How to use zipper to add files to existing zipfile?
lazarus / 21-General

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BosseB · 2021-03-29 16:10

I have a service application I am trying to port to Linux. I use
Lazarus 2.0.8 and Fpc 3.0.4 in this case but I will upgrade when I am
done porting.

So this application commands exeternal equipment to do some measures
and returns the resulting data to the server. Now these data are
packaged into several files (mostly text files), which are supposed to
go into a zip file on the output directory.

This seemed to work fine until I found that some files were missing in
the zipfile. The zip is created in two passes, one when the pure
binary communication stream is available as binary data in a few *.bin
fiiles. Then these are put into the output zipfile.
Next the processing of the binary data is done and results in the
other set of output files, which are also put into the same zipfile.
Only, when I inspect the zipfile only the files written the second
time are present..

So I wonder if there is some flag of some kind I have missed to do an
append zip operation?

This is the function I use for putting files into a zip archive
(argument FileList contains a list of the paths to all files to be
included in the zip archive):

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
implementationuses  Zipper;procedure PrintMessage(Msg: string);{This
will show the Msg string on the console window if running on acommand
line program, else nothing}begin  {$IFDEF CONSOLE}  Writeln(Msg); 
{$ENDIF}end; function ZipFiles(TargetFile: string; FileList:
TStrings): boolean;var  {$ifdef FPC}  ZW: TZipper;  {$else}  ZW:
TZipWrite;  {$endif}  i: integer;  FileName,  BaseArcFile, 
ArcFileName,  LastError: string;begin  Result := false;  {$ifdef FPC} 
ZW := TZipper.Create;  {$else}  ZW := TZipWrite.Create(TargetFile); 
{$endif}  try    PrintMessage('Zipping files to: ' + TargetFile);   
try      {$ifdef FPC}      ZW.FileName := TargetFile;      BaseArcFile
:= IncludeTrailingPathDelimiter(ChangeFileExt(ExtractFileName(TargetFi
le), ''));      {$endif}      for i := 0 to FileList.Count-1 do     
begin        FileName := FileList[i];        if not
FileExists(FileName) then Continue;        {$ifdef FPC}       
ArcFileName := BaseArcFile + ExtractFileName(FileName);       
PrintMessage('Add file to zip: ' + FileName);       
ZW.Entries.AddFileEntry(FileName, ArcFilename);        {$else}       
ZW.AddDeflated(FileName);        {$endif}      end;      {$ifdef FPC} 
    ZW.ZipAllFiles;      {$endif}      Result := true;    except     
on E: Exception do      begin        LastError := 'Zip error: ' +
E.Message;        PrintMessage(LastError);        exit;      end;   
end;  finally    ZW.Free;  end;end; 
Here is a sample of the console output when I run the program.
There are two separate instances in the process when the zipfile is
written too, first when the binary data has arrived (the bin files are
saved to the zip archive) and next after the data have been analyzed
and the output text files created:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Zipping
files to: /agi/ssremote/results/FirstTest_20210329_105418.zipAdd file
to zip: /agi/ssremote/results/FirstTest_20210329_105418.stg.binAdd
file to zip:
/agi/ssremote/results/FirstTest_20210329_105418.cmd.binAdd file to
zip: /agi/ssremote/log/CmdDir.binAdd file to zip:
/agi/ssremote/log/FileDir.binAdd file to zip:
/agi/ssremote/log/Calib.binZipping files to:
/agi/ssremote/results/FirstTest_20210329_105418.zipAdd file to zip:
/agi/ssremote/results/FirstTest_20210329_105418.stgAdd file to zip:
/agi/ssremote/results/FirstTest_20210329_105418.cmdAdd file to zip:
/agi/ssremote/results/FirstTest_20210329_105418.crs So now I expected
that the zip contained 5 bin files and 3 text files, but in fact only
the 3 text files appear.
It seems like if I call the ZipFiles twice with the same target name
if the file exists it will be overwritten rather than appended to.

Question:
Is there a setting in Zipper that allows for adding extra files into
an existing zip archive file?

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wp · 2021-03-29 16:40

My feeling is that zipper can only create new files. So, in order to
append to an existing zip, you must first use the unzipper to extract
the files from the existing archive. Then you can use zipper to pack
both old and new files into a new archive. Not very comfortable, I
guess. Of course you can alternatively execute a commandline zip
utility by means of TProcess.

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trev · 2021-03-29 23:50

Delay zipping until all wanted files are available. Simples

(I assume not relying on an external dependency was the point of using
zipper.)

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BosseB · 2021-03-30 06:06

I have walked over the code and added in the missing files in the
second invocation of the ZipFiles function so it actually makes a full
file rather than appending the new files into the zip.

Since it is existing code using a class that is originally used stand-
alone it is not so simple to only make one call, they come from
different classes. But now the last call makes the final report file
containing all needed files.
Now working (end result is OK) even though it does unnecessary
operations in this case.
Will try to refactor later.