TweetFollow Us on Twitter

PPC Data Fork Tool
Volume Number:12
Issue Number:12
Column Tag:Toolbox Techniques

Leave the Data (Fork) Alone!

A developer utility to restructure fat/PowerPC applications

By Roger Smith

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Warning!

This article may change your life forever. Okay, maybe that’s a bit dramatic, but hopefully by the time you finish reading it, you will have discarded all previous knowledge on how to structure fat binaries. The utility MoveData that we will examine shortly, grew out of a need to create a fat application which stored data in its data fork. It turns out that the default model of native applications storing code in the data fork, is merely a default. Apple designed the Power Macintosh runtime architecture with sufficient flexibility to allow you to locate code fragments just about anywhere you could imagine. Bottom line, MoveData might actually save you significant amounts of development effort!

Outline

There is a certain category of applications that allow a user to create self-running and self-contained documents. For example, a graphic artist might use a multimedia presentation program to create an informative self-running presentation to give to end users without the full package. A file compression program might create an archive that when run, automatically un-archives its contents to fill your hard drive. In addition to these documents being self-running, where appropriate, it should also be possible to re-open, edit and re-save them with a minimal amount of hassle. How many times have you just peeked inside a self-extracting archive and manually extracted 1 or 2 files without un-archiving the entire contents? It would be great if these self-running documents ran native on 68K and PPC machines.

Most applications create documents where the stored information is in the data fork of the files. These applications generally use a subset of the File Manager routines for manipulating this data. Under the 68K model, this approach lends itself easily to design a self-running document. In this instance, a stripped down version of your application checks on startup to see if its data fork is empty. If it is not [empty] it assumes that it is a self running document and proceeds to load and handle the data in the data fork. The function checkforSelfContained() (see Listing 4) shows how to do this, making use of some Process Manager routines to obtain an FSSpec for the current application. It then uses this FSSpec as a basis for the subsequent calls to the File Manager to open and process the “Data” in the data fork of the application.

Developing on Power Macintosh.

The above approach breaks under the default PowerPC model since the application would ultimately try to load itself as data, (recall that by default the code for a PowerPC application resides in the data fork). If your application were attempting to interpret sound data, it could lead to some rather interesting “industrial” music. The exercise of creating a top musical hit using this approach is left as an exercise to the readers. (Hint: start with a Microsoft application!) What is a developer supposed to do?

CFRG Resource

Apple defined ‘cfrg’ resource (code fragment), which was introduced with the Power Macintosh, as the key to understanding the MoveData utility. Using ResEdit to edit this resource is tedious at best, as you will have to roll your own template to handle a resource that contains fields that vary in size. Using Resorcerer™ makes editing and changing this resource a simple task.

.

Figure 1. Application resource list in Resourcer.

Open the ‘cfrg’ editor by double clicking on the ‘cfrg’ resource.

Figure 2. The ‘cfrg’ resource editor in Resourcer.

Normally the various fields are filled in at link time, and you need not worry about them. The two fields that form the heart of the MoveData utility are the usage field and where does fragment start. I have defined a C structure called codeFragRecord (located in the file DSGlobals.h) that mirrors this layout.


codeFragRecord
Listing 1. Structure definition to mimic the ‘cfrg’ layout illustrated in Figure 2.

typedef struct fragDescriptors
{
 long   CodeType;
 long   UpdateLevel;
 long   CurrentVersion;
 long   OldestDefVersion;
 long   AppStackSize;
 short  AppLibDirectory;
 Byte   TypeOfFrag;
 Byte   LocationOfFrag;
 long   OffsetToFrag;
 long   LengthOfFrag;
 long   Reserved1;
 long   Reserved2;
 Str255 Fragname;
}fragDescriptors;

typedef struct fragDescriptors fragDescriptors;

typedef fragDescriptors FragArray[1];

typedef struct codeFragRecord
{
 long   Reserved1;
 long   Reserved2;
 long   Version;
 long   Reserved3;
 long   Reserved4;
 long   Reserved5;
 long   Reserved6;
 long   NumberofFrags;
 FragArrayfragArray; // array[0..0] of fragDescriptors;       
}codeFragRecord;

typedef struct codeFragRecord *codeFragRecPtr, **codeFragRecHandle;

Problem Identified

Given the task of designing a fat application that stores its data in its own data fork, you could take one of the following approaches.

(1) Write additional code to handle the case of loading and saving documents. This code would need to calculate offsets to move the file’s mark to skip over the code fragment.

