TweetFollow Us on Twitter

MACINTOSH C CARBON
MACINTOSH C CARBON: A Hobbyist's Guide To Programming the Macintosh in C
Version 1.0
2001 K. J. Bricknell
Go to Contents

CHAPTER 5

CARBON AND UNIVERSAL PROCEDURE POINTERS

Introduction

Previous demonstration programs have called a function (AEInstallEventHandler) which takes a universal procedure pointer as a parameter; however, an explanation of this term has been delayed until this chapter because the AEInstallEventHandler calls were only incidental to the main purpose of those demonstrations. The demonstration programs at Chapter 7 are the first in which calls to a system software function which takes a universal procedure pointer as a parameter are central to the demonstration. As a brief but necessary prelude for what is to come, therefore, this chapter addresses the role of universal procedure pointers in the general scheme of things, when and why they were introduced, and their relevance in the Carbon environment.

In a sense, universal procedure pointers are a piece of historical baggage dragged into Carbon by Mac OS 8/9. They was first introduced with the so-called Universal Headers which, in turn, were introduced with the Power Macintosh. They had to with the ability of the Power Macintosh to run applications that use the instruction set of the Motorola 680x0 microprocessor (used in 680x0-based Macintoshes) as well as applications that use the native instruction set of the Power Macintosh's PowerPC microprocessor.

In the Chapter 7 demonstration programs, the system software function which takes a universal procedure pointer is TrackControl. This function is called by your application when a mouse-down event occurs in a control, such as a scroll bar. Prior to the introduction of the Power Macintosh and the associated introduction of the Universal Headers, the TrackControl prototype looked like this:

     Sint16  TrackControl(TrackControl(ControlHandle theControl,Point localPoint,
                          ProcPtr actionProc);

The actionProc a parameter is simply the address of an application-defined function, called a callback procedure (or, in C terminology, a callback function) that is called repeatedly while the mouse button remains down. In other words, the TrackControl function used to take a procedure pointer (or, in C terminology, a function pointer) in its actionProc parameter.

The Universal Headers, which, amongst other things, allow you to write Classic API source code capable of being compiled as either 680x0 code or native PowerPC code, changed the prototype for TrackControl to:

     ControlPartCode  TrackControl(ControlHandle theControl,Point startPoint,
                                   ControlActionUPP actionProc);

Notice that the third parameter is now of type ControlActionUPP. This means that the actionProc parameter now takes a universal procedure pointer. This prototype has been carried through to the Carbon headers, hence the necessity to gain a basic understanding of universal procedure pointers.

The 68LC040 Emulator and the Mixed Mode Manager

The Emulator

This ability of the Mac OS 8/9 system software to execute applications that use the instruction set of the Motorola 680x0 microprocessor as well as applications that use the native instruction set of the PowerPC microprocessor is provided by an emulator (the 68LC040 Emulator). The emulator, which is essentially a 680x0 microprocessor implemented in software, provides an execution environment that is virtually identical to the execution environment found on 680x0-based Macintoshes.

One important aspect of the 68LC040 emulator is that it made it possible for parts of the system software to remain as 680x0 code while other parts were progressively re-written, primarily for reasons of speed, as native PowerPC code. In this regard, it is important to understand that some of Mac OS 8/9 still remains as 680x0 code. For example, in Mac OS 8.6, parts of the Control Manager (including, possibly, TrackControl) remain in 680x0 code. For the purposes of explanation, the following assumes that, in Mac OS 8/9, TrackControl still exists as 680x0 code.

The Mixed Mode Manager

In Mac OS 8/9, the emulator works together with a manager called the Mixed Mode Manager. The Mixed Mode Manager manages mode switches between code in different instruction set architectures (ISAs).

Mode Switches

In Mac OS 8/9, mode switches are required when an application calls a system software function (or, indeed, any other code) that exists in a different ISA. For example:

  • When a PowerPC application invokes a system software function that exists only as 680x0 code, a mode switch is required to move from the native environment to the emulator environment. Then, when that system software function completes, another mode switch is required to return from the emulator to the PowerPC environment to allow the PowerPC application to continue executing.

