TweetFollow Us on Twitter

Updating Navigation

Volume Number: 16 (2000)
Issue Number: 6
Column Tag: Navigation Services

Updating Navigation Services Sample Code

by Thurman Gillespy III, M.D.

On the Road to Carbon Compliance

Introduction

A recent project gave me an excuse to delve seriously into the Navigation Services (NavServices) SDK for the first time. The SDK includes three example projects (Sampler, StExample, and SimpleText) that illustrate the NavServices API. During routine debugging of my code, however, I discovered multiple "write-to-nil" bugs that had originated in the example projects. This article describes the steps you need to fix those errors and to update the projects to work with CodeWarrior Pro 5 and Universal Headers 3.3. For a pointer to the NavServices SDK, see the References section at the end of this article.

Sampler

Sampler is a small C program that demonstrates to use the NavServices API in a document-based application. It uses NavServices functions to elicit files from the user, save files, and prompt the user to save or discard changes to a document. It also shows how to use NavServices functions to let the user choose a folder, volume, or file-system object. Sampler is a very good place to start learning how to use NavServices. So let's make Sampler usable!

Update Access Paths

In the Access Paths panel of the Sampler.PPC Settings dialog box, remove the 'Shared Libraries' and 'Cincludes' paths from the User Paths list. They are not needed. Then change the System Paths to:

{Compiler}:MacOS Support:
{Compiler}:MSL:

Save the changes to this panel by clicking the Save button.

Implied Int No Longer Allowed

In Templates.c, there is an implied return value of type int to the main function that is no longer legal in C++. Change:

main()

to:

int main(void)

Runtime Library Changes

Change the MWCRuntime.lib library (which is no longer present) to MSL RuntimePPC.Lib.

Add a Header File

Universal Headers 3.3 include the new header file ControlDefinitions.h, which contains some constants previously defined in the file Controls.h. So add the following lines to the file Common.h:

#ifndef __CONTROLDEFINITIONS__
#include <ControlDefinitions.h>
#endif

NavCBRec Field Change

Somewhere between "then and now", the fields in the NavCBRec structure changed. In file.c and menu.c, there are a total of 10 NavCBRecPtr variables to update. Change:

callBackParms->eventData.event

to:

callBackParms->eventData.eventDataParms.event

Duplicate cfrg Resource

A 'cfrg' resource is defined in TemplatePPC.r. This definition is no longer needed because the CodeWarrior IDE now generates the correct resource. I simply commented out the definition in TemplatePPC.r.

/*
resource 'cfrg' (0) {
	{
	kPowerPC,
	kFullLib,
	kNoVersionNum,kNoVersionNum,
	0,0,
	kIsApp,kOnDiskFlat,kZeroOffset,kWholeFork,
	"Template"
	}
};
*/

AEGetDescData Write-to-nil Errors

AEGetDescData (defined in Common.c) is a utility function that extracts a DescType of type typeCode from the AEDesc. In Sampler, it is used to extract an FSSpec from the AEDesc. Listing 1 shows the original function.

Listing 1: Getting data from an AEDesc structure (before)

AEGetDescData

OSErr AEGetDescData(const AEDesc *desc, DescType *typeCode,
				void *dataBuffer, ByteCount maximumSize,
				ByteCount *actualSize)
{
	*typeCode = desc->descriptorType;
	Handle h = (Handle)desc->dataHandle;
	ByteCount dataSize = GetHandleSize(h);
	if (dataSize > maximumSize)
		*actualSize = maximumSize;
	else
		*actualSize = dataSize;
	BlockMoveData(*h, dataBuffer, *actualSize);
	return noErr;
}

The function is acceptable, except for a complete lack of any error checking (a common practice in developer example code). However, AEGetDescData is called 10 times with two NULL pointers (menus.c).

if ((theErr = AEGetDescData ( &resultDesc, NULL,
		&finalFSSpec, sizeof ( FSSpec ), NULL )) == noErr)...

This code fragment results in two writes to nil (typeCode and actualSize) and one read from nil (BlockMoveData). Bad form, indeed. For a fix, I simply check for the NULL parameters; I also added a few other error checks for good measure, as shown in Listing 2.

Listing 1: Getting data from an AEDesc structure (after)

AEGetDescData
OSErr AEGetDescData(const AEDesc *desc, DescType *typeCode,
				void *dataBuffer, ByteCount maximumSize,
				ByteCount *actualSize)
{
	Handle		h = NULL;
	ByteCount	dataSize = 0,
						bytesToCopy = 0;
	OSErr			err = -1;
	
	// check for invalid NULL handles or pointers
	if (desc == NULL || desc->dataHandle == NULL ||
			dataBuffer == NULL)
		return nilHandleErr;
	
	// get the size of the object, check for errors
	h = (Handle)desc->dataHandle;
	dataSize = GetHandleSize(h);
	err = MemError();
	if (err != noErr)
		return err;
	
	// determine how many bytes to copy
	if (dataSize > maximumSize)
		bytesToCopy = maximumSize;
	else
		bytesToCopy = dataSize;

	// copy object from the handle to the buffer
	BlockMoveData(*h, dataBuffer, bytesToCopy);

	// return type code and number of bytes copied,
	// if pointers are not NULL
	if (typeCode != NULL)
		*typeCode = desc->descriptorType;
	if (actualSize != NULL)
		*actualSize = bytesToCopy;
	
	return noErr;
}

AEGetNthDesc Write-to-nil Errors

In Sampler, AEGetNthDesc writes to nil 11 times (files.c, menus.c) because the fourth parameter, a pointer to an AEKeyword structure, is set to NULL.

