Decodificar datos Base64 en Java

Tengo una imagen codificada en Base64. ¿Cuál es la mejor manera de decodificar eso en Java? Esperemos que solo use las bibliotecas incluidas con Sun Java 6.

A partir de la v6, Java SE se entrega con JAXB. javax.xml.bind.DatatypeConvertertiene métodos estáticos que lo hacen fácil. Ver parseBase64Binary()y printBase64Binary().

A partir de Java 8 , existe una API oficialmente compatible para la codificación y decodificación Base64. Con el tiempo, esto probablemente se convertirá en la opción predeterminada.

La API incluye la clase java.util.Base64y sus clases anidadas. Admite tres tipos diferentes: básico, seguro para URL y MIME.

Código de muestra usando la codificación "básica":

import java.util.Base64;

byte[] bytes = "Hello, World!".getBytes("UTF-8");
String encoded = Base64.getEncoder().encodeToString(bytes);
byte[] decoded = Base64.getDecoder().decode(encoded);

La documentaciónjava.util.Base64 incluye varios métodos más para configurar codificadores y decodificadores, y para usar diferentes clases como entradas y salidas (conjuntos de bytes, cadenas, ByteBuffers, flujos java.io).

No es necesario usar commons: Sun envía un codificador base64 con Java. Puedes importarlo como tal:

import sun.misc.BASE64Decoder;

Y luego úsalo así:

BASE64Decoder decoder = new BASE64Decoder();
byte[] decodedBytes = decoder.decodeBuffer(encodedBytes);

¿Dónde encodedBytesestá a java.lang.Stringo a java.io.InputStream. Solo tenga en cuenta que las sun.*clases no son "oficialmente compatibles" con Sun.

EDITAR: ¿Quién sabía que esta sería la respuesta más controvertida que publicaría? Sé que los paquetes sun. * No son compatibles ni se garantiza que continúen existiendo, y sí sé sobre Commons y lo uso todo el tiempo. Sin embargo, el póster solicitó una clase que estaba "incluida con Sun Java 6", y eso es lo que estaba tratando de responder. Estoy de acuerdo en que Commons es la mejor manera de ir en general.

EDIT 2: Como señala amir75 a continuación, Java 6+ se envía con JAXB, que contiene código compatible para codificar / decodificar Base64. Vea la respuesta de Jeremy Ross a continuación.

Específicamente en Commons Codec : clase Base64a decode(byte[] array)oencode(byte[] array)

La guayaba ahora tiene decodificación Base64 incorporada.

Utilice BaseEncoding.base64 (). Decode ()

En cuanto a tratar con posibles espacios en blanco en el uso de entrada

BaseEncoding.base64().decode(CharMatcher.WHITESPACE.removeFrom(...));

Vea esta discusión para más información

Mi solución es más rápida y fácil.

public class MyBase64 {

    private final static char[] ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

    private static int[]  toInt   = new int[128];

    static {
        for(int i=0; i< ALPHABET.length; i++){
            toInt[ALPHABET[i]]= i;
        }
    }

    /**
     * Translates the specified byte array into Base64 string.
     *
     * @param buf the byte array (not null)
     * @return the translated Base64 string (not null)
     */
    public static String encode(byte[] buf){
        int size = buf.length;
        char[] ar = new char[((size + 2) / 3) * 4];
        int a = 0;
        int i=0;
        while(i < size){
            byte b0 = buf[i++];
            byte b1 = (i < size) ? buf[i++] : 0;
            byte b2 = (i < size) ? buf[i++] : 0;

            int mask = 0x3F;
            ar[a++] = ALPHABET[(b0 >> 2) & mask];
            ar[a++] = ALPHABET[((b0 << 4) | ((b1 & 0xFF) >> 4)) & mask];
            ar[a++] = ALPHABET[((b1 << 2) | ((b2 & 0xFF) >> 6)) & mask];
            ar[a++] = ALPHABET[b2 & mask];
        }
        switch(size % 3){
            case 1: ar[--a]  = '=';
            case 2: ar[--a]  = '=';
        }
        return new String(ar);
    }