(2) Compile your PowerPC application as a code resource. Write additional code compiled in the 68K version of your application that checks the environment on startup. If running on a PowerPC, load and execute the PowerPC resource (often referred to as an accelerated resource).

(3) Not to write code, instead tell the Code Fragment Manager to look in a particular resource to find the code it should load and execute.

Going back to the ‘cfrg’ editor in Resorcerer™ for a moment, we see that the usage field allows us to pick one of three options for our code fragment. If generating an application, this field is set by your development environment to indicate that the fragment is an application. Internally, the code fragment manager uses this to determine how to prepare a particular fragment and load it into memory. Refer to Inside Macintosh, PowerPC System Software if you need additional information.

Figure 3. The usage field popup in the ‘cfrg’ resource.

More importantly the where does fragment start field allows you to change from the default location in the data fork.

Figure 4. The where does fragment start popup.

To indicate to the code fragment manager that it should load the code from a resource instead of the data fork, select the segmented resource option.

Figure 5. Change the location to point to a code resource.

Enter the resource type and ID.

Figure 6. Code fragment manager set to look
for PCOD resource with ID 0 on startup.

Cut and paste the code from the data fork into the resource type you specified. On a PowerPC your fat application will load and execute from a resource, and the data fork reverts to its historical role. (Note: ‘PCOD’ is an arbitrary resource type I chose, if you need to use a different resource type, change the appropriate define in the DSGlobals.h header file.)

General Notes

You may be thinking, if I can do all of this with Resorcerer™, why do I need another developer utility? I initially took this approach. However, while I was developing my fat application I ran into the situation where copying and pasting 1MB of code out of the data fork and into a new resource required me to set Resorcerer™’s preferred memory size to >10MB. This procedure is slow and tedious if part of a regular build cycle. Using the simple AppleScript I provide automates the entire build process and reduces any chance of user error.

Code Listing

All programs were developed using CodeWarrior 7 which ships with the latest universal headers (known as the 2.1 universal interfaces). If you are using a previous version of CodeWarrior, or a different development environment, you may have to do some tweaking. For example, the GetKeys interface changed from long to unsigned long in the 2.1 headers.

There are two applications that accompany this article. The MoveData utility uses the excellent DropShell framework by Marshall Clow, Leonard Rosenthol, and Stephan Somogyi. DropShell is available on the CW7 CD and on most on-line services. Refer to its documentation for more information. To use MoveData, drag the application you wish to alter over its icon, (or select it via the Open option under the File menu). MoveData will move the PowerPC code from the data fork into a code resource, and update the ‘cfrg’ resource to point to the correct location. Should you wish to reverse the operation, hold down the option key when you drop the application onto the MoveData icon. It copies the PowerPC code from the resource back to the data fork.

The Demo program is a simple program that illustrates the technique of creating a self-running fat binary that reads and writes data from its data fork. After you build and run the program for the first time, it will prompt you to locate a text file, which it will copy into its data fork. On subsequent invocations of the demo program, it will read and display the contents of the data fork, then write the contents back to the data fork of the application reversed.

UpdateCFRG
Listing 2: DSUserProcs.c
// Routine to update the ‘cfrg’ resource. Pass in the updated information and it will 
// update the ‘cfrg’ resource in the file specified by resRef. The Code fragment 
// manager checks for this resource first on startup if running on a PowerPC. 

static  OSErr UpdateCFRG(short resRef,
 Byte fragmentType,
 Byte fragmentLocation,
 long fragmentOffset,
 long   fragmentLength)
 {
 codeFragRecHandle cfrgHndl;
 codeFragRecPtr  cfrgRecPtr;
 
 OSErr  theError = -1;
 
 cfrgHndl = (codeFragRecHandle) Get1Resource(‘cfrg’,0);
 
 if (cfrgHndl != NULL)
 {
 HLock((Handle) cfrgHndl);
 (**cfrgHndl).fragArray[0].TypeOfFrag = fragmentType;
 (**cfrgHndl).fragArray[0].LocationOfFrag 
 = fragmentLocation;
 
 (**cfrgHndl).fragArray[0].OffsetToFrag= fragmentOffset;
 (**cfrgHndl).fragArray[0].LengthOfFrag= fragmentLength;
 
 HUnlock((Handle) cfrgHndl);
 ChangedResource((Handle) cfrgHndl);
 UpdateResFile(resRef);
 ReleaseResource((Handle) cfrgHndl);
 return noErr;

