encodings.java

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/*
 * Copyright 1999-2004 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.
 */
/*
 * $Id: Encodings.java,v 1.3 2005/09/28 13:49:04 pvedula Exp $
 */
package com.sun.org.apache.xml.internal.serializer;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Properties;
import java.util.StringTokenizer;
import java.security.PrivilegedAction;
import java.security.AccessController;


/**
 * Provides information about encodings. Depends on the Java runtime
 * to provides writers for the different encodings, but can be used
 * to override encoding names and provide the last printable character
 * for each encoding.
 *
 * @version $Revision: 1.3 $ $Date: 2005/09/28 13:49:04 $
 * @author <a href="mailto:[e-mail]">Assaf Arkin</a>
 */

public final class Encodings extends Object
{

    /**
     * The last printable character for unknown encodings.
     */
    private static final int m_defaultLastPrintable = 0x7F;

    /**
     * Standard filename for properties file with encodings data.
     */
    private static final String ENCODINGS_FILE = "com/sun/org/apache/xml/internal/serializer/Encodings.properties";

    /**
     * Standard filename for properties file with encodings data.
     */
    private static final String ENCODINGS_PROP = "com.sun.org.apache.xalan.internal.serialize.encodings";

    
    /**
     * Returns a writer for the specified encoding based on
     * an output stream.
     *
     * @param output The output stream
     * @param encoding The encoding
     * @return A suitable writer
     * @throws UnsupportedEncodingException There is no convertor
     *  to support this encoding
     */
    static Writer getWriter(OutputStream output, String encoding)
        throws UnsupportedEncodingException
    {

        for (int i = 0; i < _encodings.length; ++i)
        {
            if (_encodings[i].name.equalsIgnoreCase(encoding))
            {
                try
                {
                    return new OutputStreamWriter(
                        output,
                        _encodings[i].javaName);
                }
                catch (java.lang.IllegalArgumentException iae) // java 1.1.8
                {
                    // keep trying
                }
                catch (UnsupportedEncodingException usee)
                {

                    // keep trying
                }
            }
        }

        try
        {
            return new OutputStreamWriter(output, encoding);
        }
        catch (java.lang.IllegalArgumentException iae) // java 1.1.8
        {
            throw new UnsupportedEncodingException(encoding);
        }
    }
    

    /**
     * Returns the last printable character for an unspecified
     * encoding.
     *
     * @return the default size
     */
    public static int getLastPrintable()
    {
        return m_defaultLastPrintable;
    }
    
    
    
    /**
     * Returns the EncodingInfo object for the specified
     * encoding.
     * <p>
     * This is not a public API.
     *
     * @param encoding The encoding
     * @return The object that is used to determine if 
     * characters are in the given encoding.
     * @xsl.usage internal
     */
    static EncodingInfo getEncodingInfo(String encoding)
    {
        EncodingInfo ei;

        String normalizedEncoding = toUpperCaseFast(encoding);
        ei = (EncodingInfo) _encodingTableKeyJava.get(normalizedEncoding);
        if (ei == null)
            ei = (EncodingInfo) _encodingTableKeyMime.get(normalizedEncoding);
        if (ei == null) {
            // We shouldn't have to do this, but just in case.
            ei = new EncodingInfo(null,null);
        }

        return ei;
    }
 
    /**
     * A fast and cheap way to uppercase a String that is
     * only made of printable ASCII characters.
     * <p>
     * This is not a public API.
     * @param s a String of ASCII characters
     * @return an uppercased version of the input String,
     * possibly the same String.
     * @xsl.usage internal
     */
    static private String toUpperCaseFast(final String s) {

    	boolean different = false;
    	final int mx = s.length();
		char[] chars = new char[mx];
    	for (int i=0; i < mx; i++) {
    		char ch = s.charAt(i);
            // is the character a lower case ASCII one?
    		if ('a' <= ch && ch <= 'z') {
                // a cheap and fast way to uppercase that is good enough
    			ch = (char) (ch + ('A' - 'a'));
    			different = true; // the uppercased String is different
    		}
    		chars[i] = ch;
    	}
    	
    	// A little optimization, don't call String.valueOf() if
    	// the uppercased string is the same as the input string.
    	final String upper;
    	if (different) 
    		upper = String.valueOf(chars);
    	else
    		upper = s;
    		
    	return upper;
    }

    /** The default encoding, ISO style, ISO style.   */
    static final String DEFAULT_MIME_ENCODING = "UTF-8";

    /**
     * Get the proper mime encoding.  From the XSLT recommendation: "The encoding
     * attribute specifies the preferred encoding to use for outputting the result
     * tree. XSLT processors are required to respect values of UTF-8 and UTF-16.
     * For other values, if the XSLT processor does not support the specified
     * encoding it may signal an error; if it does not signal an error it should
     * use UTF-8 or UTF-16 instead. The XSLT processor must not use an encoding
     * whose name does not match the EncName production of the XML Recommendation
     * [XML]. If no encoding attribute is specified, then the XSLT processor should
     * use either UTF-8 or UTF-16."
     *
     * @param encoding Reference to java-style encoding string, which may be null,
     * in which case a default will be found.
     *
     * @return The ISO-style encoding string, or null if failure.
     */
    static String getMimeEncoding(String encoding)
    {

        if (null == encoding)
        {
            try
            {

                // Get the default system character encoding.  This may be
                // incorrect if they passed in a writer, but right now there
                // seems to be no way to get the encoding from a writer.
                encoding = System.getProperty("file.encoding", "UTF8");

                if (null != encoding)
                {

                    /*
                    * See if the mime type is equal to UTF8.  If you don't
                    * do that, then  convertJava2MimeEncoding will convert
                    * 8859_1 to "ISO-8859-1", which is not what we want,
                    * I think, and I don't think I want to alter the tables
                    * to convert everything to UTF-8.
                    */
                    String jencoding =
                        (encoding.equalsIgnoreCase("Cp1252")