TweetFollow Us on Twitter

PowerPC Code
Volume Number:10
Issue Number:4
Column Tag:Powering Up

Connecting A 68k Object File
To PowerPC Code

A robust technique for loading and calling 68K modules from your PowerPC application

By Richard Clark, Apple Computer, Inc.

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

Many developers run into a major problem when porting code to PowerPC: incorporating 68K object models which came from an outside vendor. Since you can’t just hand a 68K module to the PowerPC linker, you have to find some alternative for loading the library and calling the library’s functions. Fortunately, developers can use the Code Fragment Manager and the Mixed Mode Manager together to solve this problem.

The solution involves creating a stand-alone version of the 68K code, then assembling a “jump table” of Universal Procedure Pointers which the application can use to call this code. Since applications (and, in fact, any PowerPC code fragment) can have global variables, it makes sense to allocate this table within the application. However, since the 68K library entry points are only available to the 68K code, that code has to create the universal procedure pointers. This would create an impossible dilemma except for one fact - both Mixed Mode and the Code Fragment Manager can be called from emulation on a Power Macintosh via A-Traps.

Thus we have a solution - the application must create the jump table as a global variable, and then pass its address to the 68K code which assembles the jump table. (An alternate method involves exporting the table from the application. The 68K code must open a connection back to the application, and ask the CFM for the address of the jump table.) The 68K code creates Universal Procedure Pointers to fill the table, which allows the application to call the library functions using Mixed Mode.

Creating the Jump Table

The first step is to prepare a list of all of the functions that your application calls in the library. Next, define ProcInfo values for each of these functions, using the MixedMode.h header and any header which defines callback functions (such as Controls.h) as a guide. You should also create macros for creating and calling a UniversalProcPtr in this way.

Next, create a data structure which contains Mixed Mode “Universal Procedure Pointers” for each of these functions. Put a copy of this data structure into a global variable in your PowerPC application, and don’t declare it as “static” (i.e. hidden.) You should also export this table, for a reason that will become clear shortly.


/* 1 */
// This is a header file common to the application and 68K code 

#include <ConditionalMacros.h>
#include <MixedMode.h>

typedef void (*CallbackPtr)(void); // A pointer which is fed to the library

typedef pascal OSErr (*Routine1ProcPtr)(CallbackPtr callbackRoutine);

enum {
 uppRoutine1ProcInfo = kPascalStackBased
  | RESULT_SIZE (SIZE_CODE(sizeof(OSErr)))
  | STACK_ROUTINE_PARAMETER(1, SIZE_CODE(sizeof(CallbackPtr)))
};

#if USESROUTINEDESCRIPTORS
// Use these definitions if we're compiling for Power Macintosh or another
// Macintosh system which supports Mixed Mode
typedef UniversalProcPtr Routine1UPP;

#define CallRoutine1Proc(userRoutine, longValue)         \
 CallUniversalProc((UniversalProcPtr)(userRoutine),\
 uppRoutine1ProcInfo, longValue)
#define NewRoutine1Proc(userRoutine) \
 (RoutineUPP) NewRoutineDescriptor((ProcPtr)userRoutine, \
    uppRoutine1ProcInfo, GetCurrentISA())
#else
// Use these definitions if we're compiling for a 68K-based Macintosh
typedef Routine1ProcPtr Routine1UPP;

#define CallRoutine1Proc(userRoutine, longValue)         \
 (*((Routine1ProcPtr )userRoutine))(longValue)
#define NewRoutine1Proc(userRoutine) \
 (Routine1UPP)(userRoutine)
#endif

 
// Here's the list of Universal Procedure Pointers
struct JumpTable {
 Routine1UPProutine1;
};

typedef struct JumpTable JumpTable, *JumpTablePtr;

// === Information on calling the 68K setup functions
typedef pascal OSErr (*SetupProcPtr)(JumpTablePtr);

enum {
 uppSetupProcInfo = kPascalStackBased
  | RESULT_SIZE (SIZE_CODE(sizeof(OSErr)))
  | STACK_ROUTINE_PARAMETER(1, SIZE_CODE(sizeof(JumpTablePtr)))
};

#if USESROUTINEDESCRIPTORS
// Use these definitions if we're compiling for Power Macintosh or another
// Macintosh system which supports Mixed Mode
typedef UniversalProcPtr SetupUPP;

#define CallSetupProc(userRoutine, jumpTableAddr)        \
 CallUniversalProc((UniversalProcPtr)(userRoutine),\
 uppSetupProcInfo, jumpTableAddr)
#define NewSetupProc(userRoutine)  \
 (SetupUPP) NewRoutineDescriptor((ProcPtr)userRoutine, \
    uppSetupProcInfo, GetCurrentISA())
#else
// Use these definitions if we're compiling for a 68K-based Macintosh
typedef SetupProcPtr SetupUPP;

#define CallSetupProc(userRoutine, jumpTableAddr)        \
 (*((SetupProcPtr)userRoutine))(jumpTableAddr)
#define NewSetupProc(userRoutine)  \
 (SetupUPP)(userRoutine)
#endif

Next, you have to create the “setup” function in 68K code and link it to your 68K object library. This routine needs to fill in each of the pointers in the table. The resulting code should be compiled, linked, and made into a stand-alone 68K code resource.