    /**
     * Translates the specified Base64 string into a byte array.
     *
     * @param s the Base64 string (not null)
     * @return the byte array (not null)
     */
    public static byte[] decode(String s){
        int delta = s.endsWith( "==" ) ? 2 : s.endsWith( "=" ) ? 1 : 0;
        byte[] buffer = new byte[s.length()*3/4 - delta];
        int mask = 0xFF;
        int index = 0;
        for(int i=0; i< s.length(); i+=4){
            int c0 = toInt[s.charAt( i )];
            int c1 = toInt[s.charAt( i + 1)];
            buffer[index++]= (byte)(((c0 << 2) | (c1 >> 4)) & mask);
            if(index >= buffer.length){
                return buffer;
            }
            int c2 = toInt[s.charAt( i + 2)];
            buffer[index++]= (byte)(((c1 << 4) | (c2 >> 2)) & mask);
            if(index >= buffer.length){
                return buffer;
            }
            int c3 = toInt[s.charAt( i + 3 )];
            buffer[index++]= (byte)(((c2 << 6) | c3) & mask);
        }
        return buffer;
    } 

}

Aquí está mi propia implementación, si podría ser útil para alguien:

public class Base64Coder {

    // The line separator string of the operating system.
    private static final String systemLineSeparator = System.getProperty("line.separator");

    // Mapping table from 6-bit nibbles to Base64 characters.
    private static final char[] map1 = new char[64];
       static {
          int i=0;
          for (char c='A'; c<='Z'; c++) map1[i++] = c;
          for (char c='a'; c<='z'; c++) map1[i++] = c;
          for (char c='0'; c<='9'; c++) map1[i++] = c;
          map1[i++] = '+'; map1[i++] = '/'; }

    // Mapping table from Base64 characters to 6-bit nibbles.
    private static final byte[] map2 = new byte[128];
       static {
          for (int i=0; i<map2.length; i++) map2[i] = -1;
          for (int i=0; i<64; i++) map2[map1[i]] = (byte)i; }

    /**
    * Encodes a string into Base64 format.
    * No blanks or line breaks are inserted.
    * @param s  A String to be encoded.
    * @return   A String containing the Base64 encoded data.
    */
    public static String encodeString (String s) {
       return new String(encode(s.getBytes())); }

    /**
    * Encodes a byte array into Base 64 format and breaks the output into lines of 76 characters.
    * This method is compatible with <code>sun.misc.BASE64Encoder.encodeBuffer(byte[])</code>.
    * @param in  An array containing the data bytes to be encoded.
    * @return    A String containing the Base64 encoded data, broken into lines.
    */
    public static String encodeLines (byte[] in) {
       return encodeLines(in, 0, in.length, 76, systemLineSeparator); }

    /**
    * Encodes a byte array into Base 64 format and breaks the output into lines.
    * @param in            An array containing the data bytes to be encoded.
    * @param iOff          Offset of the first byte in <code>in</code> to be processed.
    * @param iLen          Number of bytes to be processed in <code>in</code>, starting at <code>iOff</code>.
    * @param lineLen       Line length for the output data. Should be a multiple of 4.
    * @param lineSeparator The line separator to be used to separate the output lines.
    * @return              A String containing the Base64 encoded data, broken into lines.
    */
    public static String encodeLines (byte[] in, int iOff, int iLen, int lineLen, String lineSeparator) {
       int blockLen = (lineLen*3) / 4;
       if (blockLen <= 0) throw new IllegalArgumentException();
       int lines = (iLen+blockLen-1) / blockLen;
       int bufLen = ((iLen+2)/3)*4 + lines*lineSeparator.length();
       StringBuilder buf = new StringBuilder(bufLen);
       int ip = 0;
       while (ip < iLen) {
          int l = Math.min(iLen-ip, blockLen);
          buf.append (encode(in, iOff+ip, l));
          buf.append (lineSeparator);
          ip += l; }
       return buf.toString(); }