    This situation can occur in a Carbon application running on Mac OS 8/9 because, as previously stated, not all of Mac OS 8/9 has been re-written as native PowerPC code.

  • When a 680x0 application running under the emulator calls a system software function that exists as native PowerPC code, a mode switch is required to move out of the emulator and into the native PowerPC environment. Then, when that system software function completes, another mode switch is required to return to the emulator and to allow the 680x0 application to continue executing.

    This situation cannot occur in a Carbon application running on Mac OS 8/9 because all Carbon applications must be compiled as native PowerPC code.

The Mixed Mode Manager operates transparently to most applications and other types of software, meaning that most cross-mode calls (calls to code in a different ISA from the caller's ISA) are detected automatically by the Mixed Mode Manager and handled without intervention by the calling software.

Intervention in Mode Switching

Sometimes, however, executable code needs to interact directly with the Mixed Mode Manager to ensure that a mode switch occurs at the correct time. When writing native PowerPC code, you only have to intervene in the mode-switching process when you execute code whose ISA might be different from the calling code. For example, when you pass the address of your application-defined action function (native PowerPC code) to TrackControl (680x0 code), the ISA of the code whose address you are passing is different from the ISA of the function you are passing it to. In such cases, you must ensure that the Mixed Mode Manager is called to make the necessary mode switch. You do this by explicitly signalling:

  • The type of code you are passing.

  • The code's calling conventions.

Indicating the ISA of a Callback Function - Routine Descriptors

You create a routine descriptor for a particular function to indicate the ISA of that function (see Fig 1).The first field of a routine descriptor (goMixedModeTrap) is an executable 680x0 instruction which invokes the Mixed Mode Manager. The Mixed Mode Manager having been called, it inspects the remaining fields of the routine descriptor to determine whether a mode switch is required. The Mixed Mode Manager is particularly interested in the routineRecords field.

The routineRecords field is an array of routine structures, each element of which describes a single function. In the simplest case, the array of routine structures contains a single element.

The ISA and procInfo fields are the most important fields in a routine structure:

  • ISA Field. The ISA field contains the ISA code of the function being described, and always contains one of these two constants:

         kM68kISA  = (ISAType) 0  MC680x0 architecture.
         KPowerPCISA  = (ISAType) 1  PowerPC Architecture.
    

  • procInfo Field. The procInfo field contains the function's function information, including the function's calling conventions and information about the function's parameters.

Creating a Routine Descriptor For a Control Action Function

Using the function NewControlActionUPP, you can create a routine descriptor for a control action function as follows, in which myControlAction is your application-defined control action function:

     ControlActionUPP myControlActionUPP;

     myControlActionUPP = NewControlActionUPP(myControlAction);

Notice that the result returned by NewControlActionUPP is of type ControlActionUPP. The UPP stands for a universal procedure pointer, which is defined to be either a 680x0 function pointer or a pointer to a routine descriptor (hence the term "universal"). Thus, in Mac OS 8/9, the effect of the call to NewControlActionUPP depends on whether it is executed in the 680x0 environment or the PowerPC environment:

  • In the 680x0 environment, NewControlActionUPP simply returns its first parameter, that is, a pointer to your application-defined control action function.

  • In the PowerPC environment, NewControlActionUPP creates a routine descriptor in your application heap and returns the address of that routine descriptor.

Effect of the Routine Descriptor

Once you have created the routine descriptor, you can later call TrackControl like this:

     TrackControl(myControl,myPoint,myControlActionUPP);

In Mac OS 8/9, if your application is a PowerPC application (as will be the case in Carbon), the value passed in the myControlActionUPP parameter is not the address of your action function itself, but the address of the routine descriptor. If a 680x0 version of TrackControl executes your action function, it begins by executing the instruction in the first field of the routine descriptor. That instruction invokes the Mixed Mode Manager, which inspects the ISA of the action function (contained in the ISA field of the routine structure). Since that ISA differs from the ISA of the TrackControl function, the Mixed Mode Manager causes a mode switch. (Of course, if TrackControl existed as PowerPC code, the ISAs would be identical, and the Mixed Mode Manager would simply execute the action function without switching modes.)

