Java Byte Array Decode decodeToString(byte[] arr)

Description

decode To String

License

Open Source License

Declaration

public static String decodeToString(byte[] arr) 

Method Source Code

//package com.java2s;
/**/*from ww w. ja  v  a2 s  .c  om*/
 * Copyright 2013-2014 Guoqiang Chen, Shanghai, China. All rights reserved.
 *
 *   Author: Guoqiang Chen
 *    Email: subchen@gmail.com
 *   WebURL: https://github.com/subchen
 *
 * 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.UnsupportedEncodingException;

public class Main {
    private static final int[] INV = new int[256];
    private static final String ENCODING = "UTF-8";

    public static String decodeToString(byte[] arr) {
        try {
            return new String(decode(arr), ENCODING);
        } catch (UnsupportedEncodingException ignore) {
            return null;
        }
    }

    public static String decodeToString(String s) {
        try {
            return new String(decode(s), ENCODING);
        } catch (UnsupportedEncodingException ignore) {
            return null;
        }
    }

    /**
     * Decodes a BASE64 encoded char array.
     */
    public byte[] decode(char[] arr) {
        int length = arr.length;
        if (length == 0) {
            return new byte[0];
        }

        int sndx = 0, endx = length - 1;
        int pad = arr[endx] == '=' ? (arr[endx - 1] == '=' ? 2 : 1) : 0;
        int cnt = endx - sndx + 1;
        int sepCnt = length > 76 ? (arr[76] == '\r' ? cnt / 78 : 0) << 1 : 0;
        int len = ((cnt - sepCnt) * 6 >> 3) - pad;
        byte[] dest = new byte[len];

        int d = 0;
        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
            int i = INV[arr[sndx++]] << 18 | INV[arr[sndx++]] << 12 | INV[arr[sndx++]] << 6 | INV[arr[sndx++]];

            dest[d++] = (byte) (i >> 16);
            dest[d++] = (byte) (i >> 8);
            dest[d++] = (byte) i;

            if (sepCnt > 0 && ++cc == 19) {
                sndx += 2;
                cc = 0;
            }
        }

        if (d < len) {
            int i = 0;
            for (int j = 0; sndx <= endx - pad; j++) {
                i |= INV[arr[sndx++]] << (18 - j * 6);
            }
            for (int r = 16; d < len; r -= 8) {
                dest[d++] = (byte) (i >> r);
            }
        }

        return dest;
    }

    /**
     * Decodes BASE64 encoded byte array.
     */
    public static byte[] decode(byte[] arr) {
        int length = arr.length;
        if (length == 0) {
            return new byte[0];
        }

        int sndx = 0, endx = length - 1;
        int pad = arr[endx] == '=' ? (arr[endx - 1] == '=' ? 2 : 1) : 0;
        int cnt = endx - sndx + 1;
        int sepCnt = length > 76 ? (arr[76] == '\r' ? cnt / 78 : 0) << 1 : 0;
        int len = ((cnt - sepCnt) * 6 >> 3) - pad;
        byte[] dest = new byte[len];

        int d = 0;
        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
            int i = INV[arr[sndx++]] << 18 | INV[arr[sndx++]] << 12 | INV[arr[sndx++]] << 6 | INV[arr[sndx++]];

            dest[d++] = (byte) (i >> 16);
            dest[d++] = (byte) (i >> 8);
            dest[d++] = (byte) i;

            if (sepCnt > 0 && ++cc == 19) {
                sndx += 2;
                cc = 0;
            }
        }

        if (d < len) {
            int i = 0;
            for (int j = 0; sndx <= endx - pad; j++) {
                i |= INV[arr[sndx++]] << (18 - j * 6);
            }
            for (int r = 16; d < len; r -= 8) {
                dest[d++] = (byte) (i >> r);
            }
        }

        return dest;
    }

    /**
     * Decodes a BASE64 encoded string.
     */
    public static byte[] decode(String s) {
        int length = s.length();
        if (length == 0) {
            return new byte[0];
        }

        int sndx = 0, endx = length - 1;
        int pad = s.charAt(endx) == '=' ? (s.charAt(endx - 1) == '=' ? 2 : 1) : 0;
        int cnt = endx - sndx + 1;
        int sepCnt = length > 76 ? (s.charAt(76) == '\r' ? cnt / 78 : 0) << 1 : 0;
        int len = ((cnt - sepCnt) * 6 >> 3) - pad;
        byte[] dest = new byte[len];

        int d = 0;
        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
            int i = INV[s.charAt(sndx++)] << 18 | INV[s.charAt(sndx++)] << 12 | INV[s.charAt(sndx++)] << 6
                    | INV[s.charAt(sndx++)];

            dest[d++] = (byte) (i >> 16);
            dest[d++] = (byte) (i >> 8);
            dest[d++] = (byte) i;

            if (sepCnt > 0 && ++cc == 19) {
                sndx += 2;
                cc = 0;
            }
        }

        if (d < len) {
            int i = 0;
            for (int j = 0; sndx <= endx - pad; j++) {
                i |= INV[s.charAt(sndx++)] << (18 - j * 6);
            }
            for (int r = 16; d < len; r -= 8) {
                dest[d++] = (byte) (i >> r);
            }
        }

        return dest;
    }
}

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