TweetFollow Us on Twitter

Vol Search XFCN
Volume Number:7
Issue Number:6
Column Tag:HyperChat

Related Info: File Manager

HFS Volume Search XFCN

By Mark Armstrong, Pharos Technologies

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

The SearchVol XFCN

The SearchVol XFCN searches the specified volume and returns the full path name of the file. This is extremely useful if you want to launch a document from within Hypercard but you are not sure where the file is located on the volume. SearchVol will return the full pathname of the file which you can then pass directly to the Hypertalk open command.

SearchVol uses a recursive algorithm to walk through the hierarchical file structure looking for a match. If it finds a match, it constructs the full path name by walking back up the tree. Once it has the full path name, it returns it to Hypercard. If no match is found, the XFCN will return empty. See the Other Issues section of this article for further discussion of the recursive nature of the algorithm.

SearchVol searches in the specified volume, or, if no volume is specified, in the system volume. Since PBGetVInfo prefers to have the volume specified in the form “volname:” (and since I am in the unfortunate habit of just passing “volume” without the trailing colon,) we simply check to see if there is a trailing colon on the specified volume name. If there is not, we add one.

Once we have the volume reference numbers we can begin the search. We start by determining the number of files and directories in the root directory by calling PBGetCatInfo and then we make the initial call to SearchFile, which is the real guts of the XFCN.

The Search Engine

The SearchFile function is very similar to Clifford Story’s walktree function in the October ’88 MacTutor (Programmer’s Workshop; HFS Transfer DA) Cliff wrote his in Pascal - this one is in C. But the structure of the routines is quite similar. For the gospel on searching HFS volumes, refer to Apple’s Technical Note 68.

You will notice that SearchFile consists of two for loops. The first for loop is looking for files. We look for file by accepting only the cases in which bit 4 of ioFlAttrib is not set. The second for loop is looking strictly for directories. If it is a file, then we check to see if there is a match. If it is a directory, then we look inside that directory with a recursive call to search file.

So, why the two for loops? Well, I wanted the routine to be equivalently fast for any file in a given directory. With just a single for loop, a file in the route directory named “AAAA” would most likely be found very quickly. Where as, a file named “ZZZZ” would take much longer, assuming, of course, that the volume in question was an average user’s 40 meg hard disk. Consequently, if we look through all the files first for a given directory before diving down to the next level in the hierarchy, we should be able to get a more consistent search time for files at the same hierarchical level. Once the recursive searching is complete, we check to see if a file was found. If a file was not found, fErr will contain fnfErr. On the other hand, if a file was found then we need to walk back up the hierarchy to construct the full path name that Hypercard requires for its file commands such as open, read, and print. We build the path name in the returnValue handle so it is available when we return to Hypercard.

Error Handling

In the SearchVol XFCN listed below I have included only a skeletal version of the required error handling. I have done this so as not to cloud the concepts on which I am trying to focus. However, I do have a few words about error handling that I would like to share.

There is an interesting catch-22 situation that arises for the author of external functions. The situation is this. If Hypercard is expecting you to return a value from an external function, then Hypercard needs a way to determine if the returned value is an error string or the expected result. In many XFCN’s available today, it is difficult (if not impossible) to determine in the general case if the string returned from the external is an error or not. As an example, suppose there is an XFCN that returns a file name. Furthermore, lets say that in case of error, the XFCN returns the error number. Now lets say that the XFCn is called from Hypertalk and the returned result is “-43”. Is this an error code for file not found or is it just a file that happens to be named “-43”. To avoid these problematic circumstances, the XFCN designer must make it very easy for the Hypertalk programmer to ascertain:

1) If an error occurred

2) What was the nature of the error

Another common approach is to return empty if an error occurred. Unfortunately, empty does not tell the Hypertalk programmer (to say nothing of the user) what went wrong. Consequently, it is difficult to take appropriate action.

Some programmers have circumnavigated the problem by forcing the declaration of a global variable. If an error occurs, then the global variable is set to notify Hypertalk that things did not go as planned. This method works has its advantages, but it can be an extra hassle if the Hypertalk programmer does not know he is required to declare the global. Whatever you decide to do, make your error checking rigorous and complete. Everyone will benefit.

Other Issues

SearchVol, as it is, is a foundation on which one can build. For example, one could easily search all mounted volumes by creating an outside loop that walked through the volume queue. For example:

/* 1 */

QHdrPtr QQ;
VCB     *Cur;

QQ = GetVCBQHdr();
Cur = (VCB *)(QQ->qHead);
   
do {
   /* Use Cur->vcbVN as the current volName */
   /* Put search volume code here */
   Cur = (VCB *)(Cur)->qLink;
   } while (Cur != 0L);

Another possibility is to extend the XFCN so that it returns all occurrences of the specified file - rather than just the first occurrence. In such a case, you would not return after finding a file but would simply store the full pathname of the file and then continue the search down the hierarchy. In this way, you could duplicate in Hypercard the functionality of the Find File desk accessory.

