home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Languguage OS 2
/
Languguage OS II Version 10-94 (Knowledge Media)(1994).ISO
/
a_utils
/
_archvrs
/
amiga
/
lhwarp14.lzh
/
Lhwarp.doc
< prev
Wrap
Text File
|
1990-02-13
|
12KB
|
316 lines
LHWARP 1.40
12th April, 1990
A disk tracker for the Amiga
Written by Jonathan Forbes
What is Lhwarp?
(Pronounced L-H-WARP)
Lhwarp is a program which will read tracks directly from your floppy disk,
(or any other device), compress them, and output them to a file. The
advantages of using Lhwarp are:
o The entire disk structure, including the boot block, is preserved.
o Lhwarp will always produce a smaller output file than ARC, ZOO or WARP.
(note: this is true only when the default compression algorithm is used.)
o Lhwarp will only archive sectors which contain data, by using the disk's
bitmap (however, Lhwarp will gladly compress every single sector on
the disk, if you wish.)
o Using Lhwarp is much less hassle than archiving each and every file
individually.
o The bootblock of any disk being either read or written is displayed, so
that bootblock viruses can easily be found.
o Other filing system devices (such as ram disks) may be used with Lhwarp,
so you are not limited to floppy drives.
Lhwarp will produce files which are much smaller than those produced by
Warp, since Lhwarp uses a much more efficient compression algorithm (Adaptive
Huffman Encoding); the same algorithm used in LHARC. Typically, an Lhwarp
file will be 80% of the size of an equivalent Warp file, resulting in quite
reasonable hard drive space savings.
In addition, Lhwarp will only archive sectors which contain data; deleted
information is not archived (unless you explicity request this to be done.)
When compressing or decompressing data, sectors which contain data are marked
with a '.' character, while sectors which do not contain data are marked with
a '_' character. If the -m option is specified, all sectors will be marked
with '.' automatically.
Algorithms
For those who simply must have a faster compression rate, Lhwarp provides
two additional compression algorithms; squeezing and vaporising (the latter is
the 14 bit version of UNIX Compress.) Both are faster than the LHARC Adaptive
Huffman Encoding algorithm (called "freezing.") However, neither of them comes
close to the compression ratio of freezing.
Even so, the speed increase and reasonable compression rates should appeal
to those who are less concerned with compression efficiency, and more concerned
with speed. It should be mentioned, however, that the freezing algorithm can
hold its own in terms of speed, and is the recommended algorithm for
compressing disks.
Freezing remains the default compression mode. Using the -c switch will
cause the disk to be vaporised (not literally), while the -s switch will cause
the disk to be squeezed. The -b option will cause each individual track to be
either vaporised or squeezed, depending on which produces the smallest output.
The -q option will cause Lhwarp to use its fastest and most reasonable
algorithm on the disk. Currently, this is vaporising. If no space is gained
from vaporising a track, then the track is squeezed, and if no space is gained
from squeezing a track, the track is stored (no compression.)
You cannot currently combine freezing with any other algorithm; this is for
your own benefit; I have yet to see freezing beaten by vaporising or squeezing
for any one track, ever! However, if you find that vaporising and squeezing
frequently do compress tracks more efficiently, please inform me.
To compress the NewTek DYNAMIC HI-RES demo disk:
* - Couldn't be bothered to time this
Lhwarp | --- Version 1.40 --- | --- Version 1.31 ---
Algorithm | Size Comp Decomp | Size Comp Decomp
--------- | ------ ----- ------- | ------- ----- ------
Freezing | 671940 14:50 5:24 | 671630 19:00 12:40
Vaporising | 814052 5:59 1:47 | 869515 6:30 *
Squeezing | * * * | 803714 7:30 *
Both | 770726 9:38 5:28 | 770722 10:30 *
Other programs
--------------
Warp 1.11 | 796665 16:53 1:16 (Unwarp 1.0)
Viewing
Lhwarp also supports viewing; you may see how Lhwarp has compressed a disk
(which tracks are contained in the file, which algorithm was used to compress
them, the source and destination lengths of each track, the number of sectors
compressed, and the sector map of each track.) The viewing option will also
display any attached text.
After any attached text is displayed, you must press return; this was
implemented so that the displaying of the boot block wouldn't scroll the text
off the screen.
More Information
Lhwarp output files have the suffix ".LHW". If the filename you give
Lhwarp does not end in ".LHW", Lhwarp will append ".LHW" to it. Please leave
the suffix alone, and don't change it to ".WRP".
The Adaptive Huffman Encoding algorithm was originally coded by Haruyasu
Yoshizaki, and is the same algorithm used in LHARC 1.13c. When the more
efficient LHARC 2.0 arrives from Japan, that algorithm will instead be used.
Parameters
To view Lhwarp's parameters, type "Lhwarp"; they are included within the
program. You will be presented with:
LHWARP 1.40 - Amiga disk tracker - Written by Jonathan Forbes @ 1:250/642
Copyright ⌐ Xenomiga Technology, 1990.
