Zlib decompression - Any ideas?

Brian Yennie briany at qldlearning.com
Mon Dec 29 19:09:22 EST 2008


Ken,

Unfortunately it sounds like you are dealing with a Windows "zip"  
archive which is different from a "gzip" encoded archive. See this  
post for a nutshell explanation:
http://aplawrence.com/Bofcusm/2615.html

In short, they are related but not interoperable. You will probably  
have to tap into an actual "zip" library if these files have been  
compressed using a different algorithm than gzip.

With that said, there should be command-line "zip" utilities for every  
OS, so you might still be able to include those and use shell() calls.

>> Can you compress a copy of the original file with Rev, and compare it
>> to the zlib compressed copy? Does the data look totally different, or
>> maybe just off by a few bytes / headers?
>
> Unfortunately, I don't have the original file... the files I'm  
> receiving are
> from another program on Windows that only decompresses the data in  
> memory;
> the files on disk are always in a compressed state, so the files I  
> can look
> at are always compressed.
>
>> If you have a MacOS X machine (or Linux) handy, you can use gzip and
>> gunzip as command-line equivalents of compress() and decompress() and
>> see how those results compare as well...
>
> Yeah, I've tried that already and keep getting errors that the data  
> is "not
> compressed".
>
> :-(
>
> Ken Ray
> Sons of Thunder Software, Inc.
> Email: kray at sonsothunder.com
> Web Site: http://www.sonsothunder.com/






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