Java-Base64工具类

/*
 * Base64 encoding and decoding.
 * Copyright (C) 2001-2004 Stephen Ostermiller
 * http://ostermiller.org/contact.pl?regarding=Java+Utilities
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * See COPYING.TXT for details.
 */

import java.io.*;
import gnu.getopt.*;
import java.text.MessageFormat;
import java.util.ResourceBundle;
import java.util.Locale;

/**
 * Implements Base64 encoding and decoding as defined by RFC 2045: "Multipurpose Internet
 * Mail Extensions (MIME) Part One: Format of Internet Message Bodies" page 23.
 * More information about this class is available from <a target="_top" href=
 * "http://ostermiller.org/utils/Base64.html">ostermiller.org</a>.
 *
 * <blockquote>
 * <p>The Base64 Content-Transfer-Encoding is designed to represent
 * arbitrary sequences of octets in a form that need not be humanly
 * readable.  The encoding and decoding algorithms are simple, but the
 * encoded data are consistently only about 33 percent larger than the
 * unencoded data.  This encoding is virtually identical to the one used
 * in Privacy Enhanced Mail (PEM) applications, as defined in RFC 1421.</p>
 *
 * <p>A 65-character subset of US-ASCII is used, enabling 6 bits to be
 * represented per printable character. (The extra 65th character, "=",
 * is used to signify a special processing function.)</p>
 *
 * <p>NOTE:  This subset has the important property that it is represented
 * identically in all versions of ISO 646, including US-ASCII, and all
 * characters in the subset are also represented identically in all
 * versions of EBCDIC. Other popular encodings, such as the encoding
 * used by the uuencode utility, Macintosh binhex 4.0 [RFC-1741], and
 * the base85 encoding specified as part of Level 2 PostScript, do no
 * share these properties, and thus do not fulfill the portability
 * requirements a binary transport encoding for mail must meet.</p>
 *
 * <p>The encoding process represents 24-bit groups of input bits as output
 * strings of 4 encoded characters.  Proceeding from left to right, a
 * 24-bit input group is formed by concatenating 3 8bit input groups.
 * These 24 bits are then treated as 4 concatenated 6-bit groups, each
 * of which is translated into a single digit in the base64 alphabet.
 * When encoding a bit stream via the base64 encoding, the bit stream
 * must be presumed to be ordered with the most-significant-bit first.
 * That is, the first bit in the stream will be the high-order bit in
 * the first 8bit byte, and the eighth bit will be the low-order bit in
 * the first 8bit byte, and so on.</p>
 *
 * <p>Each 6-bit group is used as an index into an array of 64 printable
 * characters.  The character referenced by the index is placed in the
 * output string.  These characters, identified in Table 1, below, are
 * selected so as to be universally representable, and the set excludes
 * characters with particular significance to SMTP (e.g., ".", CR, LF)
 * and to the multipart boundary delimiters defined in RFC 2046 (e.g.,
 * "-").</p>
 * <pre>
 *                  Table 1: The Base64 Alphabet
 *
 *   Value Encoding  Value Encoding  Value Encoding  Value Encoding
 *       0 A            17 R            34 i            51 z
 *       1 B            18 S            35 j            52 0
 *       2 C            19 T            36 k            53 1
 *       3 D            20 U            37 l            54 2
 *       4 E            21 V            38 m            55 3
 *       5 F            22 W            39 n            56 4
 *       6 G            23 X            40 o            57 5
 *       7 H            24 Y            41 p            58 6
 *       8 I            25 Z            42 q            59 7
 *       9 J            26 a            43 r            60 8
 *      10 K            27 b            44 s            61 9
 *      11 L            28 c            45 t            62 +
 *      12 M            29 d            46 u            63 /
 *      13 N            30 e            47 v
 *      14 O            31 f            48 w         (pad) =
 *      15 P            32 g            49 x
 *      16 Q            33 h            50 y
 * </pre>
 * <p>The encoded output stream must be represented in lines of no more
 * than 76 characters each.  All line breaks or other characters no
 * found in Table 1 must be ignored by decoding software.  In base64
 * data, characters other than those in Table 1, line breaks, and other
 * white space probably indicate a transmission error, about which a
 * warning message or even a message rejection might be appropriate
 * under some circumstances.</p>
 *
 * <p>Special processing is performed if fewer than 24 bits are available
 * at the end of the data being encoded.  A full encoding quantum is
 * always completed at the end of a body.  When fewer than 24 input bits
 * are available in an input group, zero bits are added (on the right)
 * to form an integral number of 6-bit groups.  Padding at the end of
 * the data is performed using the "=" character.  Since all base64
 * input is an integral number of octets, only the following cases can
 * arise: (1) the final quantum of encoding input is an integral
 * multiple of 24 bits; here, the final unit of encoded output will be
 * an integral multiple of 4 characters with no "=" padding, (2) the
 * final quantum of encoding input is exactly 8 bits; here, the final
 * unit of encoded output will be two characters followed by two "="
 * padding characters, or (3) the final quantum of encoding input is
 * exactly 16 bits; here, the final unit of encoded output will be three
 * characters followed by one "=" padding character.</p>
 *
 * <p>Because it is used only for padding at the end of the data, the
 * occurrence of any "=" characters may be taken as evidence that the
 * end of the data has been reached (without truncation in transit).  No
 * such assurance is possible, however, when the number of octets
 * transmitted was a multiple of three and no "=" characters are
 * present.</p>
 *
 * <p>Any characters outside of the base64 alphabet are to be ignored in
 * base64-encoded data.</p>
 *
 * <p>Care must be taken to use the proper octets for line breaks if base64
 * encoding is applied directly to text material that has not been
 * converted to canonical form.  In particular, text line breaks must be
 * converted into CRLF sequences prior to base64 encoding.  The
 * important thing to note is that this may be done directly by the
 * encoder rather than in a prior canonization step in some
 * implementations.</p>
 *
 * <p>NOTE: There is no need to worry about quoting potential boundary
 * delimiters within base64-encoded bodies within multipart entities
 * because no hyphen characters are used in the base64 encoding.</p>
 * </blockquote>
 *
 * @author Stephen Ostermiller http://ostermiller.org/contact.pl?regarding=Java+Utilities
 * @since ostermillerutils 1.00.00
 */
public class Base64 {

