TweetFollow Us on Twitter

Access to Traps
Volume Number:1
Issue Number:6
Column Tag:MacPascal

Access to OS traps

By Alan Wootton

MacPascal is a miracle. Although billed as an educational product, and many serious programmers probably regard it as a toy (just as many consider the Mac to be merely a toy), MacPascal can be used to prototype professional software products.

Since MacPascal is not sold and supported as a development tool, a small amount of homework is needed to assemble a useful system. First you will need MacPascal. Second you will need RMaker, the resource compiler that runs on the Mac. For some an assembler is nice. And a 68000 debugger may be needed (I use MacDB by Bill Duvall). Since there is no syntax check on inline procedures, a debugger is useful to check the stack at the start of the call even if you are relatively bad at assembly language. Eventually one needs a compiler. For now all that is available is the Lisa Pascal Workshop. Hopefully, a Mac compiler will become available. For my purposes it is necessary for the compiler to generate native code; this rules out a p-code type of system (SoftTech Pascal won’t do). Last but not least, Inside Macintosh is a must.

MacPascal provides methods to access almost all of the toolbox routines that make the Mac so great. The OS traps, however, are a bit tricky. As Steve Brecher showed us last month in MacTutor with his Advanced Mac’ing column, the undocumented GENERIC procedure is used to call OS traps. However, INLINE can also be used for OS traps, as we shall see this month in this example of using STUFFHEX from Pascal. (See Steve’s Advanced Mac’ing column in this month’s issue for an example of using STUFFHEX from Basic.)

TWO TYPES OF TOOLBOX TRAPS

There are two types of toolbox trap; those that are stack based and those that are register based. The stack based calls are supported using the INLINE procedure. The register based traps, of which most of the OS traps are typical, are more difficult to access because there is no way (other than using GENERIC) to set registers from Pascal. Fortunately, virtually all of the register traps use only D0 and A0. Therefore, if we could set D0 and A0 before the trap and read them afterwards, we would have an OS trap call mechanism using the INLINE procedure. I have written a short piece of 68000 code to accomplish this.

As an example, I have prepared a short program to read the date and time from the system. Two calls are made to the toolbox to do this; both are register based. Note that when a pointer is to be passed in A0, the @ operator must be used to set the variable to the correct value before the call. Also note that for any $A0xx calls that return a value to the calling routine, the flag $100 should be added to not preserve all registers.

GLUE ROUTINE FOR PASCAL TO OS

Our machine language routine will pop from the stack, the addresses of the variables which we wish to place in the registers A0 and D0. We will pop these addresses off the stack and use them to load the variables into the two registers. The new values returned in A0 and D0 will then be copied back into those same two Pascal variables. Note that after the inlineP call, all registers are saved so we can use them any way we please. To return to Pascal, we are using an RTS instruction so it will be necessary for our machine language routine to calculate our return address. Fortunately A0 points at the word before where we must return.

ROUTINE TO LOAD A0 AND D0 FOR OS TRAP CALLS FROM MACPASCAL.

126: 2848 MOVE.L A0,A4   ;SAVE RETURN
128: 548C ADDQ.L #$2,A4  ;POINT TO RET
;
;  get address where trap will go into A0
;
12A: 41FA 000C     LEA   *+$000E,A0
;
;  pop trap from stack and place into code
;
12E: 309F MOVE.W  (A7)+,(A0) 
;
;  get A0 and D0 from stack
;
130: 245F MOVE.L (A7)+,A2 ;POP A0 VAR
132: 265F MOVE.L (A7)+,A3 ;POP D0 VAR
134: 2052 MOVE.L (A2),A0   ;LOAD A0
136: 2013 MOVE.L (A3),D0    ;LOAD D0
;
;  this word gets overwritten by real trap
;
138: FFFF .word  $FFFF  ;do trap now
; 
;  pass back A0 and D0 contents 
;
13A: 2488 MOVE.L A0,(A2) ;SAVE RET A0
13C: 2680 MOVE.L D0,(A3) ;SAVE RET D0
13E: 4ED4 JMP  (A4);RETURN 

We will stuff the machine code for our little OS trap caller above into memory by using the STUFFHEX routine from our Pascal program. The above listing is provided to show how the machine language patch works. Two OS traps, ReadDateTime and Secs2Date will be called using our OS trap caller, returning the information in variables of our DateTime record. From this example, it should be obvious how to access other OS type traps using INLINE procedures. (As we mentioned, the undocumented GENERIC can also be used for this purpose.)

