Xceed Zip for .NET

How do I open a folder using the SfxExecuteAfter property?

Xceed admin — Fri, 10 Oct 2008 15:46:34 GMT

To open a folder with the SfxExecuteAfter property (ExecuteAfter for Xceed Zip for .NET), you need to separate the executable name from the folder name with a pipe (|). For example:

Xceed Zip ActiveX :
XceedZip1.SfxExecuteAfter = "explorer.exe|d:\test"

Xceed Zip for .NET and Xceed Zip for .NET Compact Framework
//sfx is of type XceedSfxPrefix
sfx.ExecuteAfter.Add( "explorer.exe|d:\\test" );

Can the Self-Extractor Dialogs be disabled?

Xceed admin — Fri, 10 Oct 2008 15:26:41 GMT

If you use the SfxClearMessages method when creating your executable zip file, then ALL dialogs are disabled. The only way to display a dialog, or several dialogs, is to use the SfxMessages property. For example, if you want to display the "Success Dialog" then you need to use the following code:

XceedZip1.SfxMessages(xsmSuccess) = "Unzip successful."

With Xceed Zip for .NET and Xceed Zip for .NET Compact Framework, the messages can be disabled using the following code:

sfxPrefix.DialogMessages.Clear();

How do I caculate the CRC of a group of bytes (For example 04 01 00 47) using the CalculateCrc32 method?

Xceed admin — Fri, 10 Oct 2008 13:59:45 GMT

The following example demonstrates how to calcuate the CRC for a group if bytes:

Dim data() As Byte = {&H4, &H1, &H0, &H47}

' When we wish to calculate a CRC32 in multiple calls to
' CalculateCrc32, we simply need to provide the
' "up to now" crc32 as the fourth parameter.
' On the first call, we pass zero.
Dim crc32 As Long
crc32 = ChecksumStream.CalculateCrc32(data, 0, data.Length, 0)

' To fold a crc32 to a crc16, we XOR the two halves
' of the crc32. In VB.NET, there is no "shift" operator.
' But everytime we shift one bit to the right, we divide
' by two. So shifting 16 bits to the right is the same
' as dividing by 2^16 (65536).
Dim crc16 As Integer
crc16 = (crc32 \ 65536) Xor (crc32 And &HFFFF)

Console.WriteLine("0x{0:X8} -> 0x{1:X4}", crc32, crc16)

Is it possible to create a zip file in memory using Xceed Zip?

Xceed admin — Fri, 10 Oct 2008 13:58:51 GMT

With the ActiveX version of the Xceed Zip Compression Library, it is not possible to create a zip file in memory.

As of version 2.0 of Xceed Zip for .NET, you simply need to use an instance of the MemoryFile class in the constructor of your ZipArchive class to create a zip file in memory. For example:

Dim folder As New DiskFolder( "c:\windows\fonts" )
Dim zip As New ZipArchive( New MemoryFile( "RAM_File", "fonts.zip" ) )

folder.CopyFilesTo( zip, false, true )

How do I read data from a stream to a zip file?

Xceed admin — Fri, 10 Oct 2008 13:50:08 GMT

Yes. The best way to do it would be to create a StreamFile around your stream and call the StreamFile's CopyTo method. For example:

byte[] data = System.Text.Encoding.Default.GetBytes( "This is the data in the sql db" );

using( MemoryStream stream = new MemoryStream( data ) )
{
    StreamFile file = new StreamFile( stream );
    file.Name = "file.ext";

    ZipArchive zip = new ZipArchive( new DiskFile( @"d:\test.exe" ) );
    zip.BeginUpdate();

    XceedSfxPrefix sfx = new XceedSfxPrefix( new DiskFile( @"C:\Program Files\Xceed Components\Xceed Zip Compression Library 5.0\Sfx\xcdsfx32.bin" ) );

    zip.SfxPrefix = sfx;

    file.CopyTo( zip, true );
    zip.EndUpdate();
}

How do I get the progress of the entire zip operation?

Xceed admin — Fri, 05 Sep 2008 18:53:37 GMT

In order to get the progress of the entire zip operation, you need to handle the ByteProgression, BuildingZipByteProgression and GatheringZipContentByteProgression events.

Which compression option requires less CPU usage?

Xceed admin — Fri, 05 Sep 2008 18:15:50 GMT

The format you use has no impact on what % of the CPU we use. If two processes try to use the CPU at 100%, one won't win over the other. They will share 50% of it, the system slicing their respective threads equally.

What you should consider instead is time to compress, and memory usage. That way, you will avoid pagefile swapping and use the CPU less often.