AEGetNthDesc(&(theReply.selection), index, typeFSS, NULL,
						&resultDesc)

To correct this error, simply add an appropriate AEKeyword parameter.

AEKeyword  aekw; // not used
AEGetNthDesc(&(theReply.selection), index, typeFSS, &aekw,
						&resultDesc)

Sampler CFM68k

For the Sampler.68kCFM project, make the same changes to the access paths, then update the obsolete libraries to the correct versions.

MathLibCFM68k(4i/8d).Lib			==>		MathLibCFM68k (4i_8d).Lib
MSL C.CFM68kFar(4i/8d).Lib		==>		MSL C.CFM68kFa(4i_8d).Lib
MWCFM68kRuntime.Lib					==>		MSL MWCFM68kRuntime.Lib

StExample

The StExample project is a C++ example of using NavServices that is less complete than Sampler. The StExample project is also easier to update.

  • Update the User Paths as you did for Sampler.
  • Update the Navigation library to NavigationLib.
  • In HelloWorld.cp, the last parameter to StNavGetFile must be changed from long to (void *). Change:
StNavGetFile gf1( &err, &specs, &numspecs, &rdopen,
							&navreply, false, true, &rdevt, nil,
							nil, tlh, 0xaabbccdd);

to

UInt32	usrDat = 0xaabbccdd;
StNavGetFile  gf1( &err, &specs, &numspecs, &rdopen,
								&navreply, false, true, &rdevt, nil,
								nil, tlh, (void *)&usrDat );
  • There are two write-to-nil errors, both in StNavServices.cp. Change the NULL fourth parameter in the call to AEGetNthDesc to a valid AEKeyword pointer.

SimpleText

The SimpleText project uses the obsolete QuickDrawGX, and a dated MacIncludes.h header. I decided it wasn't worth the effort to update the project.

Checking the Result

To see the write-to-nil errors, drop into Macsbug and invoke the EBBE (Even Better Bus Error) dcmd.

EBBE on
EBBE is ON (using the value $68F168F1 with a task rate of
	#17 milliseconds)

Then run the unaltered Sampler application as delivered in the SDK. You should see one or more write-to-nil errors in every call to NavServices. Both QC and Spotlight (Onyx Technology) will also catch the errors.

The EBBE dcmd has detected that location $0000
	has been overwritten

After making the corrections described here, run this test again on the compiled example applications and on any of your code based on the SDK sample code. The write-to-nil errors should be eliminated.

References

Navigation Services SDK
<http://developer.apple.com/sdk/index.html>
Onyx Technology
<http://www.onyx-tech.com/>


Thurman Gillespy III is a radiologist at the Veterans Administration Puget Sound Health Care System in Seattle, Washington. He can be reached at tg3@u.washington.edu

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Affinity Designer 1.5.5 - Vector graphic...
Affinity Designer is an incredibly accurate vector illustrator that feels fast and at home in the hands of creative professionals. It intuitively combines rock solid and crisp vector art with... Read more
djay Pro 1.4.3 - Transform your Mac into...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Jamf Pro 9.98 - Powerful sysadmin/enterp...
Jamf Pro (formerly Casper Suite) is the EMM tool that delights IT pros and the users they support by delivering on the promise of unified endpoint management for Apple devices. At Jamf, connecting... Read more
Airmail 3.2.4 - Powerful, minimal email...
Airmail is an mail client with fast performance and intuitive interaction. Support for iCloud, MS Exchange, Gmail, Google Apps, IMAP, POP3, Yahoo!, AOL, Outlook.com, Live.com. Airmail was designed... Read more
RapidWeaver 7.3.1 - Create template-base...
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
PopChar 7.7 - $16.99 (51% off)
PopChar helps you get the most out of your font collection. With its crystal-clear interface, PopChar provides a frustration-free way to access any font's special characters. Features Expanded... Read more
Apple iTunes 12.6 - Play Apple Music and...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
MacPilot 9.0.6 - Enable over 1,200 hidde...
MacPilot gives you the power of UNIX and the simplicity of Macintosh, which means a phenomenal amount of untapped power in your hands! Use MacPilot to unlock over 1,200 features, and access them all... Read more
Sparkle Pro 2.1.4 - $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
TextSoap 8.3.3 - Automate tedious text d...
TextSoap can automatically remove unwanted characters, fix up messed up carriage returns, and do pretty much anything else that we can think of to text. Save time and effort. Be more productive. Stop... Read more

