TweetFollow Us on Twitter

Desktop Stuffing

Volume Number: 14 (1998)
Issue Number: 5
Column Tag: Powerplant

Desktop Stuffing

by David Catmull

Using Aladdin Systems' StuffIt Engine

Gentlemen, Stuff Your Engines

Aladdin Systems' StuffIt has been the standard for compression on the Macintosh for quite some time now. Rather than keep it all to themselves, however, they chose to make the StuffIt features available to developers through a little file called the StuffIt Engine. Aladdin's own utilities use it to perform most of their compression operations, and they have published the API so outside developers can contribute to the StuffIt standard.

The StuffIt Engine API is organized into two parts: the general calls for Stuffing and UnStuffing, working with file segments, etc., and the "low-level" calls that let you poke around inside StuffIt archives to add and extract files individually. There are still some things that even the low-level calls don't let you do, such as deleting and re-ordering items in the archives, but unless you're writing your own StuffIt Deluxe you won't need to go that far.

The Basics

In order to use the StuffIt Engine, you must include two files from the SDK in your project: the StuffItEngineLib .rsrc resource file, and one of the CodeWarrior libraries: StuffItEngineLib, StuffItEngine LibPPC, or StuffItEngineLibA4.

If you want to have the StuffIt Engine built into your application, rather than depending on the user having it installed, you can pick and choose which parts of the engine you want to include -- Stuffing, UnStuffing, segmenting calls, and the various decoding parts (such as BinHex) can be added to your project as individual resource files.

Whether you use the engine externally or internally, you will need to obtain a license from Aladdin Systems since at the very least you will be linking their library into your program. For more details on licensing terms and fees, contact Aladdin Systems dev.sales@aladdinsys.com.

To access the StuffIt Engine in your program, you must first open it with the OpenSITEngine() call, which returns a "magic cookie" to be passed back in subsequent calls to the engine. When you are finished, use CloseSITEngine() to close your connection.

Each of the other calls to the StuffIt Engine has three types of parameters: the magic cookie obtained from OpenSITEngine(), the relevant FSSpec structures (source, destination, and result), and a set of options which can be specified using constants from StuffItEngineLib.h. These options tell the StuffIt Engine such things as whether to prompt the user for a destination, whether to delete the original items after Stuffing or UnStuffing them, what to do about linefeeds in text files, and so on.

Stuffing with PowerPlant

Metrowerks has been working on a set of classes that simplify the interface to the StuffIt Engine. PowerPlant users may have discovered the "StuffIt Classes" folder that was recently added to PowerPlant's "_In Progress" folder. The folder contains two pairs of header and source files: UStuffItSupport and LStuffItArchive. These two correspond to the two categories of calls in the StuffIt Engine (high-level and low-level). There are more than two classes, though:

  • UStuffItSupport: This class performs all the basic operations: opening and closing your connection to the StuffIt Engine, keeping track of the magic cookie, and simple Stuffing and UnStuffing operations.
  • LStuffItFileList: This is a wrapper class for the FSSpecArrayHandle type that is used for Stuffing multiple files into a single archive. In the StuffIt API, even if you're just Stuffing one file, you must still create a list with a single item; conveniently, UStuffItSupport has a call for Stuffing single files.
  • LStuffItArchive: This class is for working with the contents of an archive, covering the low-level API calls.
  • LStuffItArcObjectList: The complement to LStuffItFileList, this class wraps around StuffIt's arcObjectArrayHandle type and refers to multiple objects inside an archive.
  • StOpenStuffIt: A stack-based class which simplifies opening and closing the engine.

Their Example

The StuffIt Engine SDK includes a sample application called StuffIt Scrapbook which uses a neat trick to store its pictures in compressed resources. Since StuffIt only works with files, StuffIt Scrapbook gets around this by writing new pictures to a temporary file which is then Stuffed. The resulting archive is read in, and its data is stored as a 'Psit' resource in the scrapbook file. To display a stored picture, it goes through the reverse process.

Our Example

StuffIt Scrapbook covers the basics of using the general-purpose Stuffing and UnStuffing calls, so for this article we'll focus on the lower level. The example application is based on the Drag & Drop File Filter application from Metrowerks' PowerPlant samples. Our program accepts StuffIt archives dropped onto it, and extracts any text files that the archive contains, placing the files in the same folder as the archive.

