Java Byte Array to String by Charset encodeB(String prefix, String text, int usedCharacters, Charset charset, byte[] bytes)

Description

encode B

License

Apache License

Declaration

private static String encodeB(String prefix, String text, int usedCharacters, Charset charset, byte[] bytes) 

Method Source Code

//package com.java2s;
/****************************************************************
 * Licensed to the Apache Software Foundation (ASF) under one   *
 * or more contributor license agreements.  See the NOTICE file *
 * distributed with this work for additional information        *
 * regarding copyright ownership.  The ASF licenses this file   *
 * to you 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.nio.ByteBuffer;
import java.nio.charset.Charset;

public class Main {
    static final byte[] BASE64_TABLE = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
            'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
            'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4',
            '5', '6', '7', '8', '9', '+', '/' };
    private static final byte BASE64_PAD = '=';
    private static final String ENC_WORD_SUFFIX = "?=";
    private static final int ENCODED_WORD_MAX_LENGTH = 75;

    /**/*from   www.  j a  va2  s.  c o  m*/
     * Encodes the specified byte array using the B encoding defined in RFC 2047.
     *
     * @param bytes
     *          byte array to encode.
     * @return encoded string.
     */
    public static String encodeB(byte[] bytes) {
        StringBuilder sb = new StringBuilder();

        int idx = 0;
        final int end = bytes.length;
        for (; idx < end - 2; idx += 3) {
            int data = (bytes[idx] & 0xff) << 16 | (bytes[idx + 1] & 0xff) << 8 | bytes[idx + 2] & 0xff;
            sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
            sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
            sb.append((char) BASE64_TABLE[data >> 6 & 0x3f]);
            sb.append((char) BASE64_TABLE[data & 0x3f]);
        }

        if (idx == end - 2) {
            int data = (bytes[idx] & 0xff) << 16 | (bytes[idx + 1] & 0xff) << 8;
            sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
            sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
            sb.append((char) BASE64_TABLE[data >> 6 & 0x3f]);
            sb.append((char) BASE64_PAD);

        } else if (idx == end - 1) {
            int data = (bytes[idx] & 0xff) << 16;
            sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
            sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
            sb.append((char) BASE64_PAD);
            sb.append((char) BASE64_PAD);
        }

        return sb.toString();
    }

    private static String encodeB(String prefix, String text, int usedCharacters, Charset charset, byte[] bytes) {
        int encodedLength = bEncodedLength(bytes);

        int totalLength = prefix.length() + encodedLength + ENC_WORD_SUFFIX.length();
        if (totalLength <= ENCODED_WORD_MAX_LENGTH - usedCharacters) {
            return prefix + encodeB(bytes) + ENC_WORD_SUFFIX;
        } else {
            int splitOffset = text.offsetByCodePoints(text.length() / 2, -1);

            String part1 = text.substring(0, splitOffset);
            byte[] bytes1 = encode(part1, charset);
            String word1 = encodeB(prefix, part1, usedCharacters, charset, bytes1);

            String part2 = text.substring(splitOffset);
            byte[] bytes2 = encode(part2, charset);
            String word2 = encodeB(prefix, part2, 0, charset, bytes2);

            return word1 + " " + word2;
        }
    }

    private static int bEncodedLength(byte[] bytes) {
        return (bytes.length + 2) / 3 * 4;
    }

    private static byte[] encode(String text, Charset charset) {
        ByteBuffer buffer = charset.encode(text);
        byte[] bytes = new byte[buffer.limit()];
        buffer.get(bytes);
        return bytes;
    }
}

Related

1. decodeCHARSET(byte[] bytes, Charset charset)
2. decodeHelper(byte[] byteArray, int numberOfBytes, java.nio.charset.Charset charset)
3. decodeOrDefault(byte[] data, Charset charset, String defaultValue)
4. decodeWithReplacement(byte[] bytes, Charset cs)
5. encode(byte[] arr, Charset srcCharset, Charset dstCharset)
6. encodingIsCorrect(byte[] bytes, String charset)
7. getAverageBytesPerCharacter(Charset charset)
8. getBytes(final char[] data, String charset)
9. getBytes(final String string, final Charset charset)