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

PDFKey Pro 4.3 - Edit and print password...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Kodi 15.0.beta1 - Powerful media center...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
DiskCatalogMaker 6.4.12 - Catalog your d...
DiskCatalogMaker is a simple disk management tool which catalogs disks. Simple, light-weight, and fast. Finder-like intuitive look and feel. Super-fast search algorithm. Can compress catalog data... Read more
Macs Fan Control 1.3.0.0 - Monitor and c...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more
Lyn 1.5.11 - Lightweight image browser a...
Lyn is a lightweight and fast image browser and viewer designed for photographers, graphic artists and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it... Read more
NeoOffice 2014.11 - Mac-tailored, OpenOf...
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
LaunchBar 6.4 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Remotix 3.1.4 - Access all your computer...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features Complete Apple Screen Sharing support - including Mac OS X login, clipboard... 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
VOX 2.5.1 - Music player that supports m...
VOX is a beautiful music player that supports many filetypes. The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all... Read more

This Week at 148Apps: May 18-22, 2015
May Days at 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, standing out above the... | Read more »
Biz Builder Delux (Games)
Biz Builder Delux 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Ah, there's nothing like the rhythmic bustle of a burgeoning business burg... especially when you're the one building it... | Read more »
Auroch Digital is Bringing Back Games Wo...
| Read more »
Blades of Brim is a New Endless Runner f...
SYBO Games, the minds behind the ever-popular Subway Surfers, have announced their latest project: Blades of Brim. [Read more] | Read more »
Carbo - Handwriting in the Digital Age...
Carbo - Handwriting in the Digital Age 1.0 Device: iOS Universal Category: Productivity Price: $3.99, Version: 1.0 (iTunes) Description: | Read more »
Draggy Dead (Games)
Draggy Dead 1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1 (iTunes) Description: Ditch your dead end job and take up a rewarding career in Grave Robbing today!Guide the recently deceased to a fun filled life of... | Read more »
Bad Dinos (Games)
Bad Dinos 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: | Read more »
The Apple Watch isn't Great as a Fi...
| Read more »
Show the World What You See With Stre.am...
Live broadcasting is getting popular on mobile devices, which is why you can now get Stre.am, by Infinite Takes. [Read more] | Read more »
PhotoTime's 2.1 Update Adds Apple W...
The latest PhotoTime update is adding even more functionality to the handy photo organizing app. Yep, including Apple Watch support. [Read more] | Read more »

Price Scanner via MacPrices.net

12-inch MacBook stock status for Monday, May...
The new 12″ Retina MacBooks are still on backorder at The Apple Store with a 3-5 week waiting period. However, a few models are in stock today at Apple resellers. Stock is limited, so act now if you’... Read more
New 27-inch 3.3GHz 5K iMac in stock with free...
Adorama has the new 27″ 3.3GHz 5K iMac in stock today for $1999 including free shipping plus NY & NJ sales tax only. Adorama will include a free copy of Apple’s 3-year AppleCare Protection Plan. Read more
Memorial Day Weekend Sale: New 27-inch 3.3GHz...
Best Buy has the new 27″ 3.3GHz 5K iMac on sale for $1899.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary... Read more
OtterBox Maximizes Portability, Productivity...
From the kitchen recipe book to the boarsroom presentation, the OtterBox Agility Tablet System turns tablets into one of the most versatile pieces of handheld technology available. Available now, the... Read more
Launch of New Car App Gallery and Open Develo...
Automatic, a company on a mission to bring the power of the Internet into every car, has announced the launch of the Automatic App Gallery, an app store for nearly every car or truck on the road... Read more
Memorial Day Weekend Sale: 13-inch 1.6GHz Mac...
Best Buy has the new 13″ 1.6GHz/128GB MacBook Air on sale for $849 on their online store this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders... Read more
Memorial Day Weekend Sale: 27-inch 3.5GHz 5K...
Best Buy has the 27″ 3.5GHz 5K iMac on sale for $2099.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary.... Read more
Sale! 16GB iPad mini 3 for $349, save $50
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $349 including free shipping plus NY sales tax only. Their price is $50 off MSRP, and it’s the lowest price available for this model. Read more
Price drop on 2014 15-inch Retina MacBook Pro...
B&H Photo has dropped prices on 2014 15″ Retina MacBook Pros by $200. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799.99 save $200 - 15″ 2.5GHz... Read more
With a Mission to Make Mobile Free, Scratch W...
Scratch Wireless, claiming to be the world’s first truly free mobile service, has announced the availability of a new Scratch-enabled Android smartphone, the Coolpad Arise. The smartphone is equipped... Read more

Jobs Board

Payments Counsel, *Apple* Pay (mobile payme...
**Job Summary** Apple is looking for an atto ey to join Apple 's Legal Department to support Apple Pay. **Key Qualifications** 7+ years of relevant experience Read more
Touch Hardware Design and Integration Enginee...
…Summary** Design, develop, and launch next-generation Touch solutions in the new Apple Watch product category. The Touch team develops cutting-edge Touch solutions and Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail 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
*Apple* Retail - Multiple Positions (US) - A...
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.