    /**
     * Symbol that represents the end of an input stream
     *
     * @since ostermillerutils 1.00.00
     */
    private static final int END_OF_INPUT = -1;

    /**
     * A character that is not a valid base 64 character.
     *
     * @since ostermillerutils 1.00.00
     */
    private static final int NON_BASE_64 = -1;

    /**
     * A character that is not a valid base 64 character.
     *
     * @since ostermillerutils 1.00.00
     */
    private static final int NON_BASE_64_WHITESPACE = -2;

    /**
     * A character that is not a valid base 64 character.
     *
     * @since ostermillerutils 1.00.00
     */
    private static final int NON_BASE_64_PADDING = -3;

    /**
     * This class need not be instantiated, all methods are static.
     *
     * @since ostermillerutils 1.00.00
     */
    private Base64(){
    }

    /**
     * Table of the sixty-four characters that are used as
     * the Base64 alphabet: [A-Za-z0-9+/]
     *
     * @since ostermillerutils 1.00.00
     */
    protected static final byte[] base64Chars = {
        'A','B','C','D','E','F','G','H',
        'I','J','K','L','M','N','O','P',
        'Q','R','S','T','U','V','W','X',
        'Y','Z','a','b','c','d','e','f',
        'g','h','i','j','k','l','m','n',
        'o','p','q','r','s','t','u','v',
        'w','x','y','z','0','1','2','3',
        '4','5','6','7','8','9','+','/',
    };

    /**
     * Reverse lookup table for the Base64 alphabet.
     * reversebase64Chars[byte] gives n for the nth Base64
     * character or negative if a character is not a Base64 character.
     *
     * @since ostermillerutils 1.00.00
     */
    protected static final byte[] reverseBase64Chars = new byte[0x100];
    static {
        // Fill in NON_BASE_64 for all characters to start with
        for (int i=0; i<reverseBase64Chars.length; i++){
            reverseBase64Chars[i] = NON_BASE_64;
        }
        // For characters that are base64Chars, adjust
        // the reverse lookup table.
        for (byte i=0; i < base64Chars.length; i++){
            reverseBase64Chars[base64Chars[i]] = i;
        }
        reverseBase64Chars[' '] = NON_BASE_64_WHITESPACE;
        reverseBase64Chars['\n'] = NON_BASE_64_WHITESPACE;
        reverseBase64Chars['\r'] = NON_BASE_64_WHITESPACE;
        reverseBase64Chars['\t'] = NON_BASE_64_WHITESPACE;
        reverseBase64Chars['\f'] = NON_BASE_64_WHITESPACE;
        reverseBase64Chars['='] = NON_BASE_64_PADDING;
    }

    /**
     * Version number of this program
     *
     * @since ostermillerutils 1.00.00
     */
    public static final String version = "1.2";

    /**
     * Locale specific strings displayed to the user.
     *
     * @since ostermillerutils 1.00.00
     */
    protected static ResourceBundle labels = ResourceBundle.getBundle("com.Ostermiller.util.Base64",  Locale.getDefault());

    private static final int ACTION_GUESS = 0;
    private static final int ACTION_ENCODE = 1;
    private static final int ACTION_DECODE = 2;

    private static final int ARGUMENT_GUESS = 0;
    private static final int ARGUMENT_STRING = 1;
    private static final int ARGUMENT_FILE = 2;

