io_read_size
if (!io_read_size(sess, fd, &s->blksz)) {
} else if (!io_read_size(sess, fd, &s->len)) {
} else if (!io_read_size(sess, fd, &s->csum)) {
} else if (!io_read_size(sess, fd, &s->rem)) {
int io_read_size(struct sess *, int, size_t *);
if (!io_read_size(sess, fd, &pathlen)) {
if (!io_read_size(sess, fd, &lsz)) {
if (!io_read_size(sess, fd, &len))