TweetFollow Us on Twitter

HFS Tree Climb
Volume Number:5
Issue Number:8
Column Tag:HyperChat™

Related Info: File Manager Standard File

XCMD Corner: HFS Tree Climbing

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.

Hyper Lite

In keeping with the spirit of the summer season, this month’s XCMD is light and easy. Not too long ago, I promised to provide an XCMD that, given the name and directory id of a file, returned that file’s full pathname. Such a utility is eminently useful in the current incantation of Hypercard.

Hypercard is fully capable of opening a file, reading and writing its contents and then closing the file. Unfortunately, unless you know the full path name of the file, you are limited to accessing files in Hypercard’s working directory.

One of the first published XCMDs was a little gem from Steve Maller of Apple Computer Inc. that eliminates this MSDOS-compatible feature of Hypercard. Steve’s FileName.p presents the user with the standard file package and returns the full pathname of the file specified.

If you are a regular reader of this column, you’ll recall that I translated Steve’s XCMD from pascal to “C”. You also know that my version lost something in the translation. Rather than return a full pathname, GetFileName.c returns the file’s name and working directory id. I felt this was more useful because the file’s name and wdid open up access to most of the file manager calls for the XCMD programmer. Still, if you want to continue to use Hypercard’s built-in file I/O, getfileName won’t be of much use since it doesn’t return the full pathname required by hypercard.

Listing 1 (FullPathName.c) is a simple XCMD that accepts the filename and working directory id as input and returns the fullpathname of the file as output.

As is often the case, this XCMD first converts the input data from c-string format to pascal strings and numbers as needed. Note that the default return value will be the name of the file that was passed in param[0].

A Review of HFS

As a rule, we don’t come into contact with full pathnames very often on the Macintosh so the format may require a little explaining. If you want to explore the Hierarchical File System in greater detail, take the time to read Chapter 19 of volume IV of Inside Macintosh. If you don’t have volume IV handy, the following discussion will get help you understand the code.

Devices that can store and retrieve data on the Macintosh are called “volumes”. Files are organized on volumes in folders. Folders can contain other folders yielding a hierarchical or “Tree structure”. The order in which folders are stored in this tree structure specify a path to any file that is contained in that folder.

The root of this tree is the volume name. If we stick a “:” onto the end of the volume name, we have the beginning of a full pathname. In other words full pathnames always start with the volume name. Each path in the pathname is delineated by the “:”. Thus, Hd:folder:file specifies a valid pathname. The last item in the pathname is the name of the file itself. The folder that holds this file is referred to by a unique directory id. When the user selects a file using SFGetFile or SFPutFile, the file manager returns the file’s name as well as the directory id. For historical purposes, the directory id is stored in the vRefNum field of the reply record. This little tweak is how Apple was able to make HFS backward compatible with the flat-file system.

Tree Climbing

The folder that contains the file represents the deepest node on the tree. The next folder up the hierarchy is called the parent. Knowing the parent’s id, we can call PBGetCatInfo to get its name as well as the directory id of its parent folder. We climb the tree by continuously feeding a parent directory id into PBGetCatInfo until we detect an error (no more folders on this path).

Tree climbing suggests recursion. The routine ClimbTree in Listing 1 calls PBGetCatInfo to get information about the directory whose id was passed in. We kick it off by first getting information about the folder that holds the file. This is the directory whose id was returned in the reply record.

Each activation of climbTree uses the same catalog parameter block (cpb) which was allocated in the stack frame of FullPathName. This is legal because the only information that is unique to each activation is the directory id (passed as a parameter in child) as well as a pointer to the string the PBGetCatInfo uses to store the folder’s name. Each activation allocates memory for the name string and sets cpb’s ioNamePtr field to point to its own copy of the string.

I allocate the string, folder_name, in the heap and point to it on the stack because successful recursion dictates that one be mindful of the stack at all times. Even if there is no danger of overflowing the stack, a little defensive programming goes a long way.

A nice feature of the recursion is that we can build the string in forward order. Although we walked the tree backwards, we don’t actually put the full pathname together until we reach the root which is detected by discovering that it has no parent folder. Once we reach the root, the stack unwinds in the order of root->parent->child->filename.

