/*
 * @(#)HTML.java	1.44 10/03/23
 *
 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package javax.swing.text.html;

import java.io.*;
import java.util.Hashtable;
import javax.swing.text.AttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyleContext;

/**
 * Constants used in the <code>HTMLDocument</code>.  These
 * are basically tag and attribute definitions.
 *
 * @author  Timothy Prinzing
 * @author  Sunita Mani
 *
 * @version 1.44 03/23/10
 */
public class HTML {

    /**
     * Typesafe enumeration for an HTML tag.  Although the
     * set of HTML tags is a closed set, we have left the
     * set open so that people can add their own tag types
     * to their custom parser and still communicate to the
     * reader.
     */
    public static class Tag {

	/** @since 1.3 */
	public Tag() {}

        /**
         * Creates a new <code>Tag</code> with the specified <code>id</code>,
         * and with <code>causesBreak</code> and <code>isBlock</code>
         * set to <code>false</code>.
         *
         * @param id  the id of the new tag
         */
        protected Tag(String id) {
	    this(id, false, false);
	}

        /**
         * Creates a new <code>Tag</code> with the specified <code>id</code>;
         * <code>causesBreak</code> and <code>isBlock</code> are defined
         * by the user.
         *
         * @param id the id of the new tag
         * @param causesBreak  <code>true</code> if this tag
         *    causes a break to the flow of data
         * @param isBlock <code>true</code> if the tag is used
         *    to add structure to a document
         */
	protected Tag(String id, boolean causesBreak, boolean isBlock) {
	    name = id;
	    this.breakTag = causesBreak;
	    this.blockTag = isBlock;
	}

	/**
         * Returns <code>true</code> if this tag is a block
         * tag, which is a tag used to add structure to a
         * document.
	 * 
         * @return <code>true</code> if this tag is a block
         *   tag, otherwise returns <code>false</code>
	 */
	public boolean isBlock() {
	    return blockTag;
	}

	/**
         * Returns <code>true</code> if this tag causes a
         * line break to the flow of data, otherwise returns
         * <code>false</code>.
	 * 
	 * @return <code>true</code> if this tag causes a
         *   line break to the flow of data, otherwise returns
         *   <code>false</code>
	 */
	public boolean breaksFlow() {
	    return breakTag;
	}

	/**
	 * Returns <code>true</code> if this tag is pre-formatted,
         * which is true if the tag is either <code>PRE</code> or
         * <code>TEXTAREA</code>.
         *
         * @return <code>true</code> if this tag is pre-formatted,
         *   otherwise returns <code>false</code>
	 */
	public boolean isPreformatted() {
	    return (this == PRE || this == TEXTAREA);
	}

	/**
	 * Returns the string representation of the
	 * tag.
         *
         * @return the <code>String</code> representation of the tag
	 */
        public String toString() {
	    return name;
	}

        /**
         * Returns <code>true</code> if this tag is considered to be a paragraph
         * in the internal HTML model. <code>false</code> - otherwise.
         *
         * @return <code>true</code> if this tag is considered to be a paragraph
         *         in the internal HTML model. <code>false</code> - otherwise.
         * @see javax.swing.text.html.HTMLDocument#HTMLReader#ParagraphAction
         */
        boolean isParagraph() {
            return (
                this == P 
                   || this == IMPLIED
                   || this == DT
                   || this == H1
                   || this == H2
                   || this == H3
                   || this == H4
                   || this == H5
                   || this == H6
            );
        }

	boolean blockTag;
	boolean breakTag;
	String name;
	boolean unknown;

