Base64Coder.java

package org.jaudiotagger.tag.vorbiscomment.util;

import org.jaudiotagger.audio.generic.Utils;

/**
 * Base64Coder
 */
public class Base64Coder {
    // Mapping table from 6-bit nibbles to Base64 characters.
    private static final char[] map1 = new char[64];

    static {
        int i = 0;
        for (char c = 'A'; c <= 'Z'; c++) {
            map1[i++] = c;
        }
        for (char c = 'a'; c <= 'z'; c++) {
            map1[i++] = c;
        }
        for (char c = '0'; c <= '9'; c++) {
            map1[i++] = c;
        }
        map1[i++] = '+';
        map1[i++] = '/';
    }

    // Mapping table from Base64 characters to 6-bit nibbles.
    private static final byte[] map2 = new byte[128];

    static {
        for (int i = 0; i < map2.length; i++) {
            map2[i] = -1;
        }
        for (int i = 0; i < 64; i++) {
            map2[map1[i]] = (byte) i;
        }
    }

    /**
     * Encodes a string into Base64 format.
     * No blanks or line breaks are inserted.
     *
     * @param s a String to be encoded.
     * @return A String with the Base64 encoded data.
     */
    public static String encode(final String s) {
        return new String(encode(Utils.getDefaultBytes(s, "ISO-8859-1")));
    }

    /**
     * Encodes a byte array into Base64 format.
     * No blanks or line breaks are inserted.
     *
     * @param in an array containing the data bytes to be encoded.
     * @return A character array with the Base64 encoded data.
     */
    public static char[] encode(final byte[] in) {
        final int iLen = in.length;
        final int oDataLen = (iLen * 4 + 2) / 3;       // output length without padding
        final int oLen = ((iLen + 2) / 3) * 4;         // output length including padding
        final char[] out = new char[oLen];
        int ip = 0;
        int op = 0;
        while (ip < iLen) {
            final int i0 = in[ip++] & 0xff;
            final int i1 = ip < iLen ? in[ip++] & 0xff : 0;
            final int i2 = ip < iLen ? in[ip++] & 0xff : 0;
            final int o0 = i0 >>> 2;
            final int o1 = ((i0 & 3) << 4) | (i1 >>> 4);
            final int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
            final int o3 = i2 & 0x3F;
            out[op++] = map1[o0];
            out[op++] = map1[o1];
            out[op] = op < oDataLen ? map1[o2] : '=';
            op++;
            out[op] = op < oDataLen ? map1[o3] : '=';
            op++;
        }
        return out;
    }

    /**
     * Decodes a Base64 string.
     *
     * @param s a Base64 String to be decoded.
     * @return An array containing the decoded data bytes.
     * @throws IllegalArgumentException if the input is not valid Base64 encoded data.
     */
    public static byte[] decode(final String s) {
        return decode(s.toCharArray());
    }

    /**
     * Decodes Base64 data.
     * No blanks or line breaks are allowed within the Base64 encoded data.
     *
     * @param in a character array containing the Base64 encoded data.
     * @return An array containing the decoded data bytes.
     * @throws IllegalArgumentException if the input is not valid Base64 encoded data.
     */
    public static byte[] decode(final char[] in) {
        int iLen = in.length;
        if (iLen % 4 != 0) {
            throw new IllegalArgumentException("Length of Base64 encoded input string is not a multiple of 4.");
        }
        while (iLen > 0 && in[iLen - 1] == '=') {
            iLen--;
        }
        final int oLen = (iLen * 3) / 4;
        final byte[] out = new byte[oLen];
        int ip = 0;
        int op = 0;
        while (ip < iLen) {
            final int i0 = in[ip++];
            final int i1 = in[ip++];
            final int i2 = ip < iLen ? in[ip++] : 'A';
            final int i3 = ip < iLen ? in[ip++] : 'A';
            if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127) {
                throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
            }
            final int b0 = map2[i0];
            final int b1 = map2[i1];
            final int b2 = map2[i2];
            final int b3 = map2[i3];
            if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0) {
                throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
            }
            final int o0 = (b0 << 2) | (b1 >>> 4);
            final int o1 = ((b1 & 0xf) << 4) | (b2 >>> 2);
            final 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;
    }
}