AUTOCHOP - User's Guide

AUTOCHOP allows very large files to be split across floppy disks and then
later rejoined to re-create the original file. The intended use is for
large ZIP files, but any file type can be successfully processed with
AUTOCHOP. Several command line options permit easy, intuitive use. There
is no defined limit to the file sizes that can be handled by AUTOCHOP.

AUTOCHOP is copyright (c) 1991 by Randy Langer and MicroSphere Technology,
Inc. All right reserved. The copyright owner grants license to freely
distribute the ORIGINAL, unaltered .ZIP file to anyone, provided that:

1) No charge is made, other than a reasonable disk duplication fee and
reasonable postage/handling charges.

2) No modifications are made to any of the files; they are distributed
in their original form.

This program is shareware. You are granted a license to try this program
out for a period of thirty days. If you decide to continue using the
program after that period, you are required to register it. Regsitration
is $5.00, payable in US funds. Registered users will be notified if and
when updates to this program are available, and where such updates can be
obtained from. See the accompaning file LICENSE.DOC for the registration
form.

General Information

AUTOCHOP operates in two basic modes: splitting and rebuilding. In the
splitting mode, the "original file" is broken into a set of "segment
files", while in the rebuild mode, the segment files are combined to
recover the original file. The segment files can be identified by their
files extension, which has the format "#nn", where "nn" is a two-digit
decimal number ranging from 00 through 99. Hence, an original files can be
broken up into as many as one hundred segment files, which should be more
than adequate. Unless told otherwise, the segment files have the same
basic filename as the original, and are created in the same directory as
the original. The filename extension of the original is retained in one of
the segment files, and will be used as the default when the original is
rebuilt.

The rebuild process differ slightly from the splitting operation, in that
the default directory for the rebuilt original is the current default
directory, rather than the directory for the segment files. This is
logical, since the segment files are usually on floppies, and you normally
wouldn't want to rebuild the original there. In any case, the defaults can
always be overridden by command-line parameters.

Each segment file begins with a header structure, which is used to identify
the file as being a segment file for AUTOCHOP. When an original file is
split, a number is chosen at pseudo-random (actually, from the system's
real time clock) to serve as the "job ID". This job ID is placed in the
header of every segment file created during this split. When the original
is rebuilt, all the segment files are checked to insure they all have the
same job ID; this lessens the chance of including a segment file from a
different split operation during a rebuild, and thus creating an invalid
original. As an additional safety check, the CRC32 of the entire original
is computed during splitting and included in one of the segment files.
During rebuild, this CRC is re-computed from the segment files, and
compared the the value stored during the split. It is very unlikely that
two different files will compute out the same CRC32, so this check results
in a high degree of confidence that the rebuild generated the same file as
the original.

During splitting, AUTOCHOP will, by default, try to build the largest
segment files that will fit on the target media. So, if the target is a
floppy drive, the default action is to use all the free space on that disk
for the segment file. You can, however, specify a maximum size for the
segment files; if you do so, no segment file will be larger than this
specification. You can also specify the minimum size for a segment file;
if there is not enough room on the target media for a file of this size,
you will be so informed.

Finally, there is a "check" option. This tells AUTOCHOP to read the
segment files, but no to rebuild the original. In reading the segments,
the CRC32 is computed, and compared to the value obtained during the split.
This allows you to insure that the segments on floppies are valid before
deleting the original from hard disk.

Splitting Originals

The command line to split an original is:

AUTOCHOP [min=nnn] [max=nnn] [-p] [drive/path]filename.ext [targname]

where items in brackets are optional. "min" and "max" can be used to
specify the minimum and maximum size of the segment files, they default to
512 and infinite, respectively. Normally, AUTOCHOP tells you when it is
about to access a segment file, and asks you to kit a key to continue; this
gives you the opportunity to change floppies. By using the "-p" option,
this prompting is dispensed with (this should only be done when writing the
segment files to a hard disk). The full name of the original file,
including extension, must be specified. If the original has no filename
extension, you must "fake" one by the use of a lone period:

MYFILE.

since AUTOCHOP uses the presence or absence of a filename extension to
determine whether to split or rebuild. If you want the segment files have
a different basic filename, and/or be placed in a different directory, you
can do so by making an appropriate file specification after the name of the
original file. Any extension on this second specification is quietly
ignored, since AUTOCHOP creates its own series of extensions for the
segment files.

Some examples:

AUTOCHOP max=1000000 -p c:\work\myfile.zip

creates the set of segment files "myfile,#00", "myfile.#01", etc. in the
same directory as the original (ie., in C:\WORK\). Each file will be
limited to one megabyte in size, and you will NOT be prompted as each
segment file is created (the "-p" option).

AUTOCHOP max=1000000 -p c:\work\myfile.zip d:\janice\

works the same as the first example, except the segment files will go in
the directory "D:\JANICE\".

AUTOCHOP max=1000000 -p c:\work\myfile.zip mypieces

will split the original into segments having the name "mypieces.#00",
"mypieces.#01", etc., in the CURRENT DEFAULT directory.

AUTOCHOP c:\work\myfile.zip a:

This is probably the most common format for AUTOCHOP. This splits the
original file onto floppies, filling each floppy to its available free
space. You are prompted before each segment file is created, giving you
the chance to switch floppies as each fills.

Rebuilding From Segments

The command line for this operation is:

AUTOCHOP [-p] [drive/path]filename [targname]

Note that the first filespec has NO EXTENSION; this is the key telling
AUTOCHOP to rebuild, rather than split. If no "targname" is given, the
name of the rebuilt file is the same as that of the segment files, with the
file extension of the original restored. Otherwise, this second
specification is used as given for the output file (so it must be a valid
filespec).

Finally, to check the segment files, use:

AUTOCHOP [-p] -c [drive/path]filename

again, with no file extension.

Contacting the Author

The best way to contact the me is to leave me E-mail on the North Orange
County Computer Club BBS, 714-730-5739, USR 14.4K DS. Please use the TECH
conference for this purpose. Any future updates to this program will be
posted on this BBS first.

Otherwise, you can write to me at:

Randy Langer
MircoSphere Technology, Inc.
Box 620
Magalia, CA 95954-0620