 }
 return theError;
}


ProcessItem
Listing 3: DSUserProcs.c
// This routine gets called for each item (in our case a Fat binary) that is dropped on the
// MoveData utility. We will process and update the ‘cfrg’ resource as appropriate. Notice // the extensive 
error checking as there are several stages where things could go wrong.

static OSErr ProcessItem(FSSpecPtr myFSSPtr)
{
 OSErr  err = noErr;
 short  refNum;
 short  resRef;
 long logEOF;
 long count;
 Handle POWER_PC_CODE;
 short  resultCode;
 short  itemHit;
 
// If the option key is held down when an application is dropped onto MoveData, it will 
// reverse the process, i.e., move the PowerPC code from a resource back into the data fork.

 if (gReverseOperation)
 {
 return(ReverseProcessItem(myFSSPtr)); 
 }
 
 err = FSpOpenDF(myFSSPtr, fsRdWrPerm, &refNum);         

 if (err == noErr) 
 {
 resRef = FSpOpenResFile(myFSSPtr,fsRdWrPerm); 
 if (resRef != -1) 
 {
 err = GetEOF(refNum,&logEOF);      // Check for PPC code
 if (logEOF == 0)
 {
 itemHit = Alert(kNoDataFork,nil);
 }
 else
 {
 if (logEOF < kMaxResourceSize)  
 { 
 POWER_PC_CODE = Get1Resource(kPowerPCCode,kPowerPCID);
 if (POWER_PC_CODE != NULL) // Check for existing resource
 {
 RemoveResource(POWER_PC_CODE);  
 UpdateResFile(resRef); 
 }
 
 POWER_PC_CODE = NewHandle(logEOF);
 
 if (POWER_PC_CODE == NULL)
 POWER_PC_CODE = TempNewHandle(logEOF,&resultCode);      
 
 if (POWER_PC_CODE != NULL) { 
 count = logEOF;
 err = FSRead(refNum,&count,*POWER_PC_CODE);
 
 AddResource(POWER_PC_CODE,
 kPowerPCCode,
 kPowerPCID,
 ”\pPPC Code”);
 WriteResource(POWER_PC_CODE);
 UpdateResFile(resRef);
 ReleaseResource(POWER_PC_CODE);
 err = SetEOF(refNum,0);  // set the data fork to 0;
 err = UpdateCFRG (resRef, kUsageIsApplication,                
 kFragmentInResource,
 kPowerPCCode,kPowerPCID);
 }
 else
 itemHit = Alert(kMemErrorID,NULL);
 }
 else
 itemHit = Alert(kTooBigID,NULL);  
  }
 }
 err = FSClose(refNum);
 }
 else
 itemHit = Alert(kDataForkError,NULL);
 
 return(err);
}

checkforSelfContained
Listing 4: Demo.c
// Checks if this is a self running document, load and handle it if necessary.

OSErr checkforSelfContained(short *vRefNumToSearch)
{

 OSErr  theError;
 ProcessSerialNumber theCurrentProcess;
 ProcessInfoRec  theInfo;
 long   fileLength;
 short  refNum = 0;
 MenuHandle theMenu;

 theInfo.processName = NULL;
 theInfo.processInfoLength = sizeof(ProcessInfoRec);
 theInfo.processAppSpec = &gApplicationProcessInfo;
 
 theCurrentProcess.highLongOfPSN = 0;
 theCurrentProcess.lowLongOfPSN = kCurrentProcess; 
 
 theError = GetProcessInformation
 (&theCurrentProcess,&theInfo);
 if (theError != noErr)
 return theError;
 
 theError = FSpOpenDF(&gApplicationProcessInfo,
 fsRdWrPerm, &refNum);

 if (theError == noErr)
  theError = GetEOF(refNum, &fileLength);

 if (fileLength != 0)
 {
 theMenu = GetMHandle(FILEMENU);
 EnableItem(theMenu,clearDataFork);
 theError = processFile(&gApplicationProcessInfo,refNum,       
 fileLength);
 
 if (!theError)
 reverseFile(refNum);
 }
 else
 {
 theError = appendTextFileToApp(refNum);
 }

 theError = FSClose(refNum);

 *vRefNumToSearch = refNum;

 return theError;
}

The best way to build the Demo program is to run the Build (Fat) Demo CW7 script. If you run the PPC project immediately after building it, the program will attempt to reverse itself, and on subsequent attempts it will fail (self-destruction). Note: You will need to edit the path in the script to get it to run on your machine.

