int main(void)
{
uint8_t *p, *ep;
size_t s = syslinux_adv_size();
char buf[256];
#if 0
/* this hangs! */
openconsole(&dev_stdcon_r, &dev_stdcon_w);
#else
/* this works */
openconsole(&dev_rawcon_r, &dev_ansiserial_w);
#endif
p = syslinux_adv_ptr();
printf("ADV size: %zd bytes at %p\n", s, p);
ep = p + s; /* Need at least opcode+len */
while (p < ep - 1 && *p) {
int t = *p++;
int l = *p++;
if (p + l > ep)
break;
memcpy(buf, p, l);
buf[l] = '\0';
printf("ADV %3d: \"%s\"\n", t, buf);
p += l;
}
return 0;
}
int syslinux_setadv(int tag, size_t size, const void *data)
{
uint8_t *p, *advtmp;
size_t rleft, left;
if ((unsigned)tag - 1 > 254) {
errno = EINVAL;
return -1; /* Impossible tag value */
}
if (size > 255) {
errno = ENOSPC; /* Max 255 bytes for a data item */
return -1;
}
rleft = left = syslinux_adv_size();
p = advtmp = alloca(left);
memcpy(p, syslinux_adv_ptr(), left); /* Make working copy */
while (rleft >= 2) {
uint8_t ptag = p[0];
size_t plen = p[1] + 2;
if (ptag == ADV_END)
break;
if (ptag == tag) {
/* Found our tag. Delete it. */
if (plen >= rleft) {
/* Entire remainder is our tag */
break;
}
memmove(p, p + plen, rleft - plen);
rleft -= plen; /* Fewer bytes to read, but not to write */
} else {
/* Not our tag */
if (plen > rleft)
break; /* Corrupt tag (overrun) - overwrite it */
left -= plen;
rleft -= plen;
p += plen;
}
}
/* Now (p, left) reflects the position to write in and how much space
we have for our data. */
if (size) {
if (left < size + 2) {
errno = ENOSPC; /* Not enough space for data */
return -1;
}
*p++ = tag;
*p++ = size;
memcpy(p, data, size);
p += size;
left -= size + 2;
}
memset(p, 0, left);
/* If we got here, everything went OK, commit the write to low memory */
memcpy(syslinux_adv_ptr(), advtmp, syslinux_adv_size());
return 0;
}