#include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> static const char b64_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; static const char reverse_table[128] = {     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63,     52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,     64,  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, 64, 64, 64, 64, 64,     64, 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, 64, 64, 64, 64, 64 }; unsigned char *base64_encode(unsigned char *bindata,size_t inlen,unsigned char **out,size_t *outlen) {     size_t _outlen = *outlen;     unsigned char *_out = NULL;     size_t out_pos = 0;     if(NULL == *out)     {         _outlen = (inlen / 3 + (inlen%3 != 0)) * 4 + 1;         _out = malloc(_outlen);     }     else     {         _outlen = *outlen;         _out = *out;     }     memset(_out,'=',_outlen);     _out[_outlen-1] = 0;     unsigned int bits_collected = 0;     unsigned int accumulator = 0;     for(int i = 0; i < inlen; i++)     {         accumulator = (accumulator << 8) | (bindata[i] & 0xffu);         bits_collected += 8;         while (bits_collected >= 6)         {             bits_collected -= 6;             _out[out_pos++] = b64_table[(accumulator >> bits_collected) & 0x3fu];         }     }     if(bits_collected >= 6)     {         if(NULL == *out)         {             free(_out);         }         return NULL;     }     if (bits_collected > 0)     {         // Any trailing bits that are missing.         accumulator <<= 6 - bits_collected;         _out[out_pos++] = b64_table[accumulator & 0x3fu];     }     *outlen = _outlen;     *out = _out;     return _out; } unsigned char *base64_decode(unsigned char *bindata,size_t inlen,unsigned char **out,size_t *outlen) {     size_t _outlen = *outlen;     unsigned char *_out = NULL;     int bits_collected = 0;     unsigned int accumulator = 0;     size_t out_pos = 0;     if(NULL == *out)     {         _outlen = inlen;         _out = malloc(_outlen);     }     else     {         _outlen = *outlen;         _out = *out;     }     int c = 0;     for(int i = 0; i < inlen; i++)     {         c = bindata[i];         if (isspace(c) || c == '=')         {             // Skip whitespace and padding. Be liberal in what you accept.             continue;         }         if ((c > 127) || (c < 0) || (reverse_table[c] > 63))         {             return NULL;         }         accumulator = (accumulator << 6) | reverse_table[c];         bits_collected += 6;         if (bits_collected >= 8)         {             bits_collected -= 8;             _out[out_pos++] = (char)((accumulator >> bits_collected) & 0xffu);         }     }     *outlen = _outlen;     *out = _out;     return _out; } int main(int argc,char *argv[]) {     unsigned char *str = argv[1];     unsigned char *out = 0;     size_t len = 0;     printf("%s\n",base64_encode(str,strlen(str),&out,&len));     unsigned char *_out = 0;     size_t _len = 0;     printf("%s\n",base64_decode(out,strlen(out),&_out,&_len));     return 0; }