TweetFollow Us on Twitter

Jan 94 Tips
Volume Number:10
Issue Number:1
Column Tag:Tips & Tidbits

Tips & Tidbits

By Neil Ticktin, Editor-in-Chief

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

Tip Of The Month

The 6-byte Code Resource Stub Trick

Many Macintosh programmers who have debugged a CDEF, LDEF, MDEF, or WDEF know “the 6-byte code resource stub trick.” Its been covered in MacTech Magazine, and the wisdom is often passed along online.

To briefly summarize, instead of burying all the code inside a separate code resource where it can't see the structure of the main program (global variables and functions), the programmer creates a 6-byte code stub. In that stub is one MC68000 jump-absolute instruction (as hex in a resource: 4EF9 0000 0000). The programmer replaces the jump destination address (the trailing 32 bits of 0) at runtime with a function address, then informs the relevant Toolbox manager that it should use the resource to define a control, list, or window. (Using this trick with a menu is similar.) Since code is modified, it's always safest to flush the CPU's instruction cache to avoid confusing (read: crashing) it. Refer to the Apple DSC Technical Note "Cache As Cache Can" for the long story.

Now, instead of reading and understanding the tech note and including relevant compensations in your code, you can use a different code resource stub. This stub still includes the function address, but it uses MC68000 instructions to retrieve the address as data, avoiding the code modification problem. In hex: 2F3A 0004 4E75 0000 0000. The 32 bits of zero are again the address you replace with a function address. A disassembly might read:

/* 1 */
MOVE.L  *+$0006,-(A7); push the DC.L onto the stack for RTS
RTS; jump to the definition function
DC.L  0 ; placeholder for addr of defn function

Since the DC.L never actually runs as code, there's no risk of confusing the cache in the CPU. You can use the following C structure declaration to access the address:

/* 2 */
typedef struct
{
 short  push [2], rts;
 void *addr;
}
tCodeStub, *tCodeStubP, **tCodeStubH;

- Pete Gontier

Berkeley, CA

This column is your opportunity to spread the word about little bits of information that you find out about. These tidbits can be programming related or they can be user tips that are particularly useful to programmers.

MacTech Magazine will pay $25 for every tip used, and $50 for the Tip of the Month. Or you can take your award in orders or subscriptions.

To submit a tip, send in a letter to the magazine. E-mail is our preferred method, but feel free to send something via the US Mail. See page two for all addresses. If you do send snail mail, enclose a printed copy and a disk copy of the letter so that it does not have to be retyped.

Precomputing Static value in constants

The compiler is not always smart enough to precompute static values in your code. Static values are values that stay constant throughout the program and cannot be changed. By use of constants you can help to compile precomputed values. This saves time and space in your program.

For example, the compiler will generate code to compute the value of the next expression at runtime. The code will be larger and slower.

  someValue := 5 * 4 + anotherValue + 90;

But, if you use a constant to compute the static value in the above expression, the compiler will precompute the value and place it in your compiled object code. The code will be smaller and faster as a result. Change the above expression like this:

CONST
  kPrecomputedStaticValue = 5 * 4 + 90;

BEGIN
someValue := kPrecomputedStaticValue + 
       anotherValue;
(* Other code *)

- Marek Hajek

Incline Village, Nevada

Toggle Invisibles Part 2

I read Lee Rimar’s tip "Toggle Invisibles in MPW" in November, 1993 Tips & Tidbits column. I found Mr. Rimar's script useful, and I've modified it to avoid making assumptions about the auto-indent and lock-scroll options. The trick is to use "=~" to match a regular expression against the three-character result of Format, and extract the second character into the ®1 variable (see "help patterns" in MPW). (If you're running out of sensible Command-key combinations, you can use SetKey instead, in MPW 3.3, to set up a function key, keypad key, control key, or whatever.)

AddMenu Edit "Toggle Invisibles/¥" 
  '(evaluate "`Format "{active}" -x a`" =~ /?(?)®1?/ ) > Dev:Null ; 
  if {®1}=="i" ; 
    Format "{Active}" -a I ; 
  else ; 
    Format "{Active}" -a i ; 
  end'

- Dave Lyons

Apple Computer, Inc.