    /**
    * Encodes a byte array into Base64 format.
    * No blanks or line breaks are inserted in the output.
    * @param in  An array containing the data bytes to be encoded.
    * @return    A character array containing the Base64 encoded data.
    */
    public static char[] encode (byte[] in) {
       return encode(in, 0, in.length); }

    /**
    * Encodes a byte array into Base64 format.
    * No blanks or line breaks are inserted in the output.
    * @param in    An array containing the data bytes to be encoded.
    * @param iLen  Number of bytes to process in <code>in</code>.
    * @return      A character array containing the Base64 encoded data.
    */
    public static char[] encode (byte[] in, int iLen) {
       return encode(in, 0, iLen); }

    /**
    * Encodes a byte array into Base64 format.
    * No blanks or line breaks are inserted in the output.
    * @param in    An array containing the data bytes to be encoded.
    * @param iOff  Offset of the first byte in <code>in</code> to be processed.
    * @param iLen  Number of bytes to process in <code>in</code>, starting at <code>iOff</code>.
    * @return      A character array containing the Base64 encoded data.
    */
    public static char[] encode (byte[] in, int iOff, int iLen) {
       int oDataLen = (iLen*4+2)/3;       // output length without padding
       int oLen = ((iLen+2)/3)*4;         // output length including padding
       char[] out = new char[oLen];
       int ip = iOff;
       int iEnd = iOff + iLen;
       int op = 0;
       while (ip < iEnd) {
          int i0 = in[ip++] & 0xff;
          int i1 = ip < iEnd ? in[ip++] & 0xff : 0;
          int i2 = ip < iEnd ? in[ip++] & 0xff : 0;
          int o0 = i0 >>> 2;
          int o1 = ((i0 &   3) << 4) | (i1 >>> 4);
          int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
          int o3 = i2 & 0x3F;
          out[op++] = map1[o0];
          out[op++] = map1[o1];
          out[op] = op < oDataLen ? map1[o2] : '='; op++;
          out[op] = op < oDataLen ? map1[o3] : '='; op++; }
       return out; }

    /**
    * Decodes a string from Base64 format.
    * No blanks or line breaks are allowed within the Base64 encoded input data.
    * @param s  A Base64 String to be decoded.
    * @return   A String containing the decoded data.
    * @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
    */
    public static String decodeString (String s) {
       return new String(decode(s)); }

    /**
    * Decodes a byte array from Base64 format and ignores line separators, tabs and blanks.
    * CR, LF, Tab and Space characters are ignored in the input data.
    * This method is compatible with <code>sun.misc.BASE64Decoder.decodeBuffer(String)</code>.
    * @param s  A Base64 String to be decoded.
    * @return   An array containing the decoded data bytes.
    * @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
    */
    public static byte[] decodeLines (String s) {
       char[] buf = new char[s.length()];
       int p = 0;
       for (int ip = 0; ip < s.length(); ip++) {
          char c = s.charAt(ip);
          if (c != ' ' && c != '\r' && c != '\n' && c != '\t')
             buf[p++] = c; }
       return decode(buf, 0, p); }

    /**
    * Decodes a byte array from Base64 format.
    * No blanks or line breaks are allowed within the Base64 encoded input data.
    * @param s  A Base64 String to be decoded.
    * @return   An array containing the decoded data bytes.
    * @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
    */
    public static byte[] decode (String s) {
       return decode(s.toCharArray()); }

    /**
    * Decodes a byte array from Base64 format.
    * No blanks or line breaks are allowed within the Base64 encoded input data.
    * @param in  A character array containing the Base64 encoded data.
    * @return    An array containing the decoded data bytes.
    * @throws    IllegalArgumentException If the input is not valid Base64 encoded data.
    */
    public static byte[] decode (char[] in) {
       return decode(in, 0, in.length); }

