BZ Compressor V1.2, SX/GX
	^^^^^^^^^^^^^^^^^^^^^^^^^

--> S/SX/G/GX

[Note: This is now the standard HP48 object packer/unpacker. It's
 *very* efficient. It obsoletes everything else, except maybe UPK
 which is a tad faster at unpacking. BZ is included in the HACK
 library, but if you don't want to load that whole library, here is BZ
 by itself.  -jkh-]


(C) Mika Heiskanen, mheiskan@delta.hut.fi

Stack:	( ob --> $bz  |  $bz --> ob )
Keys:	ON-key aborts compression.
Memory:
	Fast compression requires using buffering to find matches
	fast. Two different BZ versions are provided for the user to
	select from based on the configuration of his calculator. For
	more details see the 'Programs' section below.
	Decompression requires no extra memory.

Algorithm:
	LZ77 class compressor with bit-level codes for matches and
	literal lenght fields. Literals themselves are stored as is
	at the end of output for decompression speed.
	Matches are found by separate chaining in a ring buffer.
	More details in the source code. Note that several of the
	variables are assembly time only, eg you may not be able to
	decompress with another BZ program if you change the values.

	Programs
	^^^^^^^^

	BZ4 uses a hash buffer of size #400 and thus requires
	11264 bytes (11K) of memory for the internal buffers. Intended
	for HP48 GX and other versions when 128K RAM is available.
	This is the version of BZ that's in the HACK library.

	BZ1 uses a hash buffer of size #100 and thus requires
	7424 bytes (7.25K) of memory for the internal buffers.
	Intended for HP48 S/SX/GX when in 32K RAM configuration.

	When you load the one you want, rename it to 'BZ'.

	For the effects of hash buffer size on speed see bz.s. If you
	desire to use another buffer size then just modify HSHSIZE
	to one of the listed values, change the BZ version message
	accordingly and compile the source. HSHSIZE only effects
	compression speed, not the efficiency.

	UBZ is the extracted uncompressor code which can be freely
	used in non-commercial programs.  [Note: You won't need to
	load UBZ into your HP48, since BZ packs *and* unpacks objects
	automatically.	Only load UBZ to include it in home-made
	libraries, etc.  -jkh-]


	Compression Efficiency Comparison Tables
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

All measurements were done on a GX with ~75K of free memory.

Most of the compressors can be found from

	seq.uncwil.edu:/hp48/Uploads.Dec/compress/

GZ and PK compressors are replaced by the new BZ compressor.


Input:	GZ.S	13444 bytes	( SRPL/ML source code )

	Size	%CH	CTime	UTime

BZ	6205	-53.85	 18.00	1.45
GZ 1.2	6637.5	-50.63	 13.48	0.45
PK 15	6741	-49.86	 46.62	0.92	(w/ upk)
PK 0	6771	-49.64	 25.27	0.92	(w/ upk)
LZ8B	8079	-39.91	 39.11	1.40	(lzss library w/ unpk)
LZ10	8115	-39.64	213.75	2.64	(lzss library w/ unpk)
CMPR	8795.5	-34.58	 98.27	1.89	(compress.lib w/ dcmpr)
RFPG	8796	-34.57	 82.72	1.92	(w/ rfug)

Next input produced by:
<< ERASE 'PPAR' PURGE 'SIN(X)' STEQ DRAW DRAX PICT RCL >>

Input:	grob	1098 bytes

	Size	%CH	CTime	UTime

BZ	241.5	-78.01	 5.49	0.08
GZ 1.2	265.5	-75.82	 4.56	0.03
PK 15	268	-75.69	 5.40	0.08	(w/ upk)
CMPR	285	-74.04	 5.23	0.14	(compress.lib w/ dcmpr)
RFPG	286	-73.95	 2.34	0.17	(w/ rfug)
PK 0	293.5	-73.27	 1.94	0.08	(w/ upk)
LZ8B	299	-72.77	 5.88	0.08	(lzss library w/ unpk)
LZ10	356.5	-67.53	 5.98	0.21	(lzss library w/ unpk)
PGROB	383	-65.12	 0.19	fail	(w/ upgrob)


Input:	BZ	1506 bytes	(BZ compressor binary)

	Size	%CH	CTime	UTime

BZ	1352	-10.23	 2.22	0.14
LZ10	1352.5	-10.19	49.05	0.29	(lzss library w/ unpk)
PK 15	1378	 -8.50	 3.64	0.04	(w/ upk)
PK 0	1378	 -8.50	 3.61	0.04	(w/ upk)
GZ 1.2	1380.5	 -8.33	 1.68	0.05
CMPR	1384.5	 -8.07	19.05	0.17	(compress.lib w/ dcmpr)
RFPG	1385	 -8.03	14.47	0.21	(w/ rfug)
LZ8B	-	  0	 7.44	-	(lzss library w/ unpk)


Input:	Lem.lib 11412.5 bytes	("Library 1213:  Lemmings .. V1.2")

	Size	%CH	CTime	UTime

BZ	10153.5 -11.03	 22.70	0.82
PK 15	10219.5 -10.45	113.69	0.31	(w/ upk)
PK 0	10226	-10.40	 30.34	0.31	(w/ upk)
GZ 1.2	10281.5  -9.91	 12.60	0.28
LZ10	10361.5  -9.21	401.98	2.06	(lzss library w/ unpk)
CMPR	10394.5  -8.92	137.23	0.96	(compress.lib w/ dcmpr)
RFPG	10395	 -8.92	118.00	1.26	(w/ rfug)
LZ8B	11103	 -2.71	 55.68	0.80	(lzss library w/ unpk)