The echoed script is here for your convenience.

Build (Fat) Demo
Listing 5:
// Simple Apple Script to coordinate the building a fat binary using the MoveData Utility.

set PATHNAME to “HD:DeskTop Folder:MacTech:”
set MOVEDATAFOLDER to PATHNAME & “MoveDataƒ”



with timeout of 60000 seconds
 tell application “CodeWarrior IDE 1.3.1”
 activate
 open {PATHNAME & “Demo68K.µ”}
 Make Project
 Close Project
 
 open {PATHNAME & “DemoPPC.µ”}
 Add Files PATHNAME & “Demo68K” To Segment 1
 Make Project
 Remove Files PATHNAME & “Demo68K”
 quit
 
 end tell
 
 tell application “Finder”
 activate
 select file “Demo (Fat)” of folder PATHNAME
 open selection using file “MoveData” 
 of folder MOVEDATAFOLDER
 end tell
 
end timeout

Caveats

One of the side effects of this approach is that the Finder information window for your application will not reflect that it is a PowerPC application. This is because the Virtual Memory Manager on Power Macs will only map your application into chunks that can be paged in an out, if the code resides in the data fork. By the time Copland rolls around, hopefully this issue will be moot, and the Finder will provide a better mechanism for determining if an application contains native code. With virtual memory turned on (and depending on the size of your PowerPC executable), you may notice faster application startup times since none of the virtual memory magic will apply to your application.

If you are using Jasik’s the Debugger, your debugging strategy is unaffected as the Debugger will still kick in once you launch your application. You could have several self-running documents all built using the same run time module (with different information in the data fork). Then the Debugger will kick in, provided that you name the document and system files appropriately.

Figure 7. Finder information for a PowerPC application.

Figure 8. Finder information for a PowerPC application processed using the MoveData utility.

What other usage does this technique invite? I started thinking about this one night while driving home, and it seemed like an interesting way of storing optimized versions of your application under one umbrella (i.e., self configuring software that ran at maximum speed on 601, 603 or 604 processors). It also gives the authors of virus protection programs another potential threat to consider, as this technique gives new meaning to the term Trojan program.

The Verdict

I hope the technique of moving program code out of the Data Fork and into a resource will prove useful in your own development projects. Drop me an e-mail message if you use this technique, or have any comments on this approach.

Credits

The author wishes to thank several people who contributed code to help make this article possible. In particular, I would like to thank Matthew Xavier Mora at Apple DTS for supplying the Pascal source for the original version of MoveData. I would also like to thank Lucien Dupont in the Newton Systems Group for offering his support and comments, and finally to Peter Lau (no relation to Raymond) for his suggestions.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

MacFamilyTree 8.2.1 - Create and explore...
MacFamilyTree gives genealogy a facelift: modern, interactive, convenient and fast. Explore your family tree and your family history in a way generations of chroniclers before you would have loved.... Read more
LaunchBar 6.9 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
LaunchBar 6.9 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
MacFamilyTree 8.2.1 - Create and explore...
MacFamilyTree gives genealogy a facelift: modern, interactive, convenient and fast. Explore your family tree and your family history in a way generations of chroniclers before you would have loved.... Read more
Spotify 1.0.57.474. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
VOX 2.8.26 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
beaTunes 5.0.1 - Organize your music col...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
LibreOffice 5.3.4.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
Sparkle Pro 2.2 - $79.99
Sparkle Pro will change your mind if you thought building websites wasn't for you. Sparkle is the intuitive site builder that lets you create sites for your online portfolio, team or band pages, or... Read more
calibre 3.1.1 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more

