TweetFollow Us on Twitter

Mar 97 Tips

Volume Number: 13 (1997)
Issue Number: 3
Column Tag: Tips & Tidbits

Tips & Tidbits

By Steve Sisak

Whenever you directly or indirectly modify code, you need to make sure the processor caches are synchronized in order to avoid confusing the processor and/or emulator. This includes not only self-modifying code, but also creating routine descriptors and loading code resources by hand.

If you move 68k code with BlockMove on any system (68k or PowerPC) the caches are flushed automatically (assuming blocks greater than 12 bytes). Use BlockMoveData for blocks containing no code, since they do not require the cache flushing overhead.

Note that on a PowerPC, BlockMove does not flush PPC caches at all. The only reason BlockMove flushes 68k code is for backward compatibility with software written before the '040s. It is unfortunate that a frequently-used routine like BlockMove should have to know anything about instruction caches. On the bright side, most developers do not need to copy PPC code around, since fragment preparation occurs within CFM.

On a PPC machine, calls to the 68k cache flushing routines (including FlushCodeCacheRange and indirectly via BlockMove) do everything necessary to maintain 68k instruction cache coherency. On the original 68k emulator, this meant nothing needed to be done since there was no cached code. On the DR Emulator and Speed Emulator, these calls force the emulator to "throw out" any recompiled code associated with the specified code range.

I know the different cache flushing routines are confusing and not very well documented. Here are some simple rules:

If you are dealing with 68k instructions, use BlockMove or FlushCodeCacheRange. They both specify a range of memory and therefore do not require the newer recompiling 68k emulators to perform a complete cache flush (a very time-intensive operation that can degrade performance significantly.)

If you are dealing with PPC code, you probably don't need to worry about the issue because your code was probably directly or indirectly prepared by CFM. However, if you do generate PPC code on the fly, you should call MakeDataExecutable on the range. Note that this does more than just flushing the cache. It does everything (including flushing the processor's prefetch queue) necessary to deal with newly-generated code.

Hope this helps clear things up. If you want more details, check out the tech note I wrote while I was still at Apple on the DR Emulator.

Eric Traut
Connectix Corp.

(Almost) Painless Mixing of C and Pascal Strings

It's fair to say that most of us have found ourselves in this situation: "The API wants C-style strings and all I have are these Pascsal strings!". The typical solution is to use utilities like PtoCStr and CtoPStr to shuffle the bytes around. Consider the following example where sprintf is being used to create a menu title.

void DescribeFile (Str255 title, Str255 fileName, Str255 volumeName, 
unsigned long size)
{
    // Temporarily convert fileName and volumeName to C strings
 PtoCStr (fileName);
 PtoCStr (volumeName);
    // Use sprintf to describe the file eg. "File foo on bar (120.5K)"
 sprintf ((char*) title, "File %s on %s (%.2fK)",
 (char*) fileName,
 (char*) volumeName,
 (double) size / 1024.0);
    // Convert title, fileName and volumeName to Pascal strings
    // back to Pascal strings
 CtoPStr ((char*) title);
 CtoPStr ((char*) fileName);
 CtoPStr ((char*) volumeName);
}

As you know there's at least one unused byte at the end of the Pascal string, and the string is not a literal, you can take a shortcut by making the Pascal strings "hybrid strings". A "hybrid string" is a null-terminated pascal string. Observe:

void DescribeFile (Str255 title, Str255 fileName, Str255 volumeName,unsigned 
long size)
{
    // Convert fileName and volumeName to hybrid strings
 fileName [fileName [0] + 1] = ‘\0';
 volumeName [volumeName [0] + 1] = ‘\0';
    // Use sprintf to describe the file eg. "File foo on bar (120.5K)"
    // Note that we skip the first byte of the hybrid strings
 sprintf ((char*) &title [1], "File %s on %s (%.2fK)",
 (char*) &fileName [1],
 (char*) &volumeName [1],
 (double) size / 1024.0);
    // ‘title' is not yet a hybrid string, it has an undefined length byte
 title [0] = strlen ((char*) &title [1]);
}

Remember, you can't always get away with this. In the above we know that title, fileName and volumeName are non-const strings with room for 255 characters. Since ‘fileName' and ‘volumeName' will never be more than 63 and 27 bytes respectively, we're sure there is room to add the length byte to the end. Similarly, ‘title' won't break 130 bytes.

Damon Cokenias
<http://www.netgate.net/~cokenias>

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Paragraphs 1.0.1 - Writing tool just for...
Paragraphs is an app just for writers. It was built for one thing and one thing only: writing. It gives you everything you need to create brilliant prose and does away with the rest. Everything in... Read more
BlueStacks App Player 0.9.21 - Run Andro...
BlueStacks App Player lets you run your Android apps fast and fullscreen on your Mac. Version 0.9.21: Note: Now requires OS X 10.8 or later running on a 64-bit Intel processor. Initial stable... Read more
Apple iTunes 12.2 - Play Apple Music...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Apple Security Update 2015-005 - For OS...
Apple Security Update 2015-005 is recommended for all users and improves the security of OS X. For detailed information about the security content of this update, please visit: http://support.apple.... Read more
Apple HP Printer Drivers 3.1 - For OS X...
Apple HP Printer Drivers includes the latest HP printing and scanning software for OS X Lion or later. For information about supported printer models, see this page. Version 3.1: The latest printing... Read more
Epson Printer Drivers 3.1 - For OS X 10....
Epson Printer Drivers installs the latest software for your EPSON printer or scanner for OS X Yosemite, OS X Mavericks, OS X Mountain Lion, and OS X Lion. For more information about printing and... Read more
Xcode 6.4 - Integrated development envir...
Xcode provides everything developers need to create great applications for Mac, iPhone, and iPad. Xcode brings user interface design, coding, testing, and debugging into a united workflow. The Xcode... Read more
OS X Yosemite 10.10.4 - Apple's lat...
OS X Yosemite is Apple's newest operating system for Mac. An elegant design that feels entirely fresh, yet inherently familiar. The apps you use every day, enhanced with new features. And a... Read more
Dash 3.0.2 - Instant search and offline...
Dash is an API Documentation Browser and Code Snippet Manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
FontExplorer X Pro 5.0 - Font management...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more

