How to Decompress nested GZip (TGZ) files in C#

Question

I am receiving a TGZ file that will contain one plain text file along with possibly one or more nested TGZ files. I have figured out how to decompress the main TGZ file and read the plain text file contained in it, but I have not been able to figure out how to recognize and decompress the nested TGZ files. Has anyone come across this problem before?

Also, I do not have control over the file I am receiving, so I cannot change the format of a TGZ file containing nested TGZ files. One other caveat (even though I don't think it matters) is that these files are being compressed and tarred in a Unix or Linux environment.

Thanks in advance for any help.

Answer 1

Try the SharpZipLib (http://www.icsharpcode.net/OpenSource/SharpZipLib/Download.aspx) free library.

It lets you work with TGZ and has methods to test files before trying to inflate them; so you can either rely on the file extensions being correct, or test them individually to see if you can read them as compressed files - then inflate them once the main file has been decompressed.

Answer 2

Take a look at DotNetZip on CodePlex.

"If all you want is a better DeflateStream or GZipStream class to replace the one that is built-into the .NET BCL, that is here, too. DotNetZip's DeflateStream and GZipStream are available in a standalone assembly, based on a .NET port of Zlib. These streams support compression levels and deliver much better performance that the built-in classes. There is also a ZlibStream to complete the set (RFC 1950, 1951, 1952)."

It appears that you can iterate through the compressed file and pull the individual files out of the archive. You can then test the files you uncompressed and see if any of them are themselves GZip files.

Here is a snippit from their Examples Page

using (ZipFile zip = ZipFile.Read(ExistingZipFile))
{
  foreach (ZipEntry e in zip)
  {
    e.Extract(OutputStream);
  }
}

Keith

Answer 3

To read and write .tar and .tgz (or .tar.gz ) files from .NET, you can use this one-file tar class:

http://cheeso.members.winisp.net/srcview.aspx?dir=tar&file=Tar.cs

Very simple usage. To create an archive:

string[] filenames = { ... };
Ionic.Tar.CreateArchive("archive.tar", filenames);

Create a compressed (gzip'd) tar archive:

string[] filenames = { ... };
Ionic.Tar.CreateArchive("archive.tgz", filenames, TarOptions.Compress);

Read a tar archive:

var entries = Ionic.Tar.List("archive.tar");  // also handles .tgz files

Extract all entries in a tar archive:

var entries = Ionic.Tar.Extract("archive.tar");  // also handles .tgz files