sr_block_get
xorbuf = sr_block_get(sd, len);
data = sr_block_get(sd, len);
xorbuf = sr_block_get(sd, strip_size);
xorbuf = sr_block_get(sd, strip_size);
qbuf = sr_block_get(sd, length);
pbuf = sr_block_get(sd, length);
data = sr_block_get(sd, len);
void *sr_block_get(struct sr_discipline *, long);