Java Base64 Convert to fromBase64(String data)

Description

Decode a base64 string into a byte array.

License

Apache License

Parameter

Parameter	Description
data	the encoded data.

Return

a byte array.

Declaration

public static byte[] fromBase64(String data) 

Method Source Code

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

public class Main {
    /**/*from   w ww .  j  a v a  2s.  co m*/
     * An array mapping legal base 64 characters [a-zA-Z0-9$_] to their associated 6-bit values. The source indicies
     * will be given by 7-bit ASCII characters, thus the array size needs to be 128 (actually 123 would suffice for the
     * given set of characters in use).
     */
    private static final byte[] base64Values = new byte[128];

    /**
     * Decode a base64 string into a byte array.
     * 
     * @param data
     *            the encoded data.
     * @return a byte array.
     * @see #fromBase64(String)
     */
    public static byte[] fromBase64(String data) {
        if (data == null) {
            return null;
        }

        int len = data.length();
        assert (len % 4) == 0;

        if (len == 0) {
            return new byte[0];
        }

        char[] chars = new char[len];
        data.getChars(0, len, chars, 0);

        int olen = 3 * (len / 4);
        if (chars[len - 2] == '=') {
            --olen;
        }
        if (chars[len - 1] == '=') {
            --olen;
        }

        byte[] bytes = new byte[olen];

        int iidx = 0;
        int oidx = 0;
        while (iidx < len) {
            int c0 = base64Values[chars[iidx++] & 0xff];
            int c1 = base64Values[chars[iidx++] & 0xff];
            int c2 = base64Values[chars[iidx++] & 0xff];
            int c3 = base64Values[chars[iidx++] & 0xff];
            int c24 = (c0 << 18) | (c1 << 12) | (c2 << 6) | c3;

            bytes[oidx++] = (byte) (c24 >> 16);
            if (oidx == olen) {
                break;
            }
            bytes[oidx++] = (byte) (c24 >> 8);
            if (oidx == olen) {
                break;
            }
            bytes[oidx++] = (byte) c24;
        }

        return bytes;
    }
}

Related

1. fromBase64(byte[] buf, int start, int length)
2. fromBase64(final String encoded)
3. fromBase64(final String input)
4. fromBase64(String base64)
5. fromBase64(String base64Text)
6. fromBase64(String s)
7. fromBase64(String str)
8. fromBase64decodedImageToByte(String base64encoded)
9. fromBase64Impl(String data)