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<title>PowerArc Data Compression Library</title>
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<td valign="top" width="16%"><b>Product</b></td>
<td width="84%">PowerArc 1.3 from 30 Mar 2001</td>
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<td valign="top" width="16%"><b>Description</b></td>
<td width="84%">High efficient Data Compression Library for Delphi</td>
</tr>
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<td valign="top" width="17%"><b>Author</b></td>
<td width="83%">Copyright (c) 1998-2001, SoftLab MIL-TEC Ltd<br>
Web: <a href="http://www.softcomplete.com" target="_blank">http://www.softcomplete.com</a><br>
Email: <a href="mailto:support@softcomplete.com">support@</a><a href="http://www.softcomplete.com">softcomplete.com</a></td>
</tr>
<tr>
<td valign="top" width="16%"><b>Status</b></td>
<td width="84%">Freeware (only BZIP engine)<br>
Registration for PPM, RANK and ZIP engines $99.<br>
<a href="http://www.shareit.com/programs/136048.htm" target="_blank">Online
registration is available</a>.</td>
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<tr>
<td valign="top" width="16%"><b>Limitation</b></td>
<td width="84%">work only in IDE</td>
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<td valign="top" colspan="2">
<p><font color="#FF0000"> <br>
This is a legal Agreement between you (either an single individual or
an entity, herein referred to as Licensee) and SoftLab (herein after referred
to as Licensor). By installing this software (herein after referred to
as Product), you indicate your acceptance of this Agreement.</font></p>
<p align="center"><font color="#FF0000"><b>SOFTLAB EVALUATION LICENSE AGREEMENT</b></font>
</p>
<p><font color="#FF0000"> <b>1.GRANT OF LICENSE.</b></font>
</p>
<ul>
<blockquote>
<p><font color="#FF0000"> <b>1.1</b> Licensor grants you a non-exclusive
royalty-free license to make as many copies of the Product accompanying
this agreement as you want, solely to test and to evaluate the Product
before you make the decision to purchase the Product.</font></p>
<p><font color="#FF0000"> <b>1.2</b> You shall not use, copy, rent,
lease, sell, modify, decompile, disassemble, otherwise reverse engineer,
or transfer the Product except as provided in this Agreement. Any
such unauthorized use shall result in immediate and automatic termination
of this Agreement.</font></p>
<p><font color="#FF0000"> <b>1.3</b> You may transfer and distribute
the Product in its unmodified form via electronic means to another
persons so long as their use of the Product will be strictly for the
purpose of evaluation.</font></p>
<p><font color="#FF0000"><b>1.4</b> You are specifically prohibited
from charging, or requesting donations for copies of the Product,
distributing the Product with any other products without Licensors
prior written permission.</font></p>
</blockquote>
</ul>
<p><font color="#FF0000"> <b>2. WARRANTY AND LIMITATION OF LIABILITY.</b></font></p>
<blockquote>
<p><font color="#FF0000"> The Licensor hereby disclaims all warranties
of any kind relating to the Product, whether express or implied, including
without limitation any implied warranties of merchantability or fitness
for a particular purpose. The Licensee must assume the entire risk of
using the Product.<br>
</font></p>
</blockquote>
</td>
</tr>
</table>
<p align="left"></p>
<p><b>PowerArc</b> is the high efficient Data Compression Library for use with
Delphi, C++ or VB. The library supports some algorithms of compression, both
widespread, and specialized. All algorithms are contain built in data integrity
check and thread-safe (can be work in multithread application). In the following
table briefly we shall describe them. </p>
<table width="95%" border="1" cellspacing="0" cellpadding="3" align="center">
<tr align="center">
<td>
<div align="center"><b>Method</b></div>
</td>
<td>
<div align="center"><b>Description</b></div>
</td>
</tr>
<tr>
<td width="20%" valign="top">Rank</td>
<td>Some idea of this algorithm describe in article Peter Fenwick "Symbol
Ranking Text Compression with Shannon Recodings". At small compression
the very fast and effective implementation is possible.</td>
</tr>
<tr>
<td width="20%" valign="top">ZIP</td>
<td>standart pkware zip compression algorithm.</td>
</tr>
<tr>
<td width="20%" valign="top">BZIP</td>
<td>Modern algorithm of the compressions which have appeared rather recently.
Is based on Burrows-Wheeler transform. Example of the archiver operating
this algorithm is bzip2.</td>
</tr>
<tr>
<td width="20%" valign="top">PPM</td>
<td>The similar method was applied in the archiver HA (Harri Hirvola). Allows
to reach a maximum degree of compression at the expense of a heavy expense
of memory and lowering of speed of operation. Ideally approaches for compression
of the text information. <br>
More detail about this algorithm you can find in article Mark Nelson "Arithmetic
Coding + Statistical Modeling = Data Compression" <a href="http://www.ddj.com/" target="_blank">Dr.