In short, you solve the problem of indicating a routine's ISA by creating a routine descriptor and by using the address of that routine descriptor (that is, a universal procedure pointer) where you would have used the address of the function (that is, a procedure pointer) in the 680x0 programming environment.

Disposing of Routine Descriptors

Disposing of routine descriptors is only necessary or advisable if you know that you will not be using the descriptor any more during the execution of your application or if you allocate a routine descriptor for temporary use only.

Functions Requiring Universal Procedure Pointers

Some of the functions for which universal procedure pointers must be created are as follows:

Function Type

Examples are at the Demonstration Programs Associated With:

Control action functions

Chapters 7, 14, 17, and 21.

Event filter functions

Chapters 4, 8, 14, and 21.

Apple event handling functions

Chapters 10, 18, and 26.

Key filter functions

Chapter 14.

Edit text validation functions

Chapter 14.

User pane drawing functions

Chapters 14 and 21.

User pane activate functions

Chapter 14.

Carbon event handlers

Chapters 17 to 26.

Carbon event timers

Chapter 17, 18, 21, 23, and 26.

Navigation Services event handlers

Chapter 18, 21, 23, and 26.

TextEdit click loop functions

Chapter 21.

List search functions

Chapter 22.

List definition functions

Chapter 22.

Device loop drawing functions

Chapter 25.

Universal Procedure Pointers and Carbon

Carbon supports universal procedure pointers transparently. By using the system-supplied universal procedure pointer functions, your application will operate correctly in both the Mac OS 8/9 and Mac OS X environments.

On Mac OS 8/9, the universal procedure pointer creation functions allocate routine descriptors in memory just as you would expect. On Mac OS X, the implementation of universal procedure pointers depends on various factors, including the object file format you choose. Universal procedure pointers will allocate memory if your application is compiled as a CFM binary, but are likely to return a simple procedure pointer if your application is compiled as a Mach-O binary. (All demonstration programs in this book are compiled as CFM binaries so that they will run on both Mac OS 8/9 and Mac OS X. Mach-O binaries only run on Mac OS X.)

In Carbon, routine descriptors must be disposed of using the specific disposal function associated with the creation function. For example, routine descriptors created with NewControlActionUPP must be disposed of using DisposeControlActionUPP. The generic disposal function DisposeRoutineDescriptor is not supported in Carbon.

Creation/Disposal Functions Relevant to Demonstration Programs

Creating Routine Descriptors

ControlActionUPP             NewControlActionUPP(ControlActionProcPtr userRoutine);
ModalFilterUPP               NewModalFilterUPP(ModalFilterProcPtr userRoutine);
AEEventHandlerUPP            NewAEEventHandlerUPP(AEEventHandlerProcPtr userRoutine);
ControlKeyFilterUPP          NewControlKeyFilterUPP(ControlKeyFilterProcPtr userRoutine);
ControlEditTextValidationUPP NewControlEditTextValidationUPP(ControlEditTextValidationProcPtr
                             userRoutine);
ControlUserPaneDrawUPP       NewControlUserPaneDrawUPP(ControlUserPaneDrawProcPtr
                             userRoutine);
ControlUserPaneActivateUPP   NewControlUserPaneActivateUPP(ControlUserPaneActivateProcPtr
                             userRoutine);
TEClickLoopUPP               NewTEClickLoopUPP(TEClickLoopProcPtr userRoutine);
ListSearchUPP                NewListSearchUPP(ListSearchProcPtr userRoutine);
ListDefUPP                   NewListDefUPP(ListDefProcPtr  userRoutine);
DeviceLoopDrawingUPP         NewDeviceLoopDrawingUPP(DeviceLoopDrawingProcPtr userRoutine);

