TweetFollow Us on Twitter

File Path
Volume Number:7
Issue Number:9
Column Tag:TechNotes

Related Info: File Manager File Mgr (PBxxx) Standard FIle

File Path Revisited

By Alexander Colwell, Redondo Beach, CA

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

File Path Revisited

Some of the MacTutor readers probably noticed. “Hey! Somebody has already written this article before! So, why is it here again?” Well the answer is yes, it has, but only half the story. The previous MacTutor articles in January 1986 “Programming for HFS Compatibility” by Mike Schuster and in July 1986 “Make a Path Name for HFS” by Tom Taylor discuss when given the volume reference number (vRefNum) obtained by the standard SFGetFile dialog then the file’s full file path can be derived.1 But what about when given a full file path and deriving the file’s vRefNum that would be identical number returned by the SFGetFile dialog?

There are cases when applications, DA’s, or other resource codes may want to know where the file is located between invocations. In April 1990, The Apple Technical Journal’s “d e v e l o p e “ in Macintosh Q&A section recommends saving the “DirID” number that references the directory.2 This scheme is desirable because it’s simple and easy to retrieve the file’s vRefNum by calling the PBOpenWD ROM routine that can be used either by the FSOpen or PBOpen ROM routines. Another advantage is that the user can change the directory name and the directory ID number will remain the same. There are cases when this scheme fails if the directory is backed up, deleted, and restored, then the directory ID number is likely to be changed. Therefore, the application must ask you for the location of the desired file by popping up the SFGetFile dialog again.

OK. So you bother the user again by reasking the location of the file. No big deal. But what about an application managing distributed databases of files where each user has mirror copy of the files and folders relationship on its hard disk? This could be a real pain to ask the user to find hundreds of files when they periodically receive database updates, and the directories are constantly changing. This was exactly the situation I encountered a few years ago during a Macintosh application development at my place of employment.

During the development cycle of that application, I poured over the MacTutor articles and Macintosh Technical Notes on how to do this seemingly simple procedure. To my disappointment, I could not find a method that somebody else might have hacked out! After a few weeks of off and on hacking, I finally figured out how to obtain the vRefNum based on the file path that is equivalent to the same vRefNum returned by the SFGetFile dialog.

The results are two procedures rewritten from Pascal to THINK C from my old Mac programming projects. The first procedure is “GetFilePath” (rehash from previous articles) to obtain the file path given by the vRefNum. The other inverse procedure is the “GetVolRefNbr” to obtain the vRefNum given by the file path.3

The key in the “GetVolRefNbr” procedure is the use of system working directory proc ID : ‘ERIK’. This small tidbit of information can be found in Macintosh Technical Note #77. In my case, I had to figure-out the hard way how this magic working directory proc ID ‘ERIK’ was used in the SFGetFile dialog. At the time, the technical note reference about ‘ERIK’ did not exist.

The conclusion is for those who need to save the file path and then later reconstruct the vRefNum for the FSOpen or PBOpen ROM routines other than using the “DirID” method, then these procedures are for you.

Bibliography

1 You can find additional references in Macintosh Technical Note #238.

2 Finder’s Desktop directory/folder hierarchy. Directories and folders are analogous.

3 I use these routines in the not quite popular shareware NotePad++ desk accessory to remember the last opened “NotePad++ File”.

char *GetFilePathName(vRefNum)
 short vRefNum;              /* File's vol/dir ref    */
 {
  WDParam      wDir;         /* Working directory     */
  HVolumeParam wVol;         /* Working HFS param blk */
  DirInfo      wCInfo;       /* Working cat info blk  */
  long         wDirID;       /* Working dir number    */
  Str255       wName;        /* Working directory name*/
  char         *wPtr;        /* Working string pointer*/
  long         wLength;      /* Working string length */
  char         *pathFileName;/* Working file path name*/

  wDir.ioNamePtr = 0L;       /* Init working directory*/
  wDir.ioVRefNum = vRefNum;
  wDir.ioWDIndex = 0;
  wDir.ioWDProcID = 0;
  wDir.ioWDVRefNum = vRefNum;