    	// --- Tag Names -----------------------------------

    	public static final Tag A = new Tag("a");
    	public static final Tag ADDRESS = new Tag("address");
    	public static final Tag APPLET = new Tag("applet");
    	public static final Tag AREA = new Tag("area");
    	public static final Tag B = new Tag("b");
    	public static final Tag BASE = new Tag("base");
    	public static final Tag BASEFONT = new Tag("basefont");
    	public static final Tag BIG = new Tag("big");
    	public static final Tag BLOCKQUOTE = new Tag("blockquote", true, true);
    	public static final Tag BODY = new Tag("body", true, true);
    	public static final Tag BR = new Tag("br", true, false);
    	public static final Tag CAPTION = new Tag("caption");
    	public static final Tag CENTER = new Tag("center", true, false);
    	public static final Tag CITE = new Tag("cite");
    	public static final Tag CODE = new Tag("code");
    	public static final Tag DD = new Tag("dd", true, true);
    	public static final Tag DFN = new Tag("dfn");
    	public static final Tag DIR = new Tag("dir", true, true);
    	public static final Tag DIV = new Tag("div", true, true);
    	public static final Tag DL = new Tag("dl", true, true);
    	public static final Tag DT = new Tag("dt", true, true);
    	public static final Tag EM = new Tag("em");
    	public static final Tag FONT = new Tag("font");
    	public static final Tag FORM = new Tag("form", true, false);
	public static final Tag FRAME = new Tag("frame");
	public static final Tag FRAMESET = new Tag("frameset");
    	public static final Tag H1 = new Tag("h1", true, true);
    	public static final Tag H2 = new Tag("h2", true, true);
    	public static final Tag H3 = new Tag("h3", true, true);
    	public static final Tag H4 = new Tag("h4", true, true);
    	public static final Tag H5 = new Tag("h5", true, true);
    	public static final Tag H6 = new Tag("h6", true, true);
    	public static final Tag HEAD = new Tag("head", true, true);
    	public static final Tag HR = new Tag("hr", true, false);
    	public static final Tag HTML = new Tag("html", true, false);
    	public static final Tag I = new Tag("i");
    	public static final Tag IMG = new Tag("img");
    	public static final Tag INPUT = new Tag("input");
    	public static final Tag ISINDEX = new Tag("isindex", true, false);
    	public static final Tag KBD = new Tag("kbd");
    	public static final Tag LI = new Tag("li", true, true);
    	public static final Tag LINK = new Tag("link");
    	public static final Tag MAP = new Tag("map");
    	public static final Tag MENU = new Tag("menu", true, true);
    	public static final Tag META = new Tag("meta");
	/*public*/ static final Tag NOBR = new Tag("nobr");
	public static final Tag NOFRAMES = new Tag("noframes", true, true);
    	public static final Tag OBJECT = new Tag("object");
    	public static final Tag OL = new Tag("ol", true, true);
    	public static final Tag OPTION = new Tag("option");
    	public static final Tag P = new Tag("p", true, true);
    	public static final Tag PARAM = new Tag("param");
    	public static final Tag PRE = new Tag("pre", true, true);
    	public static final Tag SAMP = new Tag("samp");
    	public static final Tag SCRIPT = new Tag("script");
    	public static final Tag SELECT = new Tag("select");
    	public static final Tag SMALL = new Tag("small");
    	public static final Tag SPAN = new Tag("span");
    	public static final Tag STRIKE = new Tag("strike");
    	public static final Tag S = new Tag("s");
    	public static final Tag STRONG = new Tag("strong");
    	public static final Tag STYLE = new Tag("style");
    	public static final Tag SUB = new Tag("sub");
    	public static final Tag SUP = new Tag("sup");
    	public static final Tag TABLE = new Tag("table", false, true);
    	public static final Tag TD = new Tag("td", true, true);
    	public static final Tag TEXTAREA = new Tag("textarea");
    	public static final Tag TH = new Tag("th", true, true);
    	public static final Tag TITLE = new Tag("title", true, true);
    	public static final Tag TR = new Tag("tr", false, true);
    	public static final Tag TT = new Tag("tt");
    	public static final Tag U = new Tag("u");
    	public static final Tag UL = new Tag("ul", true, true);
    	public static final Tag VAR = new Tag("var");

	/**
	 * All text content must be in a paragraph element.
	 * If a paragraph didn't exist when content was
	 * encountered, a paragraph is manufactured.
	 * <p>
	 * This is a tag synthesized by the HTML reader.
	 * Since elements are identified by their tag type,
	 * we create a some fake tag types to mark the elements
	 * that were manufactured.
	 */
	public static final Tag IMPLIED = new Tag("p-implied");

	/**
	 * All text content is labeled with this tag.
	 * <p>
	 * This is a tag synthesized by the HTML reader.
	 * Since elements are identified by their tag type,
	 * we create a some fake tag types to mark the elements
	 * that were manufactured.
	 */
	public static final Tag CONTENT = new Tag("content");

