Werner Pamler wrote:
Another question: I would prefer to avoid Abbrevia altogether and use
the standard zip support in fpc. There are examples in the wiki on how
to use the TDecompressionStream for inflating gzip files. But I always
get a "data error"at least with the mailinglist archive files from
http://lists.lazarus.freepascal.org/pipermail/lazarus/. If I use a
TGZFileStream instead of the TDecompressionStream by a TGZFileStream,
then the file decompresses fine. But this is not a good solution as I
would have to use temporary files which I want to avoid. How can the
TGZFileStream be modified such that it accepts a stream as input
parameter instead of a filename?
It should be possible to use inflateInit2 from paszlib.
I've found a snippet here: http://www.gocher.me/GZIP
If you take GZIPUtils.pas, at first you think it should work, but it
didn't. The only thing I found was that that code only takes a header of
9 bytes into account while the 2015-November.txt.gz has a header of 71
bytes. So if I change the following in ZUncompressStream I could
successfully extract 2015-November.txt:
On line 178:
// inStream.Position := 10; // jump over header
inStream.Position := 72; // jump over header, this needs to be
adjusted to read a string until #0
========
procedure TForm1.Button1Click(Sender: TObject);
var
inStream, outStream: TMemoryStream;
begin
inStream := TMemoryStream.Create;
outStream := TMemoryStream.Create;
try
inStream.LoadFromFile('c:\temp\2015-November.txt.gz');
if ZUncompressStream(inStream, outStream) then
begin
outStream.SaveToFile('c:\temp\2015-November.txt');
end;
finally
inStream.Free;
outStream.Free;
end;
end;
========
Of course in your final code you should read a string until #0 from the
file and position it correctly to begin at the real data.
You could also strip the deflate-part of that unit (or completely create
your own implementation from this source). It's not much code after you
strip all the things you don't need.
Grtz,
/Rik/ (rvk on forum)
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