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

How to become the ultimate robot warrior...
Chrono Strike is a delightfully immersive beat ‘em up with a sense of humor (any game with a good Sims reference gets points in my book). [Read more] | Read more »
Tips and tricks to get a higher score in...
Snow Roll is a devilish endless runner very much in the vein of Flappy Bird. It revels in its dastardly level of difficulty, and doesn’t really care how angry you get at it as it knows you’ll keep coming back for more. [Read more] | Read more »
How to win big in Slots Deluxe
Cheating while gambling is illegal and morally wrong, and in some parts of the world it leads to men with names like Vinnie "Six Knuckles" Manchenzo beating you to a pulp in a dark alley. [Read more] | Read more »
How to take over the world in Dictator 2
Running a country isn't easy - especially when you're a dictator who wants to take over the world and crush everyone in your path while you do it. [Read more] | Read more »
Tips and tricks to get a higher score in...
Tank.iois - you guessed it! - another multiplayer arena battler likeAgar.io and Slither.io. It does differentiate itself by putting you in a tiny tank though, so it's not exactly the same. To help you get that all-important high score, we've got a... | Read more »
How to unlock characters in One Tap Tenn...
As the title suggests, One Tap Tennis requires only a single tap to play its particular brand of tennis, and rewards you with a ton of unlockable characters if you perform well. Fortunately for you, we at 148Apps have got a few tips and tricks to... | Read more »
Grab it now: Game Craft’s Legend of War...
The real time strategy game is now available for you to sink your teeth into, through the App Store and Google Play. Combining elements of skill, strategy and empire building, Legend of War is a real gamers’ game. [Read more] | Read more »
Skateboard Party 3 ft. Greg Lutzka (Gam...
Skateboard Party 3 ft. Greg Lutzka 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Skateboard Party is back! This third edition of the popular sports franchise features professional skater... | Read more »
Cubious (Games)
Cubious 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: Cubious – How smart are you? How high is your IQube? Solve the impossible puzzles to find out, and help a lost little cube find his... | Read more »
Goat Simulator Waste of Space (Games)
Goat Simulator Waste of Space 1.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.1 (iTunes) Description: ** IMPORTANT - SUPPORTED DEVICESiPhone 4S, iPad 2, iPod Touch 5 or better.** | Read more »

Price Scanner via MacPrices.net

Enterprise Workers Pick Technology Over Perks...
New Adobe study shows surprising attitudes about office jobs and where the future of work is heading. Adobe has released survey findings revealing that a surprising 70 percent of U.S. office workers... Read more
Memorial Day Weekend Sale: $50-$100 off 11-in...
B&H Photo has 13″ and 11″ MacBook Airs with 256GB SSDs on sale for $50-$100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.6GHz/256GB MacBook Air: $999 $100 off MSRP... Read more
Memorial Day Weekend Sales: Apple MacBook Pro...
B&H Photo has 13″ and 15″ Retina MacBook Pros on sale for up to $210 off MSRP. Shipping is free, and B&H charges NY tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off MSRP - 15″ 2.5GHz... Read more
Memorial Day Weekend Sales: Apple iMacs and M...
Take up to $150 off the price of a new iMac or Mac mini at the following Apple resellers this Memorial Day weekend: iMacs: B&H Photo has 21″ and 27″ iMacs on sale for up to $150 off MSRP... Read more
Apple refurbished Retina MacBook Pros availab...
Apple has Certified Refurbished 2015 13″ and 15″ Retina MacBook Pros available for up to $380 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free... Read more
Apple refurbished 11-inch MacBook Airs availa...
Apple has Certified Refurbished 11″ MacBook Airs (the latest models), available for up to $170 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Goal Zero and OtterBox Partner to Expand iPh...
Goal Zero, specialists in portable power, have announced a partnership with OtterBox, brand smartphone case protection, to offer the Slide and Slide Plus Batteries as modules compatible with the new... Read more
15-inch Retina MacBook Pros on sale for up to...
B&H Photo has 15″ Retina MacBook Pros on sale for up to $210 off MSRP. Shipping is free, and B&H charges NY tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off MSRP - 15″ 2.5GHz Retina... Read more
Clearance 2015 13-inch MacBook Airs available...
B&H Photo has clearance 2015 13″ MacBook Airs available for $250 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/4GB/128GB MacBook Air (MJVE2LL/A): $799... Read more
Apple refurbished Apple TVs available for up...
Apple has Certified Refurbished 32GB and 64GB Apple TVs available for up to $30 off the cost of new models. Apple’s standard one-year warranty is included with each model, and shipping is free: -... Read more

Jobs Board

*Apple* Architect - AECOM (United States)
**Requisition/Vacancy No.** 132759BR **Position Title** Apple Architect **Job Category** Information Technology **Business Line** Government **Country** United Read more
*Apple* Solutions Consultant - APPLE (United...
Job Summary As an Apple Solutions Consultant, you'll be the link between our future customers and our products. You'll showcase your entrepreneurial spirit as you Read more
*Apple* Project Engineer - Smart Source Inc...
SmartSource is in need of an Apple Project Engineer for a 12 month contract opportunity in Pittsburg, PA. Role: Apple Project Engineer Location: Pittsburg, PA Read more
Automotive Sales Consultant - Apple Ford Linc...
…you. The best candidates are smart, technologically savvy and are customer focused. Apple Ford Lincoln Apple Valley is different, because: $30,000 annual salary Read more
Service Assistant - *Apple* Chevrolet *App...
Apple Automotive is one of the fastest growing dealer...and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive, we Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.