C++ VC Base64编解码算法系列二(编码算法)

void base64_encode(char *out, const void *in_, int inlen)

/* raw bytes in quasi-big-endian order to base 64 string (NUL-terminated) */

{
const unsigned char *in = (const unsigned char *)in_;
for (; inlen >= 3; inlen -= 3)
{
*out++ = base64digits[in[0] >> 2];
*out++ = base64digits[((in[0] << 4) & 0x30) | (in[1] >> 4)];
*out++ = base64digits[((in[1] << 2) & 0x3c) | (in[2] >> 6)];
*out++ = base64digits[in[2] & 0x3f];
in += 3;
}
if (inlen > 0)
{
unsigned char fragment;
*out++ = base64digits[in[0] >> 2];
fragment = (in[0] << 4) & 0x30;
if (inlen > 1) fragment |= in[1] >> 4;
*out++ = base64digits[fragment];
*out++ = (inlen < 2) ? '=' : base64digits[(in[1] << 2) & 0x3c];
*out++ = '=';
}
*out = '/0';
}