bio_mem_pending
if ((size_t)out_len > bio_mem_pending(bm))
out_len = bio_mem_pending(bm);
bio_mem_pending(bm));
bm->buf->length = bio_mem_pending(bm);
ret = (long)(bio_mem_pending(bm) == 0);
ret = (long)bio_mem_pending(bm);
ret = (long)bio_mem_pending(bm);
out_max = bio_mem_pending(bm);