Disposing of Routine Descriptors

void  DisposeControlActionUPP(ControlActionUPP userUPP);
void  DisposeModalFilterUPP(ModalFilterUPP userUPP);
void  DisposeAEEventHandlerUPP(AEEventHandlerUPP userUPP);
void  DisposeControlKeyFilterUPP(ControlKeyFilterUPP userUPP);
void  DisposeControlEditTextValidationUPP(ControlEditTextValidationUPP userUPP);
void  DisposeControlUserPaneDrawUPP(ControlUserPaneDrawUPP userUPP);
void  DisposeControlUserPaneActivateUPP(ControlUserPaneActivateUPP userUPP);
void  DisposeTEClickLoopUPP(TEClickLoopUPP userUPP);
void  DisposeListSearchUPP(ListSearchUPP userUPP);
void  DisposeListDefUPP(ListDefUPP userUPP);
void  DisposeDeviceLoopDrawingUPP(DeviceLoopDrawingUPP userUPP);

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Ember 1.8.3 - Versatile digital scrapboo...
Ember (formerly LittleSnapper) is your digital scrapbook of things that inspire you: websites, photos, apps or other things. Just drag in images that you want to keep, organize them into relevant... Read more
Apple iTunes 12.1 - Manage your music, m...
Apple iTunes lets you organize and play digital music and video on your computer. It can automatically download new music, app, and book purchases across all your devices and computers. And it's a... Read more
LibreOffice 4.4.3 - Free, open-source of...
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
FoldersSynchronizer 4.2.1 - Synchronize...
FoldersSynchronizer is a popular and useful utility that synchronizes and backs-up files, folders, disks and boot disks. On each session you can apply special options like Timers, Multiple Folders,... Read more
Simon 4.0.2 - Monitor changes and crashe...
Simon monitors websites and alerts you of crashes and changes. Select pages to monitor, choose your alert options, and customize your settings. Simon does the rest. Keep a watchful eye on your... Read more
Cocktail 8.1.2 - 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
Cyberduck 4.6.4 - FTP and SFTP browser....
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Herald 5.0.2 - Notification plugin for M...
Note: Versions 2.1.3 (for OS X 10.7), 3.0.6 (for OS X 10.8), and 4.0.8 (for OS X 10.9) are no longer supported by the developer. Herald is a notification plugin for Mail.app, Apple's Mac OS X email... Read more
DEVONthink Pro 2.8.3 - Knowledge base, i...
Save 10% with our exclusive coupon code: MACUPDATE10 DEVONthink Pro is your essential assistant for today's world, where almost everything is digital. From shopping receipts to important research... Read more
Boom 2 1.0.1 - System-wide pro audio app...
Boom 2 is a system-wide volume booster and equalizer app that is designed especially for OS X 10.10 Yosemite. It comes with a smart interface, self-calibrates itself according to your Mac, offers... Read more

Playworld Superheroes Review
Playworld Superheroes Review By Tre Lawrence on January 30th, 2015 Our Rating: :: HERO CRAFTINGUniversal App - Designed for iPhone and iPad It’s all about the imagination, fighting bad creatures — and looking good while doing so.   | Read more »
Join the SpongeBob Bubble Party in this...
Join the SpongeBob Bubble Party in this New Match 3 Bubble Poppin’ Frenzy Posted by Jessica Fisher on January 30th, 2015 [ permalink ] | Read more »
Handpick Review
Handpick Review By Jennifer Allen on January 30th, 2015 Our Rating: :: TANTALIZING SUGGESTIONSiPhone App - Designed for the iPhone, compatible with the iPad Handpick will make you hungry, as well as inspire you to cook something... | Read more »
Storm the Halls of Echo Base in First St...
Storm the Halls of Echo Base in First Star Wars: Galactic Defense Event Posted by Jessica Fisher on January 30th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Contradiction Review
Contradiction Review By Tre Lawrence on January 30th, 2015 Our Rating: :: SPOT THE LIEiPad Only App - Designed for the iPad Contradiction is a live action point and click adventure that’s pretty engaging.   Developer: Tim Follin... | Read more »
Unlock Sunshine Girl in Ironkill with th...
Unlock Sunshine Girl in Ironkill with this special 148Apps code Posted by Rob Rich on January 29th, 2015 [ permalink ] Robo-fighter Ironkill has been out on iOS a | Read more »
Crossroad Zombies Review
Crossroad Zombies Review By Jordan Minor on January 29th, 2015 Our Rating: :: CROSSWALKING DEADiPad Only App - Designed for the iPad Crossroad Zombies is a rough draft of a cool genre mash-up.   | Read more »
Blood Brothers 2 – Tips, Cheats, and Str...
War is hell: Is it the kind of hell you want to check out? Read our Blood Brothers 2 review to find out! Blood Brothers 2, DeNA’s follow-up to the original Blood Brothers, is an intriguing card collecting / role-playing / strategy hybrid. There’s... | Read more »
Blood Brothers 2 Review
Blood Brothers 2 Review By Nadia Oxford on January 29th, 2015 Our Rating: :: AN AGGRAVATING RELATIVEUniversal App - Designed for iPhone and iPad Blood Brothers 2 is built on a simple, solid foundation, but its free-to-play system... | Read more »
I AM BREAD, the Toast of the Town, is Ro...
Have you ever dreamt of being deliciously gluten-y? Do you feel passionate about Rye and Wheat? The guys at Bossa Studios do and that is why they are bringing I AM BREAD to iOS soon. The loafy app will feature all the new content that is being... | Read more »

