#include <stdio.h>

 #include <string.h>

 #include <assert.h>

 typedef unsigned char     uint8;

 typedef unsigned long    uint32;

 static uint8 alphabet_map[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

 static uint8 reverse_map[] =

 {

      , , , , , , , , , , , , , , , ,

      , , , , , , , , , , , , , , , ,

      , , , , , , , , , , , , , , , ,

      , , , , , , , , , , , , , , , ,

      ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  , , , , , ,

      , , , , , , , , , , , , , , , ,

      , , , , , , , , , , , , , , , ,

      , , , , , , , , , , , , , , ,

 };

 uint32 base64_encode(const uint8 *text, uint32 text_len, uint8 *encode)

 {

     uint32 i, j;

     for (i = , j = ; i+ <= text_len; i+=)

     {

         encode[j++] = alphabet_map[text[i]>>];                             //取出第一个字符的前6位并找出对应的结果字符

         encode[j++] = alphabet_map[((text[i]<<)&0x30)|(text[i+]>>)];     //将第一个字符的后2位与第二个字符的前4位进行组合并找到对应的结果字符

         encode[j++] = alphabet_map[((text[i+]<<)&0x3c)|(text[i+]>>)];   //将第二个字符的后4位与第三个字符的前2位组合并找出对应的结果字符

         encode[j++] = alphabet_map[text[i+]&0x3f];                         //取出第三个字符的后6位并找出结果字符

     }

     if (i < text_len)

     {

         uint32 tail = text_len - i;

         if (tail == )

         {

             encode[j++] = alphabet_map[text[i]>>];

             encode[j++] = alphabet_map[(text[i]<<)&0x30];

             encode[j++] = '=';

             encode[j++] = '=';

         }

         else //tail==2

         {

             encode[j++] = alphabet_map[text[i]>>];

             encode[j++] = alphabet_map[((text[i]<<)&0x30)|(text[i+]>>)];

             encode[j++] = alphabet_map[(text[i+]<<)&0x3c];

             encode[j++] = '=';

         }

     }

     return j;

 }

 uint32 base64_decode(const uint8 *code, uint32 code_len, uint8 *plain)

 {

     assert((code_len&0x03) == );  //如果它的条件返回错误，则终止程序执行。4的倍数。

     uint32 i, j = ;

     uint8 quad[];

     for (i = ; i < code_len; i+=)

     {

         for (uint32 k = ; k < ; k++)

         {

             quad[k] = reverse_map[code[i+k]];//分组，每组四个分别依次转换为base64表内的十进制数

         }

         assert(quad[]< && quad[]<);

         plain[j++] = (quad[]<<)|(quad[]>>); //取出第一个字符对应base64表的十进制数的前6位与第二个字符对应base64表的十进制数的前2位进行组合

         if (quad[] >= )

             break;

         else if (quad[] >= )

         {

             plain[j++] = (quad[]<<)|(quad[]>>); //取出第二个字符对应base64表的十进制数的后4位与第三个字符对应base64表的十进制数的前4位进行组合

             break;

         }

         else

         {

             plain[j++] = (quad[]<<)|(quad[]>>);

             plain[j++] = (quad[]<<)|quad[];//取出第三个字符对应base64表的十进制数的后2位与第4个字符进行组合

         }

     }

     return j;

 }

 /*int main(void)

 {

     char input[256];

     while (true){

     printf("Please input string: ");

     scanf("%s", input);

     uint8 *text = (uint8 *)input;

     uint32 text_len = (uint32)strlen((char *)text);

     uint8 buffer[1024], buffer2[4096];

     uint32 size = base64_encode(text, text_len, buffer2);

     buffer2[size] = 0;

     printf("%s\n", buffer2);

     size = base64_decode(buffer2, size, buffer);

     buffer[size] = 0;

     printf("%s\n", buffer);

     }

     return 0;

 }*/

 //编码

 int main(void)

 {

     char input[];

     while (true){

     printf("Please input what you want to decode: ");

     scanf("%s", input);

     uint8 *text = (uint8 *)input;

     uint32 text_len = (uint32)strlen((char *)text);

     uint8 buffer[],buffer2[];

     uint32 size = base64_decode(text, text_len, buffer);

     buffer[size] = ;

     printf("Decoded content: %s\n", buffer);

     size = base64_encode(buffer, size, buffer2);

     buffer2[size] = ;

     printf("Confirmation of the original content: %s\n", buffer2);

     }

     return ;

 }

 //解码