Since the example application class FrDropApp provides a good enough framework for processing files dropped on the application, we only override the OpenDocument method, which is called for each file:

TextractorApp::OpenDocument
Search the given file for text files to extract
void
TextractorApp::OpenDocument(FSSpec *inMacFSSpec)
{
   StOpenStuffIt openEngine;
   CStuffItArchive archive(*inMacFSSpec);
   LStuffItArcObjectList list;
   archiveObject object;
   archive.mPromptForDestination = kDontPromptForDestination;
   
   Try_ {
      // Assemble a list of text files in the archive
      archive.Reset();
      while (archive.BrowseNext(object))
         if (object.fileType == 'TEXT')
            list.Append(object);
   
      // Extract the files, if there were any
      if (list.Count() > 0)
         archive.UnStuffFromArchive(list);
   }
   Catch_(caughtErr) {
      DoQuit();
   }
}

One of the various options for the StuffIt calls is whether to prompt the user for a destination. LStuffItArchive stores the values for these options in publicly accessible data members, so the first thing we do is turn the prompt option off. This is the first step in getting the extracted files to automatically appear in the same folder as the archive.

Notice the use of our subclass CStuffItArchive instead of LStuffItArchive. The subclass was added because we needed a couple of things that LStuffItArchive doesn't provide.

First of all, there's no simple way provided to iterate through the hierarchy of an archive. LStuffItArchive gives you Next(), Up(), and Down(), but if you want to just cruise through all the items in the archive, you have to figure out for yourself when to use what. Here's how it's done:

CStuffItArchive::BrowseNext
Return the next item in the archive, going straight ahead, up, or down
Boolean
CStuffItArchive::BrowseNext(archiveObject &outObject)
{
   Open();

   if (!mIteratorInitialized) {
      Reset();
      if (mBrowseStack) {
         delete mBrowseStack;
         mBrowseStack = 0L;
      }
   }
   
   if (mIteratorAtHead) {
      mIteratorAtHead = false;
      outObject = mCurrentObject;
      return true;
   }
   
   // Reset the stack if necessary
   if (!mBrowseStack)
      mBrowseStack = new LArray(sizeof(archiveObject));
   // If it's a folder, then browse into it (unless it's empty)
   // Otherwise, try to advance to the next object at this level
   // If it's not there, pop back up a level
   archiveObject tempObject,oldObject = mCurrentObject;
   if (mCurrentObject.objectIsFolder && Down(tempObject)) {
      outObject = mCurrentObject;
      mBrowseStack->AddItem(&oldObject,sizeof(oldObject));
      return true;
   }
   else if (Next(outObject))
      return true;
   else {
      if (mBrowseStack->GetCount() > 1) {
         mBrowseStack->FetchItemAt(LArray::index_Last,&outObject);
         mBrowseStack->RemoveItemsAt(1,LArray::index_Last);
         return true;
      }
      else
         return false;
   }
}

The first couple of lines in this method are similar to the beginnings of LStuffItArchive's Next(), Up(), and Down(), with the addition of initializing the browsing stack. Then we come to the fork in the road: if the current item is a folder, we can browse into it. If it's not a folder, then just move along. If there are no more files in this folder, we're done with the current folder and it's time to pop back up a level. An array of folder objects is used to keep track of where we need to pop up to, and when it runs out, that means the entire archive has been traversed.

The second addition that CStuffItArchive gives us is an alternate version of UnStuffFromArchive(). After turning off the user prompt option, this is the second step in making the extracted files appear in the same folder as the source archive. Unlike LStuffItArchive::UnStuffFromArchive(), this function takes no destination parameter, and passes a null value for the destination to StuffIt Engine's ExpandFromArchive().

CStuffItArchive:UnStuffFromArchive
Alternate version of the LStuffItArchive call with no destination
parameter void
CStuffItArchive::UnStuffFromArchive(LStuffItArcObjectList& inObjectList, unsigned char * inPassword)
{
   Open();

   StOpenStuffIt engineOpen;
   FSSpec resultSpec;

   OSErr err = ExpandFromArchive (
            UStuffItSupport::sCookie,
            &mArchiveInfo, 
            inObjectList, 
            0L, // Null destination means expand to the archive's folder
            &resultSpec,
            mPromptForDestination, 
            mCreateFolder, 
            mStopOnAbort,
            mConflictAction, 
            mConvertTextFiles, 
            inPassword,
            mShowNoProgress, 
            mAlertCBUPP,
            mStatusCBUPP, 
            mPeriodicCBUPP);