The best choice would be to use the XceedStandardCompressionFormat, with the XceedDeflateCompressionMethod, with CompressionLevel at 1. You won't compress as much as using level 9, or using XceedBWTCompressionMethod, but "deflate" uses much less memory than "BWT", and level 1 compression does not fall too short from level 9 in term of size.

As for choosing XceedStandardCompressionFormat over GZipCompressionFormat, the later one has a bigger header, and requires some more processing. It also uses a standard CRC32 checksum calculation, as opposed to the faster XceedStandardCompressionFormat's Adler32 checksum.

How can I unzip a zip file using the CompressedStream class?

Xceed admin — Fri, 05 Sep 2008 17:57:10 GMT

The CompressedStream class can only handle Streams and not zip files. If you want to read the contents of a file contained within a zip file, then you will need to create a ZippedFile object around the file in question and use the OpenRead method to read the contents. You can then write the read contents to the text file.

Does Xceed Zip for .NET support ASP.NET?

Xceed admin — Fri, 05 Sep 2008 17:39:20 GMT

Xceed Zip for .NET supports both version 1.1 and 2.0 of the .NET Framework (thus ASP.NET).

What languages can the Self-Extractor dialog boxes display?

Xceed admin — Fri, 05 Sep 2008 17:31:02 GMT

Unfortunately, the Self-extracting library does not support any other language other than English. For the meantime, there is no other way to add any other language for this module.

ItemDoesNotExistException

Xceed admin — Fri, 05 Sep 2008 17:30:19 GMT

Since a zip file is case sensitive, you must use the appropriate case when specifying the name of the zipped file.

If you are viewing the contents of the zip file with Winzip, make sure that the "Allow all upper case file names" option in the "Options\Configuration" menu is checked so that you can view the actual file names in the case where they are all in upper case.

Icon for the Self-Extractor dialog looks distorted.

Xceed admin — Fri, 05 Sep 2008 17:29:08 GMT

You can fix this by making sure that your icon specification size is not more than 32x32 and set to 16 colors.

When using the self-extractor module with Xceed Zip for .NET Compact Framework, it is not possible to modify the icon displayed by the self-extracting zip file.

This limitation also applies to Absolute Packager.

Does Xceed Zip have any limitations in regards to the number/size of files that will be added to the zip file and the actual size of the zip file itself?

Xceed admin — Fri, 05 Sep 2008 17:18:52 GMT

Version 4.x and LOWER of the ActiveX version of Xceed Zip has a limitation of 4 gigs and 65535 files.

Even if you use the SplitSize property to create multiple parts, the limitation remains the same. If the split zip file surpasses the limitation, Xceed Zip will not be able to unzip the contents.

As of version 5.0, Xceed Zip supports the Zip64 format. The Zip64 zip file format is the 64-bit counterpart of the zip file format that is used by PKZIP 4.5 and up. It supports up to 2^64 -1files within a zip archive as well as files that have a size greater than 4GB for a zip file size that can reach up to about 18 million terrabytes ( more precisely, 264 -1bits).

Xceed Zip for .NET and Xceed Zip for .NET Compact Framework also supports Zip64.

If I use the Xceed Zip Compression Library, Xceed Zip for .NET or Xceed Zip for .NET Compact Framework in a project, do I need an Export License?

Xceed admin — Fri, 05 Sep 2008 17:18:32 GMT

Neither the Xceed Zip Compression Library, Xceed Zip for .NET nor Xceed Zip for .NET Compact Framework has no strong encryption at all. It only has password-scrambling that is 100% compatible with the PKZip 2.04g Zip file format. This is 'light' protection that will not protect against any determined users. At best, you can consider it has 32-bits of protection.

The Wassenaar agreement (http://www.wassenaar.org) stipulates that anything under 64-bits of protection for a REAL symetrical algorithm is freely exportable. The password-scrambling built into Xceed Zip is not even real symetrical encryption, it is more a CRC-based password-scrambler, considered as light protection only.

If you need strong encryption, with real protection, then you may need to be careful about exporting, like if you use the Xceed Encryption Library or any component that supports the AES (Rijndael) or other 128-bit+ encryption algorithms.

I created a zip file using Xceed Zip from my Active Server Page, however the call to Reponse.Redirect fails. Why?

Xceed admin — Fri, 05 Sep 2008 17:15:50 GMT

In most cases, this error occurs because of the permissions granted to the internet guest account (IUSER_MACHINE) or to the internet account trying to download the file.

Double check the permissions to make sure that they are sufficient to access and download the file.

I created an SFX zip file using Xceed Zip. Is it possible to extract the contents using command line parameters?

