base64编码和解码(c语言)

 

废话少说吧，base64是一种常规字符加密编码方式，编码后长度会大20%左右。一般推荐先做huffman压缩，然后在做base64编码。

#include
#include
#include  
#include  
  
// base64 tables 
static char basis_64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; 
#define CHAR64(c)  (((c) < 0 || (c) > 127) ? -1 : index_64[(c)])
char * base64_encode(const unsigned char *value, int vlen); 
unsigned char * base64_decode(const char *value, int *rlen);
 
static signed char index_64[128] = { 
     -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,-1,-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 
} ;
 
char *base64_encode(const unsigned char *value, int vlen) {
 unsigned char oval = 0 ;  
        char *result = (char *)malloc((vlen * 4) / 3 + 5) ; 
        char *out = result; 
 while (vlen >= 3) { 
         *out++ = basis_64[value[0] >> 2]; 
         *out++ = basis_64[((value[0] << 4) & 0x30) | (value[1] >> 4)]; 
         *out++ = basis_64[((value[1] << 2) & 0x3C) | (value[2] >> 6)]; 
         *out++ = basis_64[value[2] & 0x3F]; 
         value += 3; 
         vlen -= 3; 
     }
 if (vlen > 0) { 
         *out++ = basis_64[value[0] >> 2]; 
         oval = (value[0] << 4) & 0x30 ; 
         if (vlen > 1) oval |= value[1] >> 4; 
         *out++ = basis_64[oval]; 
         *out++ = (vlen < 2) ? '=' : basis_64[(value[1] << 2) & 0x3C]; 
         *out++ = '='; 
 } 
 *out = '\0';  
 return result; 
} 

unsigned char *base64_decode(const char *value, int *rlen) 
{  
 int c1, c2, c3, c4;          
        int vlen = strlen(value); 
 unsigned char *result =(unsigned char *)malloc((vlen * 3) / 4 + 1); 
 unsigned char *out = result; 
 
 *rlen = 0;
 
 while (1) { 
  if (value[0]==0) {
   *out = '\0' ;
   return result; 
  }
         c1 = value[0]; 
                if (CHAR64(c1) == -1) goto base64_decode_error;
              c2 = value[1]; 
              if (CHAR64(c2) == -1) goto base64_decode_error;
              c3 = value[2]; 
              if ((c3 != '=') && (CHAR64(c3) == -1)) goto base64_decode_error;
              c4 = value[3]; 
              if ((c4 != '=') && (CHAR64(c4) == -1)) goto base64_decode_error; 
                     value += 4; 
              *out++ = (CHAR64(c1) << 2) | (CHAR64(c2) >> 4); 
              *rlen += 1; 
              if (c3 != '=') { 
               *out++ = ((CHAR64(c2) << 4) & 0xf0) | (CHAR64(c3) >> 2); 
                 *rlen += 1; 
                 if (c4 != '=') { 
                  *out++ = ((CHAR64(c3) << 6) & 0xc0) | CHAR64(c4); 
                         *rlen += 1; 
                 }
              } 
 } 
 base64_decode_error: 
         *result = 0; 
         *rlen = 0; 
         return result; 
}

 

给出源代码，感兴趣的自己看看，在vc6和gcc下编译通过。附件是源代码。

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