   ThrowIfOSErr_(err);
}

Beyond the Documentation

Here is a collection of tips and notes that I have collected, some of which are not mentioned in the StuffIt SDK documentation:

You can convert archives to and from self-extracting format using ConvertSITtoSEA() and ConvertSEAtoSIT(), but the Engine doesn't tell you what the name of the resulting file is. This is usually not a problem, especially if you don't care what the result is, but if you do and there is a naming conflict, it could cause confusion. The way it seems to work is this: If the file has the appropriate .sit or .sea extension, it attempts to substitute the other extension. If this causes a name conflict, or if the original file didn't have the right extension, then the name is not changed.

Although, by means of the ExpandFSSpec() call, the StuffIt Engine can decode and decompress a variety of non-StuffIt formats, the only encoding available is BinHex. Again, the HQXEncodeFSSpec call doesn't tell you what the resulting file is, so you have to guess. This call, in the case of a naming conflict, appends a number to the file name: "file.hqx.1"

The segmenting functions, SegmentFSSpec() and JoinFSSpec(), will prompt the user for a destination if you do not supply one. So if you don't want any Standard File dialogs popping up, be sure to specify your destination. And the destination must be a file, not the folder you want the file to go in.

There are certain resources you must include in your program for the StuffIt Engine to use, supplied in StuffItEngineLib.rsrc. If the file containing these resources is not open when you open the Engine, you will get the StuffIt registration dialog. This will normally not be a problem for applications, but for other projects such as contextual menu plug-ins you need to watch for it.

This is pointed out in the StuffIt Scrapbook notes: every time you perform an operation with an unregistered copy of StuffIt Engine (except for opening it), the registration dialog will appear. However, there are times when you don't want that to happen, such as a Drag Manager drag receive handler. Fortunately, there is an IsSITEngineRegistered() call to help you avoid embarrassing crashes and unwanted dialog boxes.

Conclusion

If you want your application to have file compression features, the StuffIt Engine SDK provides easy access to the StuffIt standard. While it does have its shortcomings, such as not always informing you of how it resolves a naming conflict, these problems are minor and in most cases not an issue. Overall, the StuffIt Engine SDK, especially with PowerPlant's additions, is easy to use and even fun.

The StuffIt Engine SDK is available from Aladdin Systems' web site at http://www.aladdinsys.com/dev/engine/enginesdk.html.


David Catmull is a shareware programmer living in Berkeley, California. He earned a degree in Computer Science from the California State University at Hayward, and is currently studying computer animation at the Academy of Art College in San Francisco. His shareware offerings include StuffCM, a contextual menu plug-in that uses the StuffIt Engine; and CCMArea, a set of classes for adding contextual menus to PowerPlant applications. These and others are available at http://www.kagi.com/dathorc/.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

MacUpdate Desktop 6.0.8 - Search and ins...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more
BitTorrent Sync 2.1.1 - Sync files secur...
BitTorrent Sync allows you to sync unlimited files between your own devices, or share a folder with friends and family to automatically sync anything. File transfers are encrypted. Your information... Read more
Quicksilver 1.3.0 - Application launcher...
Quicksilver is a light, fast and free Mac application that gives you the power to control your Mac with keystrokes alone. Quicksilver allows you to find what you need quickly and easily, then act... Read more
iWatermark Pro 1.72 - Easily add waterma...
iWatermark Pro is the essential watermarking app for professional, business, and personal use. iWatermark, is the number 1 and only watermarking tool available for all 4 platforms iPhone/iPad, Mac,... Read more
RapidWeaver 6.3 - Create template-based...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
Adobe Photoshop CC 2015 16.0.1 - Profess...
Photoshop CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Photoshop customer). Photoshop CS6 is still available for purchase (... Read more
Together 3.4.6 - Store and organize all...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more
Monosnap 3.1.0 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture: Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with... Read more
Cocktail 8.5.1 - General maintenance and...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Vienna 3.0.6 :5eaf312: - RSS and Atom ne...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more

