base64.java

这是一个segy数据显示程序

/* ========================================================================
 * JCommon : a free general purpose class library for the Java(tm) platform
 * ========================================================================
 *
 * (C) Copyright 2000-2004, by Object Refinery Limited and Contributors.
 * 
 * Project Info:  http://www.jfree.org/jcommon/index.html
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 * 
 * -------------------------------------
 * AbstractElementDefinitionHandler.java
 * -------------------------------------
 * (C)opyright 2003, by Thomas Morgner and Contributors.
 *
 * Original Author:  Kevin Kelley <[e-mail]> -
 *                   30718 Rd. 28, La Junta, CO, 81050  USA. 
 *
 * $Id: Base64.java,v 1.11 2004/04/26 19:40:15 taqua Exp $
 *
 * Changes
 * -------------------------
 * 23.09.2003 : Initial version
 *
 */
package org.jfree.xml.util;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.CharArrayWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;

/**
 * Provides encoding of raw bytes to base64-encoded characters, and
 * decoding of base64 characters to raw bytes.
 * date: 06 August 1998
 * modified: 14 February 2000
 * modified: 22 September 2000
 *
 * @author Kevin Kelley ([e-mail])
 * @version 1.3
 */
public class Base64 {

    /**
     * returns an array of base64-encoded characters to represent the
     * passed data array.
     *
     * @param data the array of bytes to encode
     * @return base64-coded character array.
     */
    public static char[] encode(final byte[] data) {
        final char[] out = new char[((data.length + 2) / 3) * 4];

        //
        // 3 bytes encode to 4 chars.  Output is always an even
        // multiple of 4 characters.
        //
        for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
            boolean quad = false;
            boolean trip = false;

            int val = (0xFF & data[i]);
            val <<= 8;
            if ((i + 1) < data.length) {
                val |= (0xFF & data[i + 1]);
                trip = true;
            }
            val <<= 8;
            if ((i + 2) < data.length) {
                val |= (0xFF & data[i + 2]);
                quad = true;
            }
            out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
            val >>= 6;
            out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
            val >>= 6;
            out[index + 1] = alphabet[val & 0x3F];
            val >>= 6;
            out[index + 0] = alphabet[val & 0x3F];
        }
        return out;
    }

    /**
     * Decodes a BASE-64 encoded stream to recover the original
     * data. White space before and after will be trimmed away,
     * but no other manipulation of the input will be performed.
     *
     * As of version 1.2 this method will properly handle input
     * containing junk characters (newlines and the like) rather
     * than throwing an error. It does this by pre-parsing the
     * input and generating from that a count of VALID input
     * characters.
     * 
     * @param data  the character data.
     * 
     * @return The decoded data.
     */
    public static byte[] decode(final char[] data) {
        // as our input could contain non-BASE64 data (newlines,
        // whitespace of any sort, whatever) we must first adjust
        // our count of USABLE data so that...
        // (a) we don't misallocate the output array, and
        // (b) think that we miscalculated our data length
        //     just because of extraneous throw-away junk

        int tempLen = data.length;
        for (int ix = 0; ix < data.length; ix++) {
            if ((data[ix] > 255) || codes[data[ix]] < 0) {
                --tempLen; // ignore non-valid chars and padding
            }
        }
        // calculate required length:
        //  -- 3 bytes for every 4 valid base64 chars
        //  -- plus 2 bytes if there are 3 extra base64 chars,
        //     or plus 1 byte if there are 2 extra.

        int len = (tempLen / 4) * 3;
        if ((tempLen % 4) == 3) {
            len += 2;
        }
        if ((tempLen % 4) == 2) {
            len += 1;
        }

        final byte[] out = new byte[len];


        int shift = 0; // # of excess bits stored in accum
        int accum = 0; // excess bits
        int index = 0;

