[fpc-pascal] TStream descendant to compress/decompress gzip data from another stream

[José Mejuto]

El 28/03/2013 1:06, Ewald escribió:

>>> Google found an old thread on lazarus mailing list about this ("FPC,
>>> gzip and stream") but without any solution, everything mentioned there
>>> has either the limitations of TCompressionStream/TDecompressionStream
>>> (no gzip format) or TGZFileStream (not able to work wit ObjectPascal
>>> streams).
>>
>> Hello,
>>
>> .gz is a quite simple format, but it can not be implemented as a TStream (only) descendant because in a single .gz file many files could be added so something like the class to handle .zip files should be used.
>
> Sorry to just drop in on this quite late, but isn't gzip  a compression algorithm and not a file format as such? gzip (the command line utility) only compresses one file and *doesn't* put this in a multi-file container. To get `multi-file gzips`, you will first want to bundle the files and compress this bundle (files -> tar -> gzip) or compress the files separately and then bundle them together (files -> multiple separate gzipped files -> tar). Or are we talking about a different gzip here?
>

Hello,

Just quoting the RFC1952 about .gz format:

--- http://tools.ietf.org/html/rfc1952 --------

2.2. File format

       A gzip file consists of a series of "members" (compressed data
       sets).  The format of each member is specified in the following
       section.  The members simply appear one after another in the file,
       with no additional information before, between, or after them.

-----------------------------------------------

So I think it is legal to concatenate several .gz files and get a final 
.gz with several files inside.

In the other hand, yes, the usual behavior in .gz is to store only one file.

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