	/**
	 * All comments are labeled with this tag.
	 * <p>
	 * This is a tag synthesized by the HTML reader.
	 * Since elements are identified by their tag type,
	 * we create a some fake tag types to mark the elements
	 * that were manufactured.
	 */
	public static final Tag COMMENT = new Tag("comment");

	static final Tag allTags[]  = {
	    A, ADDRESS, APPLET, AREA, B, BASE, BASEFONT, BIG,
	    BLOCKQUOTE, BODY, BR, CAPTION, CENTER, CITE, CODE,
	    DD, DFN, DIR, DIV, DL, DT, EM, FONT, FORM, FRAME,
	    FRAMESET, H1, H2, H3, H4, H5, H6, HEAD, HR, HTML,
	    I, IMG, INPUT, ISINDEX, KBD, LI, LINK, MAP, MENU,
	    META, NOBR, NOFRAMES, OBJECT, OL, OPTION, P, PARAM,
	    PRE, SAMP, SCRIPT, SELECT, SMALL, SPAN, STRIKE, S,
	    STRONG, STYLE, SUB, SUP, TABLE, TD, TEXTAREA,
	    TH, TITLE, TR, TT, U, UL, VAR	
	};

	static {
	    // Force HTMLs static initialize to be loaded.
	    getTag("html");
	}
    }

    // There is no unique instance of UnknownTag, so we allow it to be
    // Serializable.
    public static class UnknownTag extends Tag implements Serializable {
	
        /**
         * Creates a new <code>UnknownTag</code> with the specified
         * <code>id</code>.
         * @param id the id of the new tag
         */
	public UnknownTag(String id) {
	    super(id);
	}

        /**
         * Returns the hash code which corresponds to the string
         * for this tag.
         */
	public int hashCode() {
	    return toString().hashCode();
	}

	/**
	 * Compares this object to the specifed object.
	 * The result is <code>true</code> if and only if the argument is not
	 * <code>null</code> and is an <code>UnknownTag</code> object
         * with the same name.
         *
	 * @param     obj   the object to compare this tag with
	 * @return    <code>true</code> if the objects are equal;
	 *            <code>false</code> otherwise
	 */
        public boolean equals(Object obj) {
	    if (obj instanceof UnknownTag) {
		return toString().equals(obj.toString());
	    }
	    return false;
	}

	private void writeObject(java.io.ObjectOutputStream s)
	             throws IOException {
	    s.defaultWriteObject();
	    s.writeBoolean(blockTag);
	    s.writeBoolean(breakTag);
	    s.writeBoolean(unknown);
	    s.writeObject(name);
	}

	private void readObject(ObjectInputStream s)
	    throws ClassNotFoundException, IOException {
	    s.defaultReadObject();
	    blockTag = s.readBoolean();
	    breakTag = s.readBoolean();
	    unknown = s.readBoolean();
	    name = (String)s.readObject();
	}
    }

    /**
     * Typesafe enumeration representing an HTML
     * attribute.
     */
    public static final class Attribute {

        /**
         * Creates a new <code>Attribute</code> with the specified
         * <code>id</code>.
         *
         * @param id the id of the new <code>Attribute</code>
         */
	Attribute(String id) {
	    name = id;
	}

        /**
         * Returns the string representation of this attribute.
         * @return the string representation of this attribute
         */
	public String toString() {
	    return name;
	}

	private String name;

