htmldtd.java

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/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xerces" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, International
 * Business Machines, Inc., http://www.apache.org.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */


// Aug 21, 2000:
//   Fixed bug in isElement and made HTMLdtd public.
//   Contributed by Eric SCHAEFFER" <[e-mail]>


package org.jasig.portal.serialize;


import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;


/**
 * Utility class for accessing information specific to HTML documents.
 * The HTML DTD is expressed as three utility function groups. Two methods
 * allow for checking whether an element requires an open tag on printing
 * ({@link #isEmptyTag}) or on parsing ({@link #isOptionalClosing}).
 * <P>
 * Two other methods translate character references from name to value and
 * from value to name. A small entities resource is loaded into memory the
 * first time any of these methods is called for fast and efficient access.
 *
 *
 * @version $Revision: 1.3 $ $Date: 2004/01/10 01:45:00 $
 * @author <a href="mailto:[e-mail]">Assaf Arkin</a>
 */
public final class HTMLdtd
{

    /**
     * Public identifier for HTML document type.
     */
    public static final String HTMLPublicId = "-//W3C//DTD HTML 4.0//EN";

    /**
     * System identifier for HTML document type.
     */
    public static final String HTMLSystemId =
        "http://www.w3.org/TR/WD-html-in-xml/DTD/xhtml1-strict.dtd";

    /**
     * Public identifier for XHTML document type.
     */
    public static final String XHTMLPublicId =
        "-//W3C//DTD XHTML 1.0 Strict//EN";

    /**
     * System identifier for XHTML document type.
     */
    public static final String XHTMLSystemId =
        "http://www.w3.org/TR/WD-html-in-xml/DTD/xhtml1-strict.dtd";
    /**
     * Table of reverse character reference mapping. Character codes are held
     * as single-character strings, mapped to their reference name.
     */
    private static Map        _byChar;


    /**
     * Table of entity name to value mapping. Entities are held as strings,
     * character references as <TT>Character</TT> objects.
     */
    private static Map        _byName;


    private static Map        _boolAttrs;


    /**
     * Holds element definitions.
     */
    private static Map        _elemDefs;


    /**
     * Locates the HTML entities file that is loaded upon initialization.
     * This file is a resource loaded with the default class loader.
     */
    private static final String     ENTITIES_RESOURCE = "HTMLEntities.res";


    /**
     * Only opening tag should be printed.
     */
    private static final int ONLY_OPENING = 0x0001;

    /**
     * Element contains element content only.
     */
    private static final int ELEM_CONTENT = 0x0002;


    /**
     * Element preserve spaces.
     */
    private static final int PRESERVE     = 0x0004;


    /**
     * Optional closing tag.
     */
    private static final int OPT_CLOSING  = 0x0008;


    /**
     * Element is empty (also means only opening tag)
     */
    private static final int EMPTY        = 0x0010 | ONLY_OPENING;


    /**
     * Allowed to appear in head.
     */
    private static final int ALLOWED_HEAD = 0x0020;


    /**
     * When opened, closes P.
     */
    private static final int CLOSE_P      = 0x0040;


    /**
     * When opened, closes DD or DT.
     */
    private static final int CLOSE_DD_DT  = 0x0080;


    /**
     * When opened, closes itself.
     */
    private static final int CLOSE_SELF   = 0x0100;


    /**
     * When opened, closes another table section.
     */
    private static final int CLOSE_TABLE  = 0x0200;


    /**
     * When opened, closes TH or TD.
     */
    private static final int CLOSE_TH_TD  = 0x04000;


    /**
     * Returns true if element is declared to be empty. HTML elements are
     * defines as empty in the DTD, not by the document syntax.
     *
     * @param tagName The element tag name (upper case)
     * @return True if element is empty
     */
    public static boolean isEmptyTag( String tagName )
    {
        return isElement( tagName, EMPTY );
    }


    /**
     * Returns true if element is declared to have element content.
     * Whitespaces appearing inside element content will be ignored,
     * other text will simply report an error.
     *
     * @param tagName The element tag name (upper case)
     * @return True if element content
     */
    public static boolean isElementContent( String tagName )
    {
        return isElement( tagName, ELEM_CONTENT );
    }


    /**
     * Returns true if element's textual contents preserves spaces.
     * This only applies to PRE and TEXTAREA, all other HTML elements
     * do not preserve space.
     *
     * @param tagName The element tag name (upper case)
     * @return True if element's text content preserves spaces
     */
    public static boolean isPreserveSpace( String tagName )
    {
        return isElement( tagName, PRESERVE );
    }


    /**
     * Returns true if element's closing tag is optional and need not
     * exist. An error will not be reported for such elements if they
     * are not closed. For example, <tt>LI</tt> is most often not closed.
     *
     * @param tagName The element tag name (upper case)
     * @return True if closing tag implied
     */
    public static boolean isOptionalClosing( String tagName )
    {
        return isElement( tagName, OPT_CLOSING );
    }


    /**
     * Returns true if element's closing tag is generally not printed.
     * For example, <tt>LI</tt> should not print the closing tag.
     *
     * @param tagName The element tag name (upper case)
     * @return True if only opening tag should be printed
     */
    public static boolean isOnlyOpening( String tagName )
    {
        return isElement( tagName, ONLY_OPENING );
    }


    /**
     * Returns true if the opening of one element (<tt>tagName</tt>) implies
     * the closing of another open element (<tt>openTag</tt>). For example,
     * every opening <tt>LI</tt> will close the previously open <tt>LI</tt>,
     * and every opening <tt>BODY</tt> will close the previously open <tt>HEAD</tt>.
     *
     * @param tagName The newly opened element
     * @param openTag The already opened element
     * @return True if closing tag closes opening tag
     */
    public static boolean isClosing( String tagName, String openTag )
    {
        // Several elements are defined as closing the HEAD
        if ( openTag.equalsIgnoreCase( "HEAD" ) )
            return ! isElement( tagName, ALLOWED_HEAD );
        // P closes iteself
        if ( openTag.equalsIgnoreCase( "P" ) )
            return isElement( tagName, CLOSE_P );
        // DT closes DD, DD closes DT
        if ( openTag.equalsIgnoreCase( "DT" ) || openTag.equalsIgnoreCase( "DD" ) )
            return isElement( tagName, CLOSE_DD_DT );
        // LI and OPTION close themselves