TweetFollow Us on Twitter

Jan 90 Letters
Volume Number:6
Issue Number:1
Column Tag:Letters

INITs First

By David E. Smith, Editor & Publisher, MacTutor

INITs in Pascal or C

Steve Brecher

Sunnyvale, CA

There are some problems in the advice and code provided in the October 1989 issue’s Pascal Procedures and C Workshop, which discuss writing INITs in the respective languages.

The VBL task shown in Pascal Procedures calls GetGDevice without checking whether Color QuickDraw is available. It assumes that the current GDevice is the monitor the mouse is on. Multiple-monitor users may be surprised to find the mouse jumping from the middle of one monitor to the opposite edge of another when they press Option for some application purpose. The code also assumes, in its reference to QuickDraw globals through CurrentA5, that QuickDraw has been initialized for the currently executing application. This is not necessarily true.

The following comments apply to the C Workshop article.

The author does not understand the function of the ioNamePtr field in File Manager parameter blocks. This field contains either a pointer to a caller- allocated string buffer or nil if the caller chooses not to pass or receive a filename string. The File Manager does not allocate a string buffer for the caller.

INIT 31 does not necessarily expand the system heap by the amount specified in your ‘sysz’ 0 resource, and it certainly does not “collapse” the heap to undo any previous expansions--CompactMem collects free blocks together; it does not shrink a heap. What INIT 31 does is expand the system heap if necessary to assure that a contiguous block of the size specified in the ‘sysz’ 0 resource is available at the time the first (and usually only) INIT resource in an INIT/

cdev/RDEV is executed. Any space gained by heap expansion that is not used by the INIT will remain free when the INIT exits--but may be sopped up by subsequent INITs or system activity.

The author unduly discounts the dangers of tail patching. A tail patch is a trap patch that calls (JSRs to) the original patch instead of JMPing to it. A tail patch may nullify an Apple-supplied ROM code patch. Such Apple patches operate by comparing their return address on the stack with certain hard-coded ROM addresses. By JSRing to the original trap code, one assures that such a comparison will always fail since the Apple patch will see one’s own return address rather than that of the original trap caller. In some cases tail patching is necessary; my own products do it. But one should at least check the latest System release to make sure that one’s tail patches do not nullify ROM code patches. And in some cases one can eat one’s cake and have it too by JSRing to the original trap code, doing necessary post-processing, and then JMPing to the original code. The original code will be executed twice, and the second execution will invoke any ROM patch code that may be installed. The JMP requires assembly language.

The example INIT ignores the fact that Resource Manager traps preserve all registers except D0/A0 (except LoadResource, which preserves all including D0/A0)--IM I-113. It also uses the Dialog Manager with no assurance that it has been intialized, not to mention QuickDraw, etc.

Writing Inits in Pascal

Roland van Straten

Dutch Macintosh Developer

Perhaps this is not the right way to inform you about bugs, but sending a letter takes a while and it has no way to send real program listings. So if this is not the way you prefer, let me know.

I’ve read the article about “Writing INITs in Pascal”, MacTutor Oct 89, Page 51, and after some study of the source code I noticed two bugs. Maybe Steve Kiene’s system and/or compiler do something special or he forgot to test it, I don’t know.

1. The MTemp location has a counterpart: RawMouse. It’s the next LongInt in Low Memory. If RawMouse is equal to MTemp the mouse handler will think the move has to be made absolute. Otherwise the move will be treated as relative (Steve Kiene’s program).

2. The CrsrNew location is a Byte value. Steve Kiene’s program declares a pointer to a Byte (^Byte). This is a two byte value. Look at IM vol1, pag 86. In order to fix this I used a standard type Ptr (^SignedByte) and exchanged $FF for -1.

Apart from these little bugs I enjoyed the article very much and found it useful. The article appeared at the time I was writing a VBL task that moves the mouse “outside” the screen (don’t ask me for the reason of this).