	public static final Attribute SIZE = new Attribute("size");
	public static final Attribute COLOR = new Attribute("color");
	public static final Attribute CLEAR = new Attribute("clear");
	public static final Attribute BACKGROUND = new Attribute("background");
	public static final Attribute BGCOLOR = new Attribute("bgcolor");
	public static final Attribute TEXT = new Attribute("text");
	public static final Attribute LINK = new Attribute("link");
	public static final Attribute VLINK = new Attribute("vlink");
	public static final Attribute ALINK = new Attribute("alink");
	public static final Attribute WIDTH = new Attribute("width");
	public static final Attribute HEIGHT = new Attribute("height");
	public static final Attribute ALIGN = new Attribute("align");
	public static final Attribute NAME = new Attribute("name");
	public static final Attribute HREF = new Attribute("href");
	public static final Attribute REL = new Attribute("rel");
	public static final Attribute REV = new Attribute("rev");
	public static final Attribute TITLE = new Attribute("title");
	public static final Attribute TARGET = new Attribute("target");
	public static final Attribute SHAPE = new Attribute("shape");
	public static final Attribute COORDS = new Attribute("coords");
	public static final Attribute ISMAP = new Attribute("ismap");
	public static final Attribute NOHREF = new Attribute("nohref");
	public static final Attribute ALT = new Attribute("alt");
	public static final Attribute ID = new Attribute("id");
	public static final Attribute SRC = new Attribute("src");
	public static final Attribute HSPACE = new Attribute("hspace");
	public static final Attribute VSPACE = new Attribute("vspace");
	public static final Attribute USEMAP = new Attribute("usemap");
	public static final Attribute LOWSRC = new Attribute("lowsrc");
	public static final Attribute CODEBASE = new Attribute("codebase");
	public static final Attribute CODE = new Attribute("code");
	public static final Attribute ARCHIVE = new Attribute("archive");
	public static final Attribute VALUE = new Attribute("value");
	public static final Attribute VALUETYPE = new Attribute("valuetype");
	public static final Attribute TYPE = new Attribute("type");
	public static final Attribute CLASS = new Attribute("class");
	public static final Attribute STYLE = new Attribute("style");
	public static final Attribute LANG = new Attribute("lang");
	public static final Attribute FACE = new Attribute("face");
	public static final Attribute DIR = new Attribute("dir");
	public static final Attribute DECLARE = new Attribute("declare");
	public static final Attribute CLASSID = new Attribute("classid");
	public static final Attribute DATA = new Attribute("data");
	public static final Attribute CODETYPE = new Attribute("codetype");
	public static final Attribute STANDBY = new Attribute("standby");
	public static final Attribute BORDER = new Attribute("border");
	public static final Attribute SHAPES = new Attribute("shapes");
	public static final Attribute NOSHADE = new Attribute("noshade");
	public static final Attribute COMPACT = new Attribute("compact");
	public static final Attribute START = new Attribute("start");
	public static final Attribute ACTION = new Attribute("action");
	public static final Attribute METHOD = new Attribute("method");
	public static final Attribute ENCTYPE = new Attribute("enctype");
	public static final Attribute CHECKED = new Attribute("checked");
	public static final Attribute MAXLENGTH = new Attribute("maxlength");
	public static final Attribute MULTIPLE = new Attribute("multiple");
	public static final Attribute SELECTED = new Attribute("selected");
	public static final Attribute ROWS = new Attribute("rows");
	public static final Attribute COLS = new Attribute("cols");
	public static final Attribute DUMMY = new Attribute("dummy");
	public static final Attribute CELLSPACING = new Attribute("cellspacing");
	public static final Attribute CELLPADDING = new Attribute("cellpadding");
	public static final Attribute VALIGN = new Attribute("valign");
	public static final Attribute HALIGN = new Attribute("halign");
	public static final Attribute NOWRAP = new Attribute("nowrap");
	public static final Attribute ROWSPAN = new Attribute("rowspan");
	public static final Attribute COLSPAN = new Attribute("colspan");
	public static final Attribute PROMPT = new Attribute("prompt");
	public static final Attribute HTTPEQUIV = new Attribute("http-equiv");
	public static final Attribute CONTENT = new Attribute("content");
	public static final Attribute LANGUAGE = new Attribute("language");
	public static final Attribute VERSION = new Attribute("version");
	public static final Attribute N = new Attribute("n");
	public static final Attribute FRAMEBORDER = new Attribute("frameborder");
	public static final Attribute MARGINWIDTH = new Attribute("marginwidth");
	public static final Attribute MARGINHEIGHT = new Attribute("marginheight");
	public static final Attribute SCROLLING = new Attribute("scrolling");
	public static final Attribute NORESIZE = new Attribute("noresize");
	public static final Attribute ENDTAG = new Attribute("endtag");
	public static final Attribute COMMENT = new Attribute("comment");
	static final Attribute MEDIA = new Attribute("media");