The following script, working with GetFileName.c (See Mactutor Vol. 5 No. 6) returns the full pathname of a file selected via standard dialog:

--1

on mouseup
 put getfilenametoOpen() into it
 if item 1 of it is not empty then
 put Fullpathname(item 1 of it, item 2 of it) into it
  end if
end mouseup

Because Hierarchical File System can’t handle pathnames longer than 256 characters, I limit the string returned by Fullpathname to 256 characters. If you want to return the full path regardless of length, you can modify the concat routine in “HyperUtils.c” to “grow” the output string on demand.

Listing:  FullPathName.c
/********************************/
/* File: FullPathName.c   */
/* Given the name and working */
/* directory of a file, walk the*/
/* directory tree to determine*/
/* what the full pathname of the*/
/* directory is... */
/* Paramters:    */
/* param0 = file namenum  */
/* param1 = directory id  */
/* Out: */
/* full pathname of the working  */
/* directory   */
/* Once again, I am indepbted to*/
/* Steve Maller of Apple  */
/* Computer Inc for illuminating*/
/* this oft too dark realm of */
/* the toolbox.  */
/********************************/
#include<MacTypes.h>
#include<OSUtil.h>
#include<MemoryMgr.h>
#include<FileMgr.h>
#include<ResourceMgr.h>
#include<pascal.h>
#include<strings.h>
#include<hfs.h>
#include  “HyperXCmd.h”
#include“HyperUtils.h”
#define nil 0L

char    colon[2] = “\p:”;

void ClimbTree( child, cpb, fullName )
 long   child;
 CInfoPBPtr cpb;
 char   *fullName;
/*************************
* Climb the directory tree
* until we reach the root
* Allocate the records in the
* heap to keep the stack frame
* as small as necessary.  Too
* large a stack frame can 
* lead to a case of terminal
* terminal.
* child is the working directory
* id of the “current folder”, vol
* is the volume reference number and
* fullName points to the 
* output string
*************************/
{
 StringPtrfolder_name= (StringPtr)NewPtr( 256 );
/*** setting the file directory index to -1***/
/*** lets us get information about the ***/
/*** directory whose id is specified inthe***/
/*** ioDrDIrID field of the parameter block***/
 folder_name[0] = ‘\0’; 
 cpb->dirInfo.ioNamePtr   = (StringPtr)folder_name;
 cpb->dirInfo.ioDrDirID   = child; 

 if( PBGetCatInfo( cpb, 0) == noErr ){
 ClimbTree(cpb->dirInfo.ioDrParID,cpb,fullName);

 Concat( (char *)fullName, (char *)folder_name );
 Concat( (char *)fullName, (char *)&colon );
 }
 DisposPtr( folder_name   );
 
}

pascal void main( paramPtr )
 XCmdBlockPtr  paramPtr;
{
 Str31  str,fName;
 short  wdid;
 WDPBRectheWDPB;
 CInfoPBRec theCPB;
 HParamBlockRec  theHPB;
 char   fullPath[256];
 char   part_Name[256]; /*** used in HPB     ***/
 char   vol_Name[256];
 OSErr  err;

 colon[0] = 1;
 colon[1] = ‘:’;
 
 vol_Name[0] = ‘\0’;
 part_Name[0]= ‘\0’;
 /*** empty is the default answer ***/
 paramPtr->returnValue = 0L;

 HLock( paramPtr->params[0] );
 ZeroToPas( paramPtr, *(paramPtr->params[0]), &fName );
 HUnlock( paramPtr->params[0] );
 
 /*** convert the wdid to a usable form ***/
 HLock( paramPtr->params[1] );
 ZeroToPas( paramPtr, *(paramPtr->params[1]), &str );
 HUnlock( paramPtr->params[1] );
 wdid = StrToNum( paramPtr, &str );
 
 /*** First, we appeal to GetVInfo to get    ***/
 /*** volume name that the file lives on     ***/
 part_Name[0]    = ‘\0’;  
 theHPB.volumeParam.ioNamePtr = (StringPtr)vol_Name;     
 theHPB.volumeParam.ioVRefNum = (short)wdid;             
 theHPB.volumeParam.ioVolIndex   = 0;  
 if(PBHGetVInfo( &theHPB, 0) != noErr )
 return;  

