Base64Encoder.java

/*
 * #%L
 * Gravia :: Resource
 * %%
 * Copyright (C) 2010 - 2014 JBoss by Red Hat
 * %%
 * 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.
 * #L%
 */

package org.jboss.gravia.utils;

import java.nio.charset.Charset;

/**
 * Bease64 encoding utilities.
 *
 * @author Niclas Hedhman
 * @author Alin Dreghiciu
 * @since 0.5.0, January 16, 2008
 */
public class Base64Encoder {
    public static final Charset base64CharSet = Charset.forName("ISO-8859-1");

    /**
     * Utility class. ment to be used via static methods.
     */
    private Base64Encoder() {
        // utility class
    }

    /**
     * Encodes a String into a base 64 String. The resulting encoding is chunked at 76 bytes.
     * <p/>
     *
     * @param s String to encode.
     * @return encoded string.
     */
    public static String encode(String s) {
        byte[] sBytes = s.getBytes();
        sBytes = encode(sBytes);
        s = new String(sBytes);
        return s;
    }

    /**
     * Decodes a base 64 String into a String.
     * <p/>
     *
     * @param s String to decode.
     * @return encoded string.
     * @throws java.lang.IllegalArgumentException
     *          thrown if the given byte array was not valid com.sun.syndication.io.impl.Base64 encoding.
     */
    public static String decode(String s)
            throws IllegalArgumentException {
        s = s.replaceAll("\n", "");
        s = s.replaceAll("\r", "");
        byte[] sBytes = s.getBytes(base64CharSet);
        sBytes = decode(sBytes);
        s = new String(sBytes, base64CharSet);
        return s;
    }

    private static final byte[] ALPHASET =
            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".getBytes();

    private static final int I6O2 = 255 - 3;
    private static final int O6I2 = 3;
    private static final int I4O4 = 255 - 15;
    private static final int O4I4 = 15;
    private static final int I2O6 = 255 - 63;
    private static final int O2I6 = 63;

    /**
     * Encodes a byte array into a base 64 byte array.
     * <p/>
     *
     * @param dData byte array to encode.
     * @return encoded byte array.
     */
    public static byte[] encode(byte[] dData) {
        if (dData == null) {
            throw new IllegalArgumentException("Cannot encode null");
        }
        byte[] eData = new byte[((dData.length + 2) / 3) * 4];

        int eIndex = 0;
        for (int i = 0; i < dData.length; i += 3) {
            int d1;
            int d2 = 0;
            int d3 = 0;
            int e1;
            int e2;
            int e3;
            int e4;
            int pad = 0;

            d1 = dData[i];
            if ((i + 1) < dData.length) {
                d2 = dData[i + 1];
                if ((i + 2) < dData.length) {
                    d3 = dData[i + 2];
                } else {
                    pad = 1;
                }
            } else {
                pad = 2;
            }

            e1 = ALPHASET[(d1 & I6O2) >> 2];
            e2 = ALPHASET[(d1 & O6I2) << 4 | (d2 & I4O4) >> 4];
            e3 = ALPHASET[(d2 & O4I4) << 2 | (d3 & I2O6) >> 6];
            e4 = ALPHASET[(d3 & O2I6)];

            eData[eIndex++] = (byte) e1;
            eData[eIndex++] = (byte) e2;
            eData[eIndex++] = (pad < 2) ? (byte) e3 : (byte) '=';
            eData[eIndex++] = (pad < 1) ? (byte) e4 : (byte) '=';

        }
        return eData;
    }

    private final static int[] CODES = new int[256];

    static {
        for (int i = 0; i < CODES.length; i++) {
            CODES[i] = 64;
        }
        for (int i = 0; i < ALPHASET.length; i++) {
            CODES[ALPHASET[i]] = i;
        }
    }

    /**
     * Dencodes a com.sun.syndication.io.impl.Base64 byte array.
     * <p/>
     *
     * @param eData byte array to decode.
     * @return decoded byte array.
     * @throws java.lang.IllegalArgumentException
     *          thrown if the given byte array was not valid com.sun.syndication.io.impl.Base64 encoding.
     */
    public static byte[] decode(byte[] eData) {
        if (eData == null) {
            throw new IllegalArgumentException("Cannot decode null");
        }
        byte[] cleanEData = eData.clone();
        int cleanELength = 0;
        for (byte anEData : eData) {
            if (anEData < 256 && CODES[anEData] < 64) {
                cleanEData[cleanELength++] = anEData;
            }
        }

        int dLength = (cleanELength / 4) * 3;
        switch (cleanELength % 4) {
            case 3:
                dLength += 2;
                break;
            case 2:
                dLength++;
                break;
        }

        byte[] dData = new byte[dLength];
        int dIndex = 0;
        for (int i = 0; i < eData.length; i += 4) {
            if ((i + 3) > eData.length) {
                throw new IllegalArgumentException(
                        "byte array is not a valid com.sun.syndication.io.impl.Base64 encoding"
                );
            }
            int e1 = CODES[cleanEData[i]];
            int e2 = CODES[cleanEData[i + 1]];
            int e3 = CODES[cleanEData[i + 2]];
            int e4 = CODES[cleanEData[i + 3]];
            dData[dIndex++] = (byte) ((e1 << 2) | (e2 >> 4));
            if (dIndex < dData.length) {
                dData[dIndex++] = (byte) ((e2 << 4) | (e3 >> 2));
            }
            if (dIndex < dData.length) {
                dData[dIndex++] = (byte) ((e3 << 6) | (e4));
            }
        }
        return dData;
    }
}