	static final Attribute allAttributes[] = {
	    FACE,
	    COMMENT,
	    SIZE,
	    COLOR,
	    CLEAR,
	    BACKGROUND,
	    BGCOLOR,
	    TEXT,
	    LINK,
	    VLINK,
	    ALINK,
	    WIDTH,
	    HEIGHT,
	    ALIGN,
	    NAME,
	    HREF,
            REL,
            REV,
            TITLE,
            TARGET,
            SHAPE,
            COORDS,
            ISMAP,
            NOHREF,
            ALT,
            ID,
            SRC,
            HSPACE,
            VSPACE,
            USEMAP,
            LOWSRC,
            CODEBASE,
            CODE,
            ARCHIVE,
            VALUE,
            VALUETYPE,
            TYPE,
            CLASS,
            STYLE,
            LANG,
            DIR,
            DECLARE,
            CLASSID,
            DATA,
            CODETYPE,
            STANDBY,
            BORDER,
            SHAPES,
            NOSHADE,
            COMPACT,
            START,
            ACTION,
            METHOD,
            ENCTYPE,
            CHECKED,
            MAXLENGTH,
            MULTIPLE,
            SELECTED,
            ROWS,
            COLS,
            DUMMY,
            CELLSPACING,
            CELLPADDING,
            VALIGN,
            HALIGN,
            NOWRAP,
            ROWSPAN,
            COLSPAN,
            PROMPT,
            HTTPEQUIV,
            CONTENT,
            LANGUAGE,
            VERSION,
            N,
            FRAMEBORDER,
            MARGINWIDTH,
            MARGINHEIGHT,
            SCROLLING,
            NORESIZE,
            MEDIA,
	    ENDTAG
	};
    }

    // The secret to 73, is that, given that the Hashtable contents
    // never change once the static initialization happens, the initial size 
    // that the hashtable grew to was determined, and then that very size
    // is used.
    //
    private static final Hashtable tagHashtable = new Hashtable(73);

    /** Maps from StyleConstant key to HTML.Tag. */
    private static final Hashtable scMapping = new Hashtable(8);

    static {

	for (int i = 0; i < Tag.allTags.length; i++ ) {
	    tagHashtable.put(Tag.allTags[i].toString(), Tag.allTags[i]);
	    StyleContext.registerStaticAttributeKey(Tag.allTags[i]);
	}
	StyleContext.registerStaticAttributeKey(Tag.IMPLIED);
	StyleContext.registerStaticAttributeKey(Tag.CONTENT);
	StyleContext.registerStaticAttributeKey(Tag.COMMENT);
	for (int i = 0; i < Attribute.allAttributes.length; i++) {
	    StyleContext.registerStaticAttributeKey(Attribute.
						    allAttributes[i]);
	}
	StyleContext.registerStaticAttributeKey(HTML.NULL_ATTRIBUTE_VALUE);
        scMapping.put(StyleConstants.Bold, Tag.B);
        scMapping.put(StyleConstants.Italic, Tag.I);
        scMapping.put(StyleConstants.Underline, Tag.U);
        scMapping.put(StyleConstants.StrikeThrough, Tag.STRIKE);
        scMapping.put(StyleConstants.Superscript, Tag.SUP);
        scMapping.put(StyleConstants.Subscript, Tag.SUB);
        scMapping.put(StyleConstants.FontFamily, Tag.FONT);
        scMapping.put(StyleConstants.FontSize, Tag.FONT);
    }

    /**
     * Returns the set of actual HTML tags that
     * are recognized by the default HTML reader.
     * This set does not include tags that are
     * manufactured by the reader.
     */
    public static Tag[] getAllTags() {
	Tag[] tags = new Tag[Tag.allTags.length];
	System.arraycopy(Tag.allTags, 0, tags, 0, Tag.allTags.length);
	return tags;
    }

    /**
     * Fetches a tag constant for a well-known tag name (i.e. one of
     * the tags in the set {A, ADDRESS, APPLET, AREA, B,
     * BASE, BASEFONT, BIG,
     * BLOCKQUOTE, BODY, BR, CAPTION, CENTER, CITE, CODE,
     * DD, DFN, DIR, DIV, DL, DT, EM, FONT, FORM, FRAME,
     * FRAMESET, H1, H2, H3, H4, H5, H6, HEAD, HR, HTML,
     * I, IMG, INPUT, ISINDEX, KBD, LI, LINK, MAP, MENU,
     * META, NOBR, NOFRAMES, OBJECT, OL, OPTION, P, PARAM,
     * PRE, SAMP, SCRIPT, SELECT, SMALL, SPAN, STRIKE, S,
     * STRONG, STYLE, SUB, SUP, TABLE, TD, TEXTAREA,
     * TH, TITLE, TR, TT, U, UL, VAR}.  If the given
     * name does not represent one of the well-known tags, then
     * <code>null</code> will be returned.
     *
     * @param tagName the <code>String</code> name requested
     * @return a tag constant corresponding to the <code>tagName</code>,
     *    or <code>null</code> if not found
     */
    public static Tag getTag(String tagName) {

