TweetFollow Us on Twitter

Apr 94 Tips
Volume Number:10
Issue Number:4
Column Tag:Tips & Tidbits

Tips & Tidbits

Edited by Scott Boyd, Editor

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

Tip Of The Month

MPW C Navigation Time Saver

MPW has a nice feature for C programmers: Using the tool CMarker, you can make a list of marks for all the functions in a source file.

Unfortunately, when you open the Mark menu, you can wind up with something unusable. For example, the list could be so long that it takes too much time to find what you’re looking for. Moreover, you are often looking for a function because you are in a piece of code in which you see it being called. It’s right there in front of you. It would be nice to be able to use that piece of context to get you to the function itself.

The following MPW Shell statement sets up a function key which jumps to a function when you highlight its name and press control-enter (or any other key you wish).


/* 1 */
setkey control-enter 'find `catenate "{Active}".§`"{Active}"'

Be sure to get all of the quotes right. MPW cares about the different quotes. Reading from left-to-right, the quotes are straight-, back-, double-, double-, back-, double-, double-, and single-quotes. The § character is option-6.

- Manuel Carlos Alcoba

Informacion, Integracion, Inteligencia

Madrid, Spain

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.

INLINE ASSEMBLY IN PASCAL

Knowing how to write inline assembly within your pascal code can sometimes save you time and trouble. For example, I use an Inline routine that returns the current stack address for debugging purposes. The routine looks like this:

 
/* 2 */
INTERFACE
  FUNCTION GetStackTop: LongInt; INLINE
   $2E8F;
My code calls it just as if it were a regular function:
VAR
 stackAddress: LongInt;
...
stackAddress := GetStackTop;

When used properly, Inline assembly provides considerable speed improvements and allows you to enhance your Pascal code in ways not possible with straight Pascal.

Define your inline routines in the INTERFACE part of a file. In my example, the hexadecimal number $2E8F represents the instruction MOVE.L A7,(A7). The compiler places this instruction directly into the code. This reduces the number of instructions needed to write and compile this routine in assembly language and also avoids calling overhead for a function. No calling overhead simply means no JSR instructions are generated in the code. When I was learning how to write inline assembly, the biggest obstacle was lack of documentation on how to obtain the hexadecimal format (e.g. $2E8F) of assembly language instructions. You can laboriously try to compose the hexadecimal instruction from some 68000 assembly books, but this usually takes several minutes, is error prone, and requires that you know exactly what you are doing. There is a much easier way to obtain the hexadecimal format of any assembly language instruction, provided you have MPW assembler. This is what you need to do:

Suppose you want to find the hexadecimal format of the MOVE.L A7,(A7) instruction.

1) In MPW, create a new file called Example.a and enter the text:

/* 3 */
RoutineName PROC
 MOVE.L A7,(A7)
 END

2) Create a ‘.o’ file with the MPW ASM tool. In this case I call the file Example.a and the ASM tool creates an Example.a.o file:

/* 4 */
 Asm Example.a

3) Now disassemble the Example.a.o file with the dumpObj MPW tool. The dumpObj takes whatever is inside a compiled file and disassembles it back into assembly language instructions. In this case it disassembles the file Example.a.o into a file called Example.o.a:

/* 5 */
dumpobj 'Example.a.o' > 'Example.o.a'

4) The disassembled file contains the line

/* 6 */
00000000: 2E8F           '..'              MOVE.L     A7,(A7)

The second number on that line, “i.e. 2E8F”, is the hexadecimal format of the assembly instruction.

From now on, anytime you need a hexadecimal format of an instruction, just add the instruction to Example.a file and execute the ASM and dumpObj MPW tools. After you do this a couple of times you will realize this is a simple repetitious process. This usually takes less than a minute and is much easier and quicker than finding the instruction from a book.

- Marek Hajek

Champaign, Illinois

Another hex-for-opcode trick

Finding the hex for an instruction can be useful in a number of situations. One situation I’ve found myself in is sitting in Macsbug on a machine and needing to change a single instruction. For example, suppose Igot a branch condition backwards, and want to change the sense of the conditional branch from BLE to BGT. I’d like to change the instruction with a SM (set memory) Macsbug command, but first I have to figure out the value to set. I could guess (don’t laugh, I’ve done it before, and even got it right after just a few guesses on a couple of occasions), but a better way is to let someone do all the guessing (or table lookups) for me. The fastest tool I’ve found is TMONPro on some handy nearby machine. Here’s how:

1) Open up an assembly window. Set its address to PlayMem. That’s a chunk of memory that TMON sets aside when it loads. It’s there for you to play with.

2) Select the first line. It probably reads something like ORI.B #$00,D0. Regardless, select the whole line.

3) Now type in the instruction you want. It replaces the selection. Now press return or enter.

4) TMONPro assembles your instruction right then and there.

5) Open a memory window and point it at PlayMem. An easy way to do that is to command-click on PlayMem’s address over on the left-hand side of the assembly window. The memory window now shows the hex values for the instruction you just typed in.

Of course, you might also just use it on the machine you’re debugging. That’s even faster because now you can simply type over the line of assembly, press enter, and the code changes in place.

