TweetFollow Us on Twitter

Catalog XCMD
Volume Number:5
Issue Number:11
Column Tag:HyperChat™

Related Info: File Manager (PBxxx)

XCMD Corner: Catalog XCMD

By Donald Koscheka, Arthur Young & Co., MacTutor Contributing Editor

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Bullet Proofing

Recently, Joe Palooka wrote to complain about a bug in the GetFileName XCMD that appeared in this column a few months back. Apparently, the xcmd bombed if you passed it more than four file types. But this letter raises a more important issue: how much bulletproofing should I do to my code examples?

Before you jump to the obvious conclusion, allow me to make my case. Bulletproofing my code examples carries three liabilities for this column, size and clarity and time. The former is obvious. This magazine can carry only a certain number of pages per issue. Exceeding that page limit on a regular basis will result in my column getting bumped or serialized. I would like to avoid either case.

Clarity is not so obvious and, in fact, is a function of size. The larger a program is, the more unreadable it becomes. Bulletproofing code tends to be fairly routine, and one can almost apply a formula to XCMDs for bulletproofing: (1) Are the input parameters defined? (2) if so, are they properly conditioned (e.g. correct number of data).

The final liability is time. My years of experience have taught me that a large amount of a programming project’s time is spent anticipating exceptions. Working under a monthly deadline, it is often necessary to eliminate this step. I don’t see any contradiction here. If you intend to use my code in your own product, then it’s incumbent on you test its effectiveness. Bulletproofing my examples will only make your job harder and even then, I have no way of anticipating your exceptions (i.e. what happens to subroutine x if I make this small change to its parameters?)

This code tends to take the form:

if( paramPtr->params[i] && **(paramPtr->params[i]) )...

Testing the input parameters is something else entirely and can easily exceed the size of the “functional code”.

This is not to belittle the need for bulletproof code. Far from it. If you intend to use the code in this column, you should use it as a starting point. In general, if you intend to use somebody else’s code, you should seek answers to these questions: what does the code do? what doesn’t the code do?

At any rate, I will leave this issue on your hands. Write to the editor and let him know your feelings.

Catalog

One good XCMD deserves another. Recently, Joe Zuffoletto called me to ask whether I had any intentions of writing an XCMD that returns a catalog of a given directory. You may recall that Joe gave us the series on adding standard Mac windows to Hypercard. Such code cannot go unrewarded and so this month’s xcmd ...

Catalog accepts parameters in one of two forms. If you pass a pathname in the first parameter, it will return a catalog of all files in that directory. If the first parameter is empty, then Catalog will use the second parameter as directory reference number. This second parameter requires further explaining by way of the file manager.

When the user selects a file from the standard file dialog, the name as well as the volume reference number is passed back to the caller. Under HFS, the volume reference number masquerades as a working directory id. In reality, this reference number acts as either a volume reference number or a working directory id. How the file manager tells them apart is subtle but important:

Volume reference numbers are small negative integers such as -1, -2, -3... In fact, if you pass such a number to Catalog, you will get a listing of the root directory of the volume in question.

Working directory id’s are x. Working directories must not be confused with directory id’s. Each file has a unique id assigned to it called a directory id. This id is a long integer that uniquely identifies a file or folder. Working directory id’s by contrast are integers and are not unique for a given folder. Working directories are very much like file reference numbers. When a working directory is opened by the call, PBOpenWD, a reference number is returned in the vRefNum field.