    /**
    * Decodes a byte array from Base64 format.
    * No blanks or line breaks are allowed within the Base64 encoded input data.
    * @param in    A character array containing the Base64 encoded data.
    * @param iOff  Offset of the first character in <code>in</code> to be processed.
    * @param iLen  Number of characters to process in <code>in</code>, starting at <code>iOff</code>.
    * @return      An array containing the decoded data bytes.
    * @throws      IllegalArgumentException If the input is not valid Base64 encoded data.
    */
    public static byte[] decode (char[] in, int iOff, int iLen) {
       if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4.");
       while (iLen > 0 && in[iOff+iLen-1] == '=') iLen--;
       int oLen = (iLen*3) / 4;
       byte[] out = new byte[oLen];
       int ip = iOff;
       int iEnd = iOff + iLen;
       int op = 0;
       while (ip < iEnd) {
          int i0 = in[ip++];
          int i1 = in[ip++];
          int i2 = ip < iEnd ? in[ip++] : 'A';
          int i3 = ip < iEnd ? in[ip++] : 'A';
          if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
             throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
          int b0 = map2[i0];
          int b1 = map2[i1];
          int b2 = map2[i2];
          int b3 = map2[i3];
          if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
             throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
          int o0 = ( b0       <<2) | (b1>>>4);
          int o1 = ((b1 & 0xf)<<4) | (b2>>>2);
          int o2 = ((b2 &   3)<<6) |  b3;
          out[op++] = (byte)o0;
          if (op<oLen) out[op++] = (byte)o1;
          if (op<oLen) out[op++] = (byte)o2; }
       return out; }

    // Dummy constructor.
    private Base64Coder() {}
}

Como una alternativa a sun.misc.BASE64Decoderlas bibliotecas o no centrales, mira javax.mail.internet.MimeUtility.decode().

public static byte[] encode(byte[] b) throws Exception {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    OutputStream b64os = MimeUtility.encode(baos, "base64");
    b64os.write(b);
    b64os.close();
    return baos.toByteArray();
}
public static byte[] decode(byte[] b) throws Exception {
    ByteArrayInputStream bais = new ByteArrayInputStream(b);
    InputStream b64is = MimeUtility.decode(bais, "base64");
    byte[] tmp = new byte[b.length];
    int n = b64is.read(tmp);
    byte[] res = new byte[n];
    System.arraycopy(tmp, 0, res, 0, n);
    return res;
}

Enlace con código completo: codificar / decodificar a / desde Base64

Otra respuesta tardía, pero mi evaluación comparativa muestra que la implementación de Jetty del codificador Base64 es bastante rápida. No tan rápido como MiGBase64 pero más rápido que iHarder Base64 .

import org.eclipse.jetty.util.B64Code;

final String decoded = B64Code.decode(encoded, "UTF-8");

También hice algunos puntos de referencia:

      library     |    encode    |    decode   
------------------+--------------+-------------
 'MiGBase64'      |  10146001.00 |  6426446.00
 'Jetty B64Code'  |   8846191.00 |  3101361.75
 'iHarder Base64' |   3259590.50 |  2505280.00
 'Commons-Codec'  |    241318.04 |   255179.96

Estas son carreras / segundo, por lo que cuanto más alto, mejor.

Dado un ejemplo de prueba de codificación / decodificación de javax.xml.bind.DatatypeConverter usando los métodos parseBase64Binary () e printBase64Binary () en referencia a @ jeremy-ross y @nightfirecat answer.

@Test
public void EncodeDecode() {
    //ENCODE
    String hello = "Hello World";
    byte[] helloBytes = hello.getBytes(StandardCharsets.UTF_8);
    String encodedHello = DatatypeConverter.printBase64Binary(helloBytes);
    LOGGER.info(hello + " encoded=> " + encodedHello);

    //DECODE
    byte[] encodedHelloBytes = DatatypeConverter.parseBase64Binary(encodedHello);
    String helloAgain = new String(encodedHelloBytes, StandardCharsets.UTF_8) ;
    LOGGER.info(encodedHello + " decoded=> " + helloAgain);

    Assert.assertEquals(hello, helloAgain);
}

Resultado:

