psbuf_expect_handle
rv = psbuf_expect_handle(pb, &fhand, &fhandlen);
int psbuf_expect_handle(struct puffs_framebuf *, char **, uint32_t *);
error = psbuf_expect_handle(pb, &psn->fhand_r, &psn->fhand_r_len);
error = psbuf_expect_handle(pb, &psn->fhand_w, &psn->fhand_w_len);
rv = psbuf_expect_handle(pb, &dhand, &dhandlen);