Listing 1:

/********************************/
/* File: Catalog.c */
/* */
/* Given the reference number of*/
/* a working directory or volume*/
/* return a list of all files & */
/* folders in that directory*/
/* */
/* if a name is given, use it,*/
/* otherwise, use the id passed  */
/********************************/

#include<MacTypes.h>
#include<OSUtil.h>
#include<MemoryMgr.h>
#include<FileMgr.h>
#include<ResourceMgr.h>
#include<pascal.h>
#include<string.h>
#include<hfs.h>
#include  “HyperXCmd.h”
#include“HyperUtils.h”

#define nil 0L

extern  GetCatalog();

pascal void main( paramPtr )
 XCmdBlockPtr  paramPtr;
{
 Handle catalog;
 Str31  str;
 short  dirID;

 /*** intialize the output container ***/
 catalog = NewHandle( 0L );
 
 /*** convert the wdid to a usable form            ***/
 if( paramPtr->params[1] ){
 HLock( paramPtr->params[1] );
 ZeroToPas( paramPtr, *(paramPtr->params[1]), &str );
 HUnlock( paramPtr->params[1] );
 dirID = (short)StrToNum( paramPtr, &str );

 /*** given the id of a directory, ***/
 /*** return a catalog for that directory ***/
 GetCatalog( dirID, catalog );
 }
 else if( paramPtr->params[0] ){ 
 char   path[256];
 CInfoPBRec catPB;
 WDPBRecwdPB;
 
 HLock( paramPtr->params[0] );
 ZeroToPas( paramPtr, *(paramPtr->params[0]), &path );
 HUnlock( paramPtr->params[0] );
 
 /*** get a directory id to this path***/          
 catPB.dirInfo.ioNamePtr  = (StringPtr)path;
 catPB.dirInfo.ioFDirIndex  = 0;
 catPB.dirInfo.ioVRefNum  = 0;
 if( PBGetCatInfo( &catPB, 0 ) == noErr )
   if( catPB.dirInfo.ioFlAttrib & 0x010 ){   /*** it’s a directory
 ***/
 wdPB.ioNamePtr  = (StringPtr)path; 
   wdPB.ioWDProcID = 0;
  
 if( PBOpenWD( &wdPB, 0 ) == noErr ){
 wdPB.ioWDVRefNum= catPB.dirInfo.ioVRefNum;
 wdPB.ioWDDirID  = catPB.dirInfo.ioDrDirID;
 GetCatalog( wdPB.ioVRefNum, catalog );
 PBCloseWD( &wdPB, 0 );
 }
   }
 }
 /*** append a null to the end of the***/
 /*** the directory for Hypercard  ***/
 AppendCharToHandle( catalog, ‘\0’ );
 
 paramPtr->returnValue = catalog;
}
Listing 2:

#include<MacTypes.h>
#include<OSUtil.h>
#include<MemoryMgr.h>
#include<FileMgr.h>
#include<ResourceMgr.h>
#include<pascal.h>
#include<hfs.h>
#include<string.h>
#include  “HyperXCmd.h”
#include“HyperUtils.h”

/*** If you read this column***/
/*** column on a regular basis***/
/*** you may want to add these***/
/*** routines to HyperUtils.c ***/
/*** If you don’t have Hyper- ***/
/*** utils.c, you can obtain it  ***/
/*** from MacTutor for a small***/
/*** handling charge ***/

#define SYNC0

AppendCharToHandle( theHand, theChar )
 Handle theHand;
 char theChar;
/****************************
* Given a valid handle, append
* the character passed in to 
* the end of the handle
* 
* This is a useful way to embed
* \r, \t or \0 into a container
* for use by hypercard.
****************************/
{
 long   hsiz = GetHandleSize( theHand );
 char   *dirP;

 SetHandleSize( theHand, hsiz + 1 );
 dirP = *theHand + hsiz;
 *dirP= theChar;
}

GetCatalog( wdref, dirH )
 short  wdref;
 Handle dirH;
/****************************
* Get a listing of the directory
* passed in.
* In:
*  wdref == reference number of the
*  the desired working directory
*dirH == handle to the output container.
* Note that we allocate all structures 
* in the heap to minimize the impact
* a high directory valence might have
* on the stack.
****************************/
{
 OSErr  done= 0; /* goes true when done searching  */
 CInfoPBPtr catPB= (CInfoPBPtr)NewPtr( sizeof(CInfoPBRec));
 WDPBPtrwdPB= (WDPBPtr)NewPtr( sizeof(WDPBRec));
 char   *fname = (char *)NewPtr( 256L );

