helper.java

已经移植好的java虚拟机

/*
 *  Copyright (c) 1999-2001 Sun Microsystems, Inc., 901 San Antonio Road,
 *  Palo Alto, CA 94303, U.S.A.  All Rights Reserved.
 *
 *  Sun Microsystems, Inc. has intellectual property rights relating
 *  to the technology embodied in this software.  In particular, and
 *  without limitation, these intellectual property rights may include
 *  one or more U.S. patents, foreign patents, or pending
 *  applications.  Sun, Sun Microsystems, the Sun logo, Java, KJava,
 *  and all Sun-based and Java-based marks are trademarks or
 *  registered trademarks of Sun Microsystems, Inc.  in the United
 *  States and other countries.
 *
 *  This software is distributed under licenses restricting its use,
 *  copying, distribution, and decompilation.  No part of this
 *  software may be reproduced in any form by any means without prior
 *  written authorization of Sun and its licensors, if any.
 *
 *  FEDERAL ACQUISITIONS:  Commercial Software -- Government Users
 *  Subject to Standard License Terms and Conditions
 */

package com.sun.cldc.i18n;

import java.io.*;

/**
 * This class provides general helper functions for the J2ME environment.
 * <p>
 * <em>No application code should reference this class directly.</em>
 *
 * @version 2.0 05/04/01
 */
public class Helper {

    /**
     * The name of the default character encoding
     */
    private static String defaultEncoding;

    /**
     * Default path to the J2ME classes
     */
    private static String defaultMEPath;

    /**
     * True if we are running on a J2ME system
     */
    private static boolean j2me = false;

    /**
     * Class initializer
     */
    static {
        /* Get the default encoding name */
        defaultEncoding = System.getProperty("microedition.encoding");
        if (defaultEncoding == null) {
            defaultEncoding = "ISO8859_1";
        }

        /* Work out if we are running on a J2ME system */
        if (System.getProperty("microedition.configuration") != null) {
            j2me = true;
        }

        /*  Get the default encoding name */
        defaultMEPath = System.getProperty("com.sun.cldc.i18n.Helper.i18npath");
        if (defaultMEPath == null) {
            defaultMEPath = "com.sun.cldc.i18n.j2me";
        }
    }

/*------------------------------------------------------------------------------*/
/*                               Character encoding                             */
/*------------------------------------------------------------------------------*/


    /**
     * Get a reader for an InputStream
     *
     * @param  is              The input stream the reader is for
     * @return                 A new reader for the stream
     */
    public static Reader getStreamReader(InputStream is) {
        try {
            return getStreamReader(is, defaultEncoding);
        } catch(UnsupportedEncodingException x) {
            try {
                defaultEncoding = "ISO8859_1";
                return getStreamReader(is, defaultEncoding);
            } catch(UnsupportedEncodingException e) {
                throw new RuntimeException("Missing default encoding "+defaultEncoding);
            }
        }
    }

    /**
     * Get a reader for an InputStream
     *
     * @param  is              The input stream the reader is for
     * @param  name            The name of the decoder
     * @return                 A new reader for the stream
     * @exception UnsupportedEncodingException  If the encoding is not known
     */
    public static Reader getStreamReader(InputStream is, String name) throws UnsupportedEncodingException {

        /* Test for null arguments */
        if(is == null || name == null) {
            throw new NullPointerException();
        }

        /* Get the reader from the encoding */
        StreamReader fr = getStreamReaderPrim(name);

        /* Open the connection and return*/
        return fr.open(is, name);
    }


    /**
     * Get a reader for an InputStream
     *
     * @param  is              The input stream the reader is for
     * @param  name            The name of the decoder
     * @return                 A new reader for the stream
     * @exception UnsupportedEncodingException  If the encoding is not known
     */
    private static StreamReader getStreamReaderPrim(String name) throws UnsupportedEncodingException {

        if(name == null) {
            throw new NullPointerException();
        }

        name = internalNameForEncoding(name);

        try {
             String className;

             /* Get the reader class name */
             if(j2me) {
                 className = defaultMEPath + '.' + name + "_Reader";
             } else {
                 className = "com.sun.cldc.i18n.j2se.Default_Reader";
             }

            /* Using the decoder names lookup a class to implement the reader */
            Class clazz = Class.forName(className);

            /* Return a new instance */
            return (StreamReader)clazz.newInstance();

        } catch(ClassNotFoundException x) {
            throw new UnsupportedEncodingException("Encoding "+name+" not found");
        } catch(InstantiationException x) {
            throw new RuntimeException("InstantiationException "+x.getMessage());
        } catch(IllegalAccessException x) {
            throw new RuntimeException("IllegalAccessException "+x.getMessage());
        } catch(ClassCastException x) {
            throw new RuntimeException("ClassCastException "+x.getMessage());
        }
    }


    /**
     * Get a writer for an OutputStream
     *
     * @param  os              The output stream the reader is for
     * @return                 A new writer for the stream
     */
    public static Writer getStreamWriter(OutputStream os) {
        try {
            return getStreamWriter(os, defaultEncoding);
        } catch(UnsupportedEncodingException x) {
            try {
                defaultEncoding = "ISO8859_1";
                return getStreamWriter(os, defaultEncoding);
            } catch(UnsupportedEncodingException e) {
                throw new RuntimeException("Missing default encoding "+defaultEncoding);
            }
        }
    }


    /**
     * Get a writer for an OutputStream
     *
     * @param  os              The output stream the reader is for
     * @param  name            The name of the decoder
     * @return                 A new writer for the stream
     * @exception UnsupportedEncodingException  If the encoding is not known
     */
    public static Writer getStreamWriter(OutputStream os, String name) throws UnsupportedEncodingException {

        /* Test for null arguments */
        if(os == null || name == null) {
            throw new NullPointerException();
        }

        /* Get the writer from the encoding */
        StreamWriter sw = getStreamWriterPrim(name);

        /* Open it on the output stream and return */
        return sw.open(os, name);
    }

    /**
     * Get a writer for an OutputStream
     *
     * @param  os              The output stream the reader is for
     * @param  name            The name of the decoder
     * @return                 A new writer for the stream
     * @exception UnsupportedEncodingException  If the encoding is not known
     */
    private static StreamWriter getStreamWriterPrim(String name) throws UnsupportedEncodingException {

        if(name == null) {
            throw new NullPointerException();
        }

        name = internalNameForEncoding(name);

        try {
             String className;

             /* Get the writer class name */
             if(j2me) {
                 className = defaultMEPath + '.' + name +"_Writer";
             } else {
                 className = "com.sun.cldc.i18n.j2se.Default_Writer";
             }

            /* Using the decoder names lookup a class to implement the writer */
            Class clazz = Class.forName(className);