TweetFollow Us on Twitter

Mar 96 Tips
Volume Number:12
Issue Number:3
Column Tag:Tips & Tidbits

Tips & Tidbits

By Steve Sisak, Contributing Editor

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

Calling PowerPC Code
From 68K Code

There is a lot of information out there about calling 68K code from PowerPC code, but there is very little about calling PowerPC code from 68K code.

Here is a nice method for calling PowerPC code from 68K code. I am using CodeWarrior 7. This is a bit lengthy so hang in there:

There are three steps required to get things up and running. Let’s look at a sample scenario:

You have a 68K application that you just can’t convert to PowerPC code (I don’t know why you can’t convert it, but just bear with me), but you can take some of the time-critical code and convert it to a PowerPC shared library and call it from the 68K code.

Suppose you have two functions that perform data compression:

long  CompressData(  unsigned char *inBuffer, 
 unsigned char *outBuffer,
 unsigned long inBufferSize );
   
long  UncompressData(unsigned char *inBuffer, 
 unsigned char *outBuffer, 
 unsigned long inBufferSize );

Step 1 - Create a PPC shared library containing your functions.

We are going to export these functions using the #pragma export directive. This is set in the PPC Prefs area of Codewarrior preferences.

“the shared library”
// Prototypes

#pragma export on

#ifdef __cplusplus
extern "C" {
#endif

long  CompressData(  unsigned char *inBuffer, 
 unsigned char *outBuffer, 
 unsigned long inBufferSize );
   
long  UncompressData(   unsigned char *inBuffer,
 unsigned char *outBuffer,
 unsigned long inBufferSize );

#ifdef __cplusplus
}
#endif

#pragma export off
// CompressData

long  CompressData( unsigned char *inBuffer, unsigned char 
   *outBuffer, unsigned long inBufferSize )
{
    ... compress data code
}

// UncompressData
   
long  UncompressData( unsigned char *inBuffer, unsigned char 
     *outBuffer, unsigned long inBufferSize )
{
    ... uncompress data code
}

Set the project type to a shared library and build the project. We now have a PowerPC shared library that we will use in Step 2.


Step 2 - Create a resource-based PEF Fragment that references our shared library.

We create a header file that defines some mixed mode information.

“the header file”
#ifdef __cplusplus
extern "C" {
#endif

typedef long (*CompressDataProcPtr)( unsigned char *inBuffer, 
 unsigned char *outBuffer, unsigned long inBufferSize );
typedef long (*UncompressDataProcPtr)( unsigned char *inBuffer, 
 unsigned char *outBuffer, unsigned long inBufferSize);

#if GENERATINGCFM || USESROUTINEDESCRIPTORS

typedef UniversalProcPtr CompressDataUPP;
typedef UniversalProcPtr UncompressDataUPP;

enum {
 uppCompressDataProcInfo = kCStackBased
 | RESULT_SIZE( SIZE_CODE( sizeof( long ) ) )
 | STACK_ROUTINE_PARAMETER( 1, SIZE_CODE( 
 sizeof( unsigned char *) ) )
 | STACK_ROUTINE_PARAMETER( 2, SIZE_CODE( 
 sizeof( unsigned char *) ) ) | STACK_ROUTINE_PARAMETER( 3, SIZE_CODE( 

 sizeof( long ) ) )
};

enum {
 uppUncompressDataProcInfo = kCStackBased
 | RESULT_SIZE( SIZE_CODE( sizeof( long ) ) )
 | STACK_ROUTINE_PARAMETER( 1, SIZE_CODE( 
 sizeof( unsigned char *) ) )
 | STACK_ROUTINE_PARAMETER( 2, SIZE_CODE( 
 sizeof( unsigned char *) ) )
 | STACK_ROUTINE_PARAMETER( 3, SIZE_CODE( 
 sizeof( long ) ) )
};

#else

typedef CompressDataProcPtr CompressDataUPP;
typedef UncompressDataProcPtr UncompressDataUPP;
#endif

//============================================================
// Extern Globals
//

#ifndef powerc

extern CompressDataUPP    myCompressDataUPP;
extern UncompressDataUPP  myUncompressDataUPP;

#endif

//============================================================
// Macros
//

#if GENERATINGPOWERPC || defined(powerc) || defined (__powerc)