	Object t =  tagHashtable.get(tagName);
	return (t == null ? null : (Tag)t);
    }

    /**
     * Returns the HTML <code>Tag</code> associated with the
     * <code>StyleConstants</code> key <code>sc</code>.
     * If no matching <code>Tag</code> is found, returns
     * <code>null</code>.
     *
     * @param sc the <code>StyleConstants</code> key
     * @return tag which corresponds to <code>sc</code>, or
     *   <code>null</code> if not found
     */
    static Tag getTagForStyleConstantsKey(StyleConstants sc) {
        return (Tag)scMapping.get(sc);
    }

    /**
     * Fetches an integer attribute value.  Attribute values
     * are stored as a string, and this is a convenience method
     * to convert to an actual integer.
     *
     * @param attr the set of attributes to use to try to fetch a value
     * @param key the key to use to fetch the value
     * @param def the default value to use if the attribute isn't
     *  defined or there is an error converting to an integer
     */
    public static int getIntegerAttributeValue(AttributeSet attr,
					       Attribute key, int def) {
	int value = def;
	String istr = (String) attr.getAttribute(key);
	if (istr != null) {
	    try {
		value = Integer.valueOf(istr).intValue();
	    } catch (NumberFormatException e) {
		value = def;
	    }
	}
	return value;
    }

    //  This is used in cases where the value for the attribute has not
    //  been specified.
    //
    public static final String NULL_ATTRIBUTE_VALUE = "#DEFAULT";

    // size determined similar to size of tagHashtable
    private static final Hashtable attHashtable = new Hashtable(77);

    static {

	for (int i = 0; i < Attribute.allAttributes.length; i++ ) {
	    attHashtable.put(Attribute.allAttributes[i].toString(), Attribute.allAttributes[i]);
	}
    }

    /**
     * Returns the set of HTML attributes recognized.
     * @return the set of HTML attributes recognized
     */
    public static Attribute[] getAllAttributeKeys() {
	Attribute[] attributes = new Attribute[Attribute.allAttributes.length];
	System.arraycopy(Attribute.allAttributes, 0, 
			 attributes, 0, Attribute.allAttributes.length);
	return attributes;
    }

    /**
     * Fetches an attribute constant for a well-known attribute name
     * (i.e. one of the attributes in the set {FACE, COMMENT, SIZE,
     * COLOR, CLEAR, BACKGROUND, BGCOLOR, TEXT, LINK, VLINK, ALINK,
     * WIDTH, HEIGHT, ALIGN, NAME, HREF, REL, REV, TITLE, TARGET,
     * SHAPE, COORDS, ISMAP, NOHREF, ALT, ID, SRC, HSPACE, VSPACE,
     * USEMAP, LOWSRC, CODEBASE, CODE, ARCHIVE, VALUE, VALUETYPE,
     * TYPE, CLASS, STYLE, LANG, DIR, DECLARE, CLASSID, DATA, CODETYPE,
     * STANDBY, BORDER, SHAPES, NOSHADE, COMPACT, START, ACTION, METHOD,
     * ENCTYPE, CHECKED, MAXLENGTH, MULTIPLE, SELECTED, ROWS, COLS,
     * DUMMY, CELLSPACING, CELLPADDING, VALIGN, HALIGN, NOWRAP, ROWSPAN,
     * COLSPAN, PROMPT, HTTPEQUIV, CONTENT, LANGUAGE, VERSION, N,
     * FRAMEBORDER, MARGINWIDTH, MARGINHEIGHT, SCROLLING, NORESIZE,
     * MEDIA, ENDTAG}).
     * If the given name does not represent one of the well-known attributes,
     * then <code>null</code> will be returned.
     *
     * @param attName the <code>String</code> requested
     * @return the <code>Attribute</code> corresponding to <code>attName</code>
     */
    public static Attribute getAttributeKey(String attName) {
	Object a = attHashtable.get(attName);
	if (a == null) {
	  return null;
	}
	return (Attribute)a;
    }

}