    /**
     * Converts the line ending on files, or standard input.
     * Run with --help argument for more information.
     *
     * @param args Command line arguments.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void main(String[] args){
        // create the command line options that we are looking for
        LongOpt[] longopts = {
            new LongOpt(labels.getString("help.option"), LongOpt.NO_ARGUMENT, null, 1),
            new LongOpt(labels.getString("version.option"), LongOpt.NO_ARGUMENT, null, 2),
            new LongOpt(labels.getString("about.option"), LongOpt.NO_ARGUMENT, null, 3),
            new LongOpt(labels.getString("encode.option"), LongOpt.NO_ARGUMENT, null, 'e'),
            new LongOpt(labels.getString("lines.option"), LongOpt.NO_ARGUMENT, null, 'l'),
            new LongOpt(labels.getString("nolines.option"), LongOpt.NO_ARGUMENT, null, 6),
            new LongOpt(labels.getString("decode.option"), LongOpt.NO_ARGUMENT, null, 'd'),
            new LongOpt(labels.getString("decodeall.option"), LongOpt.NO_ARGUMENT, null, 'a'),
            new LongOpt(labels.getString("decodegood.option"), LongOpt.NO_ARGUMENT, null, 5),
            new LongOpt(labels.getString("guess.option"), LongOpt.NO_ARGUMENT, null, 'g'),
            new LongOpt(labels.getString("ext.option"), LongOpt.OPTIONAL_ARGUMENT, null, 'x'),
            new LongOpt(labels.getString("force.option"), LongOpt.NO_ARGUMENT, null, 'f'),
            new LongOpt(labels.getString("quiet.option"), LongOpt.NO_ARGUMENT, null, 'q'),
            new LongOpt(labels.getString("reallyquiet.option"), LongOpt.NO_ARGUMENT, null, 'Q'),
            new LongOpt(labels.getString("verbose.option"), LongOpt.NO_ARGUMENT, null, 'v'),
            new LongOpt(labels.getString("noforce.option"), LongOpt.NO_ARGUMENT, null, 4),
            new LongOpt(labels.getString("file.option"), LongOpt.NO_ARGUMENT, null, 7),
            new LongOpt(labels.getString("string.option"), LongOpt.NO_ARGUMENT, null, 8),
            new LongOpt(labels.getString("newline.option"), LongOpt.NO_ARGUMENT, null, 'n'),
            new LongOpt(labels.getString("nonewline.option"), LongOpt.NO_ARGUMENT, null, 9),
        };
        String oneLetterOptions = "eldagx::fqQvVn";
        Getopt opts = new Getopt(labels.getString("base64"), args, oneLetterOptions, longopts);
        int action = ACTION_GUESS;
        String extension = "base64";
        boolean force = false;
        boolean printMessages = true;
        boolean printErrors = true;
        boolean forceDecode = false;
        boolean lineBreaks = true;
        int argumentType = ARGUMENT_GUESS;
        boolean decodeEndLine = false;
        int c;
        while ((c = opts.getopt()) != -1){
            switch(c){
                    case 1:{
                    // print out the help message
                    String[] helpFlags = new String[]{
                        "--" + labels.getString("help.option"),
                        "--" + labels.getString("version.option"),
                        "--" + labels.getString("about.option"),
                        "-g --" + labels.getString("guess.option"),
                        "-e --" + labels.getString("encode.option"),
                        "-l --" + labels.getString("lines.option"),
                        "--" + labels.getString("nolines.option"),
                        "-d --" + labels.getString("decode.option"),
                        "-a --" + labels.getString("decodeall.option"),
                        "--" + labels.getString("decodegood.option"),
                        "-x --" + labels.getString("ext.option") + " <" + labels.getString("ext.option") + ">",
                        "-f --" + labels.getString("force.option"),
                        "--" + labels.getString("noforce.option"),
                        "-v --" + labels.getString("verbose.option"),
                        "-q --" + labels.getString("quiet.option"),
                        "-Q --" + labels.getString("reallyquiet.option"),
                        "--" + labels.getString("file.option"),
                        "--" + labels.getString("string.option"),
                        "-n --" + labels.getString("newline.option"),
                        "--" + labels.getString("nonewline.option"),
                    };
                    int maxLength = 0;
                    for (int i=0; i<helpFlags.length; i++){
                        maxLength = Math.max(maxLength, helpFlags[i].length());
                    }
                    maxLength += 2;
                    System.out.println(
                        labels.getString("base64") + " [-" + StringHelper.replace(oneLetterOptions, ":", "") + "] <" + labels.getString("files") + ">\n" +
                        labels.getString("purpose.message") + "\n" +
                        "  " + labels.getString("stdin.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[0] ,maxLength, ' ') + labels.getString("help.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[1] ,maxLength, ' ') + labels.getString("version.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[2] ,maxLength, ' ') + labels.getString("about.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[3] ,maxLength, ' ') + labels.getString("g.message") + " (" + labels.getString("default") + ")\n" +
                        "  " + StringHelper.postpad(helpFlags[4] ,maxLength, ' ') + labels.getString("e.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[5] ,maxLength, ' ') + labels.getString("l.message") + " (" + labels.getString("default") + ")\n" +
                        "  " + StringHelper.postpad(helpFlags[6] ,maxLength, ' ') + labels.getString("nolines.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[7] ,maxLength, ' ') + labels.getString("d.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[8] ,maxLength, ' ') + labels.getString("a.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[9] ,maxLength, ' ') + labels.getString("decodegood.message") + " (" + labels.getString("default") + ")\n" +
                        "  " + StringHelper.postpad(helpFlags[10] ,maxLength, ' ') + labels.getString("x.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[11] ,maxLength, ' ') + labels.getString("f.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[12] ,maxLength, ' ') + labels.getString("noforce.message") + " (" + labels.getString("default") + ")\n" +
                        "  " + StringHelper.postpad(helpFlags[13] ,maxLength, ' ') + labels.getString("v.message") + " (" + labels.getString("default") + ")\n" +
                        "  " + StringHelper.postpad(helpFlags[14] ,maxLength, ' ') + labels.getString("q.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[15] ,maxLength, ' ') + labels.getString("Q.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[16] ,maxLength, ' ') + labels.getString("file.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[17] ,maxLength, ' ') + labels.getString("string.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[18] ,maxLength, ' ') + labels.getString("newline.message") + "\n" +
                        "  " + StringHelper.postpad(helpFlags[19] ,maxLength, ' ') + labels.getString("nonewline.message") + "\n"
                    );
                    System.exit(0);
                } break;
                case 2:{
                    // print out the version message
                    System.out.println(MessageFormat.format(labels.getString("version"), (Object[])new String[] {version}));
                    System.exit(0);
                } break;
                case 3:{
                    System.out.println(
                        labels.getString("base64") + " -- " + labels.getString("purpose.message") + "\n" +
                        MessageFormat.format(labels.getString("copyright"), (Object[])new String[] {"2001-2002", "Stephen Ostermiller (http://ostermiller.org/contact.pl?regarding=Java+Utilities)"}) + "\n\n" +
                        labels.getString("license")
                    );
                    System.exit(0);
                } break;
                case 'd':{
                    action = ACTION_DECODE;
                } break;
                case 'a':{
                    forceDecode = true;
                } break;
                case 5:{
                    forceDecode = false;
                } break;
                case 'e':{
                    action = ACTION_ENCODE;
                } break;
                case 'l':{
                    lineBreaks = true;
                } break;
                case 6:{
                    lineBreaks = false;
                } break;
                case 'g':{
                    action = ACTION_GUESS;
                } break;
                case 'x':{
                    extension = opts.getOptarg();
                    if (extension == null) extension = "";
                } break;
                case 'f':{
                    force = true;
                } break;
                case 4:{
                    force = false;
                } break;
                case 'v':{
                    printMessages = true;
                    printErrors = true;
                } break;
                case 'q':{
                    printMessages = false;
                    printErrors = true;
                } break;
                case 'Q':{
                    printMessages = false;
                    printErrors = false;
                } break;
                case 7: {
                    argumentType = ARGUMENT_FILE;
                } break;
                case 8: {
                    argumentType = ARGUMENT_STRING;
                } break;
                case 'n': {
                    decodeEndLine = true;
                } break;
                case 9: {
                    decodeEndLine = false;
                } break;
                default:{
                    System.err.println(labels.getString("unknownarg"));
                    System.exit(1);
                }
            }
        }

