Java String Decode decode(String in)

Description

Base 64 decodes the specified string.

License

Apache License

Parameter

Parameter	Description
in	the string to base 64 decode

Exception

Parameter	Description
IOException	if base 64 encoded string is invalid

Return

the base 64 decoded byte array

Declaration

public static byte[] decode(String in) throws IOException 

Method Source Code

//package com.java2s;
/**/*from   w w w . j  a  v  a  2s  . co m*/
 * Copyright 2012 NetDigital Sweden AB
 *
 * 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.
*/

import java.io.IOException;

public class Main {
    private static final byte[] base64CharsTo6BitNibbles = new byte[128];

    /**
     * Base 64 decodes the specified string.
     * 
     * @param in the string to base 64 decode
     * @return the base 64 decoded byte array
     * @throws IOException if base 64 encoded string is invalid
     */
    public static byte[] decode(String in) throws IOException {
        int len = in.length();

        if (len % 4 != 0) {
            throw new IOException("Length of base 64 encoded string must be a multiple of 4");
        }

        while (len > 0 && in.charAt(len - 1) == '=') {
            len--;
        }

        int oLen = (len * 3) / 4;
        byte[] out = new byte[oLen];
        int ip = 0;
        int iEnd = len;
        int op = 0;

        while (ip < iEnd) {
            int i0 = in.charAt(ip++);
            int i1 = in.charAt(ip++);
            int i2 = ip < iEnd ? in.charAt(ip++) : 'A';
            int i3 = ip < iEnd ? in.charAt(ip++) : 'A';

            if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127) {
                throw new IOException("Illegal character in base64 encoded data");
            }

            int b0 = base64CharsTo6BitNibbles[i0];
            int b1 = base64CharsTo6BitNibbles[i1];
            int b2 = base64CharsTo6BitNibbles[i2];
            int b3 = base64CharsTo6BitNibbles[i3];

            if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0) {
                throw new IOException("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;
    }
}

Related

1. decode(String bytes)
2. decode(String cipherText)
3. decode(String name)
4. decode(String s)
5. decode(String s)
6. decode(String s)