base64编码解码的函数

base64编码的实现

int Base64Enc(char *buf, char*text,int size)
{
static char *base64_encoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
int buflen = 0;

while(size>0)
{
*buf++ = base64_encoding[ (text[0] >> 2 ) & 0x3f];
if(size>2)
{
*buf++ = base64_encoding[((text[0] & 3) << 4) | (text[1] >> 4)];
*buf++ = base64_encoding[((text[1] & 0xF) << 2) | (text[2] >> 6)];
*buf++ = base64_encoding[text[2] & 0x3F];
}
else
{
switch(size)
{
case 1:
*buf++ = base64_encoding[(text[0] & 3) << 4 ];
*buf++ = '=';
*buf++ = '=';
break;
case 2:
*buf++ = base64_encoding[((text[0] & 3) << 4) | (text[1] >> 4)];
*buf++ = base64_encoding[((text[1] & 0x0F) << 2) | (text[2] >> 6)];
*buf++ = '=';
break;
}
}

text +=3;
size -=3;
buflen +=4;
}

*buf = 0;
return buflen;
}

base64解码的实现

char GetBase64Value(char ch)
{
if ((ch >= 'A') && (ch <= 'Z'))
return ch - 'A';
if ((ch >= 'a') && (ch <= 'z'))
return ch - 'a' + 26;
if ((ch >= '0') && (ch <= '9'))
return ch - '0' + 52;
switch (ch)
{
case '+':
return 62;
case '/':
return 63;
case '=': /* base64 padding */
return 0;
default:
return 0;
}
}

//进行base64解码输入应该是4的倍数(根据mime标准)
//如果不是4倍数返回错误
//注意 如果是最后一个字符 那么长度不准备 可能会多1
//返回buf长度
int Base64Dec(char *buf,char*text,int size)
{
if(size%4)
return -1;
unsigned char chunk[4];
int parsenum=0;

while(size>0)
{
chunk[0] = GetBase64Value(text[0]);
chunk[1] = GetBase64Value(text[1]);
chunk[2] = GetBase64Value(text[2]);
chunk[3] = GetBase64Value(text[3]);

*buf++ = (chunk[0] << 2) | (chunk[1] >> 4);
*buf++ = (chunk[1] << 4) | (chunk[2] >> 2);
*buf++ = (chunk[2] << 6) | (chunk[3]);

text+=4;
size-=4;
parsenum+=3;
}

return parsenum;
}