What we pass to BZIP3 Backend

BZIP3 gets a block size

lrzip-next takes as input a BZIP3 block size code from 0 to 8, associated with lrzip-next compression levels 1 to 9. These are converted to absolute block sizes Using the macro:
#define BZIP3_BLOCK_SIZE_FROM_PROP(p) (p == 8 ? 0x1FFFFFFF : (((u32)2 | ((p) & 1)) << ((p) / 2 + 24)))
which was adapted from lzma2 code.

lrzip-next level	BZIP3 bs code	BZIP3 Block Size
1	0	32MB
2	1	48MB
3	2	64MB
4	3	96MB
5	4	128MB
6	5	196MB
7	6	256MB
8	7	384MB
9	8	512MB-1

The BZIP3 Block Size is used to set up the state structure for compression/decompression.

struct bz3_state *state;
...
state = bz3_new(control->bzip3_block_size);	// allocate bzip3 state
if (!state)
  fatal("Failed to allocate %'"PRIu32" bytes bzip3 state.\n", control->bzip3_block_size);