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Bug when using the java.util.zip classes to write zip files

, 8 May 2004 CPOL 105.7K 23
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Describes an issue when writing a binary file into a zip file using the java.util.zip classes

Introduction

I was writing a little .NET app in C# and was looking for a small library that would let me read and write zip files. That's when my first Google search gave me a link to Using the Zip Classes in the J# Class Libraries to Compress Files and Data with C#. Great! - that was my first reaction, but it didn't last too long. You can read zip files alright, but when you write zip files, if you have binary files (as you most often will), the generated zip file will be corrupt and you can't read it back. Funnily, WinZip does open it (ignoring the header errors) and the suggested solution by a Microsoftie in the one of the MS NGs was to extract all files using WinZip and then to zip it back. LOL. Why'd anyone want to use the zipping libraries at all if they had the option of bringing WinZip into the picture?

There is not even a KB article on this bug - bad! I lost about half a day when I was using these classes because I initially thought it was something wrong in my code. Anyway, this is a warning to everyone. Do not use the J# class libraries for zipping/unzipping if you are using the BCL 1.1 version. Heath Stewart (C# MVP and CodeProject Editor) has informed me that the BCL 2.0 includes zipping functionality - so that's really good news. And until that comes out, a very good free alternative to the J# classes is SharpZipLib which I very strongly recommend.

Bug demo

  1. Create a new C# console app project
  2. Add a reference to vjslib (...Microsoft.NET\Framework\v1.1.4322\vjslib.dll)
  3. Copy/paste the following code into your main cs file :-
    using System;
    using System.IO;
    using java.util.zip;
    
    class MainClass
    {
      [STAThread]
      static void Main(string[] args)
      {
        BugDemo();
      }
    
      static void BugDemo()
      {
        //Write zip file
        ZipOutputStream os = new ZipOutputStream(
          new java.io.FileOutputStream("test.zip"));
        ZipEntry ze = new ZipEntry("gluk.gif");
        ze.setMethod(ZipEntry.DEFLATED);
        os.putNextEntry(ze);
        java.io.FileInputStream fs = 
          new java.io.FileInputStream("gluk.gif");
        sbyte[] buff = new sbyte[1024];
        int n = 0;
    
        while ((n=fs.read(buff,0,buff.Length))>0)
        {
          os.write(buff,0,n);
        }
        fs.close();
        os.closeEntry();      
        os.close();
    
        Console.WriteLine("Okay, the zip has been written.");
    
        //Read zip file
        try
        {
          //Bug will occur here
          ZipFile zf = new ZipFile("test.zip");  
        }
        catch
        {
          Console.WriteLine("Bug confirmed!");
        }
      }
    }
  4. Now make sure you have a gluk.gif in the same folder as the executable.

  5. Compile and run.

Workaround

There is no real workaround to the problem. You can use the alternative library I mentioned above or wait for Whidbey.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Nish Nishant
United States United States
Nish Nishant is a Software Architect/Consultant based out of Columbus, Ohio. He has over 15 years of software industry experience in various roles including Lead Software Architect, Principal Software Engineer, and Product Manager. Nish is a recipient of the annual Microsoft Visual C++ MVP Award since 2002 (13 consecutive awards as of 2014).

Nish is an industry acknowledged expert in the Microsoft technology stack. He authored
C++/CLI in Action for Manning Publications in 2005, and had previously co-authored
Extending MFC Applications with the .NET Framework for Addison Wesley in 2003. In addition, he has over 140 published technology articles on CodeProject.com and another 250+ blog articles on his
WordPress blog. Nish is vastly experienced in team management, mentoring teams, and directing all stages of software development.

Contact Nish : You can reach Nish on his google email id voidnish.

Website and Blog

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Comments and Discussions

 
Questionhow to open and read files from a zip file using jsp or java Pin
sandhyamn8-Jun-07 19:56
membersandhyamn8-Jun-07 19:56 
GeneralJava Zip Pin
SanjitP11-Apr-07 22:28
memberSanjitP11-Apr-07 22:28 
GeneralRe: Java Zip Pin
WajeehAhmed16-Apr-07 1:30
memberWajeehAhmed16-Apr-07 1:30 
QuestionAlternative? Pin
evoluzion22-Dec-06 11:02
memberevoluzion22-Dec-06 11:02 
AnswerRe: Alternative? Pin
Brad Bruce22-Dec-06 11:19
memberBrad Bruce22-Dec-06 11:19 
GeneralVB convert procedure Pin
Alessandro Betti17-May-06 6:56
memberAlessandro Betti17-May-06 6:56 
Generalon text files Pin
dvsr27-Dec-05 13:33
memberdvsr27-Dec-05 13:33 
GeneralAlternative (with code) Pin
Elmue17-Nov-05 2:30
memberElmue17-Nov-05 2:30 
GeneralA fix available from M$ Pin
rshearer31-Aug-05 10:43
memberrshearer31-Aug-05 10:43 
GeneralAnother big problem Pin
nahumtakum15-May-04 0:31
membernahumtakum15-May-04 0:31 
Questionis it really corrupt? Pin
SamJost10-May-04 21:11
memberSamJost10-May-04 21:11 
AnswerRe: is it really corrupt? Pin
Nishant S10-May-04 21:36
staffNishant S10-May-04 21:36 
Hi Sam

While WinZip opens it fine, if you try to delete one of the files inside the zip from within WinZip, WinZip will delete the file and then bring up the “errors were found” dialog box where it reports a corrupt header. This only happens on occasions – so the bug is probably not easy to track.

Also, if you read the Google links I posted in one of the below threads, you’ll see a lot of people mentioning corrupted date/time entries too.

Nish



Now with my own blog - void Nish(char* szBlog);

My MVP tips, tricks and essays web site - www.voidnish.com

Request - Could everyone who have in the past, posted on my personal forum on CP, be kind enough to delete all your posts please? I intend to start a personal non-technical blog there, now that it is RSSd and would very much like to empty the forum before I do so - because the posts that are there as of now are mostly test posts and posts that were made before we all knew it was a blog Smile | :)


GeneralRe: is it really corrupt? Pin
SamJost10-May-04 21:53
memberSamJost10-May-04 21:53 
GeneralRe: is it really corrupt? Pin
Nishant S10-May-04 22:40
staffNishant S10-May-04 22:40 
GeneralRe: is it really corrupt? Pin
SamJost10-May-04 22:44
memberSamJost10-May-04 22:44 
GeneralTry this code Pin
Valeri9-May-04 5:56
memberValeri9-May-04 5:56 
GeneralRe: Try this code Pin
Nishant S9-May-04 6:18
staffNishant S9-May-04 6:18 
GeneralRe: Try this code Pin
Roberto Ballerini12-May-04 21:54
sussRoberto Ballerini12-May-04 21:54 
GeneralRe: Try this code Pin
Valeri12-May-04 22:49
memberValeri12-May-04 22:49 
QuestionWorks fine for me ? Pin
Bee Master9-May-04 5:36
memberBee Master9-May-04 5:36 
AnswerRe: Works fine for me ? Pin
Nishant S9-May-04 6:14
staffNishant S9-May-04 6:14 
GeneralRe: Works fine for me ? Pin
Bee Master11-May-04 5:58
memberBee Master11-May-04 5:58 

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