 if( catPB && wdPB && fname ){
 catPB->dirInfo.ioNamePtr = (StringPtr)fname;
 catPB->dirInfo.ioFDirIndex = 0;
 catPB->dirInfo.ioVRefNum = wdref; 
 
 do{
 *(catPB->dirInfo.ioNamePtr) = ‘\0’;
 catPB->dirInfo.ioFDirIndex++;
 catPB->dirInfo.ioDrDirID = 0; 
 
 if( (done = PBGetCatInfo( catPB, SYNC ) ) == noErr ){
 pStrToField( fname, ‘’, dirH );
   if( catPB->dirInfo.ioFlAttrib & 0x010 ){  /*** it’s a directory
 ***/
 AppendCharToHandle( dirH, ‘:’ );
   }
   AppendCharToHandle( dirH, ‘\r’ );
 }
 }while( !done );
 
 DisposPtr( (Ptr)catPB );
 DisposPtr( (Ptr)wdPB );
 DisposPtr( (Ptr)fname );
 }
}

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Macs Fan Control 1.3.1.0 - 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
NetShade 6.3.1 - Browse privately using...
NetShade is an anonymous proxy and VPN app+service for Mac. Unblock your Internet through NetShade's high-speed proxy and VPN servers spanning seven countries. NetShade masks your IP address as you... Read more
Dragon Dictate 4.0.7 - Premium voice-rec...
With Dragon Dictate speech recognition software, you can use your voice to create and edit text or interact with your favorite Mac applications. Far more than just speech-to-text, Dragon Dictate lets... Read more
Persecond 1.0.2 - Timelapse video made e...
Persecond is the easy, fun way to create a beautiful timelapse video. Import an image sequence from any camera, trim the length of your video, adjust the speed and playback direction, and you’re done... Read more
GIMP 2.8.14p2 - Powerful, free image edi...
GIMP is a multi-platform photo manipulation tool. GIMP is an acronym for GNU Image Manipulation Program. The GIMP is suitable for a variety of image manipulation tasks, including photo retouching,... Read more
Sandvox 2.10.2 - Easily build eye-catchi...
Sandvox is for Mac users who want to create a professional looking website quickly and easily. With Sandvox, you don't need to be a Web genius to build a stylish, feature-rich, standards-compliant... Read more
LibreOffice 5.0.1.2 - 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
f.lux 36.1 - Adjusts the color of your d...
f.lux makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day. Ever notice how people texting at night have that eerie blue glow? Or wake... Read more
VirtualBox 5.0.2 - x86 virtualization so...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
File Juicer 4.43 - 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. In computer... Read more

ReBoard: Revolutionary Keyboard (Utilit...
ReBoard: Revolutionary Keyboard 1.0 Device: iOS Universal Category: Utilities Price: $1.99, Version: 1.0 (iTunes) Description: Do everything within the keyboard without switching apps! If you are in WhatsApp, how do you schedule a... | Read more »
Tiny Empire (Games)
Tiny Empire 1.1.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1.3 (iTunes) Description: Launch cannonballs and blow tiny orcs into thousands of pieces in this intuitive fantasy-themed puzzle shooter! Embark on an... | Read more »
Astropad Mini (Productivity)
Astropad Mini 1.0 Device: iOS iPhone Category: Productivity Price: $4.99, Version: 1.0 (iTunes) Description: *** 50% off introductory price! ​*** Get the high-end experience of a Wacom tablet at a fraction of the price with Astropad... | Read more »
Emo Chorus (Music)
Emo Chorus 1.0.0 Device: iOS Universal Category: Music Price: $1.99, Version: 1.0.0 (iTunes) Description: Realistic Choir simulator ranging from simple Chorus emulation to full ensemble Choir with 128 members. ### introductory offer... | Read more »
Forest Spirit (Games)
Forest Spirit 1.0.5 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.5 (iTunes) Description: | Read more »
Ski Safari 2 (Games)
Ski Safari 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The world's most fantastical, fun, family-friendly skiing game is back and better than ever! Play as Sven's sister Evana, share... | Read more »
Lara Croft GO (Games)
Lara Croft GO 1.0.47768 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.47768 (iTunes) Description: Lara Croft GO is a turn based puzzle-adventure set in a long-forgotten world. Explore the ruins of an ancient... | Read more »
Whispering Willows (Games)
Whispering Willows 1.23 Device: iOS Universal Category: Games Price: $4.99, Version: 1.23 (iTunes) Description: **LAUNCH SALE 50% OFF** - Whispering Willows is on sale for 50% off ($4.99) until September 9th. | Read more »
Calvino Noir (Games)
Calvino Noir 1.1 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: The film noir stealth game. Calvino Noir is the exploratory, sneaking adventure through the 1930s European criminal underworld.... | Read more »
Angel Sword (Games)
Angel Sword 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Prepare to adventure in the most epic full scale multiplayer 3D RPG for mobile! Experience amazing detailed graphics in full HD.... | Read more »

