/* XMLElement.java
 *
 * $Revision: 1.2 $
 * $Date: 2002/08/03 04:36:34 $
 * $Name:  $
 *
 * This file is part of NanoXML 2 Lite.
 * Copyright (C) 2000-2002 Marc De Scheemaecker, All Rights Reserved.
 *
 * This software is provided 'as-is', without any express or implied warranty.
 * In no event will the authors be held liable for any damages arising from the
 * use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 *  1. The origin of this software must not be misrepresented; you must not
 *     claim that you wrote the original software. If you use this software in
 *     a product, an acknowledgment in the product documentation would be
 *     appreciated but is not required.
 *
 *  2. Altered source versions must be plainly marked as such, and must not be
 *     misrepresented as being the original software.
 *
 *  3. This notice may not be removed or altered from any source distribution.
 *****************************************************************************/

/* JAM: hacked the source to remove unneeded methods and comments. */

package net.sourceforge.nanoxml;

import java.io.*;
import java.util.*;

import net.sourceforge.jnlp.runtime.JNLPRuntime;


/**
 * XMLElement is a representation of an XML object. The object is able to parse
 * XML code.
 * <P><DL>
 * <DT><B>Parsing XML Data</B></DT>
 * <DD>
 * You can parse XML data using the following code:
 * <UL><CODE>
 * XMLElement xml = new XMLElement();<BR>
 * FileReader reader = new FileReader("filename.xml");<BR>
 * xml.parseFromReader(reader);
 * </CODE></UL></DD></DL>
 * <DL><DT><B>Retrieving Attributes</B></DT>
 * <DD>
 * You can enumerate the attributes of an element using the method
 * {@link #enumerateAttributeNames() enumerateAttributeNames}.
 * The attribute values can be retrieved using the method
 * {@link #getStringAttribute(java.lang.String) getStringAttribute}.
 * The following example shows how to list the attributes of an element:
 * <UL><CODE>
 * XMLElement element = ...;<BR>
 * Enumeration enum = element.getAttributeNames();<BR>
 * while (enum.hasMoreElements()) {<BR>
 * &nbsp;&nbsp;&nbsp;&nbsp;String key = (String) enum.nextElement();<BR>
 * &nbsp;&nbsp;&nbsp;&nbsp;String value = element.getStringAttribute(key);<BR>
 * &nbsp;&nbsp;&nbsp;&nbsp;System.out.println(key + " = " + value);<BR>
 * }
 * </CODE></UL></DD></DL>
 * <DL><DT><B>Retrieving Child Elements</B></DT>
 * <DD>
 * You can enumerate the children of an element using
 * {@link #enumerateChildren() enumerateChildren}.
 * The number of child elements can be retrieved using
 * {@link #countChildren() countChildren}.
 * </DD></DL>
 * <DL><DT><B>Elements Containing Character Data</B></DT>
 * <DD>
 * If an elements contains character data, like in the following example:
 * <UL><CODE>
 * &lt;title&gt;The Title&lt;/title&gt;
 * </CODE></UL>
 * you can retrieve that data using the method
 * {@link #getContent() getContent}.
 * </DD></DL>
 * <DL><DT><B>Subclassing XMLElement</B></DT>
 * <DD>
 * When subclassing XMLElement, you need to override the method
 * {@link #createAnotherElement() createAnotherElement}
 * which has to return a new copy of the receiver.
 * </DD></DL>
 * <P>
 *
 * @see net.sourceforge.nanoxml.XMLParseException
 *
 * @author Marc De Scheemaecker
 *         &lt;<A href="mailto:cyberelf@mac.com">cyberelf@mac.com</A>&gt;
 * @version $Name:  $, $Revision: 1.2 $
 */
public class XMLElement
{

    /**
     * The attributes given to the element.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li>The field can be empty.
     *     <li>The field is never <code>null</code>.
     *     <li>The keys and the values are strings.
     * </ul></dd></dl>
     */
    private Hashtable attributes;


    /**
     * Child elements of the element.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li>The field can be empty.
     *     <li>The field is never <code>null</code>.
     *     <li>The elements are instances of <code>XMLElement</code>
     *         or a subclass of <code>XMLElement</code>.
     * </ul></dd></dl>
     */
    private Vector children;