        int exitCond = 0;
        boolean done = false;
        for (int i=opts.getOptind(); i<args.length; i++){
            done = true;
            File source = new File(args[i]);
            if (argumentType == ARGUMENT_STRING || (argumentType == ARGUMENT_GUESS && !source.exists())){
                try {
                    int fileAction = action;
                    if (fileAction == ACTION_GUESS){
                        if (isBase64(args[i])){
                            fileAction = ACTION_DECODE;
                        } else {
                            fileAction = ACTION_ENCODE;
                        }
                    }
                    if (fileAction == ACTION_ENCODE){
                        if (printMessages){
                            System.out.println(labels.getString("encodingarg"));
                        }
                        encode(new ByteArrayInputStream(args[i].getBytes()), System.out, lineBreaks);
                    } else {
                        if (printMessages){
                            System.out.println(labels.getString("decodingarg"));
                        }
                        decode(new ByteArrayInputStream(args[i].getBytes()), System.out, !forceDecode);
                        if (decodeEndLine) System.out.println();
                    }
                } catch (Base64DecodingException x){
                    if(printErrors){
                        System.err.println(args[i] + ": " + x.getMessage() + " " + labels.getString("unexpectedcharforce"));
                    }
                    exitCond = 1;
                } catch (IOException x){
                    if(printErrors){
                        System.err.println(args[i] + ": " + x.getMessage());
                    }
                    exitCond = 1;
                }
            } else  if (!source.exists()){
                if(printErrors){
                    System.err.println(MessageFormat.format(labels.getString("doesnotexist"), (Object[])new String[] {args[i]}));
                }
                exitCond = 1;
            } else if (!source.canRead()){
                if(printErrors){
                    System.err.println(MessageFormat.format(labels.getString("cantread"), (Object[])new String[] {args[i]}));
                }
                exitCond = 1;
            } else {
                try {
                    int fileAction = action;
                    if (fileAction == ACTION_GUESS){
                        if (isBase64(source)){
                            fileAction = ACTION_DECODE;
                        } else {
                            fileAction = ACTION_ENCODE;
                        }
                    }
                    String outName = args[i];
                    if (extension.length() > 0){
                        if (fileAction == ACTION_ENCODE){
                            outName = args[i] + "." + extension;
                        } else {
                            if (args[i].endsWith("." + extension)){
                                outName = args[i].substring(0, args[i].length() - (extension.length() + 1));
                            }
                        }
                    }
                    File outFile = new File(outName);
                    if (!force && outFile.exists()){
                        if(printErrors){
                            System.err.println(MessageFormat.format(labels.getString("overwrite"), (Object[])new String[] {outName}));
                        }
                        exitCond = 1;
                    } else if (!(outFile.exists() || outFile.createNewFile()) || !outFile.canWrite()){
                        if(printErrors){
                            System.err.println(MessageFormat.format(labels.getString("cantwrite"), (Object[])new String[] {outName}));
                        }
                        exitCond = 1;
                    } else {
                        if (fileAction == ACTION_ENCODE){
                            if (printMessages){
                                System.out.println(MessageFormat.format(labels.getString("encoding"), (Object[])new String[] {args[i], outName}));
                            }
                            encode(source, outFile, lineBreaks);
                        } else {
                            if (printMessages){
                                System.out.println(MessageFormat.format(labels.getString("decoding"), (Object[])new String[] {args[i], outName}));
                            }
                            decode(source, outFile, !forceDecode);
                        }
                    }
                } catch (Base64DecodingException x){
                    if(printErrors){
                        System.err.println(args[i] + ": " + x.getMessage() + " " + labels.getString("unexpectedcharforce"));
                    }
                    exitCond = 1;
                } catch (IOException x){
                    if(printErrors){
                        System.err.println(args[i] + ": " + x.getMessage());
                    }
                    exitCond = 1;
                }
            }
        }
        if (!done){
            try {
                if (action == ACTION_GUESS){
                    if(printErrors){
                        System.err.println(labels.getString("cantguess"));
                    }
                    exitCond = 1;
                } else if (action == ACTION_ENCODE){
                    encode(
                        new BufferedInputStream(System.in),
                        new BufferedOutputStream(System.out),
                        lineBreaks
                    );
                } else {
                    decode(
                        new BufferedInputStream(System.in),
                        new BufferedOutputStream(System.out),
                        !forceDecode
                    );
                    if (decodeEndLine) System.out.println();
                }
            } catch (Base64DecodingException x){
                if(printErrors){
                    System.err.println(x.getMessage() + " " + labels.getString("unexpectedcharforce"));
                }
                exitCond = 1;
            } catch (IOException x){
                if(printErrors){
                    System.err.println(x.getMessage());
                }
                exitCond = 1;
            }
        }
        System.exit(exitCond);
    }

    /**
     * Encode a String in Base64.
     * The String is converted to and from bytes according to the platform's
     * default character encoding.
     * No line breaks or other white space are inserted into the encoded data.
     *
     * @param string The data to encode.
     * @return An encoded String.
     *
     * @since ostermillerutils 1.00.00
     */
    public static String encode(String string){
        return new String(encode(string.getBytes()));
    }

    /**
     * Encode a String in Base64.
     * No line breaks or other white space are inserted into the encoded data.
     *
     * @param string The data to encode.
     * @param enc Character encoding to use when converting to and from bytes.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @return An encoded String.
     *
     * @since ostermillerutils 1.00.00
     */
    public static String encode(String string, String enc) throws UnsupportedEncodingException {
        return new String(encode(string.getBytes(enc)), enc);
    }

    /**
     * Encode bytes in Base64.
     * No line breaks or other white space are inserted into the encoded data.
     *
     * @param bytes The data to encode.
     * @return String with Base64 encoded data.
     *
     * @since ostermillerutils 1.04.00
     */
    public static String encodeToString(byte[] bytes){
        return encodeToString(bytes, false);
    }

    /**
     * Encode bytes in Base64.
     *
     * @param bytes The data to encode.
     * @param lineBreaks  Whether to insert line breaks every 76 characters in the output.
     * @return String with Base64 encoded data.
     *
     * @since ostermillerutils 1.04.00
     */
    public static String encodeToString(byte[] bytes, boolean lineBreaks){
        try {
            return new String(encode(bytes, lineBreaks), "ASCII");
        } catch (UnsupportedEncodingException iex){
            // ASCII should be supported
            throw new RuntimeException(iex);
        }
    }

    /**
     * Encode bytes in Base64.
     * No line breaks or other white space are inserted into the encoded data.
     *
     * @param bytes The data to encode.
     * @return Encoded bytes.
     *
     * @since ostermillerutils 1.00.00
     */
    public static byte[] encode(byte[] bytes){
        return encode(bytes, false);
    }