  PBGetWDInfo(&wDir,FALSE);  /* Get the directory ref */
  
  vRefNum = wDir.ioWDVRefNum;/* Save working vol ref #*/
  wDirID = wDir.ioWDDirID;   /* Save working dir ref #*/

  wVol.ioNamePtr = (StringPtr)&wName;/* Init vol block*/
  wVol.ioVRefNum = vRefNum;
  wVol.ioVolIndex = 0;
    
  wLength = 0L;              /* Set path length to zip*/
  pathFileName = NewPtr(0L); /* Set null file's path  */
  
  if (!PBHGetVInfo(&wVol,FALSE) &&/* Got vol info?    */
   pathFileName) {           /* Got file path pointer?*/
   if (wVol.ioVSigWord == 0x4244) {/* Check if it HFS */
    wCInfo.ioNamePtr = (StringPtr)&wName;/* Init it   */
    wCInfo.ioVRefNum = vRefNum;
    wCInfo.ioFDirIndex = -1;
    wCInfo.ioDrParID = wDirID;
    wCInfo.ioDrDirID = wDirID;

    while (wCInfo.ioDrParID != 1){/* Do full path     */
     wCInfo.ioDrDirID = wCInfo.ioDrParID;/*Move up dir*/

     if (PBGetCatInfo(&wCInfo,FALSE))/* Get dir info  */
      break;                 /* Break-out if failed!! */

     wLength += wName[0] + 1L;/* Set string length    */
     wPtr = NewPtr(wLength + 1L);/* Alloc new str     */

     if (!wPtr) {            /* Didn't get str ptr?   */
      if (pathFileName)      /* Check if got memory   */
       DisposPtr(pathFileName);/* Release it          */
      pathFileName = 0L;     /* Invalidate str pointer*/
      break;                 /* Break-out if failed!! */
     }
                             /* Shuffle file path down*/
     BlockMove(pathFileName,wPtr + wName[0] + 1,
               wLength - (long)(wName[0]));
     DisposPtr(pathFileName);/* Release old one       */
     *(wPtr + wName[0]) = ':';/* Add dir delimeter    */
     BlockMove(&wName[1],pathFileName = wPtr, (long)(wName[0]));
    }
   }
   else {                    /* Oops, get vol info    */
    wLength = wName[0] + 1L; /* Set string length     */
    wPtr = NewPtr(wLength + 1L);/* Alloc new string   */

    if (wPtr) {              /* Got string pointer?   */
     *(wPtr + wName[0]) = ':';/* Tack on dir delimeter*/
     BlockMove(&wName[1],pathFileName = wPtr,
               (long)(wName[0]));
    }

   }
   if (pathFileName)         /* Check if got da string*/
    pathFileName[wLength] = 0;/* Set end-of-string    */
  }
  return(pathFileName);      /* Return file path name */
 }
 
short GetFilePathVolRef(pathFileName)
 char *pathFileName;         /* File's path string    */
 {
  short        i;            /* Working index         */
  char         c;            /* Working input char    */
  short        vRefNum;      /* Working vol/dir ref   */
  WDParam      wDir;         /* Working directory     */
  HVolumeParam wVol;         /* Working HFS param blk */
  DirInfo      wCInfo;       /* Working cat info block*/
  long         wDirID;       /* Working directory ID  */
  Str255       wVolName;     /* Working volume name   */
  Str255       wName;        /* Working string name   */
  char         *wPtr;        /* Working string pointer*/
  short        wLength;      /* Working string length */
  
  vRefNum = 0;               /* Invalid vol/dir ref # */
  
  wVol.ioVRefNum = 0;        /* Init working vol ID # */
  wCInfo.ioDrDirID = 2;      /* Init top-most dir     */
  
  i = 0;                     /* Init working index    */
  wLength = 0;               /* Init string length    */
  
  c = pathFileName[i];       /* Set 1st input char    */
  
  while(c) {                 /* Do til get vol/dir ref*/
   if (c == ':') {           /* Check if got dir specs*/
    wName[0] = wLength - 1;  /* Set "Pascal" str len  */
    wLength = 0;             /* Reset string length   */

    if (!wVol.ioVRefNum) {   /* Check if need vol ref */
     wVol.ioNamePtr = (StringPtr)(&wVolName);

     for(wVol.ioVolIndex = 1; !PBHGetVInfo(&wVol,FALSE);
      wVol.ioVolIndex++) {
      if (EqualString(wName,wVolName,FALSE,FALSE))
       break;
      }

     vRefNum = wVol.ioVRefNum;/* Save vol ID          */
     if (wVol.ioVSigWord != 0x4244)/* MFS ?           */
      return(vRefNum);       /* Let's get out early!  */
    }
    else {                   /* Nope, get dir ref     */
     wCInfo.ioNamePtr = (StringPtr)(&wName);
     wCInfo.ioVRefNum = wVol.ioVRefNum;
     wCInfo.ioFDirIndex = 0;
     wCInfo.ioDrParID = wCInfo.ioDrDirID;