    /**
     * The name of the element.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li>The field is <code>null</code> iff the element is not
     *         initialized by either parse or setName.
     *     <li>If the field is not <code>null</code>, it's not empty.
     *     <li>If the field is not <code>null</code>, it contains a valid
     *         XML identifier.
     * </ul></dd></dl>
     */
    private String name;


    /**
     * The #PCDATA content of the object.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li>The field is <code>null</code> iff the element is not a
     *         #PCDATA element.
     *     <li>The field can be any string, including the empty string.
     * </ul></dd></dl>
     */
    private String contents;


    /**
     * Conversion table for &amp;...; entities. The keys are the entity names
     * without the &amp; and ; delimiters.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li>The field is never <code>null</code>.
     *     <li>The field always contains the following associations:
     *         "lt"&nbsp;=&gt;&nbsp;"&lt;", "gt"&nbsp;=&gt;&nbsp;"&gt;",
     *         "quot"&nbsp;=&gt;&nbsp;"\"", "apos"&nbsp;=&gt;&nbsp;"'",
     *         "amp"&nbsp;=&gt;&nbsp;"&amp;"
     *     <li>The keys are strings
     *     <li>The values are char arrays
     * </ul></dd></dl>
     */
    private Hashtable entities;


    /**
     * The line number where the element starts.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li><code>lineNr &gt= 0</code>
     * </ul></dd></dl>
     */
    private int lineNr;


    /**
     * <code>true</code> if the case of the element and attribute names
     * are case insensitive.
     */
    private boolean ignoreCase;


    /**
     * <code>true</code> if the leading and trailing whitespace of #PCDATA
     * sections have to be ignored.
     */
    private boolean ignoreWhitespace;


    /**
     * Character read too much.
     * This character provides push-back functionality to the input reader
     * without having to use a PushbackReader.
     * If there is no such character, this field is '\0'.
     */
    private char charReadTooMuch;

    /**
     * Character read too much for the comment remover.
     */
    private char sanitizeCharReadTooMuch;

    /**
     * The reader provided by the caller of the parse method.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li>The field is not <code>null</code> while the parse method
     *         is running.
     * </ul></dd></dl>
     */
    private Reader reader;


    /**
     * The current line number in the source content.
     *
     * <dl><dt><b>Invariants:</b></dt><dd>
     * <ul><li>parserLineNr &gt; 0 while the parse method is running.
     * </ul></dd></dl>
     */
    private int parserLineNr;


    /**
     * Creates and initializes a new XML element.
     * Calling the construction is equivalent to:
     * <ul><code>new XMLElement(new Hashtable(), false, true)
     * </code></ul>
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li>countChildren() => 0
     *     <li>enumerateChildren() => empty enumeration
     *     <li>enumeratePropertyNames() => empty enumeration
     *     <li>getChildren() => empty vector
     *     <li>getContent() => ""
     *     <li>getLineNr() => 0
     *     <li>getName() => null
     * </ul></dd></dl>
     *
     */
    public XMLElement()
    {
        this(new Hashtable(), false, true, true);
    }