Failbetter Games details changes coming...
Sunless Sea, Failbetter Games' dark and gloomy sea explorer, sets sail for the iPad tomorrow. Ahead of the game's launch, Failbetter took to Twitter to discuss what will be different in the mobile version of the game. Many of the changes make... | Read more »
Splish, splash! The Pokémon GO Water Fes...
Niantic is back with a new festival for dedicated Pokémon GO collectors. The Water Festival officially kicks off today at 1 P.M. PDT and runs through March 29. Magikarp, Squirtle, Totodile, and their assorted evolved forms will be appearing at... | Read more »
Death Road to Canada (Games)
Death Road to Canada 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: Get it now at the low launch price! Price will go up a dollar every major update. Update news at the bottom of this... | Read more »
Bean's Quest Beginner's Guide:...
Bean's Quest is a new take on both the classic platformer and the endless runner, and it's free on the App Store for the time being. Instead of running constantly, you can't stop jumping. That adds a surprising new level of challenge to the game... | Read more »
How to rake in the cash in Bit City
Our last Bit City guide covered the basics. Now it's time to get into some of the more advanced techniques. In the later cities, cash flow becomes much more difficult, so you'll want to develop some strategies if you want to complete each level.... | Read more »
PixelTerra (Games)
PixelTerra 1.1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1.1 (iTunes) Description: The world of PixelTerra is quite dangerous so you need to build a shelter, find some food supply and get ready to protect... | Read more »
Tokaido™ (Games)
Tokaido™ 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Discover the digital adaptation of Tokaido, the boardgame phenomenon that has already sold more than 250,000 copies worldwide, and... | Read more »
Card Thief (Games)
Card Thief 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Card Thief is a solitaire style stealth game played with a deck of cards. In Card Thief you move through a deck of cards as a... | Read more »
Smilegate’s crafting battler Super Tank...
Super Tank Rumbleputs you in the seat of your very own, handcrafted tank. You can choose from over 100 different parts to create your Super Tank before taking it out to wreak havoc on your opponents in glorious PVP combat. Now, Smilegate is upping... | Read more »
The best games to play while you wait fo...
Mass Effect: Andromeda arrives this coming Tuesday and people are getting understandably antsy. There's a whole weekend standing between us and a brand new Bioware adventure. What's a geek to do? Well, you could certainly give these fine mobile... | Read more »

Price Scanner via MacPrices.net

13-inch Touch Bar MacBook Pros on sale for up...
B&H Photo has the Apple 13″ Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.9GHz/512GB Touch Bar... Read more
Today only! 15-inch 2.7GHz Space Gray Touch B...
B&H Photo has the new 2016 15″ 2.7GHz Space Gray Apple Touch Bar MacBook Pro in stock today and on sale for $300 off MSRP for today only. Shipping is free, and B&H charges NY sales tax only... Read more
New $329 iPad A Fabulous Value; 10.5-Inch iPa...
Part of the iPad upgrade/new model puzzle is now in place. Yesterday, as KGI Securities financial services group analyst Ming-Chi Kuo last summer predicted they would, Apple released a new low-cost 9... Read more
New 9.7-Inch iPad Features All Of The Fun...
Apple today updated its most popular-sized iPad, featuring a brighter 9.7-inch Retina display and best-in-class performance at its most affordable price ever, starting at $329 (US) with 32GB of... Read more
Apple Introduces iPhone 7 and iPhone 7 Plus (...
Apple today announced iPhone 7 and iPhone 7 Plus (PRODUCT)RED Special Edition in a vibrant red matte aluminum finish, in recognition of more than 10 years of partnership between Apple and (RED). This... Read more
Apple now offering Certified Refurbished 15-i...
Apple is now offering Certified Refurbished 2016 15″ Touch Bar MacBook Pros for $360-$420 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2.6GHz... Read more
Apple Introduces Clips: A Free Innovative Way...
Apple today introduced Clips, a new app that makes it quick and fun for anyone to create expressive videos on iPhone and iPad. The app features a unique design for combining video clips, photos and... Read more
Urban Armor Gear Unveils Case For 4th Generat...
Orange County, California based Urban Armor Gear (UAG), designers of rugged, lightweight protective cases for phones, tablets and laptops, has released its latest drop-tested cases for Apple’s 4th... Read more
Most Users Continue To Prefer 5.0 to 5.3 Inch...
In the first half of 2016, US and UK smartphone users were most likely to be interested in purchasing a device with a 5.3″ or 5.0″ display. Findings in a new report from the User Experience... Read more
12-inch 1.2GHz Retina MacBooks on sale for up...
B&H has 12″ 1.2GHz Retina MacBooks on sale for up to $200 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 12″ 1.2GHz Space Gray Retina MacBook: $1439.99 $160 off MSRP - 12″ 1... Read more

Jobs Board

*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
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
Starte Dein Karriere-Abenteuer in den Hauptst...
…mehrsprachigen Teams betreust Du Kunden von bekannten globale Marken wie Apple , Mercedes, Facebook, Expedia, und vielen anderen! Funktion Du wolltest schon Read more
Starte Dein Karriere-Abenteuer in den Hauptst...
…mehrsprachigen Teams betreust Du Kunden von bekannten globale Marken wie Apple , Mercedes, Facebook, Expedia, und vielen anderen! Funktion Du wolltest schon 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.