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

Together 3.7 - Store and organize all of...
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
EtreCheck 3.1.4 - For troubleshooting yo...
EtreCheck is an app that displays the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to... Read more
Postbox 5.0.9 - Powerful and flexible em...
Postbox is a new email application that helps you organize your work life and get stuff done. It has all the elegance and simplicity of Apple Mail, but with more power and flexibility to manage even... Read more
DiskCatalogMaker 6.5.16 - Catalog your d...
DiskCatalogMaker is a simple disk management tool which catalogs disks. Simple, light-weight, and fast. Finder-like intuitive look and feel. Super-fast search algorithm. Can compress catalog data... Read more
TrailRunner 3.8.827 - Route planning for...
TrailRunner is the perfect companion for runners, bikers, hikers, and all people wandering under the sky. Plan routes on a geographical map. Import GPS or workout recordings and journalize your... Read more
VueScan 9.5.61 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Postbox 5.0.9 - Powerful and flexible em...
Postbox is a new email application that helps you organize your work life and get stuff done. It has all the elegance and simplicity of Apple Mail, but with more power and flexibility to manage even... Read more
VueScan 9.5.61 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
DiskCatalogMaker 6.5.16 - Catalog your d...
DiskCatalogMaker is a simple disk management tool which catalogs disks. Simple, light-weight, and fast. Finder-like intuitive look and feel. Super-fast search algorithm. Can compress catalog data... Read more
TrailRunner 3.8.827 - Route planning for...
TrailRunner is the perfect companion for runners, bikers, hikers, and all people wandering under the sky. Plan routes on a geographical map. Import GPS or workout recordings and journalize your... Read more

Latest Forum Discussions

See All

Amateur Surgeon 4 Guide: Become the worl...
It's time to wield your trusty pizza cutter again, as Amateur Surgeon has returned with a whole fresh set of challenges (and some old, familiar ones, too). Starting anew isn't easy, especially when all you have at your disposal is a lighter, the... | Read more »
Le Parker: Sous Chef Extraordinaire (Ga...
Le Parker: Sous Chef Extraordinaire 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »
Telltale Games really is working on a Gu...
Telltale Games' next episodic adventure is indeed Guardians of the Galaxy. A document tied to the voice actors strike suggested that the project was in the work, but now we have direct confirmation following an announcement at the Game Awards that... | Read more »
Amateur Surgeon returns to iOS and Andro...
Amateur Surgeon and its two sequels disappeared from the App Store some time and it was sad days for all. But now, just in time for the holidays, the Adult Swim favorite makes its joyous return in the shape of Amateur Surgeon 4, a remake with... | Read more »
The best board games on mobile
Sometimes you need to ditch all of the high speed, high action games in favor of something a little more traditional. If you don't feel like parting ways from your mobile device, though, there are still plenty of ways to get that old-school fix.... | Read more »
The best Facebook Messenger Instant Game...
Facebook's new Instant Games is now here, meaning you can play games with your friends directly via Facebook. It's a fun new way to connect with friends, of course, but it's also proving to be a solid gaming experience in its own right, with a... | Read more »
You can now play game's on Facebook...
Facebook launched its new Instant Games platform in an exciting new attempt to engage its user base. As a result, you can now play a number of different games directly through Facebook Messenger. All of these games run with HTML5, meaning you play... | Read more »
Apollo Justice Ace Attorney (Games)
Apollo Justice Ace Attorney 1.00.00 Device: iOS Universal Category: Games Price: $.99, Version: 1.00.00 (iTunes) Description: Court Is Back In Session Star as rookie defense attorney, Apollo Justice, as he visits crime scenes,... | Read more »
KORG iWAVESTATION (Music)
KORG iWAVESTATION 1.0 Device: iOS Universal Category: Music Price: $19.99, Version: 1.0 (iTunes) Description: A revolutionary new world of sound.The Wave Sequence Synthesizer for iPad - KORG iWAVESTATION | Read more »
Don't Grind Guide: Tips for becomin...
Don’t Grind is a surprising, derpy little one touch game with fun hand-drawn graphics. The goal is simple -- get the high score without being chopped to bits. That can be tough when you’re not used to the game, and that’s compounded by the fact... | Read more »

Price Scanner via MacPrices.net

Monday roundup of Holiday Mac sales: Up to $3...
Take up to $300 off MSRP on the price of a new Apple Mac at B&H Photo today as part of their Holiday sale. Shipping is free, and B&H charges NY sales tax only. Touch Bar MacBook Pros are in... Read more
12-inch WiFi Apple iPad Pros on sale for up t...
B&H Photo has 12″ WiFi Apple iPad Pros on sale for up to $50 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50 off MSRP... Read more
9-inch Apple WiFi iPad Pros on sale for $20-$...
B&H Photo has 9.7″ Apple WiFi iPad Pros on sale for $20-$50 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 9″ Space Gray 256GB WiFi iPad Pro: $779.95 $20 off MSRP... Read more
Holiday sale: Apple MacBook Airs available fo...
B&H Photo has 13″ MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/128GB MacBook Air (MMGF2LL/A): $899 $100 off MSRP - 13″ 1.6GHz/... Read more
13-inch Silver Touch Bar MacBook Pro in stock...
Amazon has the new 2016 13″ 2.9GHz/256GB Silver Touch Bar MacBook Pro (MLVP2LL/A) in stock today and on sale for $1749 including free shipping. That’s $50 off MSRP, and it’s the lowest price... Read more
Parallels Toolbox 1.3 for Mac Offers 25 Singl...
Parallels has launched Parallels Toolbox 1.3 for Mac, an upgrade that adds five new utilities to the stand-alone application which was released in August and is available exclusively online at http... Read more
OWC Mercury Elite Pro Dual mini Ultra-Portabl...
OWC has introduced the new OWC Mercury Elite Pro Dual mini, a powerful yet ultra-portable dual-drive RAID solution. The new Mercury Elite Pro Dual mini packs phenomenal performance into a small... Read more
Clearance 13-inch Retina MacBook Pros availab...
B&H Photo has clearance 2015 13″ Retina Apple MacBook Pros available for up to $200 off original MSRP. Shipping is free, and B&H charges NY tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro: $... Read more
Roundup of 2016 13-inch 2.0GHz MacBook Pro sa...
B&H has the non-Touch Bar 13″ MacBook Pros in stock today for $50-$100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray (MLL42LL/A): $1449 $... Read more
New 13-inch 2.0GHz Space Gray MacBook Pro in...
Adorama has the new 13″ 2.0GHz Space Gray MacBook Pro (non-Touch Bar, MLL42LL/A) in stock for $1499 including a free 3-year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax... Read more

Jobs Board

*Apple* Retail - Multiple Positions- Kansas...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions- Chicago...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Hardware Design Validation Engineer - *Apple...
The Apple Watch team is looking for a Hardware Design Validation Engineer. This person will be part of the Apple Watch hardware team with responsibilities for Read more
SW Engineer *Apple* TV Frameworks - Apple I...
The Apple TV team is looking for a software...create features that reflect the look and feel of Apple TV. Description: Were looking for someone who is Read more
*Apple* Retail - Multiple Positions- Greenwi...
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.