 /*** Next, use the working directory info   ***/
 /*** to walk the directory tree backwards   ***/
 /*** to the root directory ***/
 theWDPB.ioNamePtr = (StringPtr)part_Name;
 theWDPB.ioVRefNum = wdid;  
 theWDPB.ioWDProcID= 0;   
 theWDPB.ioWDIndex = 0;   
 if( PBGetWDInfo( &theWDPB, 0) != noErr )    
 return;
 
 fullPath[0] = ‘\0’; 
 theCPB.dirInfo.ioFDirIndex = -1; 
 theCPB.dirInfo.ioVRefNum = theHPB.volumeParam.ioVRefNum;      
 
 ClimbTree( theWDPB.ioWDDirID, 
 (CInfoPBPtr)&theCPB, 
 (StringPtr)fullPath );
 
 /*** Climbing the tree yields the names of  ***/
 /*** all the folders which we still need to ***/
 /*** add the file’s name to. ***/
 Concat( (char *)fullPath, (char *)&fName );
 paramPtr->returnValue = PasToZero( paramPtr, fullPath );
}
Listing:  HyperUtils.H
/********************************/
/* HyperUtils.H  */
/* Header file for HyperUtils.c  */
/* routines...   */
/********************************/
#define NIL 0L
#define UPFRONT  -1L
void  CenterWindow( WindowPtr wptr );
void  Concat( char * str1, char * str2 );
void  CopyPStr( char * pStr1, char * pStr2 );
short GetFileNameToOpen(SFTypeList typs,short typcnt, char *theName, 
short *theWDID);
Listing:  HyperUtils.c
/****************************/
/* HyperUtils.c  */
/* A collection of useful */
/* routines...   */
/****************************/
#include<MacTypes.h>
#include<OSUtil.h>
#include<MemoryMgr.h>
#include<FileMgr.h>
#include<ResourceMgr.h>
#include<StdFilePkg.h>
#include  “HyperXCmd.h”
#include  “HyperUtils.h”

void  CenterWindow( wptr )
 WindowPtrwptr;
/***************************
* Center a window in the current
* screen port.  Note: Does not
* attempt to work with multi-screen
* systems.
* This code is inspired by a
* similar routine written by Steve
* Maller in MPW Pascal.  Thanks Steve.
***************************/
{
 short  hWindSize = wptr->portRect.right - wptr->portRect.left;
 short  vWindSize = wptr->portRect.bottom - wptr->portRect.top;
 short  hSize = wptr->portBits.bounds.right - wptr->portBits.bounds.left;
 short  vSize = wptr->portBits.bounds.bottom - wptr->portBits.bounds.top;
 
 MoveWindow( wptr, ( hSize - hWindSize ) / 2, 
 ( vSize - vWindSize + 20) / 2, false);
}

void Concat( str1, str2 )
 char *str1;
 char *str2;
/*****************************
* Append string 2 to the end of
* string 1.  Both strings are 
* pascal-format strings.
* str1 must be large enough to hold
* the new string and is assumed to 
* be of Type Str255 (a pascal string)
*****************************/
{
 short len1 = *str1;/***number of chars in string 1***/
 short len2 = *str2++;/*** number of chars in string 2***/
 char  *temp;    /*** string pointer ***/
 
 if( len1 +len2  > 255 )
 len2 = 255 - len1;
 *str1++ += len2 ; /***add sizes together to get new size***/
 temp = str1 + len1;/*** move to end of string 1***/
 while( len2 ){
 *temp++ = *str2++;/*** add char to temp and move along***/
 --len2;/*** until all characters are added***/
 }
}

void  CopyPStr( pStr1, pStr2 )
 char *pStr1;
 char *pStr2;
/****************************
* Copy the contents of pstr1 into
* pstr2.  The strings are assumed 
* to be of type STR255 (length byte
* precedes data 
****************************/
{short  i;
 char *tstr;
 
