TweetFollow Us on Twitter

Dec 98 Tips

Volume Number: 14 (1998)
Issue Number: 12
Column Tag: Tips & Tidbits

Dec 98 Tips & Tidbits

by Jeff Clites, tips@mactech.com

WideAdd and WideSubtract Under 68K

If you use the PowerPC "wide arithmetic" routines WideAdd and WideSubtract (say to measure time intervals using the Microseconds() call) then you'll find that your code won't compile for 68K any more. Fortunately, this is easy to fix. The following code declares WideAdd and WideSubtract routines for 68K. They are extremely efficient to use because they generate inline 68K instructions, so using them doesn't even involve a function call.

#if __MC68K__

   #pragma parameter WideAddInline(__A0, __A1)
   local void WideAddInline(unsigned long *target_low_word, 
                  const unsigned long *source_low_word)
      THREEWORDINLINE(0x2011, 0xD190, 0xD189);
      // move.l (a1),d0  add.l d0,(a0)  addx.l -(a1),-(a0)
   #define WideAdd(target, source) \
               WideAddInline(&(target)->lo, &(source)->lo)

   #pragma parameter WideSubtractInline(__A0, __A1)
   local void WideSubtractInline(unsigned long 
      *target_low_word, const unsigned long *source_low_word)
      THREEWORDINLINE(0x2011, 0x9190, 0x9189);
      // move.l (a1),d0  sub.l d0,(a0)  subx.l -(a1),-(a0)
   #define WideSubtract(target, source) \
               WideSubtractInline(&(target)->lo, &(source)->lo)

#endif

The three-word 68K inline routines first add the least significant words together (or subtract them), and then do and add with carry (or subtract) on the most significant words to get the final answer. Because 68K byte order stores the low word last, the actual routines WideAdd and WideSubtract are declared as macros which first calculate the addresses of the low words of the "Wide" parameters, and then pass those addresses to the inline routines that do the actual work. The end result of this is that you can use WideAdd and WideSubtract just the same as you do in your PPC code, without any source code changes:

   WideSubtract(&target, &source);

Stuart Cheshire
cheshire@cs.stanford.edu


File Filters Under Navigation Services

There is one subtle, but important, difference between NavGetFile() and its Standard File equivalent-namely that NavGetFile() with a non-nil typeList only shows files matching the specified creator code! For example, if you include 'TEXT' in your typeList, along with your creator code, and expect NavGetFile() to show all text files, you'd be mistaken-you would only see those you created. The only easy way I know of around this is to dispense with the typeList, and do all file selection in your filter routine, something like this:

static pascal Boolean FilterTypes
(
   AEDesc             *TheItem,
   void               *info,
   void               *callBackUD,
   NavFilterModes     filterMode
)
/* file filter routine for Navigation Services that allows acceptance 
of all text files, regardless of creator. */
{
   Boolean                   IncludeIt;
   NavFileOrFolderInfo   *   TheInfo = (NavFileOrFolderInfo*)info;

   If (theItem->descriptorType != typeFSS){IncludeIt = true;}
   else if (TheInfo->isFolder)            {IncludeIt = true;}
   else
   {
      IncludeIt = 
         (TheInfo->fileAndFolder.fileInfo.finderInfo.fdType
                == 'TEXT');
   }

   return IncludeIt;
}

Note that the filter routine passes through all folders. My first attempt was mistakenly returning false for all folders, which not only was wrong, it also caused Navigation Services to crash. Also, don't forget to pass the routine to NavGetFile() using a routing descriptor rather than a raw function pointer, and to dispose of this routine descriptor using DisposeRoutineDescriptor() when you are finished with it:

NavObjectFilterUPP filterProc = 
                   NewNavObjectFilterProc(FilterTypes);

