C++实现base64编解码

Base64是常见的加密算法，代码实现了基于C++的对于base64的编码和解码。

其中注释掉的部分为编码部分，取消注释将解码部分注释掉即可实现编码，反之可以实现解码。

 #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