack = null;
        entityStack = null;
        externalEntity = null;

        tagAttributes = null;
        rawReadBuffer = null;

        symbolTable = null;
    }

    //
    // The current XML handler interface.
    //
    private SAXDriver   handler;

    //
    // I/O information.
    //
    private Reader      reader;         // current reader
    private InputStream is;             // current input stream
    private int         line;           // current line number
    private int         column;         // current column number
    private int         sourceType;     // type of input source
    private ArrayList   inputStack;     // stack of input soruces
    private URLConnection externalEntity; // current external entity
    private int         encoding;       // current character encoding
    private int         currentByteCount; // bytes read from current source

    //
    // Buffers for decoded but unparsed character input.
    //
    private char        readBuffer [];
    private int         readBufferPos;
    private int         readBufferLength;
    private int         readBufferOverflow;  // overflow from last data chunk.


    //
    // Buffer for undecoded raw byte input.
    //
    private final static int READ_BUFFER_MAX = 16384;
    private byte        rawReadBuffer [];


    //
    // Buffer for parsed character data.
    //
    private static int DATA_BUFFER_INITIAL = 4096;
    private char        dataBuffer [];
    private int         dataBufferPos;

    //
    // Buffer for parsed names.
    //
    private static int NAME_BUFFER_INITIAL = 1024;
    private char        nameBuffer [];
    private int         nameBufferPos;


    //
    // HashMaps for DTD information on elements, entities, and notations.
    //
    private HashMap     elementInfo;
    private HashMap     entityInfo;
    private HashMap     notationInfo;


    //
    // Element type currently in force.
    //
    private String      currentElement;
    private int         currentElementContent;

    //
    // Base external identifiers for resolution.
    //
    private String      basePublicId;
    private String      baseURI;
    private int         baseEncoding;
    private Reader      baseReader;
    private InputStream baseInputStream;
    private char        baseInputBuffer [];
    private int         baseInputBufferStart;
    private int         baseInputBufferLength;

    //
    // Stack of entity names, to detect recursion.
    //
    private ArrayList   entityStack;

    //
    // PE expansion is enabled in most chunks of the DTD, not all.
    // When it's enabled, literals are treated differently.
    //
    private boolean     inLiteral;
    private boolean     expandPE;
    private boolean     peIsError;

    //
    // Symbol table, for caching interned names.
    //
    private final static int SYMBOL_TABLE_LENGTH = 1087;
    private Object      symbolTable [][];

    //
    // Hash table of attributes found in current start tag.
    //
    private String      tagAttributes [];
    private int         tagAttributePos;

    //
    // Utility flag: have we noticed a CR while reading the last
    // data chunk?  If so, we will have to go back and normalise
    // CR or CR/LF line ends.
    //
    private boolean     sawCR;

    //
    // Utility flag: are we in CDATA?  If so, whitespace isn't ignorable.
    // 
    private boolean     inCDATA;
}