    /**
     * Encode bytes in Base64.
     *
     * @param bytes The data to encode.
     * @param lineBreaks  Whether to insert line breaks every 76 characters in the output.
     * @return Encoded bytes.
     *
     * @since ostermillerutils 1.04.00
     */
    public static byte[] encode(byte[] bytes, boolean lineBreaks){
        ByteArrayInputStream in = new ByteArrayInputStream(bytes);
        // calculate the length of the resulting output.
        // in general it will be 4/3 the size of the input
        // but the input length must be divisible by three.
        // If it isn't the next largest size that is divisible
        // by three is used.
        int mod;
        int length = bytes.length;
        if ((mod = length % 3) != 0){
            length += 3 - mod;
        }
        length = length * 4 / 3;
        ByteArrayOutputStream out = new ByteArrayOutputStream(length);
        try {
            encode(in, out, lineBreaks);
        } catch (IOException x){
            // This can't happen.
            // The input and output streams were constructed
            // on memory structures that don't actually use IO.
            throw new RuntimeException(x);
        }
        return out.toByteArray();
    }

    /**
     * Encode this file in Base64.
     * Line breaks will be inserted every 76 characters.
     *
     * @param fIn File to be encoded (will be overwritten).
     *
     * @since ostermillerutils 1.00.00
     */
    public static void encode(File fIn) throws IOException {
        encode(fIn, fIn, true);
    }

    /**
     * Encode this file in Base64.
     *
     * @param fIn File to be encoded (will be overwritten).
     * @param lineBreaks  Whether to insert line breaks every 76 characters in the output.
     * @throws IOException if an input or output error occurs.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void encode(File fIn, boolean lineBreaks) throws IOException {
        encode(fIn, fIn, lineBreaks);
    }

    /**
     * Encode this file in Base64.
     * Line breaks will be inserted every 76 characters.
     *
     * @param fIn File to be encoded.
     * @param fOut File to which the results should be written (may be the same as fIn).
     * @throws IOException if an input or output error occurs.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void encode(File fIn, File fOut) throws IOException {
        encode(fIn, fOut, true);
    }

    /**
     * Encode this file in Base64.
     *
     * @param fIn File to be encoded.
     * @param fOut File to which the results should be written (may be the same as fIn).
     * @param lineBreaks  Whether to insert line breaks every 76 characters in the output.
     * @throws IOException if an input or output error occurs.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void encode(File fIn, File fOut, boolean lineBreaks) throws IOException {
        File temp = null;
        InputStream in = null;
        OutputStream out = null;
        try {
            in = new BufferedInputStream(new FileInputStream(fIn));
            temp = File.createTempFile("Base64", null, null);
            out = new BufferedOutputStream(new FileOutputStream(temp));
            encode(in, out, lineBreaks);
            in.close();
            in = null;
            out.flush();
            out.close();
            out = null;
            FileHelper.move(temp, fOut, true);
        } finally {
            if (in != null){
                in.close();
                in = null;
            }
            if (out != null){
                out.flush();
                out.close();
                out = null;
            }
        }
    }

    /**
     * Encode data from the InputStream to the OutputStream in Base64.
     * Line breaks are inserted every 76 characters in the output.
     *
     * @param in Stream from which to read data that needs to be encoded.
     * @param out Stream to which to write encoded data.
     * @throws IOException if there is a problem reading or writing.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void encode(InputStream in, OutputStream out) throws IOException {
        encode(in, out, true);
    }

    /**
     * Encode data from the InputStream to the OutputStream in Base64.
     *
     * @param in Stream from which to read data that needs to be encoded.
     * @param out Stream to which to write encoded data.
     * @param lineBreaks Whether to insert line breaks every 76 characters in the output.
     * @throws IOException if there is a problem reading or writing.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void encode(InputStream in, OutputStream out, boolean lineBreaks) throws IOException {
        // Base64 encoding converts three bytes of input to
        // four bytes of output
        int[] inBuffer = new int[3];
        int lineCount = 0;

        boolean done = false;
        while (!done && (inBuffer[0] = in.read()) != END_OF_INPUT){
            // Fill the buffer
            inBuffer[1] = in.read();
            inBuffer[2] = in.read();

            // Calculate the out Buffer
            // The first byte of our in buffer will always be valid
            // but we must check to make sure the other two bytes
            // are not END_OF_INPUT before using them.
            // The basic idea is that the three bytes get split into
            // four bytes along these lines:
            //      [AAAAAABB] [BBBBCCCC] [CCDDDDDD]
            // [xxAAAAAA] [xxBBBBBB] [xxCCCCCC] [xxDDDDDD]
            // bytes are considered to be zero when absent.
            // the four bytes are then mapped to common ASCII symbols

            // A's: first six bits of first byte
            out.write(base64Chars[ inBuffer[0] >> 2 ]);
            if (inBuffer[1] != END_OF_INPUT){
                // B's: last two bits of first byte, first four bits of second byte
                out.write(base64Chars [(( inBuffer[0] << 4 ) & 0x30) | (inBuffer[1] >> 4) ]);
                if (inBuffer[2] != END_OF_INPUT){
                    // C's: last four bits of second byte, first two bits of third byte
                    out.write(base64Chars [((inBuffer[1] << 2) & 0x3c) | (inBuffer[2] >> 6) ]);
                    // D's: last six bits of third byte
                    out.write(base64Chars [inBuffer[2] & 0x3F]);
                } else {
                    // C's: last four bits of second byte
                    out.write(base64Chars [((inBuffer[1] << 2) & 0x3c)]);
                    // an equals sign for a character that is not a Base64 character
                    out.write('=');
                    done = true;
                }
            } else {
                // B's: last two bits of first byte
                out.write(base64Chars [(( inBuffer[0] << 4 ) & 0x30)]);
                // an equal signs for characters that is not a Base64 characters
                out.write('=');
                out.write('=');
                done = true;
            }
            lineCount += 4;
            if (lineBreaks && lineCount >= 76){
                out.write('\n');
                lineCount = 0;
            }
        }
        if (lineBreaks && lineCount >= 1){
            out.write('\n');
            lineCount = 0;
        }
        out.flush();
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     * The String is converted to and from bytes according to the platform's
     * default character encoding.
     *
     * @param string The data to decode.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.00.00
     */
    public static String decode(String string){
        return new String(decode(string.getBytes()));
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param string The data to decode.
     * @param enc Character encoding to use when converting to and from bytes.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.00.00
     */
    public static String decode(String string, String enc) throws UnsupportedEncodingException {
        return new String(decode(string.getBytes(enc)), enc);
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param string The data to decode.
     * @param encIn Character encoding to use when converting input to bytes (should not matter because Base64 data is designed to survive most character encodings)
     * @param encOut Character encoding to use when converting decoded bytes to output.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.00.00
     */
    public static String decode(String string, String encIn, String encOut) throws UnsupportedEncodingException {
        return new String(decode(string.getBytes(encIn)), encOut);
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     * The String is converted to and from bytes according to the platform's
     * default character encoding.
     *
     * @param string The data to decode.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.02.16
     */
    public static String decodeToString(String string){
        return new String(decode(string.getBytes()));
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param string The data to decode.
     * @param enc Character encoding to use when converting to and from bytes.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.02.16
     */
    public static String decodeToString(String string, String enc) throws UnsupportedEncodingException {
        return new String(decode(string.getBytes(enc)), enc);
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param string The data to decode.
     * @param encIn Character encoding to use when converting input to bytes (should not matter because Base64 data is designed to survive most character encodings)
     * @param encOut Character encoding to use when converting decoded bytes to output.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.02.16
     */
    public static String decodeToString(String string, String encIn, String encOut) throws UnsupportedEncodingException {
        return new String(decode(string.getBytes(encIn)), encOut);
    }

