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

VOX 2.8.30 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
Default Folder X 5.1.6b3 - Enhances Open...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
CleanMyMac 3.8.6 - $39.95
CleanMyMac makes space for the things you love. Sporting a range of ingenious new features, CleanMyMac lets you safely and intelligently scan and clean your entire system, delete large, unused files... Read more
Postbox 5.0.17 - Powerful and flexible e...
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
Amazon Chime 4.6.5852 - Amazon-based com...
Amazon Chime is a communications service that transforms online meetings with a secure, easy-to-use application that you can trust. Amazon Chime works seamlessly across your devices so that you can... Read more
coconutBattery 3.6.3 - Displays info abo...
With coconutBattery you're always aware of your current battery health. It shows you live information about your battery such as how often it was charged and how is the current maximum capacity in... Read more
VueScan 9.5.82 - 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
Thunderbird 52.3.0 - Email client from M...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
Little Snitch 4.0.2 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 52.3.0 - Email client from M...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more

The best games we played this week - Aug...
Another busy week has come to a close. We played a lot of excellent games this week and now it's time to look back and reflect on some our favorites. Here are our picks for the week of August 18. [Read more] | Read more »
War Wings beginner's guide - how to...
War Wings is the newest project from well-established game maker Miniclip. It's a World War II aerial dogfighting game with loads of different airplane models to unlock and battle. The game offers plenty of single player and multiplayer action. We... | Read more »
How to win every 2v2 battle in Clash Roy...
2v2 is coming back to Clash Royale in a big way. Although it's only been available for temporary periods of time, 2v2 has seen a hugely positive fan response, with players clamoring for more team-based gameplay. Soon we'll get yet another taste of... | Read more »
Roll to Win with Game of Dice’s new upda...
Joycity’s hit Game of Dice gets a big new update this week, introducing new maps, mechanics, and even costumes. The update sets players loose on an exciting new map, The Cursed Tower, that allows folks to use special Runes mid-match. If you feel... | Read more »
Bottom of the 9th (Games)
Bottom of the 9th 1.0.1 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: Play the most exciting moment of baseball in this fast-paced dice and card game! | Read more »
The best apps for viewing the solar ecli...
If you somehow missed the news, many parts of the United States will be witness to a total solar eclipse on August 21 for the first time in over 90 years. It'll be possible to see the eclipse in at least some capacity throughout the continental U... | Read more »
The 5 best mobile survival games
Games like ARK: Survival Evolved and Conan Exiles have taken the world of gaming by storm. The market is now flooded with hardcore survival games that send players off into the game's world with nothing but maybe the clothes on their back. Never... | Read more »
Portal Walk (Games)
Portal Walk 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Portal Walk is adventure and relaxing platform game about Eugene. Eugene stuck between worlds and trying to find way back home.... | Read more »
Technobabylon (Games)
Technobabylon 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: City of Newton, 2087. Genetic engineering is the norm, the addictive Trance has replaced almost any need for human interaction,... | Read more »
5 reasons why 2v2 is the best mode in Cl...
Supercell has been teasing fans with 2v2 windows that allow players to team up for limited periods of time. The Summer of 2v2 was just this past July, but players are already clamoring for more of that sweet, sweet team-based action. The fans have... | Read more »

Price Scanner via MacPrices.net

Weekend sale: 13-inch MacBook Pros for up to...
Amazon has new 2017 13″ MacBook Pros on sale today for up to $200 off MSRP, each including free shipping: – 13″ 3.1GHz/256GB Space Gray MacBook Pro (MPXV2LL/A): $1599.99 $200 off MSRP – 13″ 3.1GHz/... Read more
Back To School With The Edge Desk All-in-one...
Back to school is just around the corner, and the ergonomically correct Edge Desk all-in-one portable kneeling desk is ideal for students living in dorms and small apartments, Edge Desk features:... Read more
Norton Core Secure Wi-Fi Router Now Available...
First introduced at the 2017 Consumer Electronics Show (CES), Norton Core, a secure, high-performance Wi-Fi router, fundamentally changed the concept of Wi-Fi routers by making security the primary... Read more
ViewSonic Adds New 27-inch 4K UHD Monitor to...
ViewSonic Corp. has introduced the VP2785-4K, a 27-inch 4K UHD (3840×2160) monitor that delivers precise and consistent color representation and performance to ensure incredible image quality. Built... Read more
Apple now offering Certified Refurbished 2017...
Apple is now offering Certified Refurbished 2017 27″ iMacs for up to $350 off original MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: – 27″ 3.... Read more
13-inch 2.3GHz MacBook Pros on sale for $100...
Amazon has the new 2017 13″ 2.3GHz MacBook Pros on sale today for $100 off MSRP, each including free shipping: – 13″ 2.3GHz/128GB Space Gray MacBook Pro (MPXQ2LL/A): $1199.99 $100 off MSRP – 13″ 2.... Read more
Clearance 2016 13-inch MacBook Airs available...
B&H Photo has clearance 2016 13″ MacBook Airs available for up to $200 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: – 13″ 1.6GHz/128GB MacBook Air (MMGF2LL... Read more
Clearance 21-inch and 27-inch iMacs available...
B&H Photo has clearance 21″ and 27″ Apple iMacs available for up to $500 off original MSRP, each including free shipping plus NY & NJ sales tax only: – 27″ 3.3GHz iMac 5K: $1799 $500 off... Read more
New iOS 11 Productivity Features Welcome But...
The iOS community is in late summer holding mode awaiting the September arrival of the iPhone 8 and iOS 11. iOS 11 public betas have been available for months — number six was released this week —... Read more
Samsung Electronics Launches New Portable SSD...
Samsung Electronics America, Inc. has announced the launch of Samsung Portable SSD T5 – its newest portable solid state drive (PSSD) that raises the bar for the performance of external memory... Read more

Jobs Board

Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Frameworks Engineering Manager, *Apple* Wat...
Frameworks Engineering Manager, Apple Watch Job Number: 41632321 Santa Clara Valley, California, United States Posted: Jun. 15, 2017 Weekly Hours: 40.00 Job Summary Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Frameworks Engineering Manager, *Apple* Wat...
Frameworks Engineering Manager, Apple Watch Job Number: 41632321 Santa Clara Valley, California, United States Posted: Jun. 15, 2017 Weekly Hours: 40.00 Job Summary Read more
Business Development Manager - *Apple* Medi...
Job Summary Apple Music is a single, intuitive app that...- all in one place. You can stream any Apple Music song, playlist or album, and download it Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.