Java Byte Array Encode encode(byte[] data)

Description

encode the input data producing a base 64 encoded byte array.

License

Apache License

Return

a byte array containing the base 64 encoded data.

Declaration

public static byte[] encode(byte[] data) 

Method Source Code

//package com.java2s;
//License from project: Apache License 

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Main {
    protected static final byte[] encodingTable = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E',
            (byte) 'F', (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M',
            (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
            (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c',
            (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k',
            (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's',
            (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', (byte) '0',
            (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8',
            (byte) '9', (byte) '+', (byte) '/' };
    protected static byte padding = (byte) '=';

    /**/* w w  w. j a  va2  s  . c o m*/
     * encode the input data producing a base 64 encoded byte array.
     *
     * @return a byte array containing the base 64 encoded data.
     */
    public static byte[] encode(byte[] data) {
        return encode(data, 0, data.length);
    }

    /**
     * encode the input data producing a base 64 encoded byte array.
     *
     * @return a byte array containing the base 64 encoded data.
     */
    public static byte[] encode(byte[] data, int off, int length) {
        int len = (length + 2) / 3 * 4;
        ByteArrayOutputStream bOut = new ByteArrayOutputStream(len);

        try {
            encode(data, off, length, bOut);
        } catch (Exception e) {
            throw new RuntimeException("exception encoding base64 string: " + e.getMessage(), e);
        }

        return bOut.toByteArray();
    }

    /**
     * encode the input data producing a base 64 output stream.
     *
     * @return the number of bytes produced.
     */
    private static int encode(byte[] data, int off, int length, OutputStream out) throws IOException {

        int modulus = length % 3;
        int dataLength = (length - modulus);
        int a1, a2, a3;

        for (int i = off; i < off + dataLength; i += 3) {
            a1 = data[i] & 0xff;
            a2 = data[i + 1] & 0xff;
            a3 = data[i + 2] & 0xff;

            out.write(encodingTable[(a1 >>> 2) & 0x3f]);
            out.write(encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f]);
            out.write(encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f]);
            out.write(encodingTable[a3 & 0x3f]);
        }

        /*
         * process the tail end.
         */
        int b1, b2, b3;
        int d1, d2;

        switch (modulus) {
        case 0: /* nothing left to do */
            break;
        case 1:
            d1 = data[off + dataLength] & 0xff;
            b1 = (d1 >>> 2) & 0x3f;
            b2 = (d1 << 4) & 0x3f;

            out.write(encodingTable[b1]);
            out.write(encodingTable[b2]);
            out.write(padding);
            out.write(padding);
            break;
        case 2:
            d1 = data[off + dataLength] & 0xff;
            d2 = data[off + dataLength + 1] & 0xff;

            b1 = (d1 >>> 2) & 0x3f;
            b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
            b3 = (d2 << 2) & 0x3f;

            out.write(encodingTable[b1]);
            out.write(encodingTable[b2]);
            out.write(encodingTable[b3]);
            out.write(padding);
            break;
        }

        return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4);
    }
}

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