faq.txt

TCompress Component Set For Delphi Kylix BCB v9.0

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TCompress Frequently Asked Questions

Last updated: December 2004

Contents:

**** Purchasing and Licensing:
* Do I need a per-copy runtime license to distribute applications
  which use TCompress?
* What is the price to register and use TCompress?
* How much do I pay for multiple developer licences?
* How quickly will a registration request be processed?
* Can I also buy the source code if I want to?
* Which source options do I need?
* Do you take credit cards?
* Do I need to make separate registrations for different compiler versions I own?
* Can we pay with a check?

**** Performance and Capabilities
* Does TCompress create files compatible with ZIP, LHArc or
  Winzip?
* Does TCompress require any external DLLs to operate?
* Can I create a self-extracting EXE with TCompress?
* Is TCompress "industrial strength", or does it have hidden size
  limitations or problems?
* What is the Compctrl unit for?
* Can I create archives which span across several disks?
* How good is the data compression I get with TCompress?
* I have some files which don't get any smaller when compressed
  using TCompress. Why not?
* Why don't "protected" Paradox tables compress well with TCompress?
* Is there a routine or component to auto-compress entire records
  within a database?
* Is TCompress thread-safe?
* Is TCompress Year-2000 compliant

**** How To:
* Can I seek into the middle of a compressed file and decompress
  just part of it?
* Does TCompress handle updates and deletions from an archive
  nicely, or does it leave "holes"?
* How do I use TCompress/TCDBMemo etc. if I have a Data Module in my
  project?
* How can I speed up access to files in an archive?
* How can I compress a string in memory?
* How can I read string data and compress it into a blob field?

**** Problems (also see the Troubleshooting section of Compress.hlp):
* I compressed a file using TCompress, but I can't seem to decompress it. Why
  not?
* I compressed something into a stream, but I can't seem to expand it.
  Why not?
* How do I eliminate the registration popup message? Is any other
  functionality affected in an unregistered copy of TCompress?
* My application says "Requires BDE" when I run it on another machine. Does
  TCompress require the Borland Database Engine?
* What should I do if I get an "Out of Memory" message using TCompress?
* Do you have any demo programs written specifically for C++ Builder, or are
  they all Pascal?
* My application's memory use seems to increase every time I decompress
  files. Why?
* What should I do if I see an "EUnableToCompress" exception?
* How do I fix a "transliterate error" with TCDBMemo and Interbase blobs

============ And here are the answers: =================

**** Purchasing and Licensing:

* Do I need a per-copy runtime license to distribute applications which use
  TCompress?
No. You only need to buy a developers' license for each developer.

* What is the price to register and use TCompress?
See the pricing information and handy form in Registration section of the
Compress.hlp help file which comes with TCompress.

* How much do I pay for multiple developer licences?
Please contact us if you want to buy a license for more than one developer; we offer generous discounts for multiple-license purchases.

* How quickly will a registration request be processed?
Fax or Email: Usually within the same working day. Mail: you should receive
the registration codes and/or source code on disk within one week of our
receipt of the order.

* Can I also buy the source code if I want to?
Yes. All the source of TCompress is available. You can buy the source code of
the TCompress component itself (in the Compress unit), and separately buy the
source of the blob field components (CDBMemo etc) in the Compctrl unit.

* Which source options do I need?
If you are just planning on working with compressed files (singly or in multi-
file archives), you need the Compress unit source. If you will be using any
of the blob compression components or classes, you should buy both the
Compress unit AND the Compctrl unit source.

* Do you take credit cards?
Yes -- Mastercard, Visa and Amex only.

* Do I need to make separate registrations for different compiler versions I own?
No. One registration will cover one developer's use of TCompress with all of
the compiler versions supported by the release of TCompress which is licensed.

* Can we pay with a check?
Yes. In general, we will accept most cheques in most currencies provided
their value is a close match to the payment required. However, credit card
orders can be processed more quickly.


**** Performance and Capabilities

* Does TCompress create files compatible with ZIP, LHArc or Winzip?
No. TCompress uses compression methods which are comparable to those used in
the above programs. However, in order to meet its design goals (in
particular: general purpose compression capabilities, the ability to mix
compression types in one archive, and support for "custom" compression), it
does not use a file format compatible with any of the above.

HOWEVER, our TCompLHA component is specifically designed to create and manage
LHArc/LHA archives (which can also be used with WinZip).  Naturally, TCompLHA
can also read TCompress archives. For more information, see:
<A HREF="http://www.spis.co.nz/compLHA.htm">http://www.spis.co.nz/compLHA.htm</A>

* Does TCompress require any external DLLs to operate?
None whatsoever. TCompress is written in 100% native Delphi.

* Can I create a self-extracting EXE with TCompress?
Yes. In the Compress.zip file are two example projects that show how to do
this -- selfextr.dpr and selfxsml.dpr.

* Is TCompress "industrial strength", or does it have hidden size limitations
  or problems?
Hundreds of developers are using TCompress for an extremely wide range of
applications, with file sizes ranging from kilobytes up to tens of GB. They,
and we, believe it to be a trouble-free solution for the range of compression
problems for which it was designed. Limitations tend to be wholly a factor of
the deployment platform (e.g. system resources, free disk space etc). Version
8.0 supports files and archives with an overall size bigger than the 2GB
"OS-determined" limit which applied to earlier versions (there is
a new upper limit, of course, but that is 8 exabytes = 2^63 bytes).

* What is the Compctrl unit for?
It contains all the classes and components for working with database Blob
fields (CDBMemo, CDBImage, CDBRich, TCBlobfield, TCBlobstream etc). If you
don't plan to work with any of those, you don't need to install it.

* Can I create archives which span across several disks?
Yes, if you use the add-on TSegCompress component developed by Ken McClain:
<A HREF="http://www.softbreeze.net/nickel.htm">http://www.softbreeze.net/nickel.htm</A>. Or use our TCompLHA product, which includes a TSegLHA component -- see <A HREF="http://spis.co.nz/CompLHA.htm">http://spis.co.nz/CompLHA.htm</A>.

* How good is the data compression I get with TCompress?
All data compression is dependent on the method used and the nature of the
input data. For best compression use the LZH5 algorithm -- its results should
be similar to those you would get when using Zip compression with the same
file(s). See the Introduction to Data Compression section of the Compress.hlp
help file.

* I have some files which don't get any smaller when compressed using
  TCompress. Why not?