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:
* + The array must have a line length of 76 chars OR no line separators at all (one line).
* + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within
* the encoded string
* + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.
*
* @param chars The source array. Length 0 will return an empty array. null 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:
* + The array must have a line length of 76 chars OR no line separators at all (one line).
* + Line separator must be "\r\n", as specified in RFC 2045 + The array must not contain illegal characters within
* the encoded string
* + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.
*
* @param s The source string. Length 0 will return an empty array. null 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);
}
}