    /**
     * Creates and initializes a new XML element.
     * <P>
     * This constructor should <I>only</I> be called from
     * {@link #createAnotherElement() createAnotherElement}
     * to create child elements.
     *
     * @param entities
     *     The entity conversion table.
     * @param skipLeadingWhitespace
     *     <code>true</code> if leading and trailing whitespace in PCDATA
     *     content has to be removed.
     * @param fillBasicConversionTable
     *     <code>true</code> if the basic entities need to be added to
     *     the entity list (client code calling this constructor).
     * @param ignoreCase
     *     <code>true</code> if the case of element and attribute names have
     *     to be ignored.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>entities != null</code>
     *     <li>if <code>fillBasicConversionTable == false</code>
     *         then <code>entities</code> contains at least the following
     *         entries: <code>amp</code>, <code>lt</code>, <code>gt</code>,
     *         <code>apos</code> and <code>quot</code>
     * </ul></dd></dl>
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li>countChildren() => 0
     *     <li>enumerateChildren() => empty enumeration
     *     <li>enumeratePropertyNames() => empty enumeration
     *     <li>getChildren() => empty vector
     *     <li>getContent() => ""
     *     <li>getLineNr() => 0
     *     <li>getName() => null
     * </ul></dd></dl><dl>
     *
     */
    protected XMLElement(Hashtable entities,
                         boolean   skipLeadingWhitespace,
                         boolean   fillBasicConversionTable,
                         boolean   ignoreCase)
    {
        this.ignoreWhitespace = skipLeadingWhitespace;
        this.ignoreCase = ignoreCase;
        this.name = null;
        this.contents = "";
        this.attributes = new Hashtable();
        this.children = new Vector();
        this.entities = entities;
        this.lineNr = 0;
        Enumeration e = this.entities.keys();
        while (e.hasMoreElements()) {
            Object key = e.nextElement();
            Object value = this.entities.get(key);
            if (value instanceof String) {
                value = ((String) value).toCharArray();
                this.entities.put(key, value);
            }
        }
        if (fillBasicConversionTable) {
            this.entities.put("amp", new char[] { '&' });
            this.entities.put("quot", new char[] { '"' });
            this.entities.put("apos", new char[] { '\'' });
            this.entities.put("lt", new char[] { '<' });
            this.entities.put("gt", new char[] { '>' });
        }
    }


    /**
     * Adds a child element.
     *
     * @param child
     *     The child element to add.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>child != null</code>
     *     <li><code>child.getName() != null</code>
     *     <li><code>child</code> does not have a parent element
     * </ul></dd></dl>
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li>countChildren() => old.countChildren() + 1
     *     <li>enumerateChildren() => old.enumerateChildren() + child
     *     <li>getChildren() => old.enumerateChildren() + child
     * </ul></dd></dl><dl>
     *
     */
    public void addChild(XMLElement child)
    {
        this.children.addElement(child);
    }


    /**
     * Adds or modifies an attribute.
     *
     * @param name
     *     The name of the attribute.
     * @param value
     *     The value of the attribute.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>name != null</code>
     *     <li><code>name</code> is a valid XML identifier
     *     <li><code>value != null</code>
     * </ul></dd></dl>
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li>enumerateAttributeNames()
     *         => old.enumerateAttributeNames() + name
     *     <li>getAttribute(name) => value
     * </ul></dd></dl><dl>
     *
     */
    public void setAttribute(String name,
                             Object value)
    {
        if (this.ignoreCase) {
            name = name.toUpperCase();
        }
        this.attributes.put(name, value.toString());
    }


    /**
     * Returns the number of child elements of the element.
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li><code>result >= 0</code>
     * </ul></dd></dl>
     *
     */
    public int countChildren()
    {
        return this.children.size();
    }


    /**
     * Enumerates the attribute names.
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li><code>result != null</code>
     * </ul></dd></dl>
     *
     */
    public Enumeration enumerateAttributeNames()
    {
        return this.attributes.keys();
    }


    /**
     * Enumerates the child elements.
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li><code>result != null</code>
     * </ul></dd></dl>
     *
     */
    public Enumeration enumerateChildren()
    {
        return this.children.elements();
    }


    /**
     * Returns the PCDATA content of the object. If there is no such content,
     * <CODE>null</CODE> is returned.
     *
     */
    public String getContent()
    {
        return this.contents;
    }


    /**
     * Returns the line nr in the source data on which the element is found.
     * This method returns <code>0</code> there is no associated source data.
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li><code>result >= 0</code>
     * </ul></dd></dl>
     */
    public int getLineNr()
    {
        return this.lineNr;
    }


    /**
     * Returns an attribute of the element.
     * If the attribute doesn't exist, <code>null</code> is returned.
     *
     * @param name The name of the attribute.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>name != null</code>
     *     <li><code>name</code> is a valid XML identifier
     * </ul></dd></dl><dl>
     *
     */
    public Object getAttribute(String name)
    {
        if (this.ignoreCase) {
            name = name.toUpperCase();
        }
        Object value = this.attributes.get(name);
        return value;
    }


    /**
     * Returns the name of the element.
     *
     */
    public String getName()
    {
        return this.name;
    }