#define myCompressData( a, b, c )  CompressData( a, b, c )
#define myUncompressData( a, b, c )UncompressData( a, b, c )

#else

#define myCompressData( a, b, c ) \  
 (*(CompressDataUPP)myCompressDataUPP( a, b, c )
#define myUncompressData( a, b, c  ) \
 (*(CompressDataUPP)myUncompressDataUPP( a, b, c )

#endif

//============================================================
// Prototypes
//

long CompressData( unsigned char *inBuffer, unsigned char 
    *outBuffer, unsigned long inBufferSize );
long UncompressData( unsigned char *inBuffer, unsigned char 
  *outBuffer, unsigned long inBufferSize );

#ifdef __cplusplus
}
#endif

Now we define the source file:

“the source file”
#include "the header file"

#ifdef __cplusplus
extern "C" {
#endif

#if GENERATINGPOWERPC || defined(powerc) || defined (__powerc)
#pragma options align=mac68k
#endif

#ifdef __CFM68K__
#pragma lib_export on
#endif

RoutineDescriptorCompressDataRD = 
 BUILD_ROUTINE_DESCRIPTOR(  uppCompressDataProcInfo, 
 CompressData );

RoutineDescriptorUncompressDataRD = 
 BUILD_ROUTINE_DESCRIPTOR(  uppUncompressDataProcInfo, 
 UncompressData );


#ifdef __CFM68K__
#pragma lib_export off
#endif

#if GENERATINGPOWERPC || defined(powerc) || defined (__powerc)
#pragma options align=reset
#endif

#ifdef __cplusplus
}
#endif

Add the shared library we built in Step 1 to this project.

Set the project type to shared library and build the project. We now have a PowerPC shared library that we want to convert to a resource. (Note: we don’t export this as a PowerPC code resource with no header, since we would get link errors for an undefined main entry.)

Open the file up in a resource editor and create a new resource (I use a type of 'PEF ', but any will do). Move the PEF code from the data fork into this resource. (If your resource editor will not do this, then it is a simple matter of creating a small application that will do this for you; this excercise is left for the reader.)

We now have a resource file that we will add to our 68K project.


Step 3 - Add 68K support code to your project

Your 68K project needs to have a bit of support code to get the code resource and load it in as a code fragment. Add to your code:

#include "the header file"

We need to declare some globals for the universal procs that will store the address of the routine descriptors. Add to your code:

#ifndef powerc
CompressDataUPP  myCompressDataUPP;
UncompressDataUPPmyUncompressDataUPP;
#endif

The following function takes care of checking for the existence of the CFM and Mixed Mode managers. We pass it a pointer to a CFragConnectionID variable and a Handle variable, which we will use later on for clean up. Add to your code:

#ifndef powerc

// SetupPPCNativeCode

OSErr SetupPPCNativeCode( CFragConnectionID *connID, 
 Handle *PEFHandle,
   ResType codeFragmentType, 
 short codeFragmentID )
{
 OSErr  theErr = noErr;
 long   templong;
 Str255 failedFragName;
 

    // get PEF container resource from our resource fork
 
 *PEFHandle = ::Get1Resource( codeFragmentType, codeFragmentID );
 theErr = ::ResError();
 if( !(*PEFHandle) )
 {
 if( theErr )  
 return( theErr );
 else
 return( ::MemError() );
 }
 
    // Check for Mixed Mode Manager and Code Fragment Manager (CFM)
 
 Boolean  hasMixedMode = !Gestalt( gestaltMixedModeAttr, 
 &templong );
 Boolean  hasCFM = !Gestalt( gestaltCFMAttr, &templong );
 
 theErr = Gestalt( gestaltSysArchitecture, &templong );
 if( ( theErr ) || 
 ( templong == gestalt68k ) ||
 ( !hasCFM ) ||
 ( !hasMixedMode ) )
 {
 ::ReleaseResource( *PEFHandle );
 return( -1 );
 }
 
 DetachResource( *PEFHandle );
 MoveHHi( *PEFHandle );
 HLock( *PEFHandle );
 
    // Assume this is PowerPC code, so it must be “prepared”
 
 theErr = ::GetMemFragment( (Ptr)**PEFHandle, 0, 0,            
 kNewCFragCopy, connID, 0, failedFragName );
 if( theErr )
 {
 DisposeHandle( *PEFHandle );
 return( theErr );
 }

