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

Latest Forum Discussions

See All

Fresh From the Land Down Under – The Tou...
After a two week hiatus, we are back with another episode of The TouchArcade Show. Eli is fresh off his trip to Australia, which according to him is very similar to America but more upside down. Also kangaroos all over. Other topics this week... | Read more »
TouchArcade Game of the Week: ‘Dungeon T...
I’m a little conflicted on this week’s pick. Pretty much everyone knows the legend of Dungeon Raid, the match-3 RPG hybrid that took the world by storm way back in 2011. Everyone at the time was obsessed with it, but for whatever reason the... | Read more »
SwitchArcade Round-Up: Reviews Featuring...
Hello gentle readers, and welcome to the SwitchArcade Round-Up for July 19th, 2024. In today’s article, we finish up the week with the unusual appearance of a review. I’ve spent my time with Hot Lap Racing, and I’m ready to give my verdict. After... | Read more »
Draknek Interview: Alan Hazelden on Thin...
Ever since I played my first release from Draknek & Friends years ago, I knew I wanted to sit down with Alan Hazelden and chat about the team, puzzle games, and much more. | Read more »
The Latest ‘Marvel Snap’ OTA Update Buff...
I don’t know about all of you, my fellow Marvel Snap (Free) players, but these days when I see a balance update I find myself clenching my… teeth and bracing for the impact to my decks. They’ve been pretty spicy of late, after all. How will the... | Read more »
‘Honkai Star Rail’ Version 2.4 “Finest D...
HoYoverse just announced the Honkai Star Rail (Free) version 2.4 “Finest Duel Under the Pristine Blue" update alongside a surprising collaboration. Honkai Star Rail 2.4 follows the 2.3 “Farewell, Penacony" update. Read about that here. | Read more »
‘Vampire Survivors+’ on Apple Arcade Wil...
Earlier this month, Apple revealed that poncle’s excellent Vampire Survivors+ () would be heading to Apple Arcade as a new App Store Great. I reached out to poncle to check in on the DLC for Vampire Survivors+ because only the first two DLCs were... | Read more »
Homerun Clash 2: Legends Derby opens for...
Since launching in 2018, Homerun Clash has performed admirably for HAEGIN, racking up 12 million players all eager to prove they could be the next baseball champions. Well, the title will soon be up for grabs again, as Homerun Clash 2: Legends... | Read more »
‘Neverness to Everness’ Is a Free To Pla...
Perfect World Games and Hotta Studio (Tower of Fantasy) announced a new free to play open world RPG in the form of Neverness to Everness a few days ago (via Gematsu). Neverness to Everness has an urban setting, and the two reveal trailers for it... | Read more »
Meditative Puzzler ‘Ouros’ Coming to iOS...
Ouros is a mediative puzzle game from developer Michael Kamm that launched on PC just a couple of months back, and today it has been revealed that the title is now heading to iOS and Android devices next month. Which is good news I say because this... | Read more »

Price Scanner via MacPrices.net

Amazon is still selling 16-inch MacBook Pros...
Prime Day in July is over, but Amazon is still selling 16-inch Apple MacBook Pros for $500-$600 off MSRP. Shipping is free. These are the lowest prices available this weekend for new 16″ Apple... Read more
Walmart continues to sell clearance 13-inch M...
Walmart continues to offer clearance, but new, Apple 13″ M1 MacBook Airs (8GB RAM, 256GB SSD) online for $699, $300 off original MSRP, in Space Gray, Silver, and Gold colors. These are new MacBooks... Read more
Apple is offering steep discounts, up to $600...
Apple has standard-configuration 16″ M3 Max MacBook Pros available, Certified Refurbished, starting at $2969 and ranging up to $600 off MSRP. Each model features a new outer case, shipping is free,... Read more
Save up to $480 with these 14-inch M3 Pro/M3...
Apple has 14″ M3 Pro and M3 Max MacBook Pros in stock today and available, Certified Refurbished, starting at $1699 and ranging up to $480 off MSRP. Each model features a new outer case, shipping is... Read more
Amazon has clearance 9th-generation WiFi iPad...
Amazon has Apple’s 9th generation 10.2″ WiFi iPads on sale for $80-$100 off MSRP, starting only $249. Their prices are the lowest available for new iPads anywhere: – 10″ 64GB WiFi iPad (Space Gray or... Read more
Apple is offering a $50 discount on 2nd-gener...
Apple has Certified Refurbished White and Midnight HomePods available for $249, Certified Refurbished. That’s $50 off MSRP and the lowest price currently available for a full-size Apple HomePod today... Read more
The latest MacBook Pro sale at Amazon: 16-inc...
Amazon is offering instant discounts on 16″ M3 Pro and 16″ M3 Max MacBook Pros ranging up to $400 off MSRP as part of their early July 4th sale. Shipping is free. These are the lowest prices... Read more
14-inch M3 Pro MacBook Pros with 36GB of RAM...
B&H Photo has 14″ M3 Pro MacBook Pros with 36GB of RAM and 512GB or 1TB SSDs in stock today and on sale for $200 off Apple’s MSRP, each including free 1-2 day shipping: – 14″ M3 Pro MacBook Pro (... Read more
14-inch M3 MacBook Pros with 16GB of RAM on s...
B&H Photo has 14″ M3 MacBook Pros with 16GB of RAM and 512GB or 1TB SSDs in stock today and on sale for $150-$200 off Apple’s MSRP, each including free 1-2 day shipping: – 14″ M3 MacBook Pro (... Read more
Amazon is offering $170-$200 discounts on new...
Amazon is offering a $170-$200 discount on every configuration and color of Apple’s M3-powered 15″ MacBook Airs. Prices start at $1129 for models with 8GB of RAM and 256GB of storage: – 15″ M3... Read more

Jobs Board

*Apple* Systems Engineer - Chenega Corporati...
…LLC,** a **Chenega Professional Services** ' company, is looking for a ** Apple Systems Engineer** to support the Information Technology Operations and Maintenance Read more
Solutions Engineer - *Apple* - SHI (United...
**Job Summary** An Apple Solution Engineer's primary role is tosupport SHI customers in their efforts to select, deploy, and manage Apple operating systems and Read more
*Apple* / Mac Administrator - JAMF Pro - Ame...
Amentum is seeking an ** Apple / Mac Administrator - JAMF Pro** to provide support with the Apple Ecosystem to include hardware and software to join our team and Read more
Operations Associate - *Apple* Blossom Mall...
Operations Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Cashier - *Apple* Blossom Mall - JCPenney (...
Cashier - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Blossom Mall Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.