Price Scanner via MacPrices.net

Apple offering refurbished 2015 13-inch Retin...
The Apple Store is offering Apple Certified Refurbished 2015 13″ Retina MacBook Pros for up to $270 (15%) off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Apple refurbished 2015 MacBook Airs available...
The Apple Store has Apple Certified Refurbished 2015 11″ and 13″ MacBook Airs (the latest models), available for up to $180 off the cost of new models. An Apple one-year warranty is included with... Read more
21-inch iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ iMacs on sale for up to $120 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $999.99 $100 off - 21″ 2.7GHz iMac: $1199.99 $100 off - 21″ 2.9GHz iMac... Read more
5K iMacs on sale for up to $150 off MSRP, fre...
B&H Photo has the 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 $2149.99 $2199.99, $... Read more
1.4GHz Mac mini, refurbished, available for $...
The Apple Store has Apple Certified Refurbished 1.4GHz Mac minis available for $419. Apple’s one-year warranty is included, and shipping is free. Their price is $80 off MSRP, and it’s the lowest... Read more
iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
MacBook Airs on sale for $100 off MSRP
Best Buy has MacBook Airs on sale for $100 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary... Read more
Big Grips Lift Handle For iPad Air and iPad A...
KEM Ventures, Inc. which pioneered the extra-large, super-protective iPad case market with the introduction of Big Grips Frame and Stand in 2011, is launching Big Grips Lift featuring a new super-... Read more
Samsung Launches Galaxy Tab S2, Its Most Powe...
Samsung Electronics America, Inc. has announced the U.S. release of the Galaxy Tab S2, its thinnest, lightest, ultra-fast tablet. Blending form and function, elegant design and multitasking power,... Read more
Tablet Screen Sizes Expanding as iPad Pro App...
Larger screen sizes are gaining favor as the tablet transforms into a productivity device, with shipments growing 185 percent year-over-year in 2015. According to a new Strategy Analytics’ Tablet... Read more

Jobs Board

*Apple* Music, Business Operations - Apple (...
**Job Summary** This role in Apple Music and in iTunes is working with…the songs that we all enjoy listening to in Apple Music. Your job will be to work wit Read more
Hardware Systems Integration Engineer - *App...
**Job Summary** We are seeking an enthusiastic electrical engineer for the Apple Watch team. This is a design engineering position that entails working with Read more
Engineering Project Manager - *Apple* TV -...
**Job Summary** The iTunes Apps project management team oversees iTunes, Apple TV, DRM and iOS Applications. We are looking for a project manager to help manage and 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
*Apple* Retail Online Store: Customer Insigh...
**Job Summary** Apple Retail (Online Store) is seeking an experienced e-commerce analytics professional to join the Customer Insights Team. The Web e-Commerce Analyst Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.