Android Base64 Decode 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;
/*/*from w w  w.ja  v  a2s  . c o  m*/
 * Copyright 2009 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

public class Main {
    /**
     * An array mapping legal base 64 characters [a-zA-Z0-9$_] to their associated
     * 6-bit values. The source indices 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. decode(String base64)
2. decode(String data)
3. decode(String str)
4. decode(String s)
5. decode(String str)
6. decodes(String base64)
7. decodeBase64(String encodedString)
8. decoderBase64File(String base64Code, String type)
9. decode(String data, OutputStream out)