Other ideas include filtering out files by type or modification date, cataloging subdirectories on a volume, and the list goes on.

Finally, it is important to discuss the advantages and limitations of using a recursive algorithm for hierarchical searching. The advantages are that the code is small and simple. The primary limitation is that the stack grows with each recursive call. On a large hard disk or CD-ROM this could be a problem. I have used the recursive algorithm as a demonstration of recursive methods in an ideal world. Reality dictates that machines have a finite amount of memory. It is more prudent to employ methods which are not recursive if there is any possibility of exceeding available stack space.

/*------------------------------------------------
 SearchVol XFCN
 © 1989 MacTutor
 by Mark Armstrong    Pharos Technologies, Inc
 written in Think’s LightspeedC 3.0
------------------------------------------------*/

#include “HyperXCmd.h”
#include “FileMgr.h”
#include “HFS.h”
#include “ResourceMgr.h”
#include “SetUpA4.h”

#define False    0
#define True!False
#define Nil 0L

/*--------------------------------------
XFCN main function
--------------------------------------*/
pascal main(paramPtr)
   XCmdBlockPtr  paramPtr;
   {
   Str255 fName,str,fullPath,vName;
   HParamBlockRecMyHPB;
   CInfoPBRec    MyCIPB;
   OSErrfErr;
   shorttheVol;
   Handle nameH;
   long theDir,foundDir;
   
   RememberA0();
   SetUpA4();
   
   if ((paramPtr->paramCount < 1) || 
 (paramPtr->paramCount > 2)) 
   {
   SysBeep(10);
   /* return error string */
   goto Done;
   }
   
 ZeroToPas(paramPtr,*((unsigned char **)           paramPtr->params[0]), 
fName);
   if (paramPtr->paramCount == 2)
   {
   ZeroToPas(paramPtr,*((unsigned char **)               paramPtr->params[1]),vName);
   if (vName[vName[0]] != ‘:’)
   {
   vName[0]++;
   vName[vName[0]] = ‘:’;
   }
 MyHPB.volumeParam.ioCompletion = Nil;
 MyHPB.volumeParam.ioNamePtr = vName;
 MyHPB.volumeParam.ioVRefNum = 0;
 MyHPB.volumeParam.ioVolIndex = -1;
 fErr = PBHGetVInfo(&MyHPB,False);
 if (fErr)
 {
        SysBeep(10);
        /* return error string */
        goto Done;
 }
 theVol = MyHPB.volumeParam.ioVRefNum;
 }
   else theVol = GetSysVol();
   
   MyCIPB.dirInfo.ioCompletion = 0L;
   MyCIPB.dirInfo.ioNamePtr = 0L;
   MyCIPB.dirInfo.ioVRefNum = theVol;
   MyCIPB.dirInfo.ioFDirIndex = 0;
   MyCIPB.dirInfo.ioDrDirID = 2L;
   fErr = PBGetCatInfo(&MyCIPB,False);
   
   if (fErr)
 {
   SysBeep(10);
   /* return error string */
   goto Done;
 }
 else
   {
   fErr = 
 SearchFile(2L,
 MyCIPB.dirInfo.ioDrNmFls,
 theVol,
 &fName,
 &foundDir);
   if (fErr)
 {
   SysBeep(10);
   /* return error string */
   goto Done;
 }
 
   fullPath[0] = 0;
   PstrCopy(fullPath,fName);
   
   MyCIPB.dirInfo.ioCompletion = Nil;
   MyCIPB.dirInfo.ioNamePtr = str;
   MyCIPB.dirInfo.ioVRefNum = theVol;
   MyCIPB.dirInfo.ioFDirIndex = -1;
   MyCIPB.dirInfo.ioDrDirID = foundDir;
   fErr = PBGetCatInfo(&MyCIPB,False);
   PrependStr(MyCIPB.dirInfo.ioNamePtr,fullPath);
   
   do {
   MyCIPB.dirInfo.ioDrDirID =
 MyCIPB.dirInfo.ioDrParID;
   fErr = PBGetCatInfo(&MyCIPB,False);
   if (fErr == noErr)
 PrependStr(MyCIPB.dirInfo.ioNamePtr,fullPath);
   } while (fErr == noErr);
   
   paramPtr->returnValue =  PasToZero(paramPtr,(StringPtr)fullPath);
   }

Done:
   RestoreA4();
   }
  
/*--------------------------------------------
SearchFile is the recursive hierarchical search engine.  It looks at 
all the files and then all the folders in the directory specified by 
theVol and theDir for the file specified by fName
--------------------------------------------*/
SearchFile(theDir,count,theVol,fName,foundDir)
 long   theDir;
   shortcount,theVol;
   Str255 *fName;
   long *foundDir;
   {
   shortI;
   OSErrfErr;
   Str255 str;
   CInfoPBPtr    MyCIPB;
   
