htmldtd.java

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/*
 * Copyright 1999-2002,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


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


package com.sun.org.apache.xml.internal.serialize;

import com.sun.org.apache.xerces.internal.dom.DOMMessageFormatter;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.util.Hashtable;
import java.util.Locale;


/**
 * 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: 1.2.6.1 $ $Date: 2005/09/09 07:26:14 $
 * @author <a href="mailto:[e-mail]">Assaf Arkin</a>
 */
public final class HTMLdtd
{

    /**
     * Public identifier for HTML 4.01 (Strict) document type.
     */
    public static final String HTMLPublicId = "-//W3C//DTD HTML 4.01//EN";

    /**
     * System identifier for HTML 4.01 (Strict) document type.
     */
    public static final String HTMLSystemId =
        "http://www.w3.org/TR/html4/strict.dtd";

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

    /**
     * System identifier for XHTML 1.0 (Strict) document type.
     */
    public static final String XHTMLSystemId =
        "http://www.w3.org/TR/xhtml1/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 Hashtable        _byChar;


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


    private static Hashtable        _boolAttrs;


    /**
     * Holds element definitions.
     */
    private static Hashtable        _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
        if ( openTag.equalsIgnoreCase( "LI" ) || openTag.equalsIgnoreCase( "OPTION" ) )
            return isElement( tagName, CLOSE_SELF );
        // Each of these table sections closes all the others
        if ( openTag.equalsIgnoreCase( "THEAD" ) || openTag.equalsIgnoreCase( "TFOOT" ) ||
             openTag.equalsIgnoreCase( "TBODY" ) || openTag.equalsIgnoreCase( "TR" ) ||
             openTag.equalsIgnoreCase( "COLGROUP" ) )
            return isElement( tagName, CLOSE_TABLE );
        // TD closes TH and TH closes TD
        if ( openTag.equalsIgnoreCase( "TH" ) || openTag.equalsIgnoreCase( "TD" ) )
            return isElement( tagName, CLOSE_TH_TD );
        return false;
    }


    /**
     * Returns true if the specified attribute it a URI and should be
     * escaped appropriately. In HTML URIs are escaped differently
     * than normal attributes.
     *
     * @param tagName The element's tag name