Craft Your Own Archiver 1 / 3

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Introduction

Many years ago, when I start learning how to develop software, zippware is one of my first products I developed, I developed my first prototype using a demo of DelZip.

I found that developing such a product is a good way to learn how to program window programs. To build the most basic zippware, you have to learn how to do many things using the existing framework, like User Interface, IO handling, Shell, Win32 API. Once you completed the basics, you can apply most new features that you just learned, like backup support, CD burner support.

There are many ways to develop an zippware, but if you want to develop one that supports a very wide range of archive types, you will either have to purchase an expensive commercial solutions, or write a lot of code to support each archive types. I chose to write my own code, and I released them since 2001 (named CAKE), the source code is under LGPL license, you are free to use it to develop your own archiver.

Because CAKE3 lacks documentation, I write this tutorial to explain how to write the most basic archiver using CAKE3.

This tutorial includes 3 parts:

1. Archive Operations (this article)
2. File List, Directory Tree and Drag n Drop
3. Threading support

CAKE (Common Archiver Kit Experiment) History

Back in around 2001, when first developed, there were many freeware archive support components, each support a few archive formats, so CAKE is written to combine these components to support wider range of archives. Because it was developed under Delphi, users of the component have to install around 9 components before installing CAKE.

(e.g. CAKE2 <-----> Cmarc<-----> 7zip-32.dll)

In 2006, CAKE is being ported to dotNet environment (CAKE3.NET), the code of archive handling is rewritten, no longer requires the middle layer, and all external w32 DLL is called directly. To make the port easier, some Delphi commands (AppendSlash, ExtractFileName) are ported as well, all under Cake3.Utils class. Add files to archive using relative path is also possible in this version.

(e.g. CAKE3 <-----> 7-zip32.dll)

Structure of Cake

• Cake3 (Cake3.dll)
  • Cakdir3: Main class, most archive operation does here
  • ContentList: A list containing Content Type (you can read it as List<ContentType>)
  • ContentType: Represent a file in an archive
  • Defines: Definition of misc structures
    • Add / Delete / Extract / SFXOptions
  • Queue: For support threading, will be explained in future articles
    • CakdirThreadQueue
    • CakdirWorkItem
    • ThreadQueueMonitor
  • Utils: All tools available
  • {CakArchiver, connect other dotNet components or DLL}
    • Ace
    • Cmarc
    • IconLib
    • InstallBuild
    • Rar
    • SharpZipLib
    • Sqx
    • WcxPlugins

Craft Your Own Archiver 1

Please note that in the attached demo, all archive handling routines are placed in separate methods (from UI), this will make the program easier to modify.

This demo requires VS2008, if you want to use SharpDevelop, please recreate the project then add the source again.

To Open an Archive

1) Cakdir3 cakdir = new Cakdir3(archiveName); 

• Quite simple, just noted that you have to create a new instance of Cakdir3 everytime you open a new archive.

  If the archive does not exist, it will create it when you add file(s) to archive (see below).

To List Archive Contents (to a listview named lvFileList)

1) if (cakdir == null) return;
2) cakdir.List("*");
3) foreach (ContentType ct in cakdir.Archive_Contents)
4) {
5)    ListViewItem item = new ListViewItem(new string[] 
                  {ct.fileName, Utils.SizeInK(ct.fileSize) });
6)    lvFileList.Items.Add(item); 
7) }

• Line 2 requests cakdir3 to perform list content, you can specify other mask as well (keep in mind only * is supported, ? is not supported).
• Line 3, cakdir.Archive_Contents is a ContentList containing zero or more ContentTypes.
• Line 5 creates a new ListViewItem for each entry, Utils.SizeInK converts an int to kb string, (e.g. 74550000 ---> "745.50 kb")

The listing is working now, however it looks unattractive without icons, so we shall add Icon support now.

To List Archive Contents with Icons

You have to create an ImageList named (imageS, means small images) in MainForm, hook it to lvFileList.SmallIcons.

5)    ListViewItem item = new ListViewItem(new string[] 
           {ct.fileName, Utils.SizeInK(ct.fileSize) });
5.1)  item.ImageKey = Utils.ExtractFileExt(ct.fileName).ToLower();
5.2)  if (!imageS.Images.ContainsKey(item.ImageKey))
5.3)      imageS.Images.Add(item.ImageKey, Utils.GetSmallFileIcon(ct.fileName));
6)    lvFileList.Items.Add(item);  

• Line5.1 specifies an imagekey, which is based on the extension of file (Utils.ExtractFileExt extract ext from a string)
• Line5.2 and 5.3, if image list does not contain the imagekey, it will retrieve an icon for the specified extension and add it to image list.

  (Utils.GetSmallFileIcon() uses W32 API (SHGetFileInfo) to retrieve icon. You can find Utils.GetLargeFileIcon as well).

