Android Base64 Byte Array Decode decode(byte[] arr)

Description

Decodes a BASE64 encoded byte array.

Declaration

public static byte[] decode(byte[] arr) 

Method Source Code

//package com.java2s;

public class Main {
    private static final int[] INV = new int[256];

    public static byte[] decode(char[] arr) {
        int length = arr.length;
        if (length == 0)
            return new byte[0];

        int sndx = 0, endx = length - 1;
        int pad = arr[endx] == '=' ? (arr[endx - 1] == '=' ? 2 : 1) : 0;
        int cnt = endx - sndx + 1;
        int sepCnt = length > 76 ? (arr[76] == '\r' ? cnt / 78 : 0) << 1
                : 0;//from w  w w  . j  av a2  s  .c o  m
        int len = ((cnt - sepCnt) * 6 >> 3) - pad;
        byte[] dest = new byte[len];

        int d = 0;
        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
            int i = INV[arr[sndx++]] << 18 | INV[arr[sndx++]] << 12
                    | INV[arr[sndx++]] << 6 | INV[arr[sndx++]];
            dest[d++] = (byte) (i >> 16);
            dest[d++] = (byte) (i >> 8);
            dest[d++] = (byte) i;
            if (sepCnt > 0 && ++cc == 19) {
                sndx += 2;
                cc = 0;
            }
        }

        if (d < len) {
            int i = 0;
            for (int j = 0; sndx <= endx - pad; j++) {
                i |= INV[arr[sndx++]] << (18 - j * 6);
            }
            for (int r = 16; d < len; r -= 8) {
                dest[d++] = (byte) (i >> r);
            }
        }

        return dest;
    }

    /**
     * Decodes a BASE64 encoded byte array.
     */
    public static byte[] decode(byte[] arr) {
        int length = arr.length;
        if (length == 0) {
            return new byte[0];
        }

        int sndx = 0, endx = length - 1;
        int pad = arr[endx] == '=' ? (arr[endx - 1] == '=' ? 2 : 1) : 0;
        int cnt = endx - sndx + 1;
        int sepCnt = length > 76 ? (arr[76] == '\r' ? cnt / 78 : 0) << 1
                : 0;
        int len = ((cnt - sepCnt) * 6 >> 3) - pad;
        byte[] dest = new byte[len];

        int d = 0;
        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
            int i = INV[arr[sndx++]] << 18 | INV[arr[sndx++]] << 12
                    | INV[arr[sndx++]] << 6 | INV[arr[sndx++]];

            dest[d++] = (byte) (i >> 16);
            dest[d++] = (byte) (i >> 8);
            dest[d++] = (byte) i;

            if (sepCnt > 0 && ++cc == 19) {
                sndx += 2;
                cc = 0;
            }
        }

        if (d < len) {
            int i = 0;
            for (int j = 0; sndx <= endx - pad; j++) {
                i |= INV[arr[sndx++]] << (18 - j * 6);
            }
            for (int r = 16; d < len; r -= 8) {
                dest[d++] = (byte) (i >> r);
            }
        }

        return dest;
    }

    /**
     * Decodes a BASE64 encoded string.
     */
    public static byte[] decode(String s) {
        int length = s.length();
        if (length == 0) {
            return new byte[0];
        }

        int sndx = 0, endx = length - 1;
        int pad = s.charAt(endx) == '=' ? (s.charAt(endx - 1) == '=' ? 2
                : 1) : 0;
        int cnt = endx - sndx + 1;
        int sepCnt = length > 76 ? (s.charAt(76) == '\r' ? cnt / 78 : 0) << 1
                : 0;
        int len = ((cnt - sepCnt) * 6 >> 3) - pad;
        byte[] dest = new byte[len];

        int d = 0;
        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
            int i = INV[s.charAt(sndx++)] << 18
                    | INV[s.charAt(sndx++)] << 12
                    | INV[s.charAt(sndx++)] << 6 | INV[s.charAt(sndx++)];

            dest[d++] = (byte) (i >> 16);
            dest[d++] = (byte) (i >> 8);
            dest[d++] = (byte) i;

            if (sepCnt > 0 && ++cc == 19) {
                sndx += 2;
                cc = 0;
            }
        }

        if (d < len) {
            int i = 0;
            for (int j = 0; sndx <= endx - pad; j++) {
                i |= INV[s.charAt(sndx++)] << (18 - j * 6);
            }
            for (int r = 16; d < len; r -= 8) {
                dest[d++] = (byte) (i >> r);
            }
        }

        return dest;
    }
}

Related

1. decode(final byte[] data)
2. decode(char[] chars, OutputStream out)
3. decode(char[] chars, int off, int len, OutputStream out)