 CFragSymbolClassmyClass;
 
 if( !theErr )
 theErr = ::FindSymbol( *connID, 
    (ConstStr255Param)"\pCompressDataRD", 
    (Ptr*)&myCompressDataUPP, 
    &myClass );
 if( !theErr )
 theErr = ::FindSymbol( *connID, 
    (ConstStr255Param)"\pUncompressDataRD", 
    (Ptr*)&myUncompressDataUPP, 
    &myClass );

 if( theErr )
 {
 DisposeHandle( *PEFHandle );
 return( theErr );
 }
 
 return( noErr );
}

The following function takes the connection id and handle returned from SetupPPCNativeCode, frees the connection and disposes of the handle. Add to your code:

// TearDownPPCNativeCode

void TearDownPPCNativeCode( CFragConnectionID connID, Handle PEFHandle 
)
{
 ::CloseConnection( &connID );
 if( PEFHandle )
 ::DisposeHandle( PEFHandle );
}

#endif

Build your 68K project as you normally would and be sure to include the resource file we created in Step 2 and ensure the the shared library we created in Step 1 is either in the Extensions folder of the System Folder or in the same directory as the application.

Here is what you would do the call the PowerPC code from 68K:

long PowerPC_Compress( unsigned char *inBuffer, unsigned char 
    *outBuffer, unsigned long inBufferSize )
{
 #ifndef powerc
 
    // For efficiency you would probably put this call in initialization code.
    // sConnID and sPEFHandle are static globals.
 
 OSErr err = SetupPPCNativeCode( &sConnID, &sPEFHandle, 
 'PEF ', 128 );
 if( err )
 return( 0 );  // We couldn’t compress anything so return 0
 #endif
 
 long   result = 0;
 
 result = myCompressData( inBuffer, outBuffer, inBufferSize );
 
 #ifndef powerc
 
    // For efficiency you would probably put this call in termination code.
 
 TearDownPPCNativeCode( sConnID, sPEFHandle );
 #endif
}

long PowerPC_Uncompress( unsigned char *inBuffer, 
 unsigned char *outBuffer, unsigned long inBufferSize )
{
 #ifndef powerc
 
    // For efficiency you would probably put this call in initialization code.
    // sConnID and sPEFHandle are static globals.
 
 OSErr err = SetupPPCNativeCode( &sConnID, &sPEFHandle, 
 'PEF ', 128 );
 if( err )
 return( 0 );  // We couldn’t compress anything so return 0
 #endif
 
 long   result = 0;
 
 result = myUncompressData( inBuffer, outBuffer, inBufferSize );
 
 #ifndef powerc
 
    // For efficiency you would probably put this call in termination code.
 
 TearDownPPCNativeCode( sConnID, sPEFHandle );
 #endif
}


That’s all there is to it. Enjoy and happy coding.

- Chris Rudolph

[BuildRoutineDescriptor() doesn’t work right with CFM68k; use NewRoutineDescriptor() instead. BuildRoutineDescriptor() generates code so you need to call MakeDataExecutable() after it. - sgs]