INFO - Hello World encoded=> SGVsbG8gV29ybGQ=
INFO - SGVsbG8gV29ybGQ= decoded=> Hello World

Si prefiere una solución basada en el rendimiento, puede usar "MiGBase64"

http://migbase64.sourceforge.net/

public class Base64Test {
    public static void main(String[] args) {
    String encodeToString = Base64.encodeToString("JavaTips.net".getBytes(), true);
    System.out.println("encodeToString " + encodeToString);
    byte[] decodedBytes = Base64.decode(encodeToString.getBytes());
    System.out.println("decodedBytes " + new String(decodedBytes));
    }
}

Esta es una respuesta tardía , pero Joshua Bloch comprometió su Base64clase (cuando trabajaba para Sun, ejem, Oracle) bajo el java.util.prefspaquete. Esta clase existió desde JDK 1.4.

P.ej

String currentString = "Hello World";
String base64String = java.util.prefs.Base64.byteArrayToBase64(currentString.getBytes("UTF-8"));

Espero que esto te ayude:

import com.sun.org.apache.xml.internal.security.utils.Base64;
String str="Hello World";
String base64_str=Base64.encode(str.getBytes("UTF-8"));

O:

String str="Hello World";
String base64_str="";
try
   {base64_str=(String)Class.forName("java.util.prefs.Base64").getDeclaredMethod("byteArrayToBase64", new Class[]{byte[].class}).invoke(null, new Object[]{str.getBytes("UTF-8")});
   }
catch (Exception ee) {}

java.util.prefs.Base64trabaja en local rt.jar,

Pero no está en la Lista Blanca de la Clase JRE

y no en Clases disponibles que no figuran en la lista blanca de GAE / J

¡Qué pena!

PD. En Android, es fácil porque android.util.Base64se ha incluido desde el nivel 8 de la API de Android.

Puede escribir o descargar un archivo de la cadena Base64 codificada:

Base64 base64 = new Base64(); 
String encodedFile="JVBERi0xLjUKJeLjz9MKMSAwIG9iago8PCAKICAgL1R5cGUgL0NhdGFsb2cKICAgL1BhZ2VzIDIgMCBSCiAgIC9QYWdlTGF5b3V0IC9TaW5"; 
              byte[] dd=encodedFile.getBytes();
            byte[] bytes = Base64.decodeBase64(dd);

 response.setHeader("Content-disposition", "attachment; filename=\""+filename+"\"");
            response.setHeader("Cache-Control", "no-cache");
            response.setHeader("Expires", "-1");

            // actually send result bytes
            response.getOutputStream().write(bytes);

Trabajó para mí y espero que también para ti ...

La implementación de Java 8 java.util.Base64no tiene dependencias en otras clases específicas de Java 8.

No estoy seguro de si esto funcionará para el proyecto Java 6, pero es posible copiar y pegar el Base64.javaarchivo en un proyecto Java 7 y compilarlo sin otra modificación que la importación de java.util.Arrays y java.util.Objects.

Tenga en cuenta que el archivo Base64.java está cubierto por GNU GPL2

Usé android.util.base64que funciona bastante bien sin ninguna dependencia:

Uso:

byte[] decodedKey = Base64.decode(encodedPublicKey, Base64.DEFAULT);

paquete com.test;

import java.io.UnsupportedEncodingException;

/**
 * Utilities for encoding and decoding the Base64 representation of
 * binary data.  See RFCs <a
 * href="http://www.ietf.org/rfc/rfc2045.txt">2045</a> and <a
 * href="http://www.ietf.org/rfc/rfc3548.txt">3548</a>.
 */
public class Base64 {

    public static final int DEFAULT = 0;


    public static final int NO_PADDING = 1;


    public static final int NO_WRAP = 2;


    public static final int CRLF = 4;


    public static final int URL_SAFE = 8;


    public static final int NO_CLOSE = 16;

    //  --------------------------------------------------------
    //  shared code
    //  --------------------------------------------------------