     if (PBGetCatInfo(&wCInfo,FALSE))/* Check dir ?   */
      return(0);             /* Nope, break-out!!!    */
    }
   }                         /* Add to directory specs*/
   c = wName[++wLength] = pathFileName[i++];
  }
  wDir.ioNamePtr = 0L;       /* Init dir data block   */
  wDir.ioVRefNum = wVol.ioVRefNum;
  wDir.ioWDProcID = 'ERIK';  /* Magic 'SFGetFile' ID #*/
  wDir.ioWDDirID = wCInfo.ioDrDirID;
  
  if (!PBOpenWD(&wDir,FALSE))/* Check if opened dir   */
   vRefNum = wDir.ioVRefNum; /* Return vol/dir ref #  */

  return(vRefNum);           /* Return vol/dir ref #  */
 }
 

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Bookends 12.8 - Reference management and...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Apple iTunes 12.6 - Play Apple Music and...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Default Folder X 5.1.4 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Amazon Chime 4.1.5587 - Amazon-based com...
Amazon Chime is a communications service that transforms online meetings with a secure, easy-to-use application that you can trust. Amazon Chime works seamlessly across your devices so that you can... Read more
CrossOver 16.2 - Run Windows apps on you...
CrossOver can get your Windows productivity applications and PC games up and running on your Mac quickly and easily. CrossOver runs the Windows software that you need on Mac at home, in the office,... Read more
Adobe Creative Cloud 4.0.0.185 - Access...
Adobe Creative Cloud costs $19.99/month for a single app, or $49.99/month for the entire suite. Introducing Adobe Creative Cloud desktop applications, including Adobe Photoshop CC and Illustrator CC... Read more
MegaSeg 6.0.2 - Professional DJ and radi...
MegaSeg is a complete solution for pro audio/video DJ mixing, radio automation, and music scheduling with rock-solid performance and an easy-to-use design. Mix with visual waveforms and Magic... Read more
Bookends 12.8 - Reference management and...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Adobe Creative Cloud 4.0.0.185 - Access...
Adobe Creative Cloud costs $19.99/month for a single app, or $49.99/month for the entire suite. Introducing Adobe Creative Cloud desktop applications, including Adobe Photoshop CC and Illustrator CC... Read more
Default Folder X 5.1.4 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more

The best deals on the App Store this wee...
Deals, deals, deals. We're all about a good bargain here on 148Apps, and luckily this was another fine week in App Store discounts. There's a big board game sale happening right now, and a few fine indies are still discounted through the weekend.... | Read more »
The best new games we played this week
It's been quite the week, but now that all of that business is out of the way, it's time to hunker down with some of the excellent games that were released over the past few days. There's a fair few to help you relax in your down time or if you're... | Read more »
Orphan Black: The Game (Games)
Orphan Black: The Game 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Dive into a dark and twisted puzzle-adventure that retells the pivotal events of Orphan Black. | Read more »
The Elder Scrolls: Legends is now availa...
| 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 »

Price Scanner via MacPrices.net

2.6GHz Mac mini on sale for $559, $140 off MS...
Guitar Center has the 2.6GHz Mac mini (MGEN2LL/A) on sale for $559 including free shipping. Their price is $140 off MSRP, and it’s the lowest price available for this model. Read more
SSD Speeder RAM Disk SSD Life Extender App Fo...
Fehraltorf, Switzerland based B-Eng has announced they are making their SSD Speeder app for macOS publicly available for purchase on their website. SSD Speeder is a RAM disk utility that prevents... Read more
iPhone Scores Highest Overall in Smartphone D...
Customer satisfaction is much higher among smartphone owners who use their device to operate other connected home services such as smart thermostats and smart appliances, according to the J.D. Power... Read more
Swipe CRM Free Photo-Centric CRM Sales DEal C...
Swipe CRM LLC has introduced Swipe CRM: Visual Sales 1.0 for iPad, an app for creating, managing, and sharing visually stunning sales deals. Swipe CRM is targeted to small-and-medium creative... Read more
13-inch 2.0GHz Apple MacBook Pros on sale for...
B&H has the non-Touch Bar 13″ 2.0GHz MacBook Pros in stock today and on sale for $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray (... Read more
15-inch Touch Bar MacBook Pros on sale for up...
B&H Photo has the new 2016 15″ Apple 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: - 15″ 2.7GHz Touch Bar... Read more
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

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
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- Chicago...
SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.