7-zip extraction in C#

Question

I have a folder containing a million zip files which I need to extract. Two ways I have tried:

Way 1: Use the 7-zip exe file and System.Diagnostic Process as follows

 ProcessStartInfo p = new ProcessStartInfo();
 p.FileName = "7za.exe" 
 p.Arguments = "e " + sourceName; // sourceName is the name of the zip file
 p.WindowStyle = ProcessWindowStyle.Hidden;
 Process x = Process.Start(p);
 x.WaitForExit();

Way 2: Use the 7z.dll and SevenZipExtractor as follows

 SevenZipExtractor.SetLibraryPath(@"C:\Program Files\7-Zip\7z.dll");
 SevenZipExtractor zipFile = new SevenZipExtractor("inv1_0.zip");
 zipFile.ExtractArchive(@"c:\projects\extractor\extractor\bin\debug\inv1_0.dat");

Two things here:

a) Way 1 works perfectly fine. Way 2 doesn't work. Give the error "SevenZip.SevenZipArchiveException: Invalid archive: open/read error!". Can someone suggest why this could be happening when way 1 is giving the correct extracted file?

b) Since there are a million zip files, I am worried about using Way 1 : as in the Process. How expensive is to loop through a million zip files and use process for each one of them. I would really like to use Way 2 but for some reason it gives the exception.

Option 3: Write a batch file. http://stackoverflow.com/questions/138497/batch-scripting-iterating-over-files-in-a-directory — P.Brian.Mackey, Nov 21 '13 at 20:22
what is the full path to inv1_0.zip? Have you tried specifying the full path to the file? — iamkrillin, Nov 21 '13 at 20:23
@iamkrillin its all in the same folder. invalid file isn't the error here. — blue piranha, Nov 21 '13 at 20:25
Is it all files that are failing to unzip or just this one particular file? — Kim, Nov 21 '13 at 20:26
Option 4: use SharpZipLib (http://www.icsharpcode.net/opensource/sharpziplib/), I've used this in the past for handling large quantities for zip files, it's very simple to use, and never ran into this kind of weird problems :) — Jason, Nov 21 '13 at 20:31
it looks like this error msg is very generic, The full message from the source code is: "Invalid archive: open/read error! Is it encrypted and a wrong password was provided? If your archive is an exotic one, it is possible that SevenZipSharp has no signature for its format and thus decided it is TAR by mistake." — iamkrillin, Nov 21 '13 at 20:38

score 0 · Accepted Answer · edited May 23 '17 at 11:52

You can't avoid the cost of unzipping 1,000,000 files, but you can choose the way it'll cost you - processor usage, or time. If you don't want to lock your main thread, let a secondary thread handle the file processing for you.

Options:

If time isn't an issue, spawn a background thread with low priority.
If you want to abuse your processors - spawn several threads, set processor affinity for each of them, let them do their work in parallel.

But that doesn't seem to be your issue at all. It seems to me that SevenZipExtractor is behaving in a different way than the standalone .exe. I would obviously stick to the first (working) option until I figured out what's wrong with the 2nd approach.

You may also want to pay a visit to sevenzipsharp's CodePlex discussion group.

7-zip extraction in C#

1 Answers1