    /**
     * Decode a Base64 encoded String to an OutputStream.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     * The String is converted from bytes according to the platform's
     * default character encoding.
     *
     * @param string The data to decode.
     * @param out Stream to which to write decoded data.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.02.16
     */
    public static void decodeToStream(String string, OutputStream out) throws IOException {
        decode(new ByteArrayInputStream(string.getBytes()), out);
    }

    /**
     * Decode a Base64 encoded String to an OutputStream.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param string The data to decode.
     * @param enc Character encoding to use when converting to and from bytes.
     * @param out Stream to which to write decoded data.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.02.16
     */
    public static void decodeToStream(String string, String enc, OutputStream out) throws UnsupportedEncodingException, IOException {
        decode(new ByteArrayInputStream(string.getBytes(enc)), out);
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     * The String is converted from bytes according to the platform's
     * default character encoding.
     *
     * @param string The data to decode.
     * @return decoded data.
     *
     * @since ostermillerutils 1.02.16
     */
    public static byte[] decodeToBytes(String string){
        return decode(string.getBytes());
    }

    /**
     * Decode a Base64 encoded String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param string The data to decode.
     * @param enc Character encoding to use when converting from bytes.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @return decoded data.
     *
     * @since ostermillerutils 1.02.16
     */
    public static byte[] decodeToBytes(String string, String enc) throws UnsupportedEncodingException {
        return decode(string.getBytes(enc));
    }

    /**
     * Decode Base64 encoded bytes.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     * The String is converted to bytes according to the platform's
     * default character encoding.
     *
     * @param bytes The data to decode.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.02.16
     */
    public static String decodeToString(byte[] bytes){
        return new String(decode(bytes));
    }

    /**
     * Decode Base64 encoded bytes.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param bytes The data to decode.
     * @param enc Character encoding to use when converting to and from bytes.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     * @return A decoded String.
     *
     * @since ostermillerutils 1.02.16
     */
    public static String decodeToString(byte[] bytes, String enc) throws UnsupportedEncodingException {
        return new String(decode(bytes), enc);
    }

    /**
     * Decode Base64 encoded bytes.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param bytes The data to decode.
     * @return Decoded bytes.
     *
     * @since ostermillerutils 1.02.16
     */
    public static byte[] decodeToBytes(byte[] bytes){
        return decode(bytes);
    }

    /**
     * Decode Base64 encoded bytes.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param bytes The data to decode.
     * @return Decoded bytes.
     *
     * @since ostermillerutils 1.00.00
     */
    public static byte[] decode(byte[] bytes){
        ByteArrayInputStream in = new ByteArrayInputStream(bytes);
        // calculate the length of the resulting output.
        // in general it will be at most 3/4 the size of the input
        // but the input length must be divisible by four.
        // If it isn't the next largest size that is divisible
        // by four is used.
        int mod;
        int length = bytes.length;
        if ((mod = length % 4) != 0){
            length += 4 - mod;
        }
        length = length * 3 / 4;
        ByteArrayOutputStream out = new ByteArrayOutputStream(length);
        try {
            decode(in, out, false);
        } catch (IOException x){
            // This can't happen.
            // The input and output streams were constructed
            // on memory structures that don't actually use IO.
             throw new RuntimeException(x);
        }
        return out.toByteArray();
    }

    /**
     * Decode Base64 encoded bytes to the an OutputStream.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param bytes The data to decode.
     * @param out Stream to which to write decoded data.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void decode(byte[] bytes, OutputStream out) throws IOException {
        ByteArrayInputStream in = new ByteArrayInputStream(bytes);
        decode(in, out, false);
    }

    /**
     * Decode Base64 encoded bytes to the an OutputStream.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param bytes The data to decode.
     * @param out Stream to which to write decoded data.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.02.16
     */
    public static void decodeToStream(byte[] bytes, OutputStream out) throws IOException {
        ByteArrayInputStream in = new ByteArrayInputStream(bytes);
        decode(in, out, false);
    }

    /**
     * Decode Base64 encoded data from one file to the other.
     * Characters in the Base64 alphabet, white space and equals sign are
     * expected to be in urlencoded data.  The presence of other characters
     * could be a sign that the data is corrupted.
     *
     * @param fIn File to be decoded (will be overwritten).
     * @throws IOException if an IO error occurs.
     * @throws Base64DecodingException if unexpected data is encountered.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void decode(File fIn) throws IOException {
        decode(fIn, fIn, true);
    }

    /**
     * Decode Base64 encoded data from one file to the other.
     * Characters in the Base64 alphabet, white space and equals sign are
     * expected to be in urlencoded data.  The presence of other characters
     * could be a sign that the data is corrupted.
     *
     * @param fIn File to be decoded (will be overwritten).
     * @param throwExceptions Whether to throw exceptions when unexpected data is encountered.
     * @throws IOException if an IO error occurs.
     * @throws Base64DecodingException if unexpected data is encountered when throwExceptions is specified.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void decode(File fIn, boolean throwExceptions) throws IOException {
        decode(fIn, fIn, throwExceptions);
    }

