TweetFollow Us on Twitter

Apr 93 Tips, Tidbits
Volume Number:9
Issue Number:4
Column Tag:Tips & Tidbits

Related Info: Script Manager

Tips & Tidbits

By Neil Ticktin, Editor-in-Chief

This column is your opportunity to spread the word about little bits of information that you find out about. These tidbits can be programming related or they can be user tips that are particularly useful to programmers.

MacTech Magazine will pay $25 for every tip used, and $50 for the Tip of the Month. Or you can take your award in orders or subscriptions.

To submit a tip, send in a letter to the magazine. E-mail is our preferred method, but feel free to send something via the US Mail. See page two for all addresses. If you do send snail mail, enclose a printed copy and a disk copy of the letter so that it does not have to be retyped.

Tip of the month

Here is a simple routine that returns a Boolean indicating whether the monitor is currently set at black & white or color.

/* 1 */

Boolean IsColorOn( void )
{
 GDHandle hGDevice;
 long   theMode;
 
 hGDevice = GetMainDevice();
 theMode = (**hGDevice).gdMode;
 theMode &= 0x0000000F;
 
 if( theMode != 0 ) return( true );
 else return( false );
}

I figured out how to write this piece of code after struggling with the concept for many months. It’s not a very complex routine, but I searched through every source I had available and never found anything that explained how to do it. I hope this will help others having the same problem.

- Marc White, Corinth, Mississippi

Script Manager Pitfall

If you plan to work with non-Roman script (such as Kanji, Arabic, Hebrew, etc ), there is a subtle - but important - point that Inside Macintosh will not tell you.

Script Manager functions can return wrong answers if the appropriate font is not set in the current GrafPort.

For example, there is a Script Manager function called CharByte which tells you if a given character is part of a two-byte script (or not). After reading the description of CharByte in Inside Macintosh, you will conclude it will know the right answer simply by looking at a piece of text. Wrong!

Unless the current font is a Kanji font, CharByte has no way of knowing that a given character is part of a double-byte Kanji character or whether it is a single-byte Roman character.

The reason is all 256 byte values are “valid” for all Roman fonts. If the current font is, say, Geneva, CharByte will think that 1/2 of a Kanji byte is really a single Roman character.

This is neither clear in Inside Macintosh Vol 5 nor the World Script section in Vol 6, but it is a fairly major point!

- Gar, DataPak Software

Apple’s Lame Disk Cache

After seeing significant I/O performance problems with large disk caches (set via the Memory control panel) I decided to run some benchmarks. I wrote a little application that would write a 400K file to a hard disk in 8K sector aligned chunks with various disk cache sizes and return to me the number of ticks that it took. Here are the results:

400K write

disk cache size 8K at a time

32K 50 ticks

64K 50 ticks

96K 51 ticks

128K 50 ticks

192K 50 ticks

256K 50 ticks

384K 691 ticks

512K 681 ticks

1024K 681 ticks

7680K 678 ticks

It appears that the Apple’s disk cache scheme hits a wall at 384K (in this test, anyway). I linked DTS with these results and got an interesting reply. It turns out that their disk cache scheme is optimized for very small reads and writes - like an application reading one byte at a time from a file without doing it's own buffering. I guess this was a problem back when most people used floppies and small hard drives. But modern apps usually do their own file buffering anyway (read a big piece into a buffer and then take it out of the buffer one byte at a time), so the Apple disk cache scheme becomes more of a hinderance than a help.

Not all reads and writes are cached by the Apple scheme. The formula it uses to decide if any given read or write should be cached is:

/* 2 */

numCacheBlocks = user-defined cache size DIV 512;
maxCachedReadWrite = (numCacheBlocks - 1) * 16;

So, with a cache size of 256K you get:

numCacheBlocks = 512
maxCachedReadWrite = 8176

That means that any read/write larger than 8176 bytes or larger will not be cached. So in my test app, nothing was being cached until the cache was 384K or larger, at which time my 8K writes were being cached (and I got a 13x performance slow-down).

There is hope, though. Page 2-95 of the new Inside Macintosh File Manager documents the "no cache" bit of ioPosMode. You can set bit 5 of ioPosMode to prevent your reads and writes from being cached. I strongly recommend you do this except in those few cases where you know you're going to need the data again right away or where you're not doing your own intelligent sector-aligned buffering. When I set this bit in my test app, my times for writing 400K with very large caches were the same as those for writing 400K with very small caches.

That's great for your code but what about other code that you can't control and that doesn't take advantage of bit 5 of ioPosMode? The only real defense is to reduce your disk cache to the minimum (32K) at which time only very small reads and writes will be cached (1008 bytes or less). But in my own tests with compiling large projects under MPW and Think C I have found that a disk cache size of 128K gives the fastest build times. You should do your own timings based on what type of I/O operations you do most.

- Mike Scanlin

MacTech Regular Contributor

Useless Trivia or a tip?

This is perhaps more fit for “Useless Trivia” than is is for “Tips and Tidbits,” but no matter, here it is:

Nearly every piece of C code that I ever see (even in MacTech Magazine) uses parentheses around all return statements. People always seem to write:

int theirfunc()
{
  .
  .
  return (1);
}

Even the examples in K&R itself use parentheses around the return statments. But look at the actual syntax reference in K&R: “if,” “while,” “for,” and “switch” all require parens, but “return” does not. For years, using many compilers, on many machines, I've been writing:

int myfunc()
{
  .
  .
  return 1;
}

It may look odd, but try it - it does work!