    /**
     * Reads one XML element from a java.io.Reader and parses it.
     *
     * @param reader
     *     The reader from which to retrieve the XML data.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>reader != null</code>
     *     <li><code>reader</code> is not closed
     * </ul></dd></dl>
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li>the state of the receiver is updated to reflect the XML element
     *         parsed from the reader
     *     <li>the reader points to the first character following the last
     *         '&gt;' character of the XML element
     * </ul></dd></dl><dl>
     *
     * @throws java.io.IOException
     *     If an error occured while reading the input.
     * @throws net.sourceforge.nanoxml.XMLParseException
     *     If an error occured while parsing the read data.
     */
    public void parseFromReader(Reader reader)
    throws IOException, XMLParseException
    {
        this.parseFromReader(reader, /*startingLineNr*/ 1);
    }


    /**
     * Reads one XML element from a java.io.Reader and parses it.
     *
     * @param reader
     *     The reader from which to retrieve the XML data.
     * @param startingLineNr
     *     The line number of the first line in the data.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>reader != null</code>
     *     <li><code>reader</code> is not closed
     * </ul></dd></dl>
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li>the state of the receiver is updated to reflect the XML element
     *         parsed from the reader
     *     <li>the reader points to the first character following the last
     *         '&gt;' character of the XML element
     * </ul></dd></dl><dl>
     *
     * @throws java.io.IOException
     *     If an error occured while reading the input.
     * @throws net.sourceforge.nanoxml.XMLParseException
     *     If an error occured while parsing the read data.
     */
    public void parseFromReader(Reader reader,
                                int    startingLineNr)
        throws IOException, XMLParseException
    {
        this.charReadTooMuch = '\0';
        this.reader = reader;
        this.parserLineNr = startingLineNr;

        for (;;) {
            char ch = this.scanWhitespace();

            if (ch != '<') {
                throw this.expectedInput("<", ch);
            }

            ch = this.readChar();

            if ((ch == '!') || (ch == '?')) {
                this.skipSpecialTag(0);
            } else {
                this.unreadChar(ch);
                this.scanElement(this);
                return;
            }
        }
    }


    /**
     * Creates a new similar XML element.
     * <P>
     * You should override this method when subclassing XMLElement.
     */
    protected XMLElement createAnotherElement()
    {
        return new XMLElement(this.entities,
                              this.ignoreWhitespace,
                              false,
                              this.ignoreCase);
    }


    /**
     * Changes the content string.
     *
     * @param content
     *     The new content string.
     */
    public void setContent(String content)
    {
        this.contents = content;
    }


    /**
     * Changes the name of the element.
     *
     * @param name
     *     The new name.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>name != null</code>
     *     <li><code>name</code> is a valid XML identifier
     * </ul></dd></dl>
     *
     */
    public void setName(String name)
    {
        this.name = name;
    }


    /**
     * Scans an identifier from the current reader.
     * The scanned identifier is appended to <code>result</code>.
     *
     * @param result
     *     The buffer in which the scanned identifier will be put.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>result != null</code>
     *     <li>The next character read from the reader is a valid first
     *         character of an XML identifier.
     * </ul></dd></dl>
     *
     * <dl><dt><b>Postconditions:</b></dt><dd>
     * <ul><li>The next character read from the reader won't be an identifier
     *         character.
     * </ul></dd></dl><dl>
     */
    protected void scanIdentifier(StringBuffer result)
        throws IOException
    {
        for (;;) {
            char ch = this.readChar();
            if (((ch < 'A') || (ch > 'Z')) && ((ch < 'a') || (ch > 'z'))
                && ((ch < '0') || (ch > '9')) && (ch != '_') && (ch != '.')
                && (ch != ':') && (ch != '-') && (ch <= '\u007E')) {
                this.unreadChar(ch);
                return;
            }
            result.append(ch);
        }
    }


    /**
     * This method scans an identifier from the current reader.
     *
     * @return the next character following the whitespace.
     */
    protected char scanWhitespace()
        throws IOException
    {
        for (;;) {
            char ch = this.readChar();
            switch (ch) {
                case ' ':
                case '\t':
                case '\n':
                case '\r':
                    break;
                default:
                    return ch;
            }
        }
    }