 tstr = pStr2; 
 for( i = 0; i <= *pStr1; i++ )
 *tstr++ = *pStr1++;
}

short GetFileNameToOpen( typs, typCnt,theName, theWDID )
 SFTypeList typs; short   typCnt;
 char   *theName; short   *theWDID;
/*****************************
* Invokes SFOpenFile to query the 
* user for the name of a file to open.  
* In:   List of types of files to
*filter for (up to 4)
* Out:  fileName if picked in theName
*working directory in theWDID
*nil otherwise
*the file’s volum ref num.
* ( Note that the space for the 
* string must be allocated by the
* caller).
*****************************/
{
 Point  where;
 char   prompt[1];
 SFReplyreply;
 GrafPort *oldPort;
 WindowPtrdlogID;
 prompt[0]  = ‘\0’;
 /*** Get and put up the standard file ***/
 /*** dialog.  You will only see the file***/
 /*** types that you filtered for.  If ***/
 /*** you filtered for no files, then  ***/
 /*** all files will display***/
 GetPort( &oldPort );
 dlogID = GetNewDialog( (short)getDlgID, (Ptr)NIL, (Ptr)UPFRONT );
 SetPort( dlogID );
 CenterWindow( dlogID );
 where.h = dlogID->portRect.left;
 where.v = dlogID->portRect.top;
 LocalToGlobal( &where );
 SFGetFile( where, prompt, (Ptr)NIL, typCnt, typs, (Ptr)NIL, &reply );
 DisposDialog( dlogID );
 SetPort( oldPort );
 /*** If the user selected a file, let’s ***/
 /*** get the information about it ***/
 if (reply.good){
 *theWDID = reply.vRefNum;
 PtoCstr( (char *)&reply.fName );
 strcpy( theName, &reply.fName  );
 }
 return( reply.good );
}

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

VueScan 9.5.75 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Opera 44.0.2510.1449 - High-performance...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more
Opera 44.0.2510.1449 - High-performance...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more
Skim 1.4.29 - PDF reader and note-taker...
Skim is a PDF reader and note-taker for OS X. It is designed to help you read and annotate scientific papers in PDF, but is also great for viewing any PDF file. Skim includes many features and has a... Read more
FontExplorer X Pro 6.0.2 - Font manageme...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more
1Password 6.7.1 - 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
Vivaldi 1.9.818.44 - An advanced browser...
Vivaldi is a browser for our friends. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind... Read more
Vivaldi 1.9.818.44 - An advanced browser...
Vivaldi is a browser for our friends. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind... Read more
Skim 1.4.29 - PDF reader and note-taker...
Skim is a PDF reader and note-taker for OS X. It is designed to help you read and annotate scientific papers in PDF, but is also great for viewing any PDF file. Skim includes many features and has a... Read more
1Password 6.7.1 - 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

Latest Forum Discussions

See All

Fire Emblem Heroes event announces new m...
As reported yesterday, Nintendo was gearing up a live press event for their popular mobile game,Fire Emblem Heroes. While the stream revealed a lot of new things, the event was entirely in Japanese. Luckily we have a rundown of what was announced... | Read more »
Best games we played this week
Another week, another slate of new mobile games. Although there weren't as many big name releases as last week, there were plenty of unique video game titles that came out that's sure to keep you interested over the weekend. Everything from classic... | Read more »
Olli by Tinrocket (Photography)
Olli by Tinrocket 1.0 Device: iOS iPhone Category: Photography Price: $2.99, Version: 1.0 (iTunes) Description: Get drawn in with Olli by TinrocketOlli instantly turns your everyday moments into hand-drawn art and animations. • Watch... | Read more »
Penarium (Games)
Penarium 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
Fire Emblem Heroes is way more profitabl...
Profits for Nintendo's mobile game Fire Emblem Heroes are apparently impressive enough to beat out other Nintendo titles likeSuper Mario Run, despite having 10 times fewer downloads. [Read more] | Read more »
Classic series Robot Unicorn Attack 3 no...
The classic Adult Swim browser game, Robot Unicorn Attack, branched off into a series of popular mobile games. Now, the latest entry into the series, Robot Unicorn Attack 3, is available for iOS and Android mobile devices. [Read more] | Read more »
Sudoku Sweeper (Games)
Sudoku Sweeper 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A minimalist mashup of Minesweeper and Sudoku. Logic puzzle perfection. Every row, column and zone contains a bomb and one of... | Read more »
Under Leaves (Games)
Under Leaves 1.0.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.0 (iTunes) Description: Journey into the forest, the jungle or the depths of the deep blue sea. Find chestnuts for the pigs, a caterpillar for the... | Read more »
Ninja Pizza Girl (Games)
Ninja Pizza Girl 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: In the not-so-distant future, rampart traffic congestion has resulted in only one way to deliver pizzas across town in thirty... | Read more »
SCRAP (Games)
SCRAP 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: That day, for no apparent reason, SCRAP decided to wake up and run. He had to, because his activation was a mistake the "Factory" could... | Read more »