    /* package */ static abstract class Coder {
        public byte[] output;
        public int op;

        public abstract boolean process(byte[] input, int offset, int len, boolean finish);


        public abstract int maxOutputSize(int len);
    }

    //  --------------------------------------------------------
    //  decoding
    //  --------------------------------------------------------


    public static byte[] decode(String str, int flags) {
        return decode(str.getBytes(), flags);
    }

    public static byte[] decode(byte[] input, int flags) {
        return decode(input, 0, input.length, flags);
    }


    public static byte[] decode(byte[] input, int offset, int len, int flags) {
        // Allocate space for the most data the input could represent.
        // (It could contain less if it contains whitespace, etc.)
        Decoder decoder = new Decoder(flags, new byte[len*3/4]);

        if (!decoder.process(input, offset, len, true)) {
            throw new IllegalArgumentException("bad base-64");
        }

        // Maybe we got lucky and allocated exactly enough output space.
        if (decoder.op == decoder.output.length) {
            return decoder.output;
        }

        // Need to shorten the array, so allocate a new one of the
        // right size and copy.
        byte[] temp = new byte[decoder.op];
        System.arraycopy(decoder.output, 0, temp, 0, decoder.op);
        return temp;
    }

   static class Decoder extends Coder {       
        private static final int DECODE[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        };

        /**
         * Decode lookup table for the "web safe" variant (RFC 3548
         * sec. 4) where - and _ replace + and /.
         */
        private static final int DECODE_WEBSAFE[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63,
            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        };

        /** Non-data values in the DECODE arrays. */
        private static final int SKIP = -1;
        private static final int EQUALS = -2;


        private int state;   // state number (0 to 6)
        private int value;

        final private int[] alphabet;

        public Decoder(int flags, byte[] output) {
            this.output = output;

            alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE;
            state = 0;
            value = 0;
        }


        public int maxOutputSize(int len) {
            return len * 3/4 + 10;
        }

        /**
         * Decode another block of input data.
         *
         * @return true if the state machine is still healthy.  false if
         *         bad base-64 data has been detected in the input stream.
         */
        public boolean process(byte[] input, int offset, int len, boolean finish) {
            if (this.state == 6) return false;

            int p = offset;
            len += offset;

            int state = this.state;
            int value = this.value;
            int op = 0;
            final byte[] output = this.output;
            final int[] alphabet = this.alphabet;

            while (p < len) {                
                if (state == 0) {
                    while (p+4 <= len &&
                           (value = ((alphabet[input[p] & 0xff] << 18) |
                                     (alphabet[input[p+1] & 0xff] << 12) |
                                     (alphabet[input[p+2] & 0xff] << 6) |
                                     (alphabet[input[p+3] & 0xff]))) >= 0) {
                        output[op+2] = (byte) value;
                        output[op+1] = (byte) (value >> 8);
                        output[op] = (byte) (value >> 16);
                        op += 3;
                        p += 4;
                    }
                    if (p >= len) break;
                }

                int d = alphabet[input[p++] & 0xff];

                switch (state) {
                case 0:
                    if (d >= 0) {
                        value = d;
                        ++state;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 1:
                    if (d >= 0) {
                        value = (value << 6) | d;
                        ++state;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 2:
                    if (d >= 0) {
                        value = (value << 6) | d;
                        ++state;
                    } else if (d == EQUALS) {
                        // Emit the last (partial) output tuple;
                        // expect exactly one more padding character.
                        output[op++] = (byte) (value >> 4);
                        state = 4;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 3:
                    if (d >= 0) {
                        // Emit the output triple and return to state 0.
                        value = (value << 6) | d;
                        output[op+2] = (byte) value;
                        output[op+1] = (byte) (value >> 8);
                        output[op] = (byte) (value >> 16);
                        op += 3;
                        state = 0;
                    } else if (d == EQUALS) {
                        // Emit the last (partial) output tuple;
                        // expect no further data or padding characters.
                        output[op+1] = (byte) (value >> 2);
                        output[op] = (byte) (value >> 10);
                        op += 2;
                        state = 5;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 4:
                    if (d == EQUALS) {
                        ++state;
                    } else if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;