    /**
     * This method scans an identifier from the current reader.
     * The scanned whitespace is appended to <code>result</code>.
     *
     * @return the next character following the whitespace.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>result != null</code>
     * </ul></dd></dl>
     */
    protected char scanWhitespace(StringBuffer result)
        throws IOException
    {
        for (;;) {
            char ch = this.readChar();
            switch (ch) {
                case ' ':
                case '\t':
                case '\n':
                    result.append(ch);
                case '\r':
                    break;
                default:
                    return ch;
            }
        }
    }


    /**
     * This method scans a delimited string from the current reader.
     * The scanned string without delimiters is appended to
     * <code>string</code>.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>string != null</code>
     *     <li>the next char read is the string delimiter
     * </ul></dd></dl>
     */
    protected void scanString(StringBuffer string)
        throws IOException
    {
        char delimiter = this.readChar();
        if ((delimiter != '\'') && (delimiter != '"')) {
            throw this.expectedInput("' or \"");
        }
        for (;;) {
            char ch = this.readChar();
            if (ch == delimiter) {
                return;
            } else if (ch == '&') {
                this.resolveEntity(string);
            } else {
                string.append(ch);
            }
        }
    }


    /**
     * Scans a #PCDATA element. CDATA sections and entities are resolved.
     * The next &lt; char is skipped.
     * The scanned data is appended to <code>data</code>.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>data != null</code>
     * </ul></dd></dl>
     */
    protected void scanPCData(StringBuffer data)
        throws IOException
    {
        for (;;) {
            char ch = this.readChar();
            if (ch == '<') {
                ch = this.readChar();
                if (ch == '!') {
                    this.checkCDATA(data);
                } else {
                    this.unreadChar(ch);
                    return;
                }
            } else if (ch == '&') {
                this.resolveEntity(data);
            } else {
                data.append(ch);
            }
        }
    }


    /**
     * Scans a special tag and if the tag is a CDATA section, append its
     * content to <code>buf</code>.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>buf != null</code>
     *     <li>The first &lt; has already been read.
     * </ul></dd></dl>
     */
    protected boolean checkCDATA(StringBuffer buf)
        throws IOException
    {
        char ch = this.readChar();
        if (ch != '[') {
            this.unreadChar(ch);
            this.skipSpecialTag(0);
            return false;
        } else if (! this.checkLiteral("CDATA[")) {
            this.skipSpecialTag(1); // one [ has already been read
            return false;
        } else {
            int delimiterCharsSkipped = 0;
            while (delimiterCharsSkipped < 3) {
                ch = this.readChar();
                switch (ch) {
                    case ']':
                        if (delimiterCharsSkipped < 2) {
                            delimiterCharsSkipped += 1;
                        } else {
                            buf.append(']');
                            buf.append(']');
                            delimiterCharsSkipped = 0;
                        }
                        break;
                    case '>':
                        if (delimiterCharsSkipped < 2) {
                            for (int i = 0; i < delimiterCharsSkipped; i++) {
                                buf.append(']');
                            }
                            delimiterCharsSkipped = 0;
                            buf.append('>');
                        } else {
                            delimiterCharsSkipped = 3;
                        }
                        break;
                    default:
                        for (int i = 0; i < delimiterCharsSkipped; i += 1) {
                            buf.append(']');
                        }
                        buf.append(ch);
                        delimiterCharsSkipped = 0;
                }
            }
            return true;
        }
    }


    /**
     * Skips a comment.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li>The first &lt;!-- has already been read.
     * </ul></dd></dl>
     */
    protected void skipComment()
        throws IOException
    {
        int dashesToRead = 2;
        while (dashesToRead > 0) {
            char ch = this.readChar();
            if (ch == '-') {
                dashesToRead -= 1;
            } else {
                dashesToRead = 2;
            }

            // Be more tolerant of extra -- (double dashes)
            // in comments.
            if (dashesToRead == 0) {
                ch = this.readChar();
                if (ch == '>') {
                    return;
                } else {
                    dashesToRead = 2;
                    this.unreadChar(ch);
                }
            }
        }
        /*
        if (this.readChar() != '>') {
            throw this.expectedInput(">");
        }
        */
    }