Granted, this technique could prove difficult if the library depends on having an A5 world. If your 68K library requires global variables, you must apply one of the special coding techniques documented in the Macintosh Developer Technical Notes or develop magazine.) Also note that if you want this code to run on a 68K machine, you should check for the presence of Mixed Mode and react appropriately.


/* 2 */
pascal OSErr BuildJumpTable(JumpTablePtr theJumpTable)
// Build a table of pointers to functions in our linked library
{
 OSErr  err;
 // Fill in the table with pointers to each library function
 theJumpTable->routine1 = NewMyRoutineProc(Routine1);
 err = MemError();
 return err;
}

The alternate approach involves exporting the jump table from the Application using the CFM, and letting the 68K code ask the CFM for the table’s address. Note the use of a STR# resource to store the application and table name strings - this avoids needing an A5 world just for the string constants. (Note that this code will not work on a machine which doesn’t have the Code Fragment Manager or Mixed Mode.)


/* 3 */
OSErr   err;
 JumpTablePtr  theJumpTable;
 ConnectionID  connID = 0;
 Ptr    mainAddr;
 Str255 errName, appName, tableName;
 SymClass symClass;
// Locate the application that called us
 GetIndString(&appName, 128, 1); // Assuming the name is in a STR#
 err = GetSharedLibrary(&appName, kPowerPCArch, 0, 
 &connID, &mainAddr, &errName);
 if (err) goto done;
 
 // Now, locate the shared table
 // (it's a pointer stored in a global variable)
 GetIndString(&tableName, 128, 2);// The table name is in the same STR#
 err = FindSymbol(connID, &tableName, 
 (Ptr*)&myTablePointer, &symClass);
 if (err) goto done;
// Insert the code to create UniversalProcPtrs here
done:
 if (connID)
 CloseConnection(&connID);
  return err;

To initialize this table, simply load the code resource from the application and call it via Mixed Mode. When the resource returns, the jump table will be full of Universal Procedure Pointers. Therefore, you should then modify your application to use Mixed Mode and the pointers in the table to call the library functions.


/* 4 */
// include the usual macros for creating a UniversalProcPtr for our callback 
routine
JumpTable gJumpTable;
// Load the stand-alone code
Handle  theResource;
theResource= Get1IndResource('STUB', 1);
if (theResource) {
  MoveHHi(theResource);
  HLock(theResource);// Lock it -- and NEVER unlock it
  // Call the entry point, no parameters
  CallSetupProc(*theResource, &gJumpTable);  
 // we know it's 68K, so we didn't
 // bother with creating a Routine Descriptor
  // Create a UniversalProcPtr for our callback routine
  CallbackUPP ourCallback;
  ourCallback = NewCallbackProc(MyCallbackRoutine);
  result = CallRoutine1Proc(gJumpTable.routine1,ourCallback );
  DisposeRoutineDescriptor(ourCallback);
}

Note that since the library function takes a callback pointer, we had to create a UniversalProcPtr and pass that instead of the address of the actual code. (If we hadn't done this, the machine would crash.) Since this causes memory to be allocated for a Routine Descriptor, we call DisposeRoutineDescriptor afterwards to release the memory.

That’s all there is to it! This is a robust technique which is now being used in several commercial applications - perhaps it will prove useful in yours.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Together 3.6.1 - 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. Features Smart storage. With simple drag-and-drop... Read more
Cloud 4.1.1 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more
OmniFocus 2.7.1 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more
CleanApp 5.1.1 - Application deinstaller...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
ForkLift 3.0 Beta 2 - Powerful file mana...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
Sublime Text 3126 - Sophisticated text e...
Sublime Text is a sophisticated text editor for code, markup, and prose. You'll love the slick user interface, extraordinary features, and amazing performance. Features Goto Anything. Use Goto... Read more
1Password 6.3.3 - Powerful password mana...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more
WhatsApp 0.2.1880 - Desktop client for W...
WhatsApp is the desktop client for WhatsApp Messenger, a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. WhatsApp Messenger is available for... Read more
NeoFinder 6.9.3 - Catalog your external...
NeoFinder (formerly CDFinder) rapidly organizes your data, either on external or internal disks, or any other volumes. It catalogs all your data, so you stay in control of your data archive or disk... Read more
Amadeus Pro 2.3.1 - Multitrack sound rec...
Amadeus Pro lets you use your Mac computer for any audio-related task, such as live audio recording, digitizing tapes and records, converting between a variety of sound formats, etc. Thanks to its... Read more

