#include <stdio.h>
#include <string.h>
const char * base64char = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const char padding_char = '=';
int base64_encode(const unsigned char * sourcedata, char * base64)
{
int i=0, j=0;
unsigned char trans_index=0; // 索引是8位，但是高两位都为0
const int datalength = strlen((const char*)sourcedata);
for (; i < datalength; i += 3) { // 每三个一组，进行编码 要编码的数字的第一个
trans_index = ((sourcedata[i] >> 2) & 0x3f);
base64[j++] = base64char[(int)trans_index];
// 第二个
trans_index = ((sourcedata[i] << 4) & 0x30);
if (i + 1 < datalength){
trans_index |= ((sourcedata[i + 1] >> 4) & 0x0f);
base64[j++] = base64char[(int)trans_index];
}else{
base64[j++] = base64char[(int)trans_index];
base64[j++] = padding_char;
base64[j++] = padding_char;
break; // 超出总长度，可以直接break
}
// 第三个
trans_index = ((sourcedata[i + 1] << 2) & 0x3c);
if (i + 2 < datalength) { // 有的话需要编码2个
trans_index |= ((sourcedata[i + 2] >> 6) & 0x03);
base64[j++] = base64char[(int)trans_index];
trans_index = sourcedata[i + 2] & 0x3f;
base64[j++] = base64char[(int)trans_index];
}else {
base64[j++] = base64char[(int)trans_index];
base64[j++] = padding_char;
break;
}
}
base64[j] = '\0';
return 0;
}
int num_strchr(const char *str, char c)
{
const char *pindex = strchr(str, c);
if (NULL == pindex){
return -1;
}
return pindex - str;
}
int base64_decode(const char * base64, unsigned char * dedata)
{
int i = 0, j=0;
int trans[4] = {0,0,0,0};
for (;base64[i]!='\0';i+=4) { // 每四个一组，译码成三个字符
trans[0] = num_strchr(base64char, base64[i]);
trans[1] = num_strchr(base64char, base64[i+1]);
dedata[j++] = ((trans[0] << 2) & 0xfc) | ((trans[1]>>4) & 0x03);
if (base64[i+2] == '='){
continue;
}else{
trans[2] = num_strchr(base64char, base64[i + 2]);
}
dedata[j++] = ((trans[1] << 4) & 0xf0) | ((trans[2] >> 2) & 0x0f);
if (base64[i + 3] == '='){
continue;
}else{
trans[3] = num_strchr(base64char, base64[i + 3]);
}
dedata[j++] = ((trans[2] << 6) & 0xc0) | (trans[3] & 0x3f);
}
dedata[j] = '\0';
return 0;
}
int main()
{
const unsigned char str[] = "admin:abcd1234789";
const unsigned char *sourcedata = str ;
char base64[128];
base64_encode(sourcedata, base64);
printf("编码：%s\n",base64);
char dedata[128];
base64_decode(base64, (unsigned char*)dedata);
printf("译码：%s\n", dedata);
return 0;
}