    /**
     * Skips a special tag or comment.
     *
     * @param bracketLevel The number of open square brackets ([) that have
     *                     already been read.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li>The first &lt;! has already been read.
     *     <li><code>bracketLevel >= 0</code>
     * </ul></dd></dl>
     */
    protected void skipSpecialTag(int bracketLevel)
        throws IOException
    {
        int tagLevel = 1; // <
        char stringDelimiter = '\0';
        if (bracketLevel == 0) {
            char ch = this.readChar();
            if (ch == '[') {
                bracketLevel += 1;
            } else if (ch == '-') {
                ch = this.readChar();
                if (ch == '[') {
                    bracketLevel += 1;
                } else if (ch == ']') {
                    bracketLevel -= 1;
                } else if (ch == '-') {
                    this.skipComment();
                    return;
                }
            }
        }
        while (tagLevel > 0) {
            char ch = this.readChar();
            if (stringDelimiter == '\0') {
                if ((ch == '"') || (ch == '\'')) {
                    stringDelimiter = ch;
                } else if (bracketLevel <= 0) {
                    if (ch == '<') {
                        tagLevel += 1;
                    } else if (ch == '>') {
                        tagLevel -= 1;
                    }
                }
                if (ch == '[') {
                    bracketLevel += 1;
                } else if (ch == ']') {
                    bracketLevel -= 1;
                }
            } else {
                if (ch == stringDelimiter) {
                    stringDelimiter = '\0';
                }
            }
        }
    }


    /**
     * Scans the data for literal text.
     * Scanning stops when a character does not match or after the complete
     * text has been checked, whichever comes first.
     *
     * @param literal the literal to check.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>literal != null</code>
     * </ul></dd></dl>
     */
    protected boolean checkLiteral(String literal)
        throws IOException
    {
        int length = literal.length();
        for (int i = 0; i < length; i += 1) {
            if (this.readChar() != literal.charAt(i)) {
                return false;
            }
        }
        return true;
    }


    /**
     * Reads a character from a reader.
     */
    protected char readChar()
        throws IOException
    {
        if (this.charReadTooMuch != '\0') {
            char ch = this.charReadTooMuch;
            this.charReadTooMuch = '\0';
            return ch;
        } else {
            int i = this.reader.read();
            if (i < 0) {
                throw this.unexpectedEndOfData();
            } else if (i == 10) {
                this.parserLineNr += 1;
                return '\n';
            } else {
                return (char) i;
            }
        }
    }


    /**
     * Scans an XML element.
     *
     * @param elt The element that will contain the result.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li>The first &lt; has already been read.
     *     <li><code>elt != null</code>
     * </ul></dd></dl>
     */
    protected void scanElement(XMLElement elt)
        throws IOException
    {
        StringBuffer buf = new StringBuffer();
        this.scanIdentifier(buf);
        String name = buf.toString();
        elt.setName(name);
        char ch = this.scanWhitespace();
        while ((ch != '>') && (ch != '/')) {
            buf.setLength(0);
            this.unreadChar(ch);
            this.scanIdentifier(buf);
            String key = buf.toString();
            ch = this.scanWhitespace();
            if (ch != '=') {
                throw this.expectedInput("=");
            }
            this.unreadChar(this.scanWhitespace());
            buf.setLength(0);
            this.scanString(buf);
            elt.setAttribute(key, buf);
            ch = this.scanWhitespace();
        }
        if (ch == '/') {
            ch = this.readChar();
            if (ch != '>') {
                throw this.expectedInput(">");
            }
            return;
        }
        buf.setLength(0);
        ch = this.scanWhitespace(buf);
        if (ch != '<') {
            this.unreadChar(ch);
            this.scanPCData(buf);
        } else {
            for (;;) {
                ch = this.readChar();
                if (ch == '!') {
                    if (this.checkCDATA(buf)) {
                        this.scanPCData(buf);
                        break;
                    } else {
                        ch = this.scanWhitespace(buf);
                        if (ch != '<') {
                            this.unreadChar(ch);
                            this.scanPCData(buf);
                            break;
                        }
                    }
                } else {
                    buf.setLength(0);
                    break;
                }
            }
        }
        if (buf.length() == 0) {
            while (ch != '/') {
                if (ch == '!') {
                    ch = this.readChar();
                    if (ch != '-') {
                        throw this.expectedInput("Comment or Element");
                    }
                    ch = this.readChar();
                    if (ch != '-') {
                        throw this.expectedInput("Comment or Element");
                    }
                    this.skipComment();
                } else {
                    this.unreadChar(ch);
                    XMLElement child = this.createAnotherElement();
                    this.scanElement(child);
                    elt.addChild(child);
                }
                ch = this.scanWhitespace();
                if (ch != '<') {
                    throw this.expectedInput("<");
                }
                ch = this.readChar();
            }
            this.unreadChar(ch);
        } else {
            if (this.ignoreWhitespace) {
                elt.setContent(buf.toString().trim());
            } else {
                elt.setContent(buf.toString());
            }
        }
        ch = this.readChar();
        if (ch != '/') {
            throw this.expectedInput("/");
        }
        this.unreadChar(this.scanWhitespace());
        if (! this.checkLiteral(name)) {
            throw this.expectedInput(name);
        }
        if (this.scanWhitespace() != '>') {
            throw this.expectedInput(">");
        }
    }