To Extract Files from Archive

1) if (cakdir == null) return;
2) if (!cakdir.CanExtract) return;
3) cakdir.ExtractOptions.extractItem = new string[] { "*" };
4) cakdir.ExtractOptions.extractFolder = @"c:\temp"; 
5) cakdir.ExtractOptions.allowFolder = true; 
6) cakdir.ExtractOptions.extractOverwrite = true;
7) bool success = cakdir.Extract();

• Line 2, you can use CanExtract to see if files can be extracted from specified archive, there's also CanList / CanAdd

  if you want to check if archive without opening it, use (Cakdir3.GetArchiveType(".zip").CanExtract) instead.

• Line 3-6, all extract related options are located in ExtractOptions
  • archiveName : name of archive, you don't have to touch this normally.
  • allowFolder: whether use folder information
  • dialogless: some archiver DLL does show progress dialog when executing, enable this will disable the DLLs
  • extractFolder: specify where to extract.
  • extractItem: specify item to extract
  • extractOverwrite: whether to overwrite existing files
  • password: specify password
  • ResetExtractItem(): set extractItem to "*"
• Line 7 will return true if extract is success,

  alternatively you can call the following method instead.

3) cakdir.Extract(filter, extractTo, useFolder, allowOverwrite); 

The following method can extract file recursively (e.g. "outer.zip\inner.zip\core.zip")

3) Utils.ExtractArchiveRecrusive(archiveName, extrOptions); 

To Add Files to Archive

1) if (cakdir == null) return;
2) if (!cakdir.CanAdd) return;
3) cakdir.AddOptions.addFile = addFile;
4) cakdir.AddOptions.addFolder = AddOptions.folderMode.full;
5) bool success = cakdir.Add();
6) cakdir.List("*");

• Line 3-4, all add related options is located in AddOptions
  • addCompressLevel: 0..9, cake does not have individual compression method support yet
  • addFile: file to add
  • addFolder: how to store folder information, select one of folderMode below:

    folderMode	Description	if add "c:\ temp \ test \ file.txt" and set baseFolder as "c:\temp"
    full	Store full folder information.	\ temp \ test \ file.txt
    none	Store no folder information.	file.txt
    relative	Store folder information relative to baseFolder.	\ test \ file.txt

  • addMode: how to add file, select one of the updateMode below:

    updateMode	Description
    add	Add all specified files to the archive
    refresh	Update older files in the archive and add files that are new to the archive
    update	Update specified files in the archive that are older than the selected disk files
    synchronize	Replace if newer, add even if not present in archive, delete if not present in disk

  • archiveName: name of archive, you don't have to touch this normally
  • baseFolder: base folder if addFolder = relative
  • dialogless: some archiver DLL does show progress dialog when executing, enable this will disable the DLLs
  • password: specify password
  • defaultOptions(): revert back to default options
• Line 5 will return true if add is success,

  Please note that all operations (Add / Extract / Delete) are not threaded.

• Line 6 forces cakdir3 to perform list content again.

To Delete Files from Archive

1) if (cakdir == null) return;
2) if (!cakdir.CanAdd) return;
3) cakdir.DeleteOptions.deleteFile = deleteFile;
4) cakdir.Delete();
5) cakdir.List("*"); 

• Line 3, all delete related options is located in DeleteOptions
  • archiveName: Name of archive, you don't have to touch this normally
  • deleteFile: File to delete
• Line 4 will return true if add is success
• Line 5 forces cakdir3 to perform list content again

Handling Progress Message

Let user know what's working on.

1) cakdir.OnMessage += new MessageEventHandler(ProgressScreen_Message);
.....
2) void ProgressScreen_Message(object sender, MessageEventArgs e)
3) { tbMessage.Text += e.Message + Environment.NewLine; }

• Line 3 will append the message to a textbox (tbMessage)

You can show display progress using a progress bar too:

1) cakdir.OnProgress += new MessageEventHandler(ProgressScreen_Progress);
.....
2) void ProgressScreen_Progress(object sender, MessageEventArgs e)
3) { pBar.Value = e.Percent; }

• Line 3 will set the percentage of progress bar (pBar), other properties in MessageEventArgs:
  • Percent: Percentage completed (1..100)
  • Filename: File processing

Please note that progress bar is not completely working for all archivers yet.

Other events included in Cakdir3:

• OnStartWorking / OnStopWorking: Signal when start and finish
• OnError: Signal when error occurred
• OnOverwrite - When extract with extractOverwrite set to false, it signals when a file already exists. (if not overridden, internal overwrite handler is used)
• OnPassword - signal when password required
• OnItemList - usually for internal use, when Cakdir.InternalList is on, list via this event instead of Archive_Contents

When you completed this part, you should know how to use Cake3 to do most archive operations. The next article will describe how to improve the User Interface, implement virtual file list, directory tree and drag and drop support.

References

• Fesersoft's CRC32 implementation
• Using IFilter in C#
• Implementing the .NET IComparer interface to get a more natural sort order
• SharpZipLib
• IconLib
• Common Archiver Library (Cmarc)

History

• 12-05-2008 - First submitted to CodeProject