Five Nights at Freddy's 4 has Been...
In keeping with tradition, Five Nights at Freddy's 4 has made its way to the App Store with zero warning fanfare. Honestly I'd be disappointed it if happened any other way at this point. [Read more] | Read more »
Doom & Destiny Advanced (Games)
Doom & Destiny Advanced 2.3.4.0 Device: iOS Universal Category: Games Price: $.99, Version: 2.3.4.0 (iTunes) Description: ---SUPER GIGA LAUNCH DISCOUNT! Get it now for cheap or pay more later!---An additional 143 MB download is... | Read more »
Five Nights at Freddys 4 (Games)
Five Nights at Freddys 4 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: This time, the terror has followed you home. | Read more »
This Week at 148Apps: July 27-31, 2015
Winding Down July With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out... | Read more »
You'll Want to Keep an Eye Out for...
If you're the kind of person who had fun hunting down and completing all the codex puzzles in Assassin's Creed 2, then are you ever in for a treat. The Guides looks like it's going to be a very robust collection of similarily odd, seemingly... | Read more »
Vivid Games has Announced Real Boxing 2...
The original Real Boxing was a pretty impressive bit of fisticuffs, but if the trailer Vivid Games is showing off for GamesCom is any indication Real Boxing 2 is going to be even better. [Read more] | Read more »
PAC-MAN Championship Edition DX - Tips,...
[Read more] | Read more »
Card King: Dragon Wars - Tips, Tricks an...
[Read more] | Read more »
Pac-Man Championship Edition DX has brou...
Bandai Namco has released Pac-Man Championship Edition DX on iOS and Android, which features the classic arcade gameplay that we've all grown to love. Pac-Man Championship Edition DX can be enjoyed in much shorter bursts than the arcade versions... | Read more »
Cosmonautica (Games)
Cosmonautica 1.1 Device: iOS Universal Category: Games Price: $6.99, Version: 1.1 (iTunes) Description: Cast off! Are you ready for some hilarious adventures in outer space? | Read more »

Price Scanner via MacPrices.net

MacBook 12 Retina Pundit’s New Favorite Mac
If you’re eyeing the purchase of a new 12-inch Retina MacBook, but wondering if you can live with a single USB-C port, 2011-level CPU performance, and the unorthodox keyboard, you should find... Read more
PDF Element Tool Kit For PDF For Windows 10,...
South Surrey, British Columbia based software developer Wondershare has posted an interesting infographic tracking the development of Microsoft’s flagship Windows operating system over the years,... Read more
27-inch 3.5GHz 5K iMac on sale for $81 off MS...
Adorama has the 27″ 3.5GHz 5K iMac on sale for $2218, $81 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... Read more
Back-to-School with Tablet and Smartphone Acc...
Belkin helps you prepare for the coming school year with a wide variety of the latest mobile and tablet accessories to outfit both grade school and college students. The line-up includes charging... Read more
11-inch MacBook Airs on sale for $100 off MSR...
Best Buy has 11-inch MacBook Airs on sale for $100 off MSRP. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - 11″ 1.6GHz... Read more
iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
Sale! 13-inch MacBook Pros on sale for $100 o...
B&H Photo has 13″ MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.5GHz/500GB MacBook Pro: $999.99 save $100 - 13″ 2.7GHz/128GB Retina... Read more
Sale! Save $100 on 13-inch MacBook Airs this...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model.... Read more
Worldwide Tablet Market Decline Continues, Ap...
The worldwide tablet market declined -7.0% year-over-year in the second quarter of 2015 (2Q15) with shipments totaling 44.7 million units according to preliminary data from the International Data... Read more
TP-LINK TL-PA8030P KIT Powerline Featuring Ho...
Consumer and business networking products provider TP-LINK is now shipping its TL-PA8030P KIT AV1200 3-Port Gigabit Passthrough Powerline Starter Kit that expands your home’s network over its... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Infrastructure Engineer - *Apple* /Mac - Hil...
Infrastructure Engineer - Apple /Mac Job Code: 1608 # of openings: 1 Description Our fortune 500 client is looking to hire an experienced Infrastructure Engineer to join Read more
Executive Administrative Assistant, *Apple*...
…supporting presentation development for senior leadership. * User experience with Apple hardware and software is preferred. Additional Requirements The following list Read more
*Apple* Bus Company is now hirin - Apple Bus...
Apple Bus Company is now hiring school bus drivers in the Pettis County area. Class B CDL preferred. Free training provided. No nights or weekends required. Flexible Read more
*Apple* Certified Mac Technician - Updated 6...
…and friendly, hands-on technical support to customers troubleshooting and repairing Apple /Mac products with courtesy, speed and skill. Use your problem-solving skills Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.