- Ken Gladstone

MacTech Technical Editor

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Bookends 12.5.8 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Access the power of Bookends directly from Mellel, Nisus Writer Pro, or MS Word (... Read more
Chromium 44.0.2403.125 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 44.0.2403.125: This release contains a number... Read more
iMazing 1.2.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Audio Hijack 3.2.0 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
FontExplorer X Pro 5.0.1 - Font manageme...
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
Calcbot 1.0.2 - Intelligent calculator a...
Calcbot is an intelligent calculator and unit converter for the rest of us. Featuring an easy-to-read history tape, expression view, intuitive conversion, and much more! Features History Tape -... Read more
MTR 5.0.0.1 - The Mac's oldest and...
MTR (was MacTheRipper)--the Mac's oldest and smartest DVD-backup app--is now updated to version 5.001 MTR -- the complete toolbox, not a one-trick, point-and-click extractor. MTR is intended for... Read more
LibreOffice 4.4.5.2 - Free, open-source...
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
Adobe Lightroom 6.1.1 - Import, develop,...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
File Juicer 4.41 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. It finds and... Read more

Pac-Man Championship Edition DX has brou...
Bandai Namco has released Pac-Man Championship Edition DX on iOS and Android, which features the classic arcade gameplay that we've all grown to love. Pac-Man Championship Edition DX can be enjoyed in much shorter bursts than the arcade versions... | Read more »
Cosmonautica (Games)
Cosmonautica 1.1 Device: iOS Universal Category: Games Price: $6.99, Version: 1.1 (iTunes) Description: Cast off! Are you ready for some hilarious adventures in outer space? | Read more »
Rescue humanity from a Demon horde in An...
Angel Stone is Fincon's follow up to the massively successful Hello Hero and is out now on iOS and Android. You play as a member of The Resistance, a group of mighty human warriors who have risen up in defiance of the Demon horde threatening to... | Read more »
Gallery Doctor (Photography)
Gallery Doctor 1.0 Device: iOS iPhone Category: Photography Price: $2.99, Version: 1.0 (iTunes) Description: Free up valuable iCloud and iPhone storage with Gallery Doctor, the only iPhone cleaner that automatically identifies the... | Read more »
You Against Me (Games)
You Against Me 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: A simple game… You. Me. Claim, steal, lock, score, win! | Read more »
Yep, it's True - Angry Birds 2 is O...
The not exactly rumors were true and the birds are back. Angry Birds 2 has come to the App Store and the world will... well I suppose it'll still be the same, but now we have more bird-flinging options! [Read more] | Read more »
You Could Design Your Own Card for Chain...
If you've ever wanted to create your own item, weapon, trap, or even monster for Chainsaw Warrior: Lords of the Night, this is your chance. Auroch Digital is currently holding a contest so that fans can fight to the death (not really) to see which... | Read more »
Bitcoin Billionaire is Going Back in Tim...
If you thought you managed to buy everything there is to buy in Bitcoin Billionaire and make all the money, well you though wrong. Those of you who made it far enough might remember investing in time travel - and it looks like that investment is... | Read more »
Domino Drop (Games)
Domino Drop 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Domino Drop is a delightful new puzzle game with dominos and gravity!Learn how to play it in a minute, master it day by day.Your... | Read more »
OPERATION DRACULA (Games)
OPERATION DRACULA 1.0.1 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0.1 (iTunes) Description: 25% off launch sale!!! 'Could prove to be one of the most accurate representations of the Japanese bullet hell shmup... | Read more »

Price Scanner via MacPrices.net

Sale! 13-inch MacBook Pros on sale for $100 o...
B&H Photo has 13″ MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.5GHz/500GB MacBook Pro: $999.99 save $100 - 13″ 2.7GHz/128GB Retina... Read more
Sale! Save $100 on 13-inch MacBook Airs this...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model.... Read more
Worldwide Tablet Market Decline Continues, Ap...
The worldwide tablet market declined -7.0% year-over-year in the second quarter of 2015 (2Q15) with shipments totaling 44.7 million units according to preliminary data from the International Data... Read more
TP-LINK TL-PA8030P KIT Powerline Featuring Ho...
Consumer and business networking products provider TP-LINK is now shipping its TL-PA8030P KIT AV1200 3-Port Gigabit Passthrough Powerline Starter Kit that expands your home’s network over its... Read more
Apple refurbished iPad Air 2s available for u...
The Apple Store has Apple Certified Refurbished iPad Air 2s available for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB... Read more
Updated Apple iPad Price Trackers
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers. Read more
Apple refurbished 2014 13-inch 128GB MacBook...
The Apple Store has Apple Certified Refurbished 2014 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 13″ 1.4GHz/128GB... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store has Apple Certified Refurbished Mac Pros available 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
Mac Pros on sale for up to $260 off MSRP
B&H Photo has Mac Pros on sale for up to $260 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3719.99... Read more

Jobs Board

Executive Administrative Assistant, *Apple*...
…supporting presentation development for senior leadership. * User experience with Apple hardware and software is preferred. Additional Requirements The following list Read more
*Apple* Bus Company is now hirin - Apple Bus...
Apple Bus Company is now hiring school bus drivers in the Pettis County area. Class B CDL preferred. Free training provided. No nights or weekends required. Flexible Read more
*Apple* Certified Mac Technician - Updated 6...
…and friendly, hands-on technical support to customers troubleshooting and repairing Apple /Mac products with courtesy, speed and skill. Use your problem-solving skills Read more
Infrastructure Engineer - *Apple* /Mac Envir...
…a part of a team Requires proven problem solving skills Preferred Additional Apple Certified System Administrator (ACSA) Apple Certified Technical Coordinator (ACTC) 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.