International system Tip

Attention all single-byte developers!! Your software is ugly on double-byte machines! (see screen shot) Why? Because any resource that contains an odd number of text characters has an extra character added to the end (the second byte). Here in Japan, quality is very important and having funky looking characters on every menu and dialog box certainly doesn't convey quality. So what to do?

1. Startup your Mac with a double-byte system disk (check any CD-ROMS you have from Apple for a Japanese "Disk Tools" image.) Don't worry if you can't read Japanese because the menu items and short-cut keys are the same.

2. Launch ResEdit and open your application's resources (also notice ResEdit has the extra characters too! A little sloppy for Apple.)

3. Simply open each of you application's resources and find the foreign characters and backspace over them. Be sure to check everything!! Buttons, dialogs, text strings, etc. If it has text, it is possible there is problems.

4. When your finished, launch your application (while still in Japanese mode) and verify that it looks and runs correctly.

5. Restart your system and you're back to where you were! (Warning: depending upon the version you use, your desktop may be rebuilt on restart)

Even if you don't officially sell your software in Japan, most titles are available as gray market imports (even though the package says in big letters "For Sale in The USA Only".) So take a few minutes to improve your reputation for quality!

- Brett Bibby

Tokyo, Japan

 
AAPL
$103.37
Apple Inc.
+0.90
MSFT
$44.68
Microsoft Corpora
-0.21
GOOG
$536.25
Google Inc.
+9.71

MacTech Search:
Community Search:

Software Updates via MacUpdate

Apple Security Update 2014-005 - For OS...
Apple Security Update is recommended for all users and improves the security of Mac OS X. For information on the security content of this update, please visit this website: http://support.apple.com/... Read more
EyeTV 3.6.6 - Watch and record TV on you...
EyeTV brings a rich TV experience to your Mac. Watch live TV on your Mac. Pause, rewind, and record whenever you want. EyeTV gives you powerful control over what you watch and how you watch it. Put... Read more
RapidWeaver 6.0 - Create template-based...
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
NTFS 12.0.39 - Provides full read and wr...
Paragon NTFS breaks down the barriers between Windows and OS X. Paragon NTFS effectively solves the communication problems between the Mac system and NTFS, providing full read and write access to... Read more
RestoreMeNot 2.0.3 - Disable window rest...
RestoreMeNot provides a simple way to disable the window restoration for individual applications so that you can fine-tune this behavior to suit your needs. Please note that RestoreMeNot is designed... Read more
Macgo Blu-ray Player 2.10.9.1750 - Blu-r...
Macgo Mac Blu-ray Player can bring you the most unforgettable Blu-ray experience on your Mac. Overview Macgo Mac Blu-ray Player can satisfy just about every need you could possibly have in a Blu-ray... Read more
Apple iOS 8.1 - The latest version of Ap...
The latest version of iOS can be downloaded through iTunes. Apple iOS 8 comes with big updates to apps you use every day, like Messages and Photos. A whole new way to share content with your family.... Read more
TechTool Pro 7.0.5 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
PDFKey Pro 4.0.2 - Edit and print passwo...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Yasu 2.9.1 - System maintenance app; per...
Yasu was originally created with System Administrators who service large groups of workstations in mind, Yasu (Yet Another System Utility) was made to do a specific group of maintenance tasks... Read more