Heroki (Games)
Heroki 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: CLEAR THE SKIES FOR A NEW HERO!The peaceful sky village of Levantia is in danger! The dastardly Dr. N. Forchin and his accomplice,... | Read more »
Hands-On With Raceline CC
Set for release soon, Rebellion’s motorbike racing game, Raceline CC certainly looks stylish. But how does it play? I got my hands on a preview build to answer exactly that. | Read more »
Siegefall - Tips, Tricks, and Strategies...
So, you fancy establishing a base and ruling the world again. Siegefall is a convenient place to do that, but how about some great tips and tricks on how best to go about it? Here are a few ideas on how to get ahead as a beginner to this medieval... | Read more »
The WWE Comes to Racing Rivals - Because...
Racing Rivals is a racing game that's all about, well, rivalry. And who knows rivalry better than WWE superstars (shhhh, that was rhetorical)? [Read more] | Read more »
Hey, Who Put Apple Music in My SoundHoun...
One of the App Store's popular music discovery sources - SoundHound - has already been updated to include Apple's own music discovery source - Apple Music. That was fast! [Read more] | Read more »
Arcane Legends has a New Expansion Calle...
Arcane Legends has been going strong since it debuted at the tail end of 2012. So well, in fact, that it's already up to its sixth expansion. [Read more] | Read more »
Vector 2 is Officially a Thing and it...
Vector is a pretty cool parkour-driven runner that's gotten a pretty decent following since it first came out - although personally I think more people could stand to show it some love. Anyway, Nekki has announced that a sequel isofficially on its... | Read more »
Get Ready to Trucksform and Roll Out (an...
It looks like NuOxygen is bringing the truck-transforming racer Trucksform (get it?) to iOS in a couple of weeks. Although really it's more of an auto-driver than a racer. But still, transforming trucks! [Read more] | Read more »
This Week at 148Apps:June 22-26, 2015
June's Summer Journey Continues With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice,... | Read more »
LEGO® Minifigures Online (Games)
LEGO® Minifigures Online 1.0.1 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

Logo Pop Free Vector Logo Design App For OS X...
128bit Technologies has released of Logo Pop Free 1.2 for Mac OS X, a vector based, full-fledged, logo design app available exclusively on the Mac App Store for the agreeable price of absolutely free... Read more
21-inch 1.4GHz iMac on sale for $999, save $1...
B&H Photo has new 21″ 1.4GHz iMac on sale for $999 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Best Buy has the 21″ 1.4GHz iMac on sale for $999.99 on their... Read more
16GB iPad mini 3 on sale for $339, save $60
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $339 including free shipping plus NY tax only. Their price is $60 off MSRP. Read more
Save up to $40 on iPad Air 2, NY tax only, fr...
B&H Photo has iPad Air 2s on sale for up to $40 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $489 $10 off - 64GB iPad Air 2 WiFi: $559 $40 off - 128GB iPad Air... Read more
Apple Releases OS X 10.10.4 With WIFi Fix, iO...
On Tuesday, Apple released final versions of OS X 10.10.4 and iOS 8.4, as well as updates for the Safari browser for OS X Yosemite, Mavericks, and Mountain Lion. The OS X 10.10.4 update focuses on... Read more
Dual-Band High-Gain Antennas for Home Wi-Fi N...
Linksys has announced what it claims are the first dual-band, omni-directional high-gain antennas for the consumer market. The new Linksys high-gain antennas available in a 2- and 4-pack (WRT004ANT... Read more
Apple refurbished 2014 15-inch Retina MacBook...
The Apple Store has Apple 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... Read more
Clearance 2014 MacBook Airs available for up...
Adorama has 2014 MacBook Airs on sale for up to $301 off original MSRP including NY + NJ sales tax and free shipping: - 11″ 256GB MacBook Air: $798 $301 off original MSRP - 13″ 128GB MacBook Air: $... Read more
5K iMacs on sale for $100 off MSRP, free ship...
B&H Photo has the new 27″ 3.3GHz 5K iMac on sale for $1899.99 including free shipping plus NY tax only. Their price is $100 off MSRP. They have the 27″ 3.5GHz 5K iMac on sale for $2199, also $100... Read more
27-inch 3.2GHz iMac on sale for $1679, save $...
B&H Photo has the 27″ 3.2GHz iMac on sale for $1679.99 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Read more

Jobs Board

Senior Payments Security Manager - *Apple*...
**Job Summary** Apple , Inc. is looking for a highly motivated, innovative and hands-on senior payments security manager to join the Apple Pay security team. You will Read more
Project Manager - *Apple* Pay Security - Ap...
**Job Summary** The Apple Pay Security team is seeking a highly organized, results-driven Project Manager to drive the development of Apple Pay Security. If you are Read more
Web Developer, *Apple* Online Store Innovat...
**Job Summary** The Apple Online Store Innovation Lab team is seeking a talented individual with strong web development and design skills to prototype future Apple Read more
*Apple* TV Live Streaming Frameworks Test En...
**Job Summary** Work and contribute towards the engineering of Apple 's state-of-the-art products involving video, audio, and graphics in Interactive Media Group (IMG) at Read more
Project Manager, WW *Apple* Fulfillment Ope...
…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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.