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.

 
AAPL
$102.99
Apple Inc.
+0.52
MSFT
$44.38
Microsoft Corpora
-0.50
GOOG
$532.71
Google Inc.
+6.17

MacTech Search:
Community Search:

Software Updates via MacUpdate

OmniOutliner 4.1.3 - Organize your ideas...
OmniOutliner is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually designed to help you think. It's... Read more
BBEdit 11.0 - Powerful text and HTML edi...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
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
Command-C 1.1.5 - Clipboard sharing tool...
Command-C is a revolutionary app which makes easy to share your clipboard between iOS and OS X using your local WiFi network, even if the app is not currently opened. Copy anything (text, pictures,... 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

Latest Forum Discussions

See All

TinType by Hipstamatic (Photography)
TinType by Hipstamatic 1.0 Device: iOS iPhone Category: Photography Price: $.99, Version: 1.0 (iTunes) Description: Create hauntingly beautiful, soul capturing portraits with TinType by Hipstamatic. Inspired by daguerreotypes,... | Read more »
The Latest Update for Heroes of Dragon A...
The Latest Update for Heroes of Dragon Age Introduces Daily PvE Challenges Posted by Ellis Spice on October 22nd, 2014 [ permalink ] | Read more »
A New Trailer has Been Revealed for Epic...
A New Trailer has Been Revealed for Epic of Kings Posted by Jessica Fisher on October 22nd, 2014 [ permalink ] Dead Mage Inc. has released a new, action-packed trailer for the upcoming Epic of Kings. | Read more »
Find the Line Review
Find the Line Review By Campbell Bird on October 22nd, 2014 Our Rating: :: INSLIDE THE LINESUniversal App - Designed for iPhone and iPad Tease out beautiful line drawings in this unique, free-to-play puzzle game.   | Read more »
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 »

Price Scanner via MacPrices.net

Save with Best Buy’s College Student Deals
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through November 1st. Anyone with a valid .EDU email address can take advantage... Read more
iPad Air 2 & iPad mini 3 Best Tablets Yet...
The new iPads turned out to be pretty much everything I’d been hoping for and more than I’d expected.”More” particularly in terms of a drinking-from-a-firehose choice of models and configurations,... Read more
Drafts 4 Reinvents iOS Productivity App
N Richland Hills, Texas based Agile Tortoise has announced the release of Drafts 4 for iPhone and iPad. Drafts is a quick capture note taking app with flexible output actions. Drafts 4 scales from... Read more
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

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.