Base64编码----C++实现

base64编码表如下： 索引 字符 索引 字符 索引 字符 索引 字符 0 A 17 R 34 i 51 z 1 B 18 S 35 j 52 0 2 C 19 T 36 k 53 1 3 D 20 U 37 l 54 2 4 E 21 V 38 m 55 3 5 F 22 W 39 n 56 4 6 G 23 X 40 o 57 5 7 H 24 Y 41 p 58 6 8 I 25 Z 42 q 59 7 9 J 26 a 43 r 60 8 10 K 27 b 44 s 61 9 11 L 28 c 45 t 62 + 12 M 29 d 46 u 63 / 13 N 30 e 47 v     14 O 31 f 48 w pad = 15 P 32 g 49 x     16 Q 33 h 50 y     #include<iostream.h> #include<string.h> char base64EncodeChars[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; char base64DecodeChars[]= { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, 0, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1 }; //参数1：in,被编码字符串 //参数2：out,编码后字符指针，必须有足够的长度 //参数3：in_len,被编码字符串的长度 void base64Encode(char*in,char*out,int in_len) { int i=0,index=0; unsigned char c1,c2,c3; while(i<in_len) {    c1=*(in+i);    i++;    if(i == in_len)    {     out[index++]= base64EncodeChars[(c1 & 0XFF)>> 2];     out[index++]= base64EncodeChars[(c1 & 0X03) << 4];     out[index++]= '=';     out[index++]= '=';     break;    }    c2=*(in+i);    i++;    if(i == in_len)    {      out[index++]= base64EncodeChars[(c1 & 0XFF)>>2];               out[index++]= base64EncodeChars[((c1 & 0X3)<< 4) | ((c2 & 0XF0) >> 4)];     out[index++]= base64EncodeChars[(c2 & 0X0F) << 2];     out[index++]= '=';     break;    }       c3=*(in+i);    i++;    out[index++]= base64EncodeChars[(c1 & 0XFF) >> 2];    out[index++]= base64EncodeChars[((c1 & 0X03)<< 4) | ((c2 & 0XF0) >> 4)];    out[index++]= base64EncodeChars[((c2 & 0X0F) << 2) | ((c3 & 0XC0) >>6)];    out[index++]= base64EncodeChars[c3 & 0X3F]; } out[index]='\0'; } //参数1：in,被解码字符串 //参数2：out,解码后字符指针，必须有足够的长度 //参数3：in_len,被解码字符串的长度 void base64Decode(char*in,char*out,int in_len) { int i=0,index=0; unsigned char c1,c2,c3,c4; if(in_len<4)    return; //检查被解码的字符串是否是base64编码的 for(int j=0;j<in_len;j++)    if(in[j]<0||     (unsigned char)in[j]>=128||     base64DecodeChars[in[j] & 0XFF]==-1)     return; while(i<in_len) {     c1 = base64DecodeChars[in[i++] & 0XFF];    c2 = base64DecodeChars[in[i++] & 0XFF];    out[index++]= (c1 << 2) | ((c2 & 0X30) >> 4);       c3 =in[i++];    if (c3 == '=')     break;    c3 = base64DecodeChars[c3];    out[index++]= ((c2 & 0XF) << 4) | ((c3 & 0X3C) >> 2);    c4 =in[i++];    if (c4 == '=')     break;    c4 = base64DecodeChars[c4];    out[index++]= ((c3 & 0X03) << 6) | c4; } out[index]='\0'; } void main()  { char p[]="k我0地98中国5人o"; int p_len=strlen(p); int q_len=p_len/3*4; if(p_len%3!=0)    q_len=q_len+4; char *q=new char[q_len];   cout<<p<<endl; base64Encode(p,q,strlen(p)); cout<<q<<endl; int r_len=q_len*3/4; char *r=new char[r_len]; base64Decode(q,r,strlen(q)); cout<<r<<endl<<endl; char temp[]="UExBWSBydHNwOi8vcXVpY2t0aW1lLnV2bS5lZHU6MTU1NC93YXcvd2RpMDVoczJiLm1vdiBSVFNQLzEuMA0KQ1NlcTogNA0KUmFuZ2U6IG5wdD0wLjAwMDAwMC0xODQ2LjMzMzMzMw0KeC1wcmVidWZmZXI6IG1heHRpbWU9Mi4wMDAwMDANCngtdHJhbnNwb3J0LW9wdGlvbnM6IGxhdGUtdG9sZXJhbmNlPTEwDQpTZXNzaW9uOiA4MTA3MTkwMzE4NDQwODE3Njk5DQpVc2VyLUFnZW50OiBRdWlja1RpbWUvNy42LjUgKHF0dmVyPTcuNi41O29zPVdpbmRvd3MgTlQgNS4xU2VydmljZSBQYWNrIDMpDQoNCg=="; char base[300]; base64Decode(temp,base,strlen(temp)); cout<<base<<endl; }