Price Scanner via MacPrices.net

13-inch 2.7GHz Retina MacBook Pro, Apple refu...
Apple has Certified Refurbished 13″ 2.7GHz/128GB Retina MacBook Pros available for $200 off MSRP. An Apple one-year warranty is included with each model, and shipping is free: - 13″ 2.7GHz/128GB... Read more
13-inch Gray 2.9GHz/512GB Touch Bar MacBook P...
Amazon has the 13″ Space Gray 2.9GHz/512GB Touch Bar MacBook Pro (model MNQF2LL/A) in stock today and on sale for $150 off MSRP. Shipping is free: - 13″ 2.9GHz/512GB Touch Bar MacBook Pro Space Gray... Read more
15-inch 2.7GHz Space Gray Touch Bar MacBook P...
B&H Photo has the 15″ 2.7GHz Space Gray Touch Bar MacBook Pro in stock today and on sale for $2599…$200 off MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 15″ 2.7GHz... Read more
13-inch 2.9GHz/256GB Space Gray Touch Bar Mac...
B&H Photo has the 13″ 2.9GHz/256GB Space Gray Touch Bar MacBook Pro in stock today and on sale for $150 off MSRP including free shipping plus NY & NJ sales tax only: - 13″ 2.9GHz/256GB Touch... Read more
21-inch iMacs on sale for up to $151 off MSRP
B&H Photo has 21″ iMacs on sale for up to $151 off MSRP, each including free shipping plus NY sales tax only: - 21″ 3.1GHz iMac 4K: $1348 $151 off MSRP - 21″ 2.8GHz iMac: $1199.99 $100 off MSRP... Read more
Weekend deal: Up to $420 off new MacBook Pros...
Apple has Certified Refurbished 2016 15″ and 13″ MacBook Pros available for $230 to $420 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2.6GHz... Read more
Price drop: 15-inch 2.2GHz Retina MacBook Pro...
Amazon has dropped their price on 15″ 2.2GHz Retina MacBook Pros (MJLQ2LL/A) to $1709.99 including free shipping. Their price is $290 off MSRP for this model. Note that stock may sell out quickly at... Read more
2.8GHz Mac mini on sale for $899, save $100
B&H Photo has the 2.8GHz Mac mini (model number MGEQ2LL/A) on sale for $899 including free shipping plus NY & NJ sales tax only. Their price is $100 off MSRP. Read more
Check Apple prices on any device with the iTr...
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... Read more
New System Clock for macOS by B-Eng Now Avail...
Fehraltorf, Switzerland based B-Eng has announced the release and immediate availability of System Clock, the company’s new system monitor and information app developed exclusively for macOS. System... Read more

Jobs Board

Product Manager, *Apple* Platforms - Viacom...
…Product Manager to drive the execution of its iOS and AppleTV experiences. The Apple Platform Product Manager will be a leader in our Agile/Scrum environment and Read more
*Apple* Mobile Master - Best Buy (United Sta...
**493714BR** **Job Title:** Apple Mobile Master **Location Number:** 001024-Weatherford-Store **Job Description:** **What does a Best Buy Apple Mobile Master Read more
*Apple* OS X Server Administrator (Active Se...
** Apple OS X Server Administrator \(Active Secret Clearance\)** **Description** Come be a part of a top notch team, apply today\!\! Tuva TUVA provides turnkey Read more
*Apple* Mac Computer Technician - GeekHampto...
…complex computer issues over the phone and in person? GeekHampton, Long Island's Apple Premium Service Provider, is looking for you! Come work with our crew Read more
Best Buy *Apple* Computing Master - Best Bu...
**501846BR** **Job Title:** Best Buy Apple Computing Master **Location Number:** 001126-South Bay Center-Store **Job Description:** **What does a Best Buy Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.