   MyCIPB = (CInfoPBPtr)NewPtr(sizeof(CInfoPBRec));
   for (I=1;I<=count;I++)
   {
   str[0] = 0;
   MyCIPB->dirInfo.ioCompletion = Nil;
   MyCIPB->dirInfo.ioNamePtr = str;
   MyCIPB->dirInfo.ioVRefNum = theVol;
   MyCIPB->dirInfo.ioFDirIndex = I;
   MyCIPB->dirInfo.ioDrDirID = theDir;
   fErr = PBGetCatInfo(MyCIPB,False);
   if (fErr) 
   {
   SysBeep(10);
   return (fErr);
   }
   else
   {
   if (!(MyCIPB->dirInfo.ioFlAttrib &  0x10))
   {
   if (EqualString(fName,
 MyCIPB->dirInfo.ioNamePtr,
 False,True))
   {
   *foundDir = 
 MyCIPB->hFileInfo.ioFlParID;
   return (0);
   }
   }
   }
   }
   
   for (I=1;I<=count;I++)
   {
   str[0] = 0;
   MyCIPB->dirInfo.ioCompletion = Nil;
   MyCIPB->dirInfo.ioNamePtr = str;
   MyCIPB->dirInfo.ioVRefNum = theVol;
   MyCIPB->dirInfo.ioFDirIndex = I;
   MyCIPB->dirInfo.ioDrDirID = theDir;
   fErr = PBGetCatInfo(MyCIPB,False);
   if (fErr) 
   {
   SysBeep(10);
   return (fErr);
   }
   else
   {
   if (MyCIPB->dirInfo.ioFlAttrib & 0x10)
   {
   fErr = 
 SearchFile(
 MyCIPB->dirInfo.ioDrDirID,
   MyCIPB->dirInfo.ioDrNmFls,
   theVol,
   fName,
   foundDir);
   if (!fErr) return (0);
   }
   }
   }
   
   DisposPtr(MyCIPB);
   return (fnfErr);
   }

/*--------------------------------------------
PrependStr puts string s1 and a colon before string s2.
--------------------------------------------*/
PrependStr(s1,s2)
 char   *s1,*s2;
 {
 Str255 temp;
 PstrCopy(temp,s2);
 s1[0]++;
 s1[s1[0]] = ‘:’;
 PstrCopy(s2,s1);
 BlockMove(&(temp[1]),&(s2[s2[0]+1]),
 (long)temp[0]);
 s2[0] += temp[0];
 }

/*--------------------------------------------
PstrCopy copies string s2 into string s1
--------------------------------------------*/
PstrCopy(s1,s2)
 char   *s1,*s2;
 {
 short  len;
 for (len=*s2;len>=0;--len) *s1++ = *s2++;
 }

/*--------------------------------------------
GetSysVol returns the vRefNum of the startup system volume.
--------------------------------------------*/
GetSysVol()
   {
   shortvRefNum;
   OSErrFErr;
   FErr = GetVRefNum(SysMap,&vRefNum);
   return vRefNum;
   }

[Mark Armstrong is presently the Vice President of Technical Operations for Pharos Technologies, Inc., a system integration and software development firm. He is the author of UNITize™, and has contributed to several other projects such as Milo™ and Marble Madness™.]

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

1Password 6.6.4 - Powerful password mana...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more
Cocktail 10.3.1 - General maintenance an...
Cocktail is a general purpose utility for macOS that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Safari Technology Preview 10.2 - The new...
Safari Technology Preview contains the most recent additions and improvements to WebKit and the latest advances in Safari web technologies. And once installed, you will receive notifications of... Read more
Together 3.8 - Store and organize all of...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Features Smart storage. With simple drag-and-drop... Read more
GraphicConverter 10.4 - $39.95
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
beaTunes 4.6.13 - Organize your music co...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
Vienna 3.1.9 :e81515b: - RSS and Atom ne...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more
iExplorer 4.0.12.0 - View and transfer f...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
OpenEmu 2.0.5 - Open Source game-emulati...
OpenEmu is about to change the world of video game emulation, one console at a time... For the first time, the 'It just works' philosophy now extends to open source video game emulation on the Mac.... Read more
TextSoap 8.3.3 - Automate tedious text d...
TextSoap can automatically remove unwanted characters, fix up messed up carriage returns, and do pretty much anything else that we can think of to text. Save time and effort. Be more productive. Stop... Read more