Price Scanner via MacPrices.net

Intel Aims to Transform Workplace With 5th-Ge...
Intel Corporation today announced the availability of its 5th generation Intel Core vPro processor family that provides cutting-edge features to enable a new and rapidly shifting workplace. To meet... Read more
iOS App Sharalike Introduces New Instant Smar...
Sharalike slideshow and photo management software for iOS, is making it easier than ever to create shareable meaningful moments with its new instant SmartShow technology. Staying organized is a goal... Read more
Apple Becomes World’s Largest Smartphone Vend...
According to the latest research data from Strategy Analytics, as global smartphone shipments grew 31 percent annually to reach a record 380 million units in the fourth quarter of 2014. Apple became... Read more
Cut the Cord: OtterBox Resurgence Power Case...
Dead batteries and broken phones are two of the biggest issues for smartphone users today. Otterbox addresses both with the new Resurgence Power Case for Apple iPhone 6, promising to make those panic... Read more
13-inch Retina MacBook Pros on sale for up to...
B&H Photo has 13″ Retina MacBook Pros on sale for $200 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.6GHz/128GB Retina MacBook Pro: $1199.99 save $100 - 13″ 2.6GHz/... Read more
15-inch 2.5GHz Retina MacBook Pro on sale for...
 B&H Photo has the 15″ 2.5GHz Retina MacBook Pro on sale for $2319.99 including free shipping plus NY sales tax only. Their price is $180 off MSRP, and it’s the lowest price available for this... Read more
Back in stock: Refurbished iPod nanos for $99...
The Apple Store has Apple Certified Refurbished 16GB iPod nanos available for $99 including free shipping and Apple’s standard one-year warranty. That’s $50 off the cost of new nanos. Most colors are... Read more
Apple lowers price on refurbished 256GB MacBo...
The Apple Store has lowered prices on Apple Certified Refurbished 2014 MacBook Airs with 256GB SSDs, now available for up to $200 off the cost of new models. An Apple one-year warranty is included... Read more
New Good Management Suite Simplifies Enterpri...
Good Technology has announced the availability of the Good Management Suite, a comprehensive cross-platform solution for organizations getting started with mobile business initiatives. Built on the... Read more
15-inch 2.0GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished previous-generation 15″ 2.0GHz Retina MacBook Pros available for $1489 including free shipping plus Apple’s standard one-year warranty. Their price is... Read more

Jobs Board

*Apple* Solutions Consultant- Retail Sales (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Event Director, *Apple* Retail Marketing -...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global engagement strategy and team. Delivering an overarching brand Read more
At-Home Chat Specialist- *Apple* Online Stor...
**Job Summary** At Apple , we believe in hard work, a fun environment, and the kind of creativity and innovation that only comes about when talented people from diverse Read more
SW QA Engineer - *Apple* TV - Apple (United...
**Job Summary** The Apple TV team is looking for experienced Quality Assurance Engineers with a passion for delivering first in class home entertainment solutions. **Key Read more
*Apple* Retail - Multiple Positions(US) - Ap...
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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.