jsread
if ((error = jsread(js, base, &sub, sizeof(sub))) != 0) {
jsread(js, 0, &head, sizeof(head));
if ((error = jsread(js, base, &sub, sizeof(sub))) != 0)
if ((error = jsread(js, base, &sub, sizeof(sub))) != 0)
jsread(js, 0, &head, sizeof(head));
int jsread(struct jstream *js, off_t off, void *buf, int bytes);
error = jsread(js, off, js->js_alloc_buf, bytes);