Ticket to Earth beginner's guide: H...
Robot Circus launched Ticket to Earth as part of the App Store's indie games event last week. If you're not quite digging the space operatics Mass Effect: Andromeda is serving up, you'll be pleased to know that there's a surprising alternative on... | Read more »
Leap to victory in Nexx Studios new plat...
You’re always a hop, skip, and a jump away from a fiery death in Temple Jump, a new platformer-cum-endless runner from Nexx Studio. It’s out now on both iOS and Android if you’re an adventurer seeking treasure in a crumbling, pixel-laden temple. | Read more »
Failbetter Games details changes coming...
Sunless Sea, Failbetter Games' dark and gloomy sea explorer, sets sail for the iPad tomorrow. Ahead of the game's launch, Failbetter took to Twitter to discuss what will be different in the mobile version of the game. Many of the changes make... | Read more »
Splish, splash! The Pokémon GO Water Fes...
Niantic is back with a new festival for dedicated Pokémon GO collectors. The Water Festival officially kicks off today at 1 P.M. PDT and runs through March 29. Magikarp, Squirtle, Totodile, and their assorted evolved forms will be appearing at... | Read more »
Death Road to Canada (Games)
Death Road to Canada 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: Get it now at the low launch price! Price will go up a dollar every major update. Update news at the bottom of this... | Read more »
Bean's Quest Beginner's Guide:...
Bean's Quest is a new take on both the classic platformer and the endless runner, and it's free on the App Store for the time being. Instead of running constantly, you can't stop jumping. That adds a surprising new level of challenge to the game... | Read more »
How to rake in the cash in Bit City
Our last Bit City guide covered the basics. Now it's time to get into some of the more advanced techniques. In the later cities, cash flow becomes much more difficult, so you'll want to develop some strategies if you want to complete each level.... | Read more »
PixelTerra (Games)
PixelTerra 1.1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1.1 (iTunes) Description: The world of PixelTerra is quite dangerous so you need to build a shelter, find some food supply and get ready to protect... | Read more »
Tokaido™ (Games)
Tokaido™ 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Discover the digital adaptation of Tokaido, the boardgame phenomenon that has already sold more than 250,000 copies worldwide, and... | Read more »
Card Thief (Games)
Card Thief 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Card Thief is a solitaire style stealth game played with a deck of cards. In Card Thief you move through a deck of cards as a... | Read more »

Price Scanner via MacPrices.net

Apple’s iPhone 6s Tops Best-Selling Smartphon...
In terms of shipments, the iPhone 6s from Apple bested all competitors for sales in 2016, according to new analysis from IHS Markit, a world leader in critical information, analytics and solutions.... Read more
Logitech Rugged Combo Protective iPad Case an...
Logitech has announced its Logitech Rugged Combo, Logitech Rugged Case, and Logitech Add-on Keyboard for Rugged Case for Apple’s new, more affordable $329 9.7-inch iPad, a complete solution designed... Read more
T-Mobile To Offer iPhone 7 and iPhone 7 Plus...
T-Mobile has announced it will offer iPhone 7 and iPhone 7 Plus (PRODUCT)RED Special Edition in a vibrant red aluminum finish. The introduction of this special edition iPhone celebrates Apple’s 10... Read more
9-inch 128GB iPad Pros on sale for $50-$70 of...
B&H Photo has 9.7″ 128GB Apple WiFi iPad Pros on sale for up to $70 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 9″ Space Gray 128GB WiFi iPad Pro: $649 $50... Read more
27-inch iMacs on sale for up to $200 off MSRP...
B&H Photo has 27″ Apple iMacs on sale for up to $200 off MSRP, each including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2099 $200 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has 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 following... Read more
Save $230 with Apple Certified Refurbished 13...
Apple is now offering Certified Refurbished 2016 13″ 2.0GHz non-Touch Bar MacBook Pros for $230 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: - 13″... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
13-inch Touch Bar MacBook Pros on sale for up...
B&H Photo has the Apple 13″ Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.9GHz/512GB Touch Bar... Read more
Today only! 15-inch 2.7GHz Space Gray Touch B...
B&H Photo has the new 2016 15″ 2.7GHz Space Gray Apple Touch Bar MacBook Pro in stock today and on sale for $300 off MSRP for today only. Shipping is free, and B&H charges NY sales tax only... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Director, *Apple* Program - ERP & Cloud...
Leading Pharmaceutical / Biotech Company is announcing a Director, Apple Program - ERP & Cloud Platform Architecture Lead opportunity in Northbrook, IL. Purpose & Read more
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
Starte Dein Karriere-Abenteuer in den Hauptst...
…mehrsprachigen Teams betreust Du Kunden von bekannten globale Marken wie Apple , Mercedes, Facebook, Expedia, und vielen anderen! Funktion Du wolltest schon Read more
*Apple* Retail - Multiple Positions - Apple,...
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.