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
$97.89
Apple Inc.
+0.22
MSFT
$44.03
Microsoft Corpora
-0.47
GOOG
$585.34
Google Inc.
-3.68

MacTech Search:
Community Search:

Software Updates via MacUpdate

Bartender 1.2.20 - Organize your menu ba...
Bartender lets you organize your menu bar apps. Features: Lets you tidy your menu bar apps how you want. See your menu bar apps when you want. Hide the apps you need to run, but do not need to... Read more
TotalFinder 1.6.2 - Adds tabs, hotkeys,...
TotalFinder is a universally acclaimed navigational companion for your Mac. Enhance your Mac's Finder with features so smart and convenient, you won't believe you ever lived without them. Tab-based... Read more
Vienna 3.0.0 RC 2 :be5265e: - RSS and At...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more
VLC Media Player 2.1.5 - Popular multime...
VLC Media Player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, MP3, OGG, ...) as well as DVDs, VCDs, and various streaming protocols. It... Read more
Default Folder X 4.6.7 - Enhances Open a...
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... Read more
TinkerTool 5.3 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Audio Hijack Pro 2.11.0 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more
Intermission 1.1.1 - Pause and rewind li...
Intermission allows you to pause and rewind live audio from any application on your Mac. Intermission will buffer up to 3 hours of audio, allowing users to skip through any assortment of audio... Read more
Autopano Giga 3.6 - Stitch multiple imag...
Autopano Giga allows you to stitch 2, 20, or 2,000 images. Version 3.0 integrates impressive new features that will definitely make you adopt Autopano Pro or Autopano Giga: Choose between 9... Read more
Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more

Latest Forum Discussions

See All

Exploration Focused Puzzle Game Beatbudd...
Exploration Focused Puzzle Game Beatbuddy Set to Make Transition from PC to iOS this September Posted by Jennifer Allen on July 28th, 2014 [ permalink ] | Read more »
PlanetHD
PlanetHD By Nadia Oxford on July 28th, 2014 Our Rating: :: SPACE MADNESSUniversal App - Designed for iPhone and iPad PlanetHD will keep players busy for a while, though its unpredictable physics are a handful to deal with.   | Read more »
This Week at 148Apps: July 21-25, 2014
Another Week of Expert App Reviews   At 148Apps, we help you sort through the great ocean of apps to find the ones we think you’ll like and the ones you’ll need. Our top picks become Editor’s Choice, our stamp of approval for apps with that little... | Read more »
Reddme for iPhone - The Reddit Client (...
Reddme for iPhone - The Reddit Client 1.0 Device: iOS iPhone Category: News Price: $.99, Version: 1.0 (iTunes) Description: Reddme for iPhone is an iOS 7-optimized Reddit client that offers a refreshing new way to experience Reddit... | Read more »
Jacob Jones and the Bigfoot Mystery : Ep...
Jacob Jones and the Bigfoot Mystery : Episode 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Jacob Jones is back in Episode 2 of one of Apples 'Best of 2013' games and an App Store... | Read more »
New Trailer For Outcast Odyssey, A New K...
New Trailer For Outcast Odyssey, A New Kind of Card Battler Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Out this Fall is a new kind of card battle game: Outcast Odyssey. | Read more »
Hay Day – Tip, Tricks, Strategies, and C...
Recently got into Supercell’s other huge hit, Hay Day and could do with some advice on what to do? We’ve got you covered with some helpful trips and tricks to bear in mind! Ticking Along One of the key things to keep in mind while building up that... | Read more »
Monster Head Review
Monster Head Review By Nadia Oxford on July 25th, 2014 Our Rating: :: FEEDING TIMEUniversal App - Designed for iPhone and iPad Racking up a high score with Monster Head is trickier than it first appears. The appeal wears out fairly... | Read more »
Garfield: Survival of the Fattest Coming...
Garfield: Survival of the Fattest Coming to iOS this Fall Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Who loves lasagna? Me. Also everyone’s favorite grumpy fat cat, Garfield. | Read more »
Happy Flock Review
Happy Flock Review By Andrew Fisher on July 25th, 2014 Our Rating: :: HERD IT ALL BEFOREUniversal App - Designed for iPhone and iPad Underneath the gloss of Happy Flock’s visuals is a game of very little substance. It’s cute, but... | Read more »

Price Scanner via MacPrices.net

13-inch 2.5GHz MacBook Pro on sale for $1099,...
Best Buy has the 13″ 2.5GHz MacBook Pro available for $1099.99 on their online store. Choose free shipping or free instant local store pickup (if available). Their price is $100 off MSRP. Price is... Read more
Roundup of Apple refurbished MacBook Pros, th...
The Apple Store has Apple Certified Refurbished 13″ and 15″ MacBook Pros available for up to $400 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. Their prices... Read more
Record Mac Shipments In Q2/14 Confound Analys...
A Seeking Alpha Trefis commentary notes that Apple’s fiscal Q3 2014 results released July 22, beat market predictions on earnings, although revenues were slightly lower than anticipated. Apple’s Mac’... Read more
Intel To Launch Core M Silicon For Use In Not...
Digitimes’ Monica Chen and Joseph Tsai, report that Intel will launch 14nm-based Core M series processors specifically for use in fanless notebook/tablet 2-in-1 models in Q4 2014, with many models to... Read more
Apple’s 2014 Back to School promotion: $100 g...
 Apple’s 2014 Back to School promotion includes a free $100 App Store Gift Card with the purchase of any new Mac (Mac mini excluded), or a $50 Gift Card with the purchase of an iPad or iPhone,... Read more
iMacs on sale for $150 off MSRP, $250 off for...
Best Buy has iMacs on sale for up to $160 off MSRP for a limited time. Choose free home shipping or free instant local store pickup (if available). Prices are valid for online orders only, in-store... Read more
Mac minis on sale for $100 off MSRP, starting...
Best Buy has Mac minis on sale for $100 off MSRP. Choose free shipping or free instant local store pickup. Prices are for online orders only, in-store prices may vary: 2.5GHz Mac mini: $499.99 2.3GHz... Read more
Global Tablet Market Grows 11% in Q2/14 Notwi...
Worldwide tablet sales grew 11.0 percent year over year in the second quarter of 2014, with shipments reaching 49.3 million units according to preliminary data from the International Data Corporation... Read more
New iPhone 6 Models to Have Staggered Release...
Digitimes’ Cage Chao and Steve Shen report that according to unnamed sources in Apple’s upstream iPhone supply chain, the new 5.5-inch iPhone will be released several months later than the new 4.7-... Read more
New iOS App Helps People Feel Good About thei...
Mobile shoppers looking for big savings at their favorite stores can turn to the Goodshop app, a new iOS app with the latest coupons and deals at more than 5,000 online stores. In addition to being a... Read more

Jobs Board

*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
*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
WW Sales Program Manager, *Apple* Online St...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
Lead Software Engineer, *Apple* Online Stor...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
Manager, *Apple* Fullfillment Operation (AF...
…cross-functional teams to drive the highest level of program management quality for Apple . You will help plan launch strategy and demand generation programs with Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.