program show_date_time;

{ This is a test of a method of accessing   }
{ the Mac OS toolbox traps from Mac         }
{ Pascal that are register based, using    }
{ A0 and D0 only. The call will be:            }
{inlineP($4E75,@d0, @a0, trap,@access)}
{ d0 and a0 hold values of registers D0      }
{ and A0 before and after the call. Trap   }
{ refers to the trap address being called.}

type
 DaTimRec = record
 year: integer;
 month: integer;
 day: integer;
 hour: integer;
 minute: integer;
 second: integer;
 dayofweek: integer;
 end;

var
 currentTime: DatimRec;

procedure GetTime(var date: DaTimRec);
 var
 access: array[0..12] of integer;
 d0,a0, secs: longint;
begin
 stuffhex(@access,’2848548C41FA000C309F245F265F20522013FFFF248826804ED4');
a0:=ord(@secs);

inlineP($4E75,@d0,@a0,$A139, @access);
{ReadDateTime, pointer to secs in A0}

a0:=ord(@date);

inlineP($4E75,@secs,@a0,$A9C6,@access);
{Secs2Date, secs in d0, pointer to record}
{is in A0.}

end;
begin {main}
 GetTime(currentTime);
 with currentTime do
 begin
 writeln(‘year is’, year);
 writeln(‘month is’, month);
 writeln(‘day is’, day);
 writeln(‘hour is’, hour);
 writeln(‘minute is’, minute);
 writeln(‘second is’, second);
 writeln(‘year is’, year);
 writeln(‘day of week is’, dayofweek);
 end;
end.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

GraphicConverter 10.5.1 - $39.95
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
Delicious Library 3.7 - Import, browse a...
Delicious Library allows you to import, browse, and share all your books, movies, music, and video games with Delicious Library. Run your very own library from your home or office using our... Read more
Adobe Animate CC 2017 18.0.0.107 - Anima...
Animate CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Flash Professional customer). Animate CC 2018 (was Flash CC) lets you... Read more
Adobe After Effects CC 2018 15.0 - Creat...
After Effects CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous After Effects customer). The new, more connected After Effects CC... Read more
Adobe Premiere Pro CC 2018 12.0.0 - Digi...
Premiere Pro CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Premiere Pro customer). Adobe Premiere Pro CC 2018 lets you edit... Read more
Alarm Clock Pro 10.3 - $19.95
Alarm Clock Pro isn't just an ordinary alarm clock. Use it to wake you up in the morning, send and compose e-mails, remind you of appointments, randomize the iTunes selection, control an internet... Read more
Adobe Lightroom 20170919-1412-ccb76bd] -...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
Adobe Illustrator CC 2018 22.0.0 - Profe...
Illustrator CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Illustrator customer). Adobe Illustrator CC 2018 is the industry... Read more
Hopper Disassembler 4.3.0- - Binary disa...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
Adobe InDesign CC 2018 13.0.0.125 - Prof...
InDesign CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous InDesign customer). Adobe InDesign CC 2018 is part of Creative Cloud.... Read more

ICEY (Games)
ICEY 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: ICEY is a 2D side-scrolling action game. As you follow the narrator's omnipresent voice, you will see through ICEY's eyes and learn the... | Read more »
The best new games we played this week -...
We've made it, folks. Another weekend is upon us. It's time to sit back and relax with the best new releases of the week. Puzzles, strategy RPGs, and arcade games abound this week. There's a lot of quality stuff to unpack this week, so let's hop... | Read more »
Wheels of Aurelia (Games)
Wheels of Aurelia 1.0.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0.1 (iTunes) Description: | Read more »
Halcyon 6: Starbase Commander guide - ti...
Halcyon 6 is a well-loved indie RPG with stellar tactical combat and some pretty good writing, too. It's now landed on the App Store, so mobile fans, if you're itching for a good intergalactic adventure, here's your game. Being a strategy RPG, the... | Read more »
Game of Thrones: Conquest guide - how to...
Fans of base building games might be excited to know that yet another entry in the genre has materialized - Game of Thrones: Conquest. Yes, you can now join the many kingdoms of the famed book series, or create your own, as you try to conquer... | Read more »
Halcyon 6: Starbase Commander (Games)
Halcyon 6: Starbase Commander 1.4.2.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.4.2.0 (iTunes) Description: An epic space strategy RPG with base building, deep tactical combat, crew management, alien diplomacy,... | Read more »
Legacy of Discord celebrates its 1 year...
It’s been a thrilling first year for fans of Legacy of Discord, the stunning PvP dungeon-crawling ARPG from YOOZOO Games, and now it’s time to celebrate the game’s first anniversary. The developers are amping up the festivities with some exciting... | Read more »
3 reasons to play Thunder Armada - the n...
The bygone days of the Battleship board game might have past, but naval combat simulators still find an audience on mobile. Thunder Armada is Chinese developer Chyogames latest entry into the genre, drawing inspiration from the explosive exchanges... | Read more »
Experience a full 3D fantasy MMORPG, as...
Those hoping to sink their teeth into a meaty hack and slash RPG that encourages you to fight with others might want to check out EZFun’s new Eternity Guardians. Available to download for iOS and Android, Eternity Guardians is an MMORPG that lets... | Read more »
Warhammer Quest 2 (Games)
Warhammer Quest 2 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Dungeon adventures in the Warhammer World are back! | Read more »