Latest Forum Discussions

See All

This War of Mine gets a new ending and m...
This War of Mine just got a big new update, featuring free DLC that adds a new ending to the game, among other exciting changes. The update is celebrating the game's two-year release anniversary. Apart from the new ending, which will be quite... | Read more »
Summon eight new heroes in Fire Emblem H...
Nintendo keeps coming at us with Fire Emblem Heroes updates, and it doesn't look like that trend is stopping anytime soon. The folks behind the game have just announced the new War of the Clerics Voting Gauntlet, expected to start next Tuesday. [... | Read more »
The best deals on the App Store this wee...
iOS publishers are pulling out all the stops this week -- there's a huge number of seriously great games at discounted prices this week. Let's not waste any time and get right down to business. [Read more] | Read more »
The House of da Vinci (Games)
The House of da Vinci 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enter The House of Da Vinci, a new must-try 3D puzzle adventure game. Solve mechanical puzzles, discover hidden... | Read more »
Solve the disappearance of history’s gre...
Blue Brain Games invites you to indulge in an immersive hands-on 3D puzzle adventure in similar vein to The Room series, with its debut release The House of Da Vinci. Set during the historic period of the Italian Renaissance (when Leonardo himself... | Read more »
Age of Rivals (Games)
Age of Rivals 3.3 Device: iOS Universal Category: Games Price: $.99, Version: 3.3 (iTunes) Description: Deep civilization-building strategy in a fast-paced card game! | Read more »
Panthera Frontier (Games)
Panthera Frontier 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Angry Birds Evolution beginner's gu...
Angry Birds changes things up a fair bit in its latest iteration, Angry Birds Evolution. The familiar sling-shot physics mechanics are still there, but the game now features team-based gameplay, RPG elements, and a new top-down view. With all of... | Read more »
Sega Forever is for the retro game fans
Sega is launching a new retro games service titled Sega Forever, in a move that's sure to delight games enthusiasts with a bit of nostalgia. Sega's releasing five classic games for free. The titles include Sonic the Hedgehog, Phantasy Star II,... | Read more »
The Little Acre (Games)
The Little Acre 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

ABBYY TextGrabber 6 for iOS Implements Instan...
ABBYY has announced the release of TextGrabber 6.0.0, an important feature update to the company’s productivity app developed for iOS and Android devices. TextGrabber 6.0 now offers Real-Time... Read more
vPhone, First Smartphone That Can’t Be Lost,...
Austin, Texas based Hypori has introduced the vPhone, a virtual smartphone that affords every business user the benefits of separate work and personal phones, conveniently delivered on a single... Read more
Save this weekend with 2016 refurbished MacBo...
Apple has dropped prices on Certified Refurbished 2016 15″ and 13″ MacBook Pros by as much as $590 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: -... Read more
New 27-inch 3.4GHz iMac on sale for $1699, sa...
MacMall has the new 2017 27″ 3.4GHz iMac (MNE92LL/A) in stock and on sale for $1699 including free shipping. Their price is $100 off MSRP. Read more
Clearance 2016 MacBook Pros available for up...
B&H Photo has clearance 2016 13″ and 15″ MacBook Pros in stock today and on sale for up to $400 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 15″ 2.7GHz... Read more
Apple Ranks 9th In comScore Top 50 U.S. Digit...
comScore, Inc. has released its monthly ranking of U.S. online activity at the top digital media properties for May 2017 based on data from comScore Media Metrix Multi-Platform. * Entity has... Read more
10.5-inch iPad Pros available for up to $20 o...
B&H Photo has the new 2017 10.5″ iPad Pros available for up to $20 off MSRP including free shipping plus NY & NJ sales tax only: - 64GB iPad Pro WiFi: $649 - 256GB iPad Pro WiFi: $749 - 512GB... Read more
Three Off-The-Beaten-Track iOS Apps That Dese...
One of the great things about using iPads and iPhones is the vast selection of apps available for most anything you want or need to do. The three outlined in this article have been in my core app... Read more
Apple No. 1 Spot In Gartner Top 100 Vendors i...
Gartner, Inc. has unveiled the top global 100 vendors in IT in 2016 based on their revenue across IT (excluding communication services) and component market segments. In the Gartner Global Top 100:... Read more
Clearance iMacs available for up to $300 off...
B&H Photo has clearance 21″ and 27″ Apple iMacs available starting at $949, each including free shipping plus NY & NJ sales tax only: - 27″ 3.3GHz iMac 5K: $1999 $300 off original MSRP - 27″... Read more

Jobs Board

*Apple* News Product Marketing Mgr., Publish...
…organizational consensus on strategy and vision for publisher tools, authoring, and Apple News Format.Carries this strategy and vision across the organization to Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject matter Read more
Lead *Apple* Solutions Consultant - Apple I...
…integrity, and trust.Success Metrics/Key Performance Indicators:Quantitative* Year over Year growth in Apple Product and Beyond the Box sales in the assigned Point of Read more
*Apple* Solutions Consultant till v%u00E5r...
…ethics, integrity, and trust.Success Metrics/Key Performance Indicators:QuantitativeYear over Year growth in Apple Product and Beyond the Box sales in the assigned Point Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.