    /**
     * Decode Base64 encoded data from one file to the other.
     * Characters in the Base64 alphabet, white space and equals sign are
     * expected to be in urlencoded data.  The presence of other characters
     * could be a sign that the data is corrupted.
     *
     * @param fIn File to be decoded.
     * @param fOut File to which the results should be written (may be the same as fIn).
     * @throws IOException if an IO error occurs.
     * @throws Base64DecodingException if unexpected data is encountered.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void decode(File fIn, File fOut) throws IOException {
        decode(fIn, fOut, true);
    }

    /**
     * Decode Base64 encoded data from one file to the other.
     * Characters in the Base64 alphabet, white space and equals sign are
     * expected to be in urlencoded data.  The presence of other characters
     * could be a sign that the data is corrupted.
     *
     * @param fIn File to be decoded.
     * @param fOut File to which the results should be written (may be the same as fIn).
     * @param throwExceptions Whether to throw exceptions when unexpected data is encountered.
     * @throws IOException if an IO error occurs.
     * @throws Base64DecodingException if unexpected data is encountered when throwExceptions is specified.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void decode(File fIn, File fOut, boolean throwExceptions) throws IOException {
        File temp = null;
        InputStream in = null;
        OutputStream out = null;
        try {
            in = new BufferedInputStream(new FileInputStream(fIn));
            temp = File.createTempFile("Base64", null, null);
            out = new BufferedOutputStream(new FileOutputStream(temp));
            decode(in, out, throwExceptions);
            in.close();
            in = null;
            out.flush();
            out.close();
            out = null;
            FileHelper.move(temp, fOut, true);
        } finally {
            if (in != null){
                try {
                    in.close();
                } catch (IOException ignore){
                     if (throwExceptions) throw ignore;
                }
                in = null;
            }
            if (out != null){
                try {
                    out.flush();
                    out.close();
                } catch (IOException ignore){
                     if (throwExceptions) throw ignore;
                }
                out = null;
            }
        }
    }

    /**
     * Reads the next (decoded) Base64 character from the input stream.
     * Non Base64 characters are skipped.
     *
     * @param in Stream from which bytes are read.
     * @param throwExceptions Throw an exception if an unexpected character is encountered.
     * @return the next Base64 character from the stream or -1 if there are no more Base64 characters on the stream.
     * @throws IOException if an IO Error occurs.
     * @throws Base64DecodingException if unexpected data is encountered when throwExceptions is specified.
     *
     * @since ostermillerutils 1.00.00
     */
    private static final int readBase64(InputStream in, boolean throwExceptions) throws IOException {
        int read;
        int numPadding = 0;
        do {
            read = in.read();
            if (read == END_OF_INPUT) return END_OF_INPUT;
            read = reverseBase64Chars[(byte)read];
            if (throwExceptions && (read == NON_BASE_64 || (numPadding > 0 && read > NON_BASE_64))){
                throw new Base64DecodingException (
                    MessageFormat.format(
                        labels.getString("unexpectedchar"),
                        (Object[])new String[] {
                            "'" + (char)read + "' (0x" + Integer.toHexString(read) + ")"
                        }
                    ),
                    (char)read
                );
            }
            if (read == NON_BASE_64_PADDING){
                numPadding++;
            }
        } while (read <= NON_BASE_64);
        return read;
    }

    /**
     * Decode Base64 encoded data from the InputStream to a byte array.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param in Stream from which to read data that needs to be decoded.
     * @return decoded data.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.00.00
     */
    public static byte[] decodeToBytes(InputStream in) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        decode(in, out, false);
        return out.toByteArray();
    }

    /**
     * Decode Base64 encoded data from the InputStream to a String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     * Bytes are converted to characters in the output String according to the platform's
     * default character encoding.
     *
     * @param in Stream from which to read data that needs to be decoded.
     * @return decoded data.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.02.16
     */
    public static String decodeToString(InputStream in) throws IOException {
        return new String(decodeToBytes(in));
    }

    /**
     * Decode Base64 encoded data from the InputStream to a String.
     * Characters that are not part of the Base64 alphabet are ignored
     * in the input.
     *
     * @param in Stream from which to read data that needs to be decoded.
     * @param enc Character encoding to use when converting bytes to characters.
     * @return decoded data.
     * @throws IOException if an IO error occurs.Throws:
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     *
     * @since ostermillerutils 1.02.16
     */
    public static String decodeToString(InputStream in, String enc) throws IOException {
        return new String(decodeToBytes(in), enc);
    }

    /**
     * Decode Base64 encoded data from the InputStream to the OutputStream.
     * Characters in the Base64 alphabet, white space and equals sign are
     * expected to be in urlencoded data.  The presence of other characters
     * could be a sign that the data is corrupted.
     *
     * @param in Stream from which to read data that needs to be decoded.
     * @param out Stream to which to write decoded data.
     * @throws IOException if an IO error occurs.
     * @throws Base64DecodingException if unexpected data is encountered.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void decode(InputStream in, OutputStream out) throws IOException {
        decode(in, out, true);
    }

    /**
     * Decode Base64 encoded data from the InputStream to the OutputStream.
     * Characters in the Base64 alphabet, white space and equals sign are
     * expected to be in urlencoded data.  The presence of other characters
     * could be a sign that the data is corrupted.
     *
     * @param in Stream from which to read data that needs to be decoded.
     * @param out Stream to which to write decoded data.
     * @param throwExceptions Whether to throw exceptions when unexpected data is encountered.
     * @throws IOException if an IO error occurs.
     * @throws Base64DecodingException if unexpected data is encountered when throwExceptions is specified.
     *
     * @since ostermillerutils 1.00.00
     */
    public static void decode(InputStream in, OutputStream out, boolean throwExceptions) throws IOException {
        // Base64 decoding converts four bytes of input to three bytes of output
        int[] inBuffer = new int[4];

        // read bytes unmapping them from their ASCII encoding in the process
        // we must read at least two bytes to be able to output anything
        boolean done = false;
        while (!done && (inBuffer[0] = readBase64(in, throwExceptions)) != END_OF_INPUT
            && (inBuffer[1] = readBase64(in, throwExceptions)) != END_OF_INPUT){
            // Fill the buffer
            inBuffer[2] = readBase64(in, throwExceptions);
            inBuffer[3] = readBase64(in, throwExceptions);

            // Calculate the output
            // The first two bytes of our in buffer will always be valid
            // but we must check to make sure the other two bytes
            // are not END_OF_INPUT before using them.
            // The basic idea is that the four bytes will get reconstituted
            // into three bytes along these lines:
            // [xxAAAAAA] [xxBBBBBB] [xxCCCCCC] [xxDDDDDD]
            //      [AAAAAABB] [BBBBCCCC] [CCDDDDDD]
            // bytes are considered to be zero when absent.