Price Scanner via MacPrices.net

9″ iPads on sale for $30 off, starting at $29...
MacMall has 9″ iPads on sale for $30 off including free shipping: – 9″ 32GB iPad: $299 – 9″ 128GB iPad: $399 Read more
Apple restocks full line of refurbished 13″ M...
Apple has restocked a full line of Apple Certified Refurbished 2017 13″ MacBook Pros for $200-$300 off MSRP. A standard Apple one-year warranty is included with each MacBook, and shipping is free.... Read more
13″ 3.1GHz/256GB MacBook Pro on sale for $167...
Amazon has the 2017 13″ 3.1GHz/256GB Space Gray MacBook Pro on sale today for $121 off MSRP including free shipping: – 13″ 3.1GHz/256GB Space Gray MacBook Pro (MPXV2LL/A): $1678 $121 off MSRP Keep an... Read more
13″ MacBook Pros on sale for up to $120 off M...
B&H Photo has 2017 13″ MacBook Pros in stock today and on sale for up to $120 off MSRP, each including free shipping plus NY & NJ sales tax only: – 13-inch 2.3GHz/128GB Space Gray MacBook... Read more
15″ MacBook Pros on sale for up to $200 off M...
B&H Photo has 15″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray (MPTR2LL/A): $2249, $150... Read more
Roundup of Apple Certified Refurbished iMacs,...
Apple has a full line of Certified Refurbished 2017 21″ and 27″ iMacs available starting at $1019 and ranging up to $350 off original MSRP. Apple’s one-year warranty is standard, and shipping is free... Read more
Sale! 27″ 3.8GHz 5K iMac for $2098, save $201...
Amazon has the 27″ 3.8GHz 5K iMac (MNED2LL/A) on sale today for $2098 including free shipping. Their price is $201 off MSRP, and it’s the lowest price available for this model (Apple’s $1949... Read more
Sale! 10″ Apple WiFi iPad Pros for up to $100...
B&H Photo has 10.5″ WiFi iPad Pros in stock today and on sale for $50-$100 off MSRP. Each iPad includes free shipping, and B&H charges sales tax in NY & NJ only: – 10.5″ 64GB iPad Pro: $... Read more
Apple iMacs on sale for up to $130 off MSRP w...
B&H Photo has 21-inch and 27-inch iMacs in stock and on sale for up to $130 off MSRP including free shipping. B&H charges sales tax in NY & NJ only: – 27″ 3.8GHz iMac (MNED2LL/A): $2179 $... Read more
2017 3.5GHz 6-Core Mac Pro on sale for $2799,...
B&H Photo has the 2017 3.5GHz 6-Core Mac Pro (MD878LL/A) on sale today for $2799 including free shipping plus NY & NJ sales tax only . Their price is $200 off MSRP. 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
Commerce Engineer, *Apple* Media Products -...
Commerce Engineer, Apple Media Products (New York City) Job Number: 113028813New York City, New York, United StatesPosted: Sep. 20, 2017Weekly Hours: 40.00 Job Read more
US- *Apple* Store Leader Program - Apple (Un...
US- Apple Store Leader Program Job Number: VariousUnited StatesPosted: Oct. 19, 2017Retail Store Job Summary Learn and grow as you explore the art of leadership at Read more
Product Manager - *Apple* Pay on the *Appl...
Job Summary Apple is looking for a talented product manager to drive the expansion of Apple Pay on the Apple Online Store. This position includes a unique Read more
*Apple* Retail - Multiple Positions - Farmin...
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.