秋梦无痕

from: http://cvs.sourceforge.net/viewcvs.py/xine/xine-lib/src/input/input_http.c?rev=1.110

static int http_basicauth (const char *user, const char *password, char* dest, int len) {
static char *enctable = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
char *tmp;
char *sptr;
char *dptr;
int totlen;
int enclen;
int count;

totlen = strlen (user) + 1;
if(password != NULL)
totlen += strlen (password);

enclen = ((totlen + 2) / 3 ) * 4 + 1;

if (len < enclen)
return -1;

tmp = malloc (sizeof(char) * (totlen + 1));
strcpy (tmp, user);
strcat (tmp, ":");
if (password != NULL)
strcat (tmp, password);

count = strlen(tmp);
sptr = tmp;
dptr = dest;
while (count >= 3) {
dptr[0] = enctable[(sptr[0] & 0xFC) >> 2];
dptr[1] = enctable[((sptr[0] & 0x3) << 4) | ((sptr[1] & 0xF0) >> 4)];
dptr[2] = enctable[((sptr[1] & 0x0F) << 2) | ((sptr[2] & 0xC0) >> 6)];
dptr[3] = enctable[sptr[2] & 0x3F];
count -= 3;
sptr += 3;
dptr += 4;
}

if (count > 0) {
dptr[0] = enctable[(sptr[0] & 0xFC) >> 2];
dptr[1] = enctable[(sptr[0] & 0x3) << 4];
dptr[2] = '=';

if (count > 1) {
dptr[1] = enctable[((sptr[0] & 0x3) << 4) | ((sptr[1] & 0xF0) >> 4)];
dptr[2] = enctable[(sptr[1] & 0x0F) << 2];
}

dptr[3] = '=';
dptr += 4;
}

dptr[0] = '\0';

free(tmp);
return 0;
}

其实，说白了，就是在Header中加入：
Authorization: Basic (<username:password>的base64编码)

建议参考http://dev.w3.org/cvsweb/2001/head/来看。

关于http协议，请参看rfc2616。