Latest Forum Discussions

See All

The Silent Age Episode 2 Review
The Silent Age Episode 2 Review By Jennifer Allen on October 22nd, 2014 Our Rating: :: ROUNDING THINGS OFF NICELYUniversal App - Designed for iPhone and iPad Rounding off a great point and click adventure comes The Silent Age... | Read more »
Craft Your Own Mini-Games with Papercade
Craft Your Own Mini-Games with Papercade Posted by Jessica Fisher on October 22nd, 2014 [ permalink ] iPad Only App - Designed for the iPad Scrapbookers move over, Scrapgaming is the new thing. | Read more »
Reshape Review
Reshape Review By Jennifer Allen on October 22nd, 2014 Our Rating: :: SIMPLE SHAPESUniversal App - Designed for iPhone and iPad Match triangles together to form cubes in this fast-paced and twitchy game.   | Read more »
Miika (Games)
Miika 1.0.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.0 (iTunes) Description: Miika is a beautiful 3D puzzle game based on camera perspectives combined with the use of optical illusions. Miika challenges... | Read more »
Infuse Pro (Photography)
Infuse Pro 3.0 Device: iOS Universal Category: Photography Price: $9.99, Version: 3.0 (iTunes) Description: ** All-new version 3 includes fully licensed and certified DTS® and DTS-HD® audio! ** | Read more »
Swap Heroes (Games)
Swap Heroes 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: **Half price for a limited time only** Swap Heroes is a casual turn-based strategy adventure. Form a group of heroes and guide them... | Read more »
Ghost Blade (Games)
Ghost Blade 1.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.1 (iTunes) Description: Get the most outstanding 3D Action Game from App Store NOW! For those who dare pursue dreams. Masterpiece of Yu Shi Game ---China... | Read more »
Fiete – A Day on a Farm Review
Fiete – A Day on a Farm Review By Amy Solomon on October 21st, 2014 Our Rating: :: A MEMORABLE EXPERIENCEUniversal App - Designed for iPhone and iPad Fiete – A day on a farm in an interactive app for young children full of... | Read more »
Tilt to Live: Gauntlet’s Revenge is Almo...
Tilt to Live: Gauntlet’s Revenge is Almost Here Posted by Jessica Fisher on October 21st, 2014 [ permalink ] One Man Left has announced the official release date of Tilt to Live: Gauntlet’s Re | Read more »
Starfly Review
Starfly Review By Jennifer Allen on October 21st, 2014 Our Rating: :: CHANGE OF PACEiPad Only App - Designed for the iPad Want a slightly different browsing experience? Starfly is a pretty personalized one but it’s also buggy.   | Read more »

Price Scanner via MacPrices.net

AT&T accepting preorders for new iPads fo...
AT&T Wireless is accepting preorders for the new iPad Air 2 and iPad mini 3, cellular models, for $100 off MSRP with a 2-year service agreement: - 16GB iPad Air 2 WiFi + Cellular: $529.99 - 64GB... Read more
Apple offering refurbished Mac Pros for up to...
The Apple Store is offering Apple Certified Refurbished 2013 Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
Select MacBook Airs $100 off MSRP, free shipp...
B&H Photo has 2014 a couple of MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels Desktop and LoJack for... Read more
13-inch 2.5GHz MacBook Pro on sale for $100 o...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Strong iPhone, Mac And App Store Sales Drive...
Apple on Monday announced financial results for its fiscal 2014 fourth quarter ended September 27, 2014. The Company posted quarterly revenue of $42.1 billion and quarterly net profit of $8.5 billion... Read more
Apple Posts How-To For OS X Recovery
OS X 10.7 Lion and later include OS X Recovery. This feature includes all of the tools you need to reinstall OS X, repair your disk, and even restore from a Time Machine backup. OS X Recovery... Read more
Mac OS X Versions (Builds) Supported By Vario...
Apple Support has posted a handy resource explaining which Mac OS X versions (builds) originally shipped with or are available for your computer via retail discs, downloads, or Software Update. Apple... Read more
Deals on 2011 13-inch MacBook Airs, from $649
Daily Steals has the Mid-2011 13″ 1.7GHz i5 MacBook Air (4GB/128GB) available for $699 with a 90 day warranty. The Mid-2011 13″ 1.7GHz i5 MacBook Air (4GB/128GB SSD) is available for $649 at Other... Read more
2013 15-inch 2.0GHz Retina MacBook Pro availa...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros now available for $1599 including free shipping plus NY sales tax only. Their price is $400 off original MSRP. B&H... Read more
Updated iPad Prices
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers, including the new iPad Air 2 and the... Read more

Jobs Board

Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**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
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.