Dobb's Journal</a> February, 1991 </td>
</tr>
</table>
<p>Each algorithm is realized as the separate DLL-unit and has the unitized interface:
</p>
<blockquote>
<p><font face="Courier New, Courier, mono" size="-1"><b>const<br>
</b>PowerArcModuleSignature = 'AA6F3C60-37D7-11D4-B4BF-D80DBEC04C01';
<b><br>
<br>
type</b><br>
TPowerArcModuleInfo = <b>packed record</b><br>
Signature: PChar; <b><font color="#0000FF">//
must be eq to PowerArcModuleSignature</font></b><br>
Name: PChar;
<font color="#0000FF"><b>// module name</b></font><br>
Description: PChar; <font color="#0000FF"><b>//
full module description</b></font><br>
Options: PChar; <b><font color="#0000FF">//
options list delimited with #0</font></b><br>
DefaultBPC: integer; <b><font color="#0000FF">//
bit per char on calgary corpus *100</font></b><br>
MaxBPC: integer; <br>
<b>case</b> integer <b>of</b> <font color="#0000FF"><b> //
unique module ID</b></font><br>
0: ( ModuleID: <b>packed array</b>[0..7]
<b>of</b> Char );<br>
1: ( ModuleIDW: <b>packed array</b>[0..1]
<b>of</b> integer );<br>
<b>end</b>;<br>
PPowerArcModuleInfo = ^TPowerArcModuleInfo;<br>
<br>
TReadFunc = <b>function</b> (Data: Pointer; <b>var</b> Buffer;
Size: integer): integer; <b>stdcall</b>;<br>
TWriteFunc = <b>function</b> (Data: Pointer; <b>const</b> Buffer;
Size: integer): integer; <b>stdcall</b>;</font></p>
<p><font face="Courier New, Courier, mono" size="-1"><b><font color="#0000FF">{
set default compression options }<br>
</font>procedure</b> SetOptions(Opt: PChar); <b>stdcall</b>; <br>
<b><font color="#0000FF">{ compress stream }<br>
</font>procedure</b> Compress(Data: Pointer; Opt: PChar; ReadFunc: TReadFunc;
WriteFunc: TWriteFunc); <b>stdcall</b>; <br>
<b><font color="#0000FF">{ compress memory buffer }<br>
</font>procedure</b> CompressMem(Data: Pointer; Opt: PChar; Mem: Pointer;
MemSize: integer; WriteFunc: TWriteFunc); <b>stdcall</b>; <br>
<b><font color="#0000FF">{ decompress stream }<br>
</font>function</b> Decompress(Data: Pointer; ReadFunc: TReadFunc; WriteFunc:
TWriteFunc): Boolean; <b>stdcall</b>; <br>
<b><font color="#0000FF">{ get module information }<br>
</font>function</b> GetPowerArcModuleInfo: PPowerArcModuleInfo; <b>stdcall</b>;
</font></p>
</blockquote>
<p>On the following to a graphics the comparative outcomes of operation of different
algorithms on <a href="ftp://ftp.cpsc.ucalgary.ca/pub/projects/text.compression.corpus/" target="_blank">Calgary
Text Corpus</a> are exhibited (click on image for more detail). These outcomes
were obtained on slow computer with Pentium-166 CPU.</p>
<p align="center"><img src="img/calg1.gif" width="700" height="547" border="1" usemap="#Map"><map name="Map"><area shape="rect" coords="26,184,300,524" href="detail1.html" target="_blank"></map></p>
<p align="left">The same outcomes are indicated in the following table (cases
of best compression and best speed are selected):</p>
<table width="100%" border="1" cellspacing="0" cellpadding="3">
<tr align="center">
<td colspan="3"><font size="-1"><b>Rank</b></font></td>
<td colspan="3"><font size="-1"><b>ZIP</b></font></td>
<td colspan="3"><font size="-1"><b>BZIP</b></font></td>
<td colspan="3"><font size="-1"><b>PPM</b></font></td>
</tr>
<tr align="center">
<td><font size="-1">Opt</font></td>
<td><font size="-1"><u>bits</u><br>
char</font></td>
<td><font size="-1"><u>MByte</u><br>
sec </font></td>
<td><font size="-1">Opt</font></td>
<td><font size="-1"><u>bits</u><br>
char</font></td>
<td><font size="-1"><u>MByte</u><br>
sec </font></td>
<td><font size="-1">Opt</font></td>
<td><font size="-1"><u>bits</u><br>
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