host_read
if ((n = host_read(s, banner, sizeof(banner)-1)) <= 0) {
ssize_t (*host_read)(int, void *, size_t);
n = host_read(fd, (uint8_t*)&spc->spc_hdr + spc->spc_off, left);
n = host_read(fd, spc->spc_buf + (spc->spc_off - HDRSZ), left);