 
UNIT CursorWrap;

{MacTutor ©1989, issue October 1989, page 51, “Writing INITs in Pascal” 
by Steve Kiene}

{MPW 3.0 version - October 1989 - ROLAnd van Straten - ALink HOL0027}

INTERFACE

USES
 MemTypes,QuickDraw,OSIntf,ToolIntf;

PROCEDURE SETUPVBL;
PROCEDURE Wrap;

IMPLEMENTATION

PROCEDURE SETUPVBL;
VAR
 theVBL : VBLTask;
 myQElem: QElemPtr;
 myErr  : OSErr;
 SaveZone : THz;
 SizeNeeded:LongInt;
 PatchPtr : Ptr;
 theCode: Handle;
 thePtr : ^LongInt;

BEGIN
 theCode:= Get1Resource(‘INIT’,1);
 SaveZone := GetZone;
 SetZone(SystemZone);
 
 SizeNeeded := SizeResource(theCode) - (LongInt(@SetUpVBL) - LongInt(theCode^)) 
+ SizeOf(QElem);
 ResrvMem(SizeNeeded);
 IF MemError <> NoErr THEN BEGIN
 SysBeep(1); SetZone(SaveZone); Exit(SetUpVBL); END;
 
 PatchPtr := NewPtr(SizeNeeded + 4) ;{get ptr for our code}
 BlockMove(@Wrap, Pointer(ORD(PatchPtr)+4), SizeNeeded);
 myQElem := QElemPtr(NewPtr(SizeOf(QElem)));
 SetZone(SaveZone);
 
 {put vbl task ptr addr into ptr where our patch will be}
 thePtr := Pointer(PatchPtr);
 thePtr^ := LongInt(myQElem);
 
 WITH theVBL DO BEGIN
 qType  := ORD(vType);
 vblAddr  := Pointer(ORD(PatchPtr)+4);
 vblCount := 6;
 vblPhase := 0;
 END;
 myQElem^.vblQElem := theVBL;
 myErr := VInstall(myQElem);
END;

PROCEDURE Wrap;
{Wrap cursor when option key is down

 MTemp  has latest mouse value
 RawMouse has the un-jerked mouse value
 CrsrNew  must be set to “-1” to indentify “moved”
 
 If MTemp and RawMouse are different there only will be a relative change 
of the mouse position. This looks like unstable moves on the screen. 
 Fixed this bug by moving RawMouse into the arena.
 CrsrNew is a byte. The used pointer type was a ^Byte. This is in fact 
a two byte value (WRONG). Look in IM.1 pag 68 for details on this. So 
in order to fix this use the standard Ptr type and put the value -1 into 
the addressed byte.
}

CONST
 CurrentA5 = $904;
 MTemp  = $828;  {Low-level interrupt mouse location [long]}
 RawMouse = $82C; {un-jerked mouse coordinates [long]}
 CrsrNew= $8CE; {Cursor changed? [byte]}
 OptionKey= 58;

TYPE
 LPtr = ^LongInt;

VAR
 myQElem: QElemPtr;
 currGDevice: GDHandle;
 theMap : KeyMap;
 changed: Boolean;
 myRectPtr: ^Rect;
 mouseRect, myRect : Rect;
 myPtr,myPtr2    : LPtr;
 PPtr,P2Ptr : ^Point;

BEGIN
 GetKeys(theMap);
 IF theMap[OptionKey] THEN BEGIN
 changed := FALSE;
 currGDevice :=GetGDevice;
 IF currGDevice <> NIL THEN
 mouseRect := currGDevice^^.gdRect
 ELSE
 BEGIN {use A5 to get offset to screenbits.bounds}
 myPtr  := Pointer(CurrentA5);
 myPtr2 := Pointer(myPtr^);
 myRectPtr := Pointer(myPtr2^-116);
 mouseRect := myRectPtr^;
 END;
 InSetRect(mouseRect,1,1);
 
 PPtr := Pointer(MTemp); P2Ptr := Pointer(RawMouse);
 IF PPtr^.v <= mouseRect.top THEN BEGIN {check cursor pos for wrap}
 PPtr^.v  := mouseRect.bottom -1;
 P2Ptr^.v := mouseRect.bottom -1;
 changed  := TRUE; END
 ELSE
 IF PPtr^.v >= mouseRect.bottom THEN BEGIN
 PPtr^.v  := mouseRect.top +1;
 P2Ptr^.v := mouseRect.top +1;
 changed  := TRUE; END
 ELSE
 IF PPtr^.h <= mouseRect.left THEN BEGIN
 PPtr^.h  := mouseRect.right -1;
 P2Ptr^.h := mouseRect.right -1;
 changed  := TRUE; END
 ELSE
 IF PPtr^.h >= mouseRect.right THEN BEGIN
 PPtr^.h  := mouseRect.left +1;
 P2Ptr^.h := mouseRect.left +1;
 changed:= TRUE; END;
 
 IF changed THEN 
 Ptr(CrsrNew)^ := -1;{cursor has changed}
 
 END;
 
 myQElem := QElemPtr(LPtr(Pointer(ORD(@Wrap)-4))^);      {get ptr to 
vbl task, and reset it}
 myQElem^.vblQElem.vblCount := 6;
END;

END.

