memcpy(dst, b->cb_buf, rc);
memcpy(dst, b->cb_buf + off, rc);
cvs_buf_copy(BUF *b, size_t off, void *dst, size_t len){	size_t rc;	if (off > b->cb_len)		return (-1);	rc = MIN(len, (b->cb_len - off));	memcpy(dst, b->cb_buf, rc);	return (ssize_t)rc;}