            // six A and two B
            out.write(inBuffer[0] << 2 | inBuffer[1] >> 4);
            if (inBuffer[2] != END_OF_INPUT){
                // four B and four C
                out.write(inBuffer[1] << 4 | inBuffer[2] >> 2);
                if (inBuffer[3] != END_OF_INPUT){
                    // two C and six D
                    out.write(inBuffer[2] << 6 | inBuffer[3]);
                } else {
                    done = true;
                }
            } else {
                done = true;
            }
        }
        out.flush();
    }

    /**
     * Determines if the byte array is in base64 format.
     * <p>
     * Data will be considered to be in base64 format if it contains
     * only base64 characters and whitespace with equals sign padding
     * on the end so that the number of base64 characters is divisible
     * by four.
     * <p>
     * It is possible for data to be in base64 format but for it to not
     * meet these stringent requirements.  It is also possible for data
     * to meet these requirements even though decoding it would not make
     * any sense.  This method should be used as a guide but it is not
     * authoritative because of the possibility of these false positives
     * and false negatives.
     * <p>
     * Additionally, extra data such as headers or footers may throw
     * this method off the scent and cause it to return false.
     *
     * @param bytes data that could be in base64 format.
     *
     * @since ostermillerutils 1.00.00
     */
    public static boolean isBase64(byte[] bytes){
        try {
            return isBase64(new ByteArrayInputStream(bytes));
        } catch (IOException x){
            // This can't happen.
            // The input and output streams were constructed
            // on memory structures that don't actually use IO.
            return false;
        }
    }

    /**
     * Determines if the String is in base64 format.
     * The String is converted to and from bytes according to the platform's
     * default character encoding.
     * <p>
     * Data will be considered to be in base64 format if it contains
     * only base64 characters and whitespace with equals sign padding
     * on the end so that the number of base64 characters is divisible
     * by four.
     * <p>
     * It is possible for data to be in base64 format but for it to not
     * meet these stringent requirements.  It is also possible for data
     * to meet these requirements even though decoding it would not make
     * any sense.  This method should be used as a guide but it is not
     * authoritative because of the possibility of these false positives
     * and false negatives.
     * <p>
     * Additionally, extra data such as headers or footers may throw
     * this method off the scent and cause it to return false.
     *
     * @param string String that may be in base64 format.
     * @return Best guess as to whether the data is in base64 format.
     *
     * @since ostermillerutils 1.00.00
     */
    public static boolean isBase64(String string){
        return isBase64(string.getBytes());
    }

    /**
     * Determines if the String is in base64 format.
     * <p>
     * Data will be considered to be in base64 format if it contains
     * only base64 characters and whitespace with equals sign padding
     * on the end so that the number of base64 characters is divisible
     * by four.
     * <p>
     * It is possible for data to be in base64 format but for it to not
     * meet these stringent requirements.  It is also possible for data
     * to meet these requirements even though decoding it would not make
     * any sense.  This method should be used as a guide but it is not
     * authoritative because of the possibility of these false positives
     * and false negatives.
     * <p>
     * Additionally, extra data such as headers or footers may throw
     * this method off the scent and cause it to return false.
     *
     * @param string String that may be in base64 format.
     * @param enc Character encoding to use when converting to bytes.
     * @return Best guess as to whether the data is in base64 format.
     * @throws UnsupportedEncodingException if the character encoding specified is not supported.
     */
    public static boolean isBase64(String string, String enc) throws UnsupportedEncodingException {
        return isBase64(string.getBytes(enc));
    }

    /**
     * Determines if the File is in base64 format.
     * <p>
     * Data will be considered to be in base64 format if it contains
     * only base64 characters and whitespace with equals sign padding
     * on the end so that the number of base64 characters is divisible
     * by four.
     * <p>
     * It is possible for data to be in base64 format but for it to not
     * meet these stringent requirements.  It is also possible for data
     * to meet these requirements even though decoding it would not make
     * any sense.  This method should be used as a guide but it is not
     * authoritative because of the possibility of these false positives
     * and false negatives.
     * <p>
     * Additionally, extra data such as headers or footers may throw
     * this method off the scent and cause it to return false.
     *
     * @param fIn File that may be in base64 format.
     * @return Best guess as to whether the data is in base64 format.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.00.00
     */
    public static boolean isBase64(File fIn) throws IOException {
        return isBase64(new BufferedInputStream(new FileInputStream(fIn)));
    }

    /**
     * Reads data from the stream and determines if it is
     * in base64 format.
     * <p>
     * Data will be considered to be in base64 format if it contains
     * only base64 characters and whitespace with equals sign padding
     * on the end so that the number of base64 characters is divisible
     * by four.
     * <p>
     * It is possible for data to be in base64 format but for it to not
     * meet these stringent requirements.  It is also possible for data
     * to meet these requirements even though decoding it would not make
     * any sense.  This method should be used as a guide but it is not
     * authoritative because of the possibility of these false positives
     * and false negatives.
     * <p>
     * Additionally, extra data such as headers or footers may throw
     * this method off the scent and cause it to return false.
     *
     * @param in Stream from which to read data to be tested.
     * @return Best guess as to whether the data is in base64 format.
     * @throws IOException if an IO error occurs.
     *
     * @since ostermillerutils 1.00.00
     */
    public static boolean isBase64(InputStream in) throws IOException {
        long numBase64Chars = 0;
        int numPadding = 0;
        int read;

        while ((read = in.read()) != -1){
            read = reverseBase64Chars[read];
            if (read == NON_BASE_64){
                return false;
            } else if (read == NON_BASE_64_WHITESPACE){
            } else if (read == NON_BASE_64_PADDING){
                numPadding++;
                numBase64Chars++;
            } else if (numPadding > 0){
                return false;
            } else {
                numBase64Chars++;
            }
        }
        if (numBase64Chars == 0) return false;
        if (numBase64Chars % 4 != 0) return false;
        return true;
    }
}