        // we now go through the entire array (NOT using the 'tempLen' value)
        for (int ix = 0; ix < data.length; ix++) {
            final int value = (data[ix] > 255) ? -1 : codes[data[ix]];

            if (value >= 0) { // skip over non-code
                accum <<= 6; // bits shift up by 6 each time thru
                shift += 6; // loop, with new bits being put in
                accum |= value; // at the bottom.
                if (shift >= 8) { // whenever there are 8 or more shifted in,
                    shift -= 8; // write them out (from the top, leaving any
                    out[index++] = // excess at the bottom for next iteration.
                        (byte) ((accum >> shift) & 0xff);
                }
            }
            // we will also have skipped processing a padding null byte ('=') here;
            // these are used ONLY for padding to an even length and do not legally
            // occur as encoded data. for this reason we can ignore the fact that
            // no index++ operation occurs in that special case: the out[] array is
            // initialized to all-zero bytes to start with and that works to our
            // advantage in this combination.
        }

        // if there is STILL something wrong we just have to throw up now!
        if (index != out.length) {
            throw new Error("Miscalculated data length (wrote " 
                + index + " instead of " + out.length + ")");
        }

        return out;
    }


    //
    // code characters for values 0..63
    //
    private static char[] alphabet =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray();

    //
    // lookup table for converting base64 characters to value in range 0..63
    //
    private static byte[] codes = new byte[256];

    static {
        for (int i = 0; i < 256; i++) {
            codes[i] = -1;
        }
        for (int i = 'A'; i <= 'Z'; i++) {
            codes[i] = (byte) (i - 'A');
        }
        for (int i = 'a'; i <= 'z'; i++) {
            codes[i] = (byte) (26 + i - 'a');
        }
        for (int i = '0'; i <= '9'; i++) {
            codes[i] = (byte) (52 + i - '0');
        }
        codes['+'] = 62;
        codes['/'] = 63;
    }




    ///////////////////////////////////////////////////
    // remainder (main method and helper functions) is
    // for testing purposes only, feel free to clip it.
    ///////////////////////////////////////////////////

    /**
     * Entry point.
     * 
     * @param args  the command line arguments.
     */
    public static void main(final String[] args) {
        boolean decode = false;

        if (args.length == 0) {
            System.out.println("usage:  java Base64 [-d[ecode]] filename");
            System.exit(0);
        }
        for (int i = 0; i < args.length; i++) {
            if ("-decode".equalsIgnoreCase(args[i])) {
                decode = true;
            }
            else if ("-d".equalsIgnoreCase(args[i])) {
                decode = true;
            }   
        }

        final String filename = args[args.length - 1];
        final File file = new File(filename);
        if (!file.exists()) {
            System.out.println("Error:  file '" + filename + "' doesn't exist!");
            System.exit(0);
        }

        if (decode) {
            final char[] encoded = readChars(file);
            final byte[] decoded = decode(encoded);
            writeBytes(file, decoded);
        }
        else {
            final byte[] decoded = readBytes(file);
            final char[] encoded = encode(decoded);
            writeChars(file, encoded);
        }
    }

    private static byte[] readBytes(final File file) {
        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            final InputStream fis = new FileInputStream(file);
            final InputStream is = new BufferedInputStream(fis);

            int count;
            final byte[] buf = new byte[16384];
            while ((count = is.read(buf)) != -1) {
                if (count > 0) {
                    baos.write(buf, 0, count);
                }   
            }
            is.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

        return baos.toByteArray();
    }

    private static char[] readChars(final File file) {
        final CharArrayWriter caw = new CharArrayWriter();
        try {
            final Reader fr = new FileReader(file);
            final Reader in = new BufferedReader(fr);
            int count;
            final char[] buf = new char[16384];
            while ((count = in.read(buf)) != -1) {
                if (count > 0) {
                    caw.write(buf, 0, count);
                }
            }
            in.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

        return caw.toCharArray();
    }

    private static void writeBytes(final File file, final byte[] data) {
        try {
            final OutputStream fos = new FileOutputStream(file);
            final OutputStream os = new BufferedOutputStream(fos);
            os.write(data);
            os.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void writeChars(final File file, final char[] data) {
        try {
            final Writer fos = new FileWriter(file);
            final Writer os = new BufferedWriter(fos);
            os.write(data);
            os.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
    ///////////////////////////////////////////////////
    // end of test code.
    ///////////////////////////////////////////////////

}