自己写的Base64编码函数非常蹩脚,有待改进。
发现有一个错误。不能拿着用
/**
* Base64转换用到了Java的位运算
* & , |, >>, <<, >>>
* http://zh.wikipedia.org/wiki/Base64
*/
public class Base64Demo{
//Base64查询表
public static final char[] encodeLine={'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','+','/'};
public static void main(String[] args){
String name = "shao";
String girl = "xinh";
Base64Demo be = new Base64Demo();
System.out.println(be.encode(girl.getBytes()));
//利用一个大牛写的类来验证是否是正确的Base64编码
//BASE64Encoder encoder = new BASE64Encoder();
//System.out.println(encoder.encode(girl.getBytes()));
}
/*Base64编码*/
protected String encode(byte[] buf){
StringBuilder encodeResult = new StringBuilder();
byte op; //用来提取bit位
byte oe; //用来提取bit位
//第1个字符分离
int oneh=0xfc;//11111100B
int onel=0x03;//00000011B
//第2个字符分离
int twoh=0xf0;//11110000B
int twol=0x0f;//00001111B
//第3个字符分离
int threeh=0xc0;//11000000B
int threel=0x3f;//00111111B
int count = buf.length / 3;
for(int j=0;j<count;j++){
for(int i=0;i<4;i++){
if((j * 3+2) > buf.length){break;}
switch(i){
case 0:
//第一组
op = buf[j *3 + 0];
op &= oneh;//01111000B
//System.out.println(encodeLine[op>>>2]);
encodeResult.append(encodeLine[op>>>2]);
break;
case 1:
//第二组
op = buf[j *3 + 0];
oe = buf[j *3 + 1];
op &= onel;
oe &= twoh;
op <<= 4;
oe >>>= 4;
//System.out.println(encodeLine[op | oe]);
encodeResult.append(encodeLine[op | oe]);
break;
case 2:
//第三组
oe = buf[j *3 + 1];
op = buf[j *3 + 2];
//2字节低四位3自己接高二位
oe &= twol;
oe <<= 2; //左移2位
op &= threeh;
op >>>=6; //右移6位
//System.out.println(encodeLine[oe | op]);
encodeResult.append(encodeLine[oe | op]);
break;
case 3:
//第四组
op = buf[j *3 + 2];
op &= threel;
//System.out.println(encodeLine[op]);
encodeResult.append(encodeLine[op]);
break;
}
}
}
//字节数不是3的倍数的情况
if(buf.length % 3 != 0){
int k = buf.length % 3;
if(k==1){
op = buf[buf.length-1];
op &= oneh;
//System.out.println(encodeLine[op>>>2]);
encodeResult.append(encodeLine[op>>>2]);
op = buf[buf.length-1];
op &= onel;
encodeResult.append(encodeLine[op << 4]);
encodeResult.append("==");
}else if(k==2){
op = buf[buf.length-2];
oe = buf[buf.length-1];
op &= oneh;
encodeResult.append(encodeLine[op>>>2]);
op = buf[buf.length-2]; op &= onel;
oe &= twoh;
op <<= 4;
oe >>>= 4;
encodeResult.append(encodeLine[op | oe]);
oe = buf[buf.length-1];
oe &= twol;
encodeResult.append(encodeLine[oe<<2]);
encodeResult.append("=");
}
}
return encodeResult.toString();
}
}
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