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

Slack 2.8.2 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.8.2: A small release containing nothing but another Electron... Read more
Smultron 10.0.2 - Easy-to-use, powerful...
Smultron 10 is an elegant and powerful text editor that is easy to use. You can use Smultron 10 to create or edit any text document. Everything from a web page, a note or a script to any single piece... Read more
Capto 1.2.5 - $29.99
Capto (was Voila) is an easy-to-use app that takes capturing, recording, video and image editing to the next level. With an intelligent file manager and quick sharing options, Capto is perfect for... Read more
ScreenFlow 7.1.1 - Create screen recordi...
ScreenFlow is powerful, easy-to-use screencasting software for the Mac. With ScreenFlow you can record the contents of your entire monitor while also capturing your video camera, microphone and your... Read more
Xcode 9.0.1 - Integrated development env...
Xcode includes everything developers need to create great applications for Mac, iPhone, iPad, and Apple Watch. Xcode provides developers a unified workflow for user interface design, coding, testing... Read more
TotalFinder 1.10.2 - Adds tabs, hotkeys,...
TotalFinder is a universally acclaimed navigational companion for your Mac. Enhance your Mac's Finder with features so smart and convenient, you won't believe you ever lived without them. Features... Read more
Adobe Flash Player 27.0.0.170 - Plug-in...
Adobe Flash Player is a cross-platform, browser-based application runtime that provides uncompromised viewing of expressive applications, content, and videos across browsers and operating systems.... Read more
VirtualBox 5.1.30 - x86 virtualization s...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
VirtualBox 5.1.30 - x86 virtualization s...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
ScreenFlow 7.1.1 - Create screen recordi...
ScreenFlow is powerful, easy-to-use screencasting software for the Mac. With ScreenFlow you can record the contents of your entire monitor while also capturing your video camera, microphone and your... Read more

Home Street guide - how to make friends...
From the creators of Food Street comes Home Street, a new simulation game that tasks you with building a social network and designing a beautiful home. It's a bit like The Sims, but you won't have to worry about the daily chores involved (feeding,... | Read more »
Color Ballz guide - how to bounce to the...
Color Ballz is an addictive new arcade title from Ketchapp Studios. It takes old school mechanics from games like Brickles and puts a fun twist on it. Your job? To catch balls with a paddle and send them back into a chute to be carried back to... | Read more »
Q&A: A-33 Studio explains why Combat...
When it comes to mobile FPS, it’s often tricky to get the fundamentals right on a platform lacking a physical controller, large display and hefty RAM. With Combat Squad: Project Wednesday, A-33 Studio bravely took on the challenge of making a... | Read more »
Taichi Panda 3: Dragon Hunter guide - ti...
Taichi Panda 3: Dragon Hunter launched this week to players all over the world. It's a beautiful mobile MMORPG that blends elements of Eastern and Western fantasy. It reminds us of a mix between World of Warcraft and Jade Empire. MMO's can have a... | Read more »
The best new games we played this week -...
Phew. It has been a week, but now it's time to relax, put your feet up, and enjoy some brand new mobile games. It was a bit of slow week, but there's still plenty of new titles to add to your collection. Here are four of our favorites. [Read... | Read more »
Yoink - Improved Drag and Drop (Product...
Yoink - Improved Drag and Drop 1.0 Device: iOS Universal Category: Productivity Price: $2.99, Version: 1.0 (iTunes) Description: Yoink for iPad and iPhone lets you easily and quickly store items you drag, copy or share, for later use... | Read more »
Cottage Garden (Games)
Cottage Garden 1.11 Device: iOS Universal Category: Games Price: $4.99, Version: 1.11 (iTunes) Description: | Read more »
Into the Dead 2 guide - how to survive t...
Into the Dead 2 is an endless gunner, of sorts, with a lot of grit and satisfying gunplay behind it. The game looks amazing, and tells an effective story to boot. Plus, it has some quality voice acting behind it to really bring the story to life... | Read more »
Smash Up - The Card Game (Games)
Smash Up - The Card Game 1.0.7 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.7 (iTunes) Description: ***“It’s a goofy theme with fun art and high replayability, but beneath that veneer of casual play is a great... | Read more »
Dive in to Combat Squad if you’re lookin...
Earlier this year, A-33 Studio made the leap from developing Counter Strike Online to launching its very own FPS for the mobile. Combat Squad: Project Wednesday pits your team of mercs against the world in multiplayer death matches, so if you’re on... | Read more »

Price Scanner via MacPrices.net

15″ MacBook Pros on sale for up to $200 off M...
B&H Photo has 15″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray (MPTR2LL/A): $2249, $150... Read more
Roundup of Apple Certified Refurbished iMacs,...
Apple has a full line of Certified Refurbished 2017 21″ and 27″ iMacs available starting at $1019 and ranging up to $350 off original MSRP. Apple’s one-year warranty is standard, and shipping is free... Read more
Sale! 27″ 3.8GHz 5K iMac for $2098, save $201...
Amazon has the 27″ 3.8GHz 5K iMac (MNED2LL/A) on sale today for $2098 including free shipping. Their price is $201 off MSRP, and it’s the lowest price available for this model (Apple’s $1949... Read more
Sale! 10″ Apple WiFi iPad Pros for up to $100...
B&H Photo has 10.5″ WiFi iPad Pros in stock today and on sale for $50-$100 off MSRP. Each iPad includes free shipping, and B&H charges sales tax in NY & NJ only: – 10.5″ 64GB iPad Pro: $... Read more
Apple iMacs on sale for up to $130 off MSRP w...
B&H Photo has 21-inch and 27-inch iMacs in stock and on sale for up to $130 off MSRP including free shipping. B&H charges sales tax in NY & NJ only: – 27″ 3.8GHz iMac (MNED2LL/A): $2179 $... Read more
2017 3.5GHz 6-Core Mac Pro on sale for $2799,...
B&H Photo has the 2017 3.5GHz 6-Core Mac Pro (MD878LL/A) on sale today for $2799 including free shipping plus NY & NJ sales tax only . Their price is $200 off MSRP. Read more
12″ 1.2GHz Space Gray MacBook on sale for $11...
Amazon has the 2017 12″ 1.2GHz Space Gray Retina MacBook on sale for $100 off MSRP. Shipping is free: 12″ 1.2GHz Space Gray MacBook: $1199.99 $100 off MSRP Read more
Bare Bones Software Releases macOS High Sierr...
Bare Bones Software has announced the release and immediate availability of BBEdit 12.0, a significant upgrade to its professional strength text and code editor. BBEdit 12 introduces a new foundation... Read more
Yale Announces Availability of Apple HomeKit-...
Yale Locks & Hardware has announced that Apple HomeKit support for its Assure Lock family is available this month. The new Yale iM1 Network Module, which provides support for the Apple Home app... Read more
Clearance 2016 13″ MacBook Pros, refurbished,...
Apple has Certified Refurbished 2016 13″ MacBook Pros available starting at $1189. An Apple one-year warranty is included with each model, and shipping is free: – 13″ 2.9GHz/512GB Touch Bar Gray... Read more

Jobs Board

Lead *Apple* Solution Consultant - Apple In...
…develop a team of diverse partner employees focusing on excellence to deliver the Apple story. Even when you're not present, you will maintain a consistent influence Read more
watchOS Frameworks Engineering Manager, *App...
Job Summary Join the team that is shaping the future of software development for Apple Watch! Apple is looking for an exceptional software engineering leader to Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, 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
*Apple* Retail - Multiple Positions - Farmin...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.