Paperback: The Game (Games)
Paperback: The Game 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: You are an author trying to finish kitschy paperback novels. Complete Westerns, Science Fiction, Romance or even a Crime... | Read more »
How to Rule With a Firm Hand in My Majes...
My Majesty is a kingdom management sim not unlike August’s magisterial hit, Reigns. It’s essentially a reskin of developer Tigrido’s previous management sim, Dictator. As supreme ruler of the land, you must consult with a number of subjects to... | Read more »
Our 5 Favorite iMessage Sticker Packs
At long last, iMessage joins the ranks of messaging apps the likes of LINE and Whatsapp, adding an impressive collection of stickers. They’re a great way to add a little something extra to your daily conversations. [Read more] | Read more »
How to get past Vulture Island's tr...
Vulture Island is a colorful and quirky mish-mash of platforming and puzzles. It’s creative and fresh, but sometimes the game can throw a curveball at you, leaving you stuck as to how you should progress. These tips will help you explore smoothly... | Read more »
The new Clash of Kings is just for Weste...
If you’ve played the original Clash of Kings, you’ll probably recognise the city building, alliance forging and strategic battles in Clash of Kings: The West. What sets this version apart is that it’s tailor made for a Western audience and the... | Read more »
Frost - Survival card game (Games)
Frost - Survival card game 1.12.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.12.1 (iTunes) Description: *Warning: the game will work on iPhone 5C and above and iPad Pro / 4. Other devices are not supported* | Read more »
How to build and care for your team in D...
Before you hit the trail and become a dog sledding legend, there’s actually a fair bit of prep work to be done. In Dog Sled Saga, you’re not only racing, you’re also building and caring for a team of furry friends. There’s a lot to consider—... | Read more »
How to win every race in Dog Sled Saga
If I had to guess, I’d say Dog Sled Saga is the most adorable racing game on the App Store right now. It’s a dog sled racing sim full of adorable, loyal puppies. Just look at those fluffy little tails wagging. Behind that cute, pixelated facade is... | Read more »
Let the war games commence in Gunship Ba...
Buzz Lightyear famously said, “This isn’t flying, this is falling – with style!” In the case of Gunship Battle: Second War, though, this really is flying - with style! The flight simulator app from Joycity puts you in control of 20 faithfully... | Read more »
How to get a high score in Fired Up
Fired Up is Noodlecake Games’ high score chasing, firefighting adventure. You take control of a wayward firefighter who propels himself up the side of a highrise with blasts of water. Sound silly? It is. It’s also pretty difficult. You can’t... | Read more »

Price Scanner via MacPrices.net

15-inch 2.2GHz Retina MacBook Pro on sale for...
B&H Photo has the 2015 15″ 2.2GHz Retina MacBook Pro (MJLQ2LL/A) on sale for $1799, including free shipping plus NY sales tax only. Amazon also has the 2015 15″ 2.2GHz Retina MacBook Pro (... Read more
Toughbook Celebrates 20 Years of Ruggedized M...
Panasonic System Communications Company of North America, Division of Panasonic Corporation of North America (Panasonic) today celebrates the 20th anniversary of its industry-leading Toughbook mobile... Read more
12-inch 1.1GHz Gray Retina MacBook on sale fo...
B&H Photo has the 2016 12″ 1.1GHz Gray Retina MacBook on sale for $1199.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
13-inch 2.5GHz MacBook Pro (Apple refurbished...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz MacBook Pros... Read more
Save 30% on Camera Guard’s Secure Protection...
To celebrate the release of macOS Sierra, Miami-based security solutions company, ProtectStar has announced a special 30% discount on Camera Guard Professional for Mac 2016. This innovative security... Read more
DVDFab Special Deal – Get a 1-Year Free Licen...
Beijing, China based specialist in the field of DVD, Blu-ray and video backup solutions, Fengtao Software has launched its Autumn Special Deals 2016, giving a 1-year free license of a randomly picked... Read more
21-inch iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ iMacs on sale for up to $120 off MSRP including free shipping plus NY sales tax only: - 21″ 3.1GHz iMac 4K: $1379 $120 off MSRP - 21″ 2.8GHz iMac: $1199.99 $100 off MSRP - 21″ 1... Read more
13-inch 2.7GHz/256GB Retina MacBook Pro on sa...
Amazon.com has the 13″ 2.7GHz/256GB Retina Apple MacBook Pro on sale for $151 off MSRP including free shipping: - 13″ 2.7GHz/256GB Retina MacBook Pro (sku MF840LL/A): $1348 $151 off MSRP Read more
Apple TVs on sale for up to $50 off MSRP
Best Buy has 32GB and 64GB Apple TVs on sale for $40-$50 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store... Read more
Apple refurbished 13-inch Retina MacBook Pros...
Apple has Certified Refurbished 13″ Retina MacBook Pros available for up to $270 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 13″ 2.7GHz... Read more

Jobs Board

Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
Sr. *Apple* Mac Engineer - Net2Source Inc....
…staffing, training and technology. We have following position open with our client. Sr. Apple Mac Engineer6+ Months CTH Start date : 19th Sept Travelling Job If Read more
*Apple* Retail - Multiple Positions-Norfolk,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
Lead *Apple* Solutions Consultant - Apple (...
# Lead Apple Solutions Consultant Job Number: 51829230 Detroit, Michigan, United States Posted: Sep. 19, 2016 Weekly Hours: 40.00 **Job Summary** The Lead ASC is an Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.