    /**
     * Resolves an entity. The name of the entity is read from the reader.
     * The value of the entity is appended to <code>buf</code>.
     *
     * @param buf Where to put the entity value.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li>The first &amp; has already been read.
     *     <li><code>buf != null</code>
     * </ul></dd></dl>
     */
    protected void resolveEntity(StringBuffer buf)
        throws IOException
    {
        char ch = '\0';
        StringBuffer keyBuf = new StringBuffer();
        for (;;) {
            ch = this.readChar();
            if (ch == ';') {
                break;
            }
            keyBuf.append(ch);
        }
        String key = keyBuf.toString();
        if (key.charAt(0) == '#') {
            try {
                if (key.charAt(1) == 'x') {
                    ch = (char) Integer.parseInt(key.substring(2), 16);
                } else {
                    ch = (char) Integer.parseInt(key.substring(1), 10);
                }
            } catch (NumberFormatException e) {
                throw this.unknownEntity(key);
            }
            buf.append(ch);
        } else {
            char[] value = (char[]) this.entities.get(key);
            if (value == null) {
                throw this.unknownEntity(key);
            }
            buf.append(value);
        }
    }


    /**
     * Pushes a character back to the read-back buffer.
     *
     * @param ch The character to push back.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li>The read-back buffer is empty.
     *     <li><code>ch != '\0'</code>
     * </ul></dd></dl>
     */
    protected void unreadChar(char ch)
    {
        this.charReadTooMuch = ch;
    }


    /**
     * Creates a parse exception for when an invalid valueset is given to
     * a method.
     *
     * @param name The name of the entity.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>name != null</code>
     * </ul></dd></dl>
     */
    protected XMLParseException invalidValueSet(String name)
    {
        String msg = "Invalid value set (entity name = \"" + name + "\")";
        return new XMLParseException(this.getName(), this.parserLineNr, msg);
    }


    /**
     * Creates a parse exception for when an invalid value is given to a
     * method.
     *
     * @param name  The name of the entity.
     * @param value The value of the entity.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>name != null</code>
     *     <li><code>value != null</code>
     * </ul></dd></dl>
     */
    protected XMLParseException invalidValue(String name,
                                             String value)
    {
        String msg = "Attribute \"" + name + "\" does not contain a valid "
                   + "value (\"" + value + "\")";
        return new XMLParseException(this.getName(), this.parserLineNr, msg);
    }


    /**
     * Creates a parse exception for when the end of the data input has been
     * reached.
     */
    protected XMLParseException unexpectedEndOfData()
    {
        String msg = "Unexpected end of data reached";
        return new XMLParseException(this.getName(), this.parserLineNr, msg);
    }


    /**
     * Creates a parse exception for when a syntax error occured.
     *
     * @param context The context in which the error occured.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>context != null</code>
     *     <li><code>context.length() &gt; 0</code>
     * </ul></dd></dl>
     */
    protected XMLParseException syntaxError(String context)
    {
        String msg = "Syntax error while parsing " + context;
        return new XMLParseException(this.getName(), this.parserLineNr, msg);
    }