INIT Inhibition

David Dunham

Seattle, WA

Just a quick note about Peter Hoddie’s article on INITs. He suggests that INITs not install themselves when the mouse button is down.

In fact, there is a fairly standard method of inhibiting INITs: the shift key. Not all INITs use this, but probably half the ones I’m familiar with do. My own INITs also disable themselves when their initial letter (e.g. ‘f’ for Findswell) is held at boot time.

The problem with using the mouse button is that it instructs the Mac to eject the internal disk at boot time. Disabling INITs shouldn’t be a matter of timing just when to click the mouse.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Apple Remote Desktop 3.8 - Remotely cont...
Apple Remote Desktop is the best way to manage the Mac computers on your network. Distribute software, provide real-time online help to end users, create detailed software and hardware reports, and... Read more
NeoOffice 2014.7 - Mac-tailored, OpenOff...
NeoOffice is a complete office suite for OS X. With NeoOffice, users can view, edit, and save OpenOffice documents, PDF files, and most Microsoft Word, Excel, and PowerPoint documents. NeoOffice 3.x... Read more
DesktopLyrics 2.6.6 - Displays current i...
DesktopLyrics is an application that displays the lyrics of the song currently playing in "iTunes" right on your desktop. The lyrics for the song have to be set in iTunes; DesktopLyrics does nothing... Read more
Ember 1.8.3 - Versatile digital scrapboo...
Ember (formerly LittleSnapper) is your digital scrapbook of things that inspire you: websites, photos, apps or other things. Just drag in images that you want to keep, organize them into relevant... Read more
Apple iTunes 12.1 - Manage your music, m...
Apple iTunes lets you organize and play digital music and video on your computer. It can automatically download new music, app, and book purchases across all your devices and computers. And it's a... Read more
LibreOffice 4.4.3 - Free, open-source of...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
FoldersSynchronizer 4.2.1 - Synchronize...
FoldersSynchronizer is a popular and useful utility that synchronizes and backs-up files, folders, disks and boot disks. On each session you can apply special options like Timers, Multiple Folders,... Read more
Simon 4.0.2 - Monitor changes and crashe...
Simon monitors websites and alerts you of crashes and changes. Select pages to monitor, choose your alert options, and customize your settings. Simon does the rest. Keep a watchful eye on your... Read more
Cocktail 8.1.2 - General maintenance and...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Cyberduck 4.6.4 - FTP and SFTP browser....
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more

Playworld Superheroes Review
Playworld Superheroes Review By Tre Lawrence on January 30th, 2015 Our Rating: :: HERO CRAFTINGUniversal App - Designed for iPhone and iPad It’s all about the imagination, fighting bad creatures — and looking good while doing so.   | Read more »
Join the SpongeBob Bubble Party in this...
Join the SpongeBob Bubble Party in this New Match 3 Bubble Poppin’ Frenzy Posted by Jessica Fisher on January 30th, 2015 [ permalink ] | Read more »
Handpick Review
Handpick Review By Jennifer Allen on January 30th, 2015 Our Rating: :: TANTALIZING SUGGESTIONSiPhone App - Designed for the iPhone, compatible with the iPad Handpick will make you hungry, as well as inspire you to cook something... | Read more »
Storm the Halls of Echo Base in First St...
Storm the Halls of Echo Base in First Star Wars: Galactic Defense Event Posted by Jessica Fisher on January 30th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Contradiction Review
Contradiction Review By Tre Lawrence on January 30th, 2015 Our Rating: :: SPOT THE LIEiPad Only App - Designed for the iPad Contradiction is a live action point and click adventure that’s pretty engaging.   Developer: Tim Follin... | Read more »
Unlock Sunshine Girl in Ironkill with th...
Unlock Sunshine Girl in Ironkill with this special 148Apps code Posted by Rob Rich on January 29th, 2015 [ permalink ] Robo-fighter Ironkill has been out on iOS a | Read more »
Crossroad Zombies Review
Crossroad Zombies Review By Jordan Minor on January 29th, 2015 Our Rating: :: CROSSWALKING DEADiPad Only App - Designed for the iPad Crossroad Zombies is a rough draft of a cool genre mash-up.   | Read more »
Blood Brothers 2 – Tips, Cheats, and Str...
War is hell: Is it the kind of hell you want to check out? Read our Blood Brothers 2 review to find out! Blood Brothers 2, DeNA’s follow-up to the original Blood Brothers, is an intriguing card collecting / role-playing / strategy hybrid. There’s... | Read more »
Blood Brothers 2 Review
Blood Brothers 2 Review By Nadia Oxford on January 29th, 2015 Our Rating: :: AN AGGRAVATING RELATIVEUniversal App - Designed for iPhone and iPad Blood Brothers 2 is built on a simple, solid foundation, but its free-to-play system... | Read more »
I AM BREAD, the Toast of the Town, is Ro...
Have you ever dreamt of being deliciously gluten-y? Do you feel passionate about Rye and Wheat? The guys at Bossa Studios do and that is why they are bringing I AM BREAD to iOS soon. The loafy app will feature all the new content that is being... | Read more »