Xceed admin — Fri, 05 Sep 2008 17:02:14 GMT

Unfortunatley, it is not possible to pass command line parameters to the self-extracting zip file.

What type of encryption does Xceed Zip use/support?

Xceed admin — Fri, 05 Sep 2008 16:56:28 GMT

The encryption algorithm used by the Xceed Zip Compression Library, Xceed Zip for .NET, Xceed Zip for .NET Compact Framework, Xceed Backup and Absolute Packager is the same one used by the PKZip 2.04g program.

This type of encryption can resist attacks by amateurs if the password is well chosen and long enough (at least 16 characters) but it will probably not resist attacks by determined users or experts. Therefore, we suggest that you always use long passwords, and when possible, do not rely solely on this encryption system to protect sensitive data.

Xceed Zip Compression library 6.0 also supports AES encryption. Xceed Zip for .NET will support AES encryption in the May 2006 release.

I need to be able to add a specialized header to the beginning of the zip file that I am creating. Is this possible with Xceed Zip?

Xceed admin — Fri, 05 Sep 2008 16:55:25 GMT

The ActiveX version of Xceed Zip does not allow for custom headers to be added to the zip file. You can use the "comment" section for each file (or the one for the entire zip file) to add custom info.

As of version 2.0 of Xceed Zip for .NET, custom zip file headers are supported via the SfxPrefix class.

I found a zip file that Xceed Zip cannot unzip but that WinZip can. Is this a bug?

Xceed admin — Fri, 05 Sep 2008 16:22:51 GMT

For over 7 years as of this writing, the PKZip v2.0 zip file format has been available and in widespread use. That's the format Xceed Zip uses to read and write Zip files. The reason Xceed Zip won't unzip that file is because Xceed Zip is not backwards compatible with old Zip files made with PKZip v1.x. The extra code required in order to unzip these older Zip files is not required by most developers and was intentionally left out in order to provide lighter components.

You claim that Xceed Zip is 100% compatible with the PKZIP 2.04g zip file format. However, I have files that can be unzipped by PKZIP 2.04g (or up) but will not be unzipped by Xceed Zip. Why?

Xceed admin — Fri, 05 Sep 2008 16:21:57 GMT

Keep in mind that Xceed Zip is compatible with the 2.04g file format - not the actual 2.04g application itself. In other words, any Zip file created by PKZIP 2.04g can be unzipped by Xceed Zip, and any Zip file created with Xceed Zip can be unzipped by PKZIP 2.04g. However, some zip files made with versions of PKZIP before 2.0 (over 7 years old) would compress files with older, less efficient algorithms. Xceed Zip is not backwards compatible with these old zip files. The PKZIP application retains backwards compatibility.

I have .GZ files that I would like to unzip. Is it possible with Xceed Zip?

Xceed admin — Fri, 05 Sep 2008 16:15:13 GMT

Xceed Zip for .NET supports TAR and GZip.

Xceed Zip Compression Library (activex) does not however, support .TAR. It is however possible to decompress GZip files using Xceed Streaming Compression library.

Is it possible to write a zip file to a CD-R or CD-RW?

Xceed admin — Fri, 05 Sep 2008 16:12:56 GMT

In order to write to a CD-R or CD-RW, you will need to do the following:

1- You will need DirectCD (or a similar application)
2- Format the CD to be able to access it through a drive letter
3- Let DirectCD take "control" of the CD before starting the backup
4- Start the backup

Once the first disk has been filled, you will need to let DirectCD unlock the CD and relock the new one before you confirm that a new CD has been provided via the InsertMedia event.

Is XceedCompression compatible with ZLib?

Xceed admin — Fri, 05 Sep 2008 16:11:49 GMT

The compressed data returned by the XceedCompression object (Xceed Zip ActiveX) or the XceedCompressedStream class (Xceed Streaming Compression for .NET and Xceed Zip for .NET Compact Framework) contains a custom header, consisting of a single byte at the beginning, and four bytes (An Adler-32 checksum) at the end.

That is why ZLib is not able to uncompress the data correctly.

For ZLib compatiblity, use the Xceed Streaming Compression Library or the ZLibCompressedStream class of Xceed Streaming Compression for .NET or Xceed Zip for .NET Compact Framework.

Can the Xceed Backup Library or the Xceed Zip Compression Library write to tape drives?

Xceed admin — Fri, 05 Sep 2008 15:54:14 GMT

The Xceed Backup Library, Xceed Zip Compression Library, and Xceed Zip for .NET are only capable of writing to random-access devices such as CDR or zip/jazz drives. They are not capable of writing to a tape drive.