                case 5:
                    if (d != SKIP) {
                        this.state = 6;
                        return false;
                    }
                    break;
                }
            }

            if (!finish) {
                // We're out of input, but a future call could provide
                // more.
                this.state = state;
                this.value = value;
                this.op = op;
                return true;
            }


            switch (state) {
            case 0:
                break;
            case 1:
                this.state = 6;
                return false;
            case 2:
                output[op++] = (byte) (value >> 4);
                break;
            case 3:
               output[op++] = (byte) (value >> 10);
                output[op++] = (byte) (value >> 2);
                break;
            case 4:
                this.state = 6;
                return false;
            case 5:
                break;
            }

            this.state = state;
            this.op = op;
            return true;
        }
    }

    //  --------------------------------------------------------
    //  encoding
    //  --------------------------------------------------------    
    public static String encodeToString(byte[] input, int flags) {
        try {
            return new String(encode(input, flags), "US-ASCII");
        } catch (UnsupportedEncodingException e) {
            // US-ASCII is guaranteed to be available.
            throw new AssertionError(e);
        }
    }


    public static String encodeToString(byte[] input, int offset, int len, int flags) {
        try {
            return new String(encode(input, offset, len, flags), "US-ASCII");
        } catch (UnsupportedEncodingException e) {
            // US-ASCII is guaranteed to be available.
            throw new AssertionError(e);
        }
    }


    public static byte[] encode(byte[] input, int flags) {
        return encode(input, 0, input.length, flags);
    }


    public static byte[] encode(byte[] input, int offset, int len, int flags) {
        Encoder encoder = new Encoder(flags, null);

        // Compute the exact length of the array we will produce.
        int output_len = len / 3 * 4;

        // Account for the tail of the data and the padding bytes, if any.
        if (encoder.do_padding) {
            if (len % 3 > 0) {
                output_len += 4;
            }
        } else {
            switch (len % 3) {
                case 0: break;
                case 1: output_len += 2; break;
                case 2: output_len += 3; break;
            }
        }

        // Account for the newlines, if any.
        if (encoder.do_newline && len > 0) {
            output_len += (((len-1) / (3 * Encoder.LINE_GROUPS)) + 1) *
                (encoder.do_cr ? 2 : 1);
        }

        encoder.output = new byte[output_len];
        encoder.process(input, offset, len, true);

        assert encoder.op == output_len;

        return encoder.output;
    }

    /* package */ static class Encoder extends Coder {
        /**
         * Emit a new line every this many output tuples.  Corresponds to
         * a 76-character line length (the maximum allowable according to
         * <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>).
         */
        public static final int LINE_GROUPS = 19;

        /**
         * Lookup table for turning Base64 alphabet positions (6 bits)
         * into output bytes.
         */
        private static final byte ENCODE[] = {
            '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', '+', '/',
        };

        /**
         * Lookup table for turning Base64 alphabet positions (6 bits)
         * into output bytes.
         */
        private static final byte ENCODE_WEBSAFE[] = {
            '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', '-', '_',
        };

        final private byte[] tail;
        /* package */ int tailLen;
        private int count;

        final public boolean do_padding;
        final public boolean do_newline;
        final public boolean do_cr;
        final private byte[] alphabet;

        public Encoder(int flags, byte[] output) {
            this.output = output;

            do_padding = (flags & NO_PADDING) == 0;
            do_newline = (flags & NO_WRAP) == 0;
            do_cr = (flags & CRLF) != 0;
            alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;

            tail = new byte[2];
            tailLen = 0;

            count = do_newline ? LINE_GROUPS : -1;
        }

        /**
         * @return an overestimate for the number of bytes {@code
         * len} bytes could encode to.
         */
        public int maxOutputSize(int len) {
            return len * 8/5 + 10;
        }

        public boolean process(byte[] input, int offset, int len, boolean finish) {
            // Using local variables makes the encoder about 9% faster.
            final byte[] alphabet = this.alphabet;
            final byte[] output = this.output;
            int op = 0;
            int count = this.count;

            int p = offset;
            len += offset;
            int v = -1;

