java编解码base64

在alibaba的fastjson中base64上增加的一些方法

package littlehow.base64;import java.nio.charset.Charset;import java.util.Arrays;/** * 引用阿里巴巴fastjson中的base64工具 * 自己实现encode方法 * @author     wh * @createtime 2015-11-19 上午11:48:38 * */public class Base64 {    public static final char[] CA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();    public static final int[]  IA = new int[256];    static {        Arrays.fill(IA, -1);        for (int i = 0, iS = CA.length; i < iS; i++)            IA[CA[i]] = i;        IA['='] = 0;    }    /**     * Decodes a BASE64 encoded char array that is known to be resonably well formatted. The method is about twice as     * fast as {@link #decode(char[])}. The preconditions are:<br>     * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>     * + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within     * the encoded string<br>     * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>     *     * @param chars The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.     * @return The decoded array of bytes. May be of length 0.     */    public final static byte[] decodeFast(char[] chars, int offset, int charsLen) {        // Check special case        if (charsLen == 0) {            return new byte[0];        }        int sIx = offset, eIx = offset + charsLen - 1; // Start and end index after trimming.        // Trim illegal chars from start        while (sIx < eIx && IA[chars[sIx]] < 0)            sIx++;        // Trim illegal chars from end        while (eIx > 0 && IA[chars[eIx]] < 0)            eIx--;        // get the padding count (=) (0, 1 or 2)        int pad = chars[eIx] == '=' ? (chars[eIx - 1] == '=' ? 2 : 1) : 0; // Count '=' at end.        int cCnt = eIx - sIx + 1; // Content count including possible separators        int sepCnt = charsLen > 76 ? (chars[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;        int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes        byte[] bytes = new byte[len]; // Preallocate byte[] of exact length        // Decode all but the last 0 - 2 bytes.        int d = 0;        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {            // Assemble three bytes into an int from four "valid" characters.            int i = IA[chars[sIx++]] << 18 | IA[chars[sIx++]] << 12 | IA[chars[sIx++]] << 6 | IA[chars[sIx++]];            // Add the bytes            bytes[d++] = (byte) (i >> 16);            bytes[d++] = (byte) (i >> 8);            bytes[d++] = (byte) i;            // If line separator, jump over it.            if (sepCnt > 0 && ++cc == 19) {                sIx += 2;                cc = 0;            }        }        if (d < len) {            // Decode last 1-3 bytes (incl '=') into 1-3 bytes            int i = 0;            for (int j = 0; sIx <= eIx - pad; j++)                i |= IA[chars[sIx++]] << (18 - j * 6);            for (int r = 16; d < len; r -= 8)                bytes[d++] = (byte) (i >> r);        }        return bytes;    }    public final static byte[] decodeFast(String chars, int offset, int charsLen) {        // Check special case        if (charsLen == 0) {            return new byte[0];        }        int sIx = offset, eIx = offset + charsLen - 1; // Start and end index after trimming.        // Trim illegal chars from start        while (sIx < eIx && IA[chars.charAt(sIx)] < 0)            sIx++;        // Trim illegal chars from end        while (eIx > 0 && IA[chars.charAt(eIx)] < 0)            eIx--;        // get the padding count (=) (0, 1 or 2)        int pad = chars.charAt(eIx) == '=' ? (chars.charAt(eIx - 1) == '=' ? 2 : 1) : 0; // Count '=' at end.        int cCnt = eIx - sIx + 1; // Content count including possible separators        int sepCnt = charsLen > 76 ? (chars.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;        int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes        byte[] bytes = new byte[len]; // Preallocate byte[] of exact length        // Decode all but the last 0 - 2 bytes.        int d = 0;        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {            // Assemble three bytes into an int from four "valid" characters.            int i = IA[chars.charAt(sIx++)] << 18 | IA[chars.charAt(sIx++)] << 12 | IA[chars.charAt(sIx++)] << 6 | IA[chars.charAt(sIx++)];            // Add the bytes            bytes[d++] = (byte) (i >> 16);            bytes[d++] = (byte) (i >> 8);            bytes[d++] = (byte) i;            // If line separator, jump over it.            if (sepCnt > 0 && ++cc == 19) {                sIx += 2;                cc = 0;            }        }        if (d < len) {            // Decode last 1-3 bytes (incl '=') into 1-3 bytes            int i = 0;            for (int j = 0; sIx <= eIx - pad; j++)                i |= IA[chars.charAt(sIx++)] << (18 - j * 6);            for (int r = 16; d < len; r -= 8)                bytes[d++] = (byte) (i >> r);        }        return bytes;    }    /**     * Decodes a BASE64 encoded string that is known to be resonably well formatted. The method is about twice as fast     * as {@link #decode(String)}. The preconditions are:<br>     * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>     * + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within     * the encoded string<br>     * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>     *     * @param s The source string. Length 0 will return an empty array. <code>null</code> will throw an exception.     * @return The decoded array of bytes. May be of length 0.     */    public final static byte[] decodeFast(String s) {        // Check special case        int sLen = s.length();        if (sLen == 0) {            return new byte[0];        }        int sIx = 0, eIx = sLen - 1; // Start and end index after trimming.        // Trim illegal chars from start        while (sIx < eIx && IA[s.charAt(sIx) & 0xff] < 0)            sIx++;        // Trim illegal chars from end        while (eIx > 0 && IA[s.charAt(eIx) & 0xff] < 0)            eIx--;        // get the padding count (=) (0, 1 or 2)        int pad = s.charAt(eIx) == '=' ? (s.charAt(eIx - 1) == '=' ? 2 : 1) : 0; // Count '=' at end.        int cCnt = eIx - sIx + 1; // Content count including possible separators        int sepCnt = sLen > 76 ? (s.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;        int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes        byte[] dArr = new byte[len]; // Preallocate byte[] of exact length        // Decode all but the last 0 - 2 bytes.        int d = 0;        for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {            // Assemble three bytes into an int from four "valid" characters.            int i = IA[s.charAt(sIx++)] << 18 | IA[s.charAt(sIx++)] << 12 | IA[s.charAt(sIx++)] << 6                    | IA[s.charAt(sIx++)];            // Add the bytes            dArr[d++] = (byte) (i >> 16);            dArr[d++] = (byte) (i >> 8);            dArr[d++] = (byte) i;            // If line separator, jump over it.            if (sepCnt > 0 && ++cc == 19) {                sIx += 2;                cc = 0;            }        }        if (d < len) {            // Decode last 1-3 bytes (incl '=') into 1-3 bytes            int i = 0;            for (int j = 0; sIx <= eIx - pad; j++)                i |= IA[s.charAt(sIx++)] << (18 - j * 6);            for (int r = 16; d < len; r -= 8)                dArr[d++] = (byte) (i >> r);        }        return dArr;    }    //  ############################# 以下不属于fast json base64 内容  ##########################    public static String decode(String s){        try {            return new String(decodeFast(s), UTF8);        } catch (Exception e) {            return null;        }    }    public static String decodeGbk(String s){        try {            return new String(decodeFast(s), GBK);        } catch (Exception e) {            return null;        }    }    /** 编码方式 */    public static final Charset UTF8 = Charset.forName("UTF-8");    public static final Charset GBK = Charset.forName("GBK");    /**     * 按照utf-8编码字符     * @param s  -- 待编码字符     * @return     */    public static String encode(String s){        try{            return encode(s.getBytes(UTF8));        }catch(Exception e){            e.printStackTrace();            return null;        }    }    /**     * 按照gbk解码字符     * @param s     * @return     */    public static String encodeGbk(String s){        try{            return encode(s.getBytes(GBK));        }catch(Exception e){            e.printStackTrace();            return null;        }    }    /**     * base编码     * @param target     * @return     */    public static String encode(byte[] target){        if(target==null||target.length==0) return null;        int length = target.length;        /** 判断最后补位数 */        int replenish = length%3;        /** 判断target长度是否为总循环次数 */        int loop = length/3 + (replenish==0?0:1);        byte[] ret = new byte[4 * loop];        /** 下标 */        int index = 0;        int retIndex = 0;        int one,two,three;        while((--loop)>0){            one = target[index++] & 0xff;            two = target[index++] & 0xff;            three = target[index++] & 0xff;            ret[retIndex++] = (byte)CA[one>>>2&0x3f];            ret[retIndex++] = (byte)CA[(one<<4|two>>>4)&0x3f];            ret[retIndex++] = (byte)CA[(two<<2|three>>>6)&0x3f];            ret[retIndex++] = (byte)CA[three&0x3f];        }        //判断最后是否还有剩余,有补等号的情况出现        switch(replenish){            case 0:                one = target[index++] & 0xff;                two = target[index++] & 0xff;                three = target[index++] & 0xff;                ret[retIndex++] = (byte)CA[one>>>2&0x3f];                ret[retIndex++] = (byte)CA[(one<<4|two>>>4)&0x3f];                ret[retIndex++] = (byte)CA[(two<<2|three>>>6)&0x3f];                ret[retIndex++] = (byte)CA[three&0x3f];                break;            case 1://补两个=                one = target[length-1] & 0xff;                ret[retIndex++] = (byte)CA[one>>>2&0x3f];                ret[retIndex++] = (byte)CA[one<<4&0x3f];                ret[retIndex++] = (byte) '=';                ret[retIndex++] = (byte) '=';                break;            case 2://补一个=                one = target[target.length - 2] & 0xff;                two = target[target.length - 1] & 0xff;                ret[retIndex++] = (byte)CA[one>>>2&0x3f];                ret[retIndex++] = (byte)CA[(one<<4|two>>>4)&0x3f];                ret[retIndex++] = (byte)CA[two<<2 & 0x3f];                ret[retIndex++] = (byte) '=';                break;        }        return new String(ret);    }}