Price Scanner via MacPrices.net

Amazon offers 15-inch 2.2GHz Retina MacBook P...
 Amazon.com has the 15″ 2.2GHz Retina MacBook Pro on sale for $1879 including free shipping. Their price is $120 off MSRP, and it’s the lowest price available for this model from any reseller (except... Read more
Intel Aims to Transform Workplace With 5th-Ge...
Intel Corporation today announced the availability of its 5th generation Intel Core vPro processor family that provides cutting-edge features to enable a new and rapidly shifting workplace. To meet... Read more
iOS App Sharalike Introduces New Instant Smar...
Sharalike slideshow and photo management software for iOS, is making it easier than ever to create shareable meaningful moments with its new instant SmartShow technology. Staying organized is a goal... Read more
Apple Becomes World’s Largest Smartphone Vend...
According to the latest research data from Strategy Analytics, as global smartphone shipments grew 31 percent annually to reach a record 380 million units in the fourth quarter of 2014. Apple became... Read more
Cut the Cord: OtterBox Resurgence Power Case...
Dead batteries and broken phones are two of the biggest issues for smartphone users today. Otterbox addresses both with the new Resurgence Power Case for Apple iPhone 6, promising to make those panic... Read more
13-inch Retina MacBook Pros on sale for up to...
B&H Photo has 13″ Retina MacBook Pros on sale for $200 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.6GHz/128GB Retina MacBook Pro: $1199.99 save $100 - 13″ 2.6GHz/... Read more
15-inch 2.5GHz Retina MacBook Pro on sale for...
 B&H Photo has the 15″ 2.5GHz Retina MacBook Pro on sale for $2319.99 including free shipping plus NY sales tax only. Their price is $180 off MSRP, and it’s the lowest price available for this... Read more
Back in stock: Refurbished iPod nanos for $99...
The Apple Store has Apple Certified Refurbished 16GB iPod nanos available for $99 including free shipping and Apple’s standard one-year warranty. That’s $50 off the cost of new nanos. Most colors are... Read more
Apple lowers price on refurbished 256GB MacBo...
The Apple Store has lowered prices on Apple Certified Refurbished 2014 MacBook Airs with 256GB SSDs, now available for up to $200 off the cost of new models. An Apple one-year warranty is included... Read more
New Good Management Suite Simplifies Enterpri...
Good Technology has announced the availability of the Good Management Suite, a comprehensive cross-platform solution for organizations getting started with mobile business initiatives. Built on the... Read more

Jobs Board

At-Home Chat Specialist- *Apple* Online Stor...
**Job Summary** At Apple , we believe in hard work, a fun environment, and the kind of creativity and innovation that only comes about when talented people from diverse Read more
Sr. Mac Expert- *Apple* Online Store - Apple...
**Job Summary** The World Wide Apple Online Store (AOS) Sales and Service team is looking for motivated, outgoing, and tech savvy individuals who want to offer Apple Read more
*Apple* Solutions Consultant- Retail Sales (...
**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
Event Director, *Apple* Retail Marketing -...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global engagement strategy and team. Delivering an overarching brand Read more
At-Home Chat Specialist- *Apple* Online Stor...
**Job Summary** At Apple , we believe in hard work, a fun environment, and the kind of creativity and innovation that only comes about when talented people from diverse Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.