- Ned Flanders

Springfield

Playing a sound asynchronously and continuously

When allocating your channel, pass a callbackproc. When playing the sound using bufferCmd, immediately play a callbackCmd as well. Your callback will be called when there is about 50ms of sound left to play, and can queue a new bufferCmd in the same channel (even though it's at interrupt time).

- Jon W{tte

Sweden

[When asked about the { in his name, Jon replied :

“For reference, it's option-u a, or a-umlaut - ä. However, I'm trying to push the brace as the next character to be included in the Swedish naming character set :-)” ]

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

CSR Racing 2: Your guide to what's...
CSR Racing 2, or CSR2, as it likes to call itself, has finally arrived. The follow-up to the immensely popular drag racing game CSR Racing is the first release from NaturalMotion since the studio's acquisition by Zynga in early 2014. [Read more] | Read more »
Nanuleu (Games)
Nanuleu 1.1 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1 (iTunes) Description: Nanuleu is a strategy game where you take control of ancient magical trees that protect the land from an invading dark force. A... | Read more »
The Slaughter: Act One (Games)
The Slaughter: Act One 1.0.323 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0.323 (iTunes) Description: “The game mixes realism and surrealism to create a story that can cause just as much laughter as fear. A-” -... | Read more »
NEO TURF MASTERS (Games)
NEO TURF MASTERS 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: NEOGEO’s legendary golf game is back, in a brand-new mobile version with touch controls! NEO TURF MASTERS (also known as “BIG... | Read more »
How to send money to a friend with the F...
Facebook is already a lot of things to a lot of people. It's a social network, sure, but also a tool for catologing memories, chatting with friends, and much more. [Read more] | Read more »
Branch out into the Chinese market with...
Created a game that you’re super enthused about, only to find yourself struggling to get it the exposure that you believe it duly deserves? With the time, energy and money that goes into development, it’s only right that games should be given the... | Read more »
Pocket Arcade Story (Games)
Pocket Arcade Story 1.00 Device: iOS Universal Category: Games Price: $4.99, Version: 1.00 (iTunes) Description: Here comes a new challenger: it's the arcade simulation game you've been waiting for! Build your very own gaming... | Read more »
How to get coins faster in Rodeo Stamped...
There comes a time in a cowboy or cowgirl's life when all the riding and lassoing skills in the world aren't enough. You're going to need some cold, hard cash to keep your sky zoo expanding in Rodeo Stampede. [Read more] | Read more »
How to out-do Cam Newton in Can You Dab?
The thing about dance crazes is that you're never really sure when they've run their course. Take the Dab, for instance. Propelled by its adoption as the touchdown celebration of choice for Carolina Panthers quarterback Cam Newton, the Dab seemed... | Read more »
Artik Games releases Splashy Cats for An...
Splashy Cats had us hooked from the title alone, and when we found out the game was literally just zig-zagging one of our favourite pop-culture references, guised as a playable cat character, down a river – our appetites were whetted to say the... | Read more »

Price Scanner via MacPrices.net

New App Reminds Us to Put Down Our Phones and...
Mode, a new smartphone app that makes us more mindful of how we use our devices, debuts in the app stores today. The Mode app tracks time spent in different modes of day-to-day life without... Read more
ZuumSpeed Personalized Speedometer + HUD For...
RMKapps has announced the release and immediate availability of ZuumSpeed 1.0, its personalized speedometer plus heads up display for iOS devices. ZuumSpeed gives users over 18 custom fonts available... Read more
Apple refurbished clearance 15-inch Retina Ma...
Apple has Certified Refurbished 2014 15″ 2.2GHz Retina MacBook Pros available for $1609, $390 off original MSRP. Apple’s one-year warranty is included, and shipping is free. They have refurbished 15... Read more
9-inch 128GB Silver iPad Pro on sale for $50...
B&H Photo has the 9.7″ 128GB Silver Apple iPad Pro on sale for $699 including free shipping plus NY tax only. Their price is $50 off MSRP. Read more
Why Use Indie Opera And Vivaldi Instead Of Sa...
For many years my web browser workhorses were various permutations and spinoffs of the Netscape/Mozilla/Firefox Open Source platform, and the Norwegian indie browser Opera, which I took a shine to... Read more
Western Digital Launches Worlds Fastest 256GB...
At the Mobile World Congress in Shanghai Western Digital Corporation this week introduced a new suite of 256 gigabyte (GB) microSD cards, which includes the new 256GB SanDisk Extreme microSDXC UHS-I... Read more
KeyCue 8.1 Integrates With Typinator To Displ...
Ergonis Software has released KeyCue 8.1, a new version of the company’s keyboard shortcut cheat sheet. KeyCue 8 introduced a new way to define a wide variety of triggers, which can be used to... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available 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 following... Read more
21-inch 2.8GHz iMac on sale for $1199, save $...
Amazon has the 21″ 2.8GHz iMac (model #MK442LL/A) on sale for $1199.99 including free shipping. Their price is $100 off MSRP, and it’s the lowest price available for this model. Read more
13-inch 2.5GHz MacBook Pro (Apple refurbished...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz MacBook Pros... 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
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* Retail - Multiple Positions, Willow...
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.