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1994-02-20
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┌─────────────────────────────────────────────────────────────────────────╖
│ ║
│ RCmpLib version 3.0 (20/02/94) ║
│ ║
│ ║
│ (c) 1994 Rolf van Gelder, EINDHOVEN - All rights reserved ║
│ ║
╘═════════════════════════════════════════════════════════════════════════╝
1 INTRODUCTION --------------------------------------------------------
RCmpLib is a CA-CLIPPER LIBRARY with data compression functions.
Because RCmpLib is partially written in ASSEMBLER its functions are
VERY FAST !
Two libraries are enclosed :
RCmpLib.lib - Library for CA-Clipper version 5.xx
RCmpS87.lib - Library for Nantucket Clipper Summer '87
RCmpLib is a Shareware product :
You have the opportunity to try the program 30 days at no charge
to see if it meets your needs.
If you continue to use the program after evaluation,
please complete the included registration form (RCmpLib.REG,
for DUTCH users Dutch.REG) and send it with the applicable
registration fee to the author.
FEATURES :
* COMPRESSION of MULTIPLE FILES into one ARCHIVE FILE
(Optional DELETION of FILES after COMPRESSION)
* EXTRACTION of ONE OR MORE FILES from an ARCHIVE FILE
* OPTIONAL DISPLAY of PROGRESSION BARS during COMPRESSION and
DECOMPRESSION of FILES
* USER INTERRUPTABLE COMPRESSION/DECOMPRESSION
* FUNCTIONS TO COMPRESS & DECOMPRESS STRINGS and MEMO-FIELDS
* OPTIONAL PASSWORD ENCRYPTION of COMPRESSED FILES and STRINGS
* IMPROVED MEMORY MANAGEMENT
(Consumes ca. 16Kb less base memory than previous versions !)
* FAST & RELIABLE COMPRESSION with a GOOD COMPRESSION FACTOR
* A NORTON GUIDE with a description of all functions in the library
* EXOSPACE COMPATIBLE
* CA-CLIPPER 5.XX DEMO PROGRAM with EXAMPLES
* NANTUCKET CLIPPER SUMMER '87 DEMO PROGRAM with EXAMPLES
2 COMPRESSION AND DECOMPRESSION ---------------------------------------
2.1 COMPRESSION ALGORITHM -----------------------------------------------
The compression and decompression functions of RCmpLib are based on
the so-called Lempel-Ziv principle, to be specific the LZW algorithm.
This base principle is used by almost all famous compression programs
(as LHARC, ARJ and PKZIP).
The principle works in short as follows :
(Sub-)Strings that appear often in the file to compress are being
replaced by numerical codes.
While decompressing, these codes are replaced again by the original
strings.
2.2 THE USE OF COMPRESSION IN CLIPPER APPLICATIONS ----------------------
FILE COMPRESSION
The most common use of compression function in Clipper applications
is the following scenario :
Decompress all Clipper data files (.DBF,.DBT,.NTX,.FRM,... etc.) at
the beginning of an application. While the application is running
all the files are accessible in their normal, uncompressed form.
Compress all the Clipper data files (.DBF,.DBT,.NTX,.FRM,... etc.)
at the termination of the application.
Advantages of this method :
- During the execution of the application all is normal
(all the files are uncompressed on the disk)
- After the termination of the program, the application will consume
much less disk space (the data files are compressed)
- Backups of the application consume much less floppy disk space
(data files are backupped in their compressed form)
- One of the greatest advantages is :
After the application is terminated all data files will be
UNACCESSIBLE to the user (or other persons).
A compressed file is UNREADABLE !!
Files with secret information can't be examined using an editor
or list program.
It will be IMPOSSIBLE to manipulate the files with for example
dBASE or any other .DBF viewer/editor :
The (compressed) database can't be corrupted doing that way.
If you want to prevent that an other RCmpLib user can decompress
the files you can protect your archive using the PASSWORD option.
STRING COMPRESSION
With RCmpLib v3.0 it is also possible to compress memo-fields !
If you are compressing existing memo-fields of a database the size
of the .DBT file will not immediately decrease ...
You have to reorganize (only the first time) the memo file to see
the result.
One method for reorganizing is the following :
1) Copy the .DBF and the .DBT files to temporary files
2) Zap the original files
3) Append all the records from the temporary files
4) Delete the temporary files
2.3 QUALITY OF THE COMPRESSION ------------------------------------------
The compression method used by RCmpLib is fast, reliable and gives
a good compression factor.
In comparison with the commercial compression programs as PKZIP 2.04
and ARJ 2.41, RCmpLib will score a little less.
The comparison is not completely fair because PKZIP and ARJ standalone
programs are with only one goal : compression.
RCmpLib is a part of a complete Clipper application and has to deal
with less resources (as memory).
3 FUNCTIONS IN RCMPLIB ------------------------------------------------
A complete, detailed description of the functions (with examples)
can be found in the Norton Guide (RCmpLib.NG).
Both a Clipper 5.xx and a Summer '87 version of the functions is
described in the Guide.
4 REGISTRATION --------------------------------------------------------
RCmpLib is a SHAREWARE product. It is available world-wide through
Users Groups, Bulletin Boards, FTP-Servers, etc.
You have the opportunity to try the program 30 days at no charge,
to see if it meets your needs.
If you continue to use the program after evaluation, please complete
the included registration form (RCmpLib.REG, for DUTCH users Dutch.REG)
and send it to:
┌────────────────────────╖
│ Ing. R.P.B. van Gelder ║
│ Binnenwiertzstraat 27 ║
│ 5615 HG EINDHOVEN ║
│ THE NETHERLANDS ║
╘════════════════════════╝
REGISTRATION FEE
If you are a NEW RCMPLIB USER, the registration fee is :
DELIVERY BY E-MAIL : US $ 25
DELIVERY BY POST : US $ 30
UPGRADE OFFER
If you already are a REGISTERED USER of RCmpLib,
the upgrade costs are :
DELIVERY BY E-MAIL : US $ 10
DELIVERY BY POST : US $ 15
PAYMENT
Just include the appropriate amount of money (IN CASH !!) with the
registration form (RCmpLib.REG, for DUTCH users Dutch.REG)
and send it to the address as mentioned above.
┌────────────────────────────────────────────────────────────────╖
│ -+- IMPORTANT -+- ║
│ ║
│ NORMALLY I DON'T ACCEPT ANY FOREIGN BANK CHECK, MONEY ORDERS ║
│ NOR CREDIT CARDS. BECAUSE IF I REMIT THE MONEY TO MY DUTCH ║
│ ACCOUNT, THE BANK WILL CHARGE ME $ 10 US (!) FOR TRANSFER ║
│ COSTS !!! I AM VERY SORRY FOR THAT ... ║
│ ║
│ HOWEVER, IF