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Overview
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This project from Benjamin Dowse
(bendowse@dingoblue.net.au)
provides a reusable DLL which allows you to compress and decompress
byte arrays and strings. You can compress data in memory, or using file IO
in Visual Basic you can also compress files.
ZLib is an excellent compression technique and has been re-used in many other places
where a free source and patent-free method of compression is needed. One of the notable
recent applications is as part of the PNG (Portable Network Graphics)
file format specification. So you're in good company if you choose to use it yourself!
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How to use it
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First, you need to ensure zlib.dll is unzipped into your Windows\System folder.
zlib.dll is a straight Win32 DLL written in C by the ZLib authors, and does not
need to be registered.
Then fire up the project group in the download. The demonstration code includes the
CompressZItLib DLL and a sample application, which demos compression and decompression of
in-memory data and files.
The methods of the DLL are straightforward: to compress and decompress string data, use
the CompressString and DecompressString functions. To compress and decompress
binary data, use the CompressData and DecompressData functions and pass in
the data as a byte array. Note that when you decompress data, you need to know how large
the data was before it was compressed, so if you are storing in a file you will probably
want to save the size as the first thing in the file. The helper properties OriginalSize
and CompressedSize allow you to query information about the data, but note that
when decompressing original size is a parameter, and when compressing compressed size is only
valid once the data has been compressed.
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