    /**
     * Creates a parse exception for when the next character read is not
     * the character that was expected.
     *
     * @param charSet The set of characters (in human readable form) that was
     *                expected.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>charSet != null</code>
     *     <li><code>charSet.length() &gt; 0</code>
     * </ul></dd></dl>
     */
    protected XMLParseException expectedInput(String charSet)
    {
        String msg = "Expected: " + charSet;
        return new XMLParseException(this.getName(), this.parserLineNr, msg);
    }

    /**
     * Creates a parse exception for when the next character read is not
     * the character that was expected.
     *
     * @param charSet The set of characters (in human readable form) that was
     *                expected.
     * @param ch The character that was received instead.
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>charSet != null</code>
     *     <li><code>charSet.length() &gt; 0</code>
     * </ul></dd></dl>
     */
    protected XMLParseException expectedInput(String charSet, char ch)
    {
        String msg = "Expected: '" + charSet +"'" + " but got: '" + ch + "'";
        return new XMLParseException(this.getName(), this.parserLineNr, msg);
    }

    /**
     * Creates a parse exception for when an entity could not be resolved.
     *
     * @param name The name of the entity.
     *
     * </dl><dl><dt><b>Preconditions:</b></dt><dd>
     * <ul><li><code>name != null</code>
     *     <li><code>name.length() &gt; 0</code>
     * </ul></dd></dl>
     */
    protected XMLParseException unknownEntity(String name)
    {
        String msg = "Unknown or invalid entity: &" + name + ";";
        return new XMLParseException(this.getName(), this.parserLineNr, msg);
    }

    /**
     * Reads an xml file and removes the comments, leaving only relevant
     * xml code.
     *
     * @param isr The reader of the InputStream containing the xml.
     * @param pout The PipedOutputStream that will be receiving the filtered
     *             xml file.
     */
    public void sanitizeInput(InputStreamReader isr, PipedOutputStream pout) {
        try {
            PrintStream out = new PrintStream(pout);

            this.sanitizeCharReadTooMuch = '\0';
            this.reader = isr;
            this.parserLineNr = 0;
            int newline = 2;
            char prev = ' ';

            while(true) {
                char ch;
                if (this.sanitizeCharReadTooMuch != '\0') {
                    ch = this.sanitizeCharReadTooMuch;
                    this.sanitizeCharReadTooMuch = '\0';
                } else {

                    int i = this.reader.read();
                    if (i == -1) {
                        // no character in buffer, and nothing read
                        out.flush();
                        break;
                    } else if (i == 10) {
                        ch = '\n';
                    } else {
                        ch = (char) i;
                    }
                }

                char next;
                int i = this.reader.read();
                if (i == -1) {
                    // character in buffer and nothing read. write out
                    // what's in the buffer
                    out.print(ch);
                    out.flush();
                    if (JNLPRuntime.isDebug()) {
                        if (ch == 10) {
                            System.out.println();
                            System.out.print("line: " + newline + " ");
                            newline++;
                        } else {
                            System.out.print(ch);
                        }
                    }
                    break;
                } else if (i == 10) {
                    next = '\n';
                } else {
                    next = (char) i;
                }

                this.sanitizeCharReadTooMuch = next;

                // If the next char is a ? or !, then we've hit a special tag,
                // and should skip it.
                if (prev == '<' && (next == '!' || next == '?')) {
                    this.skipSpecialTag(0);
                    this.sanitizeCharReadTooMuch = '\0';
                }
                // Otherwise we haven't hit a comment, and we should write ch.
                else {
                    out.print(ch);
                    if (JNLPRuntime.isDebug()) {
                        if (ch == 10) {
                            System.out.println();
                            System.out.print("line: " + newline + " ");
                            newline++;
                        } else {
                            System.out.print(ch);
                        }
                    }
                }
                prev = next;
            }

            out.close();
            isr.close();
        } catch (Exception e) {
            // Print the stack trace here -- xml.parseFromReader() will
            // throw the ParseException if something goes wrong.
            e.printStackTrace();
        }
    }
}