Usage: LHWARP [-options] Command Unit Filename Start End [Textfile]
Command Options: -m: Ignore disk bitmap
-q: Quick compression
-s: Squeeze algorithm
-c: Compress/14 (Vaporise) algorithm
-b: Both Squeeze and Compress
-v: View format of output file
-n: No prompting for return
-dxxx: Use device name 'xxx'
Command: Read (disk->file) or Write (file->disk)
Unit: Drive number (0 for internal, 1 ... 3 for external)
Filename: Output or input filename
StartTrack: Track number (0 ... 79) [valid only in read mode]
EndTrack: Track number (0 ... 79) [valid only in read mode]
TextFile: Attach text in 'TextFile' to output file
Examples are:
a) Lhwarp READ 0 MyDisk 0 79
This will read tracks 0 to 79 of the disk in drive 0 (i.e. the entire
disk), and will output the result to "MyDisk.lhw" Only sectors which contain
data will be archived.
b) Lhwarp READ 0 MyDisk 0 79 MyText
This will read tracks 0 to 79 of the disk in drive 0 (i.e. the entire
disk), and will output the result to "MyDisk.lhw". Only sectors which contain
data will be archived. The text from the file "MyText" will be imported to
the output file. Any text stored in the output file will be displayed when
the disk is unarchived.
c) Lhwarp -m READ 0 MyDisk 0 79
This will read tracks 0 to 79 of the disk in drive 0 (i.e. the entire
disk), and will output the result to "MyDisk.lhw". All sectors will be
archived, regardless of whether or not they contain data; the disk's bitmap
is ignored with the '-m' option.
d) Lhwarp WRITE 1 MyDisk
This will output all tracks stored in MyDisk.lhw to drive 1. If any
text was in the output file, it will be displayed.
e) Lhwarp -c READ 0 MyDisk 0 79
Same as a), except that the disk will be "vaporised."
f) Lhwarp -s READ 0 MyDisk 0 79
Same as a), except that the disk will be "squeezed."
g) Lhwarp -b READ 0 MyDisk 0 79
Same as a), except that tracks will be either squeezed or vaporisied,
depending on which is more efficient.
h) Lhwarp -m -c READ 0 MyDisk 0 79
Same as e), except that the bitmap will be ignored.
i) Lhwarp -v mydisk
View composition of the file "MyDisk.lhw."
j) Lhwarp -dramdrive.device READ 0 MyDisk 0 79
Same as a), but read from the ramdrive.device instead of the floppy
drive (trackdisk.device.)
k) Lhwarp -n READ 0 MyDisk 0 79
Same as a), but don't prompt for return.
Please note that you must combine options in the format of:
'Lhwarp -a -b -c ...'
Not:
'Lhwarp -abc ...'
The latter may have unpredictable results (most probably all options but
'-a' will be ignored.)
Using other devices
If you decide to use the -d option of Lhwarp (i.e. use a non-floppy device
such as ramdrive.device), then the device which you use must be a replica of a
floppy disk in terms of data layout; it must have a lower track boundary of 0,
and an upper track boundary of 79. It must also have 2 heads (surfaces) and 11
blocks per track, (512 bytes per sector are assumed); i.e. it should contain
the following mountlist entry lines:
Surfaces = 2
BlocksPerTrack = 11
LowCyl = 0; HighCyl = 79
It is very important that the device has exactly the same configuration as a
floppy drive; you will, most likely, receive a system message (the "GURU" no
longer exists in 1.4) if this is not the case. Do not assume that because you
have a 120 track ramdrive.device, an 80 track disk will decompress properly
into it; it won't! You cannot mix disk sizes.
You CANNOT use Lhwarp to read and write tracks from/to non-80 track devices,
even if you read and write from/to the same device; Lhwarp assumes many things,
just one of them being that the root block of the device will be at track 40!
This may be fixed in a later version, but for now, don't experiment!
Obviously you will be unable to "remove and re-insert" the disk as asked
after write activity, if the disk is a ram drive. The DISKCHANGE command
should instead be used.
Virus detection
Some people have complained about Warp because it aids the spreading of
boot block viruses. It is for this reason that Lhwarp will display the
bootblock of any disk it reads or writes, so that one can see what is being
Lhwarp'd. Any non-standard looking bootblock should be viewed with suspicion.
If you see a non-standard bootblock in read mode, this means that the disk
you are reading from might possibly contain a virus. If you see this in write
mode, it means that the file you are writing out to your disk may contain a
virus. In either case, you should load a virus checker to make sure (such as
VirusX 4.0)
Specifications
Lhwarp uses ETD_READ and ETD_FORMAT to read/write directly from/to the
trackdisk.device. The 16 bytes of label information for each sector are
preserved in the output file. A 32-bit CRC protects data integrity.
Acknowledgements
Huffman routines - Haruyasu Yoshizaki (lzhuf.c, v1.13c)
Compress - S.Thomas, J.McKie, S.Davies, K.Turkowski, J.Woods,
and J.Orost (compress.c)
Squeezing - William Swan (sq.c/usq.c)
Bitmap information - Leo Schwab (diskmap2.c)
This Program
Lhwarp is a freely distributable, copyrighted piece of software. You do
not have to pay money to use it, and may upload it wherever you choose, but
you are not allowed to sell Lhwarp for profit, or include Lhwarp on a disk
which is sold for profit, without the author's (Jonathan Forbes) permission.
I can be contacted on Canada Remote Systems as "Jonathan Forbes" (isn't
that better than some 20 digit ID code?)
My BBS (416-921-6638) is currently down, pending completion of Xenolink,
a full featured FidoNet-compatible BBS program for the Amiga, which I have
almost finished.
Disclaimer
I am in no way responsible for anything this program does; you are using
it entirely at your own risk, so if all of the cats in your neighbourhood
cause a nuclear feline revolution, wiping out most of the human population in
your part of the world, don't blame me!
Stack Size
Lhwarp appears to function correctly with a stack size of 10,000 bytes (and
maybe even less), but if you have any problems, you should increase it.
--- EOF