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Six fantastic ways to spend National Vid...
As if anyone needed an excuse to play games today, I am about to give you one: it is National Video Games Day. A day for us to play games, like we no doubt do every day. Let’s not look a gift horse in the mouth. Instead, feast your eyes on this... | Read more »
Old School RuneScape players turn out in...
The sheer leap in technological advancements in our lifetime has been mind-blowing. We went from Commodore 64s to VR glasses in what feels like a heartbeat, but more importantly, the internet. It can be a dark mess, but it also brought hundreds of... | Read more »
Today's Best Mobile Game Discounts...
Every day, we pick out a curated list of the best mobile discounts on the App Store and post them here. This list won't be comprehensive, but it every game on it is recommended. Feel free to check out the coverage we did on them in the links below... | Read more »
Nintendo and The Pokémon Company's...
Unless you have been living under a rock, you know that Nintendo has been locked in an epic battle with Pocketpair, creator of the obvious Pokémon rip-off Palworld. Nintendo often resorts to legal retaliation at the drop of a hat, but it seems this... | Read more »
Apple exclusive mobile games don’t make...
If you are a gamer on phones, no doubt you have been as distressed as I am on one huge sticking point: exclusivity. For years, Xbox and PlayStation have done battle, and before this was the Sega Genesis and the Nintendo NES. On console, it makes... | Read more »
Regionally exclusive events make no sens...
Last week, over on our sister site AppSpy, I babbled excitedly about the Pokémon GO Safari Days event. You can get nine Eevees with an explorer hat per day. Or, can you? Specifically, you, reader. Do you have the time or funds to possibly fly for... | Read more »
As Jon Bellamy defends his choice to can...
Back in March, Jagex announced the appointment of a new CEO, Jon Bellamy. Mr Bellamy then decided to almost immediately paint a huge target on his back by cancelling the Runescapes Pride event. This led to widespread condemnation about his perceived... | Read more »
Marvel Contest of Champions adds two mor...
When I saw the latest two Marvel Contest of Champions characters, I scoffed. Mr Knight and Silver Samurai, thought I, they are running out of good choices. Then I realised no, I was being far too cynical. This is one of the things that games do best... | Read more »
Grass is green, and water is wet: Pokémo...
It must be a day that ends in Y, because Pokémon Trading Card Game Pocket has kicked off its Zoroark Drop Event. Here you can get a promo version of another card, and look forward to the next Wonder Pick Event and the next Mass Outbreak that will be... | Read more »
Enter the Gungeon review
It took me a minute to get around to reviewing this game for a couple of very good reasons. The first is that Enter the Gungeon's style of roguelike bullet-hell action is teetering on the edge of being straight-up malicious, which made getting... | Read more »

Price Scanner via MacPrices.net

Take $150 off every Apple 11-inch M3 iPad Air
Amazon is offering a $150 discount on 11-inch M3 WiFi iPad Airs right now. Shipping is free: – 11″ 128GB M3 WiFi iPad Air: $449, $150 off – 11″ 256GB M3 WiFi iPad Air: $549, $150 off – 11″ 512GB M3... Read more
Apple iPad minis back on sale for $100 off MS...
Amazon is offering $100 discounts (up to 20% off) on Apple’s newest 2024 WiFi iPad minis, each with free shipping. These are the lowest prices available for new minis among the Apple retailers we... Read more
Apple’s 16-inch M4 Max MacBook Pros are on sa...
Amazon has 16-inch M4 Max MacBook Pros (Silver and Black colors) on sale for up to $410 off Apple’s MSRP right now. Shipping is free. Be sure to select Amazon as the seller, rather than a third-party... Read more
Red Pocket Mobile is offering a $150 rebate o...
Red Pocket Mobile has new Apple iPhone 17’s on sale for $150 off MSRP when you switch and open up a new line of service. Red Pocket Mobile is a nationwide MVNO using all the major wireless carrier... Read more
Switch to Verizon, and get any iPhone 16 for...
With yesterday’s introduction of the new iPhone 17 models, Verizon responded by running “on us” promos across much of the iPhone 16 lineup: iPhone 16 and 16 Plus show as $0/mo for 36 months with bill... Read more
Here is a summary of the new features in Appl...
Apple’s September 2025 event introduced major updates across its most popular product lines, focusing on health, performance, and design breakthroughs. The AirPods Pro 3 now feature best-in-class... Read more
Apple’s Smartphone Lineup Could Use A Touch o...
COMMENTARY – Whatever happened to the old adage, “less is more”? Apple’s smartphone lineup. — which is due for its annual refresh either this month or next (possibly at an Apple Event on September 9... Read more
Take $50 off every 11th-generation A16 WiFi i...
Amazon has Apple’s 11th-generation A16 WiFi iPads in stock on sale for $50 off MSRP right now. Shipping is free: – 11″ 11th-generation 128GB WiFi iPads: $299 $50 off MSRP – 11″ 11th-generation 256GB... Read more
Sunday Sale: 14-inch M4 MacBook Pros for up t...
Don’t pay full price! Amazon has Apple’s 14-inch M4 MacBook Pros (Silver and Black colors) on sale for up to $220 off MSRP right now. Shipping is free. Be sure to select Amazon as the seller, rather... Read more
Mac mini with M4 Pro CPU back on sale for $12...
B&H Photo has Apple’s Mac mini with the M4 Pro CPU back on sale for $1259, $140 off MSRP. B&H offers free 1-2 day shipping to most US addresses: – Mac mini M4 Pro CPU (24GB/512GB): $1259, $... Read more

Jobs Board

All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.