Lawrence D'Oliveiro
ldo@geek-central.gen.nz

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Combo Quest (Games)
Combo Quest 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: Combo Quest is an epic, time tap role-playing adventure. In this unique masterpiece, you are a knight on a heroic quest to retrieve... | Read more »
Hero Emblems (Games)
Hero Emblems 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: ** 25% OFF for a limited time to celebrate the release ** ** Note for iPhone 6 user: If it doesn't run fullscreen on your device... | Read more »
Puzzle Blitz (Games)
Puzzle Blitz 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Puzzle Blitz is a frantic puzzle solving race against the clock! Solve as many puzzles as you can, before time runs out! You have... | Read more »
Sky Patrol (Games)
Sky Patrol 1.0.1 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.1 (iTunes) Description: 'Strategic Twist On The Classic Shooter Genre' - Indie Game Mag... | Read more »
The Princess Bride - The Official Game...
The Princess Bride - The Official Game 1.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: An epic game based on the beloved classic movie? Inconceivable! Play the world of The Princess Bride... | Read more »
Frozen Synapse (Games)
Frozen Synapse 1.0 Device: iOS iPhone Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Frozen Synapse is a multi-award-winning tactical game. (Full cross-play with desktop and tablet versions) 9/10 Edge 9/10 Eurogamer... | Read more »
Space Marshals (Games)
Space Marshals 1.0.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: ### IMPORTANT ### Please note that iPhone 4 is not supported. Space Marshals is a Sci-fi Wild West adventure taking place... | Read more »
Battle Slimes (Games)
Battle Slimes 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: BATTLE SLIMES is a fun local multiplayer game. Control speedy & bouncy slime blobs as you compete with friends and family.... | Read more »
Spectrum - 3D Avenue (Games)
Spectrum - 3D Avenue 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: "Spectrum is a pretty cool take on twitchy/reaction-based gameplay with enough complexity and style to stand out from the... | Read more »
Drop Wizard (Games)
Drop Wizard 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Bring back the joy of arcade games! Drop Wizard is an action arcade game where you play as Teo, a wizard on a quest to save his... | Read more »

Price Scanner via MacPrices.net

Our MacBook Price Trackers will show you the...
Our Apple award-winning MacBook Price Trackers are continually updated with the latest information on prices, bundles, and availability for 16″ and 14″ MacBook Pros along with 13″ and 15″ MacBook... Read more
Amazon is offering a 10% discount on Apple’s...
Don’t pay full price! Amazon has 16-inch M4 Pro MacBook Pros (Silver and Black colors) on sale today for 10% off Apple’s MSRP. Shipping is free. These are the lowest prices currently available for 16... Read more
13-inch M4 MacBook Airs on sale for $150 off...
Amazon has new 13″ M4 MacBook Airs on sale for $150 off MSRP right now, starting at $849. Sale prices apply to most colors and configurations. Be sure to select Amazon as the seller, rather than a... Read more
15-inch M4 MacBook Airs on sale for $150 off...
Amazon has new 15″ M4 MacBook Airs on sale for $150 off Apple’s MSRP, starting at $1049. Be sure to select Amazon as the seller, rather than a third-party: – 15″ M4 MacBook Air (16GB/256GB): $1049, $... Read more
Amazon is offering a $50 discount on Apple’s...
Amazon has Apple’s 11th-generation A16 iPads in stock on sale for $50 (or a little more) off MSRP this week. Shipping is free: – 11″ 11th-generation 128GB WiFi iPads: $299 $50 off MSRP – 11″ 11th-... Read more
Clearance 13-inch M1 MacBook Airs available f...
Walmart has clearance, but new, Apple 13″ M1 MacBook Airs (8GB RAM, 256GB SSD) available online for $649, $360 off original MSRP, in Space Gray, Silver, and Gold colors. These are new MacBooks for... Read more
iPad minis on sale for $100 off Apple’s MSRP...
Amazon is offering $100 discounts (up to 20% off) on Apple’s newest 2024 WiFi iPad minis, each with free shipping. These are the lowest prices available for new minis among the Apple retailers we... Read more
AirPods Max headphones on sale for $479, $70...
Amazon has AirPods Max with USB-C on sale for $479.99 in all colors. Shipping is free. Their price is $70 off Apple’s MSRP, and it’s the lowest price available today for AirPods Max. Keep an eye on... Read more
14-inch M4 Pro/M4 Max MacBook Pros on sale th...
Don’t pay full price! Get a new 14″ MacBook Pro with an M4 Pro or M4 Max CPU for up to $320 off Apple’s MSRP this weekend at these retailers…they are the lowest prices available for these MacBook... Read more
Get a 15-inch M4 MacBook Air for $150 off App...
A couple of Apple retailers are offering $150 discounts on new 15″ M4 MacBook Airs this weekend. Prices at these retailers start at $1049: (1): Amazon has new 15″ M4 MacBook Airs on sale for $150 off... Read more

Jobs Board

All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.