            // First we need to concatenate the tail of the previous call
            // with any input bytes available now and see if we can empty
            // the tail.

            switch (tailLen) {
                case 0:
                    // There was no tail.
                    break;

                case 1:
                    if (p+2 <= len) {
                        // A 1-byte tail with at least 2 bytes of
                        // input available now.
                        v = ((tail[0] & 0xff) << 16) |
                            ((input[p++] & 0xff) << 8) |
                            (input[p++] & 0xff);
                        tailLen = 0;
                    };
                    break;

                case 2:
                    if (p+1 <= len) {
                        // A 2-byte tail with at least 1 byte of input.
                        v = ((tail[0] & 0xff) << 16) |
                            ((tail[1] & 0xff) << 8) |
                            (input[p++] & 0xff);
                        tailLen = 0;
                    }
                    break;
            }

            if (v != -1) {
                output[op++] = alphabet[(v >> 18) & 0x3f];
                output[op++] = alphabet[(v >> 12) & 0x3f];
                output[op++] = alphabet[(v >> 6) & 0x3f];
                output[op++] = alphabet[v & 0x3f];
                if (--count == 0) {
                    if (do_cr) output[op++] = '\r';
                    output[op++] = '\n';
                    count = LINE_GROUPS;
                }
            }

            // At this point either there is no tail, or there are fewer
            // than 3 bytes of input available.

            // The main loop, turning 3 input bytes into 4 output bytes on
            // each iteration.
            while (p+3 <= len) {
                v = ((input[p] & 0xff) << 16) |
                    ((input[p+1] & 0xff) << 8) |
                    (input[p+2] & 0xff);
                output[op] = alphabet[(v >> 18) & 0x3f];
                output[op+1] = alphabet[(v >> 12) & 0x3f];
                output[op+2] = alphabet[(v >> 6) & 0x3f];
                output[op+3] = alphabet[v & 0x3f];
                p += 3;
                op += 4;
                if (--count == 0) {
                    if (do_cr) output[op++] = '\r';
                    output[op++] = '\n';
                    count = LINE_GROUPS;
                }
            }

            if (finish) {

                if (p-tailLen == len-1) {
                    int t = 0;
                    v = ((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 4;
                    tailLen -= t;
                    output[op++] = alphabet[(v >> 6) & 0x3f];
                    output[op++] = alphabet[v & 0x3f];
                    if (do_padding) {
                        output[op++] = '=';
                        output[op++] = '=';
                    }
                    if (do_newline) {
                        if (do_cr) output[op++] = '\r';
                        output[op++] = '\n';
                    }
                } else if (p-tailLen == len-2) {
                    int t = 0;
                    v = (((tailLen > 1 ? tail[t++] : input[p++]) & 0xff) << 10) |
                        (((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 2);
                    tailLen -= t;
                    output[op++] = alphabet[(v >> 12) & 0x3f];
                    output[op++] = alphabet[(v >> 6) & 0x3f];
                    output[op++] = alphabet[v & 0x3f];
                    if (do_padding) {
                        output[op++] = '=';
                    }
                    if (do_newline) {
                        if (do_cr) output[op++] = '\r';
                        output[op++] = '\n';
                    }
                } else if (do_newline && op > 0 && count != LINE_GROUPS) {
                    if (do_cr) output[op++] = '\r';
                    output[op++] = '\n';
                }

                assert tailLen == 0;
                assert p == len;
            } else {
                // Save the leftovers in tail to be consumed on the next
                // call to encodeInternal.

                if (p == len-1) {
                    tail[tailLen++] = input[p];
                } else if (p == len-2) {
                    tail[tailLen++] = input[p];
                    tail[tailLen++] = input[p+1];
                }
            }

            this.op = op;
            this.count = count;

            return true;
        }
    }

    private Base64() { }   // don't instantiate
}