SOPEN_RASIZE
f->f_rabuf = malloc(SOPEN_RASIZE);
if (f->f_rabuf == NULL || resid >= SOPEN_RASIZE) {
errno = (f->f_ops->fo_read)(f, f->f_rabuf, SOPEN_RASIZE,
f->f_ralen = SOPEN_RASIZE - cresid;