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

beaTunes 5.0.4 - Organize your music col...
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
Yasu 4.0.4 - System maintenance app.
Yasu was created with system administrators who service large groups of workstations in mind, Yasu (Yet Another System Utility) was made to do a specific group of maintenance tasks quickly within a... Read more
NetNewsWire 4.0.4 - RSS and Atom news re...
NetNewsWire is the best way to keep up with the sites and authors you read most regularly. Let NetNewsWire pull down the latest articles, and read them in a distraction-free and Mac-like way. Native... Read more
Chromium 60.0.3112.101 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 60.0.3112.101: Release notes were unavailable... Read more
MegaSeg 6.0.4 - 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
iWatermark Pro 2.0.2 - Easily add waterm...
iWatermark Pro is the essential watermarking app for professional, business, and personal use. Easily secure and protect your photos with text, a graphic, a signature, or a QR watermark. Once added... Read more
Daylite 6.2.1 - Dynamic business organiz...
Daylite helps businesses organize themselves with tools such as shared calendars, contacts, tasks, projects, notes, and more. Enable easy collaboration with features such as task and project... Read more
Chromium 60.0.3112.101 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 60.0.3112.101: Release notes were unavailable... Read more
MegaSeg 6.0.4 - 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
Daylite 6.2.1 - Dynamic business organiz...
Daylite helps businesses organize themselves with tools such as shared calendars, contacts, tasks, projects, notes, and more. Enable easy collaboration with features such as task and project... Read more

5 reasons why 2v2 is the best mode in Cl...
Supercell has been teasing fans with 2v2 windows that allow players to team up for limited periods of time. The Summer of 2v2 was just this past July, but players are already clamoring for more of that sweet, sweet team-based action. The fans have... | Read more »
The best deals on the App Store this wee...
It seems like the week's only just started, and yet here we are with a huge pile of discounted games to sort through. There are some real doozies on sale this week. We're talking some truly stellar titles. Let's take a look at four of the best... | Read more »
Cat Quest Guide - How to become a purrfe...
Cat Quest is an absolutely charming open-world RPG that's taken the gaming world quite by storm. This game about a world populated by furry kitty warriors is actually a full-length RPG with sturdy mechanics and a lovely little story. It's certainly... | Read more »
Silly Walks Guide - How to strut your st...
Silly Walks is an all new adventure game that lives up to its name. It sees you playing as a variety of snack foods as you teeter-totter your way to rescue your friends from the evil blender and his villainous minions. It's all very . . . well... | Read more »
The best mobile point-and-click adventur...
Nostalgia for classic point-and-click adventure games has reached an all-time high in recent years, and the rise of mobile games have provided a perfect platform for this old-school genre. This week we're going to take a look at some of the best... | Read more »
Titanfall: Assault Beginner's Guide...
Respawn's dazzling mech battler Titanfall has gotten its first mobile game at long last -- Titanfall: Assault. Assault transforms that parkour FPS action into a card battler not dissimilar to Clash Royale. Titanfall: Assault isn't just another... | Read more »
Unobstruct (Utilities)
Unobstruct 1.0 Device: iOS Universal Category: Utilities Price: $.99, Version: 1.0 (iTunes) Description: You’re already reading web pages on a pretty small screen. Don’t let floating social media sharing toolbars and the like get in... | Read more »
Burgle Bros (Games)
Burgle Bros 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Burgle Bros requires stealth, planning and a little bit of luck. In the tradition of classic heist movies like Ocean's 11 and The... | Read more »
The best new games we played this week -...
The hits continue to come fast and strong this month, as August welcomes in game after game, many of them of very high quality. It's been another busy week, but we're not complaining. This week saw the arrival of some of the best mobile games... | Read more »
CSR Racing 2: How to master Live Races
Getting better at racing the AI in CSR Racing 2 is a pretty straightforward process. You run enough races with a particular car to get its shift timing down, continually improve it by buying upgrades whenever you can, and add any fusion parts you... | Read more »

Price Scanner via MacPrices.net

WaterField Unveils Collaboratively-Designed,...
In collaboration with customers and seasoned travelers, San Francisco maker WaterField Designs set out to create the preeminent carry-on system to improve the experience of frequent fliers. The... Read more
Miya Notes Mac-Client for Google Keep (Launch...
MacPlus Software has announced te launch of Miya Notes for Google Keep 1.0, a powerful Mac-client for Google Keep. Millions of people use Google Keep on their phones and online, but a convenient Mac... Read more
Apple refurbished iMacs available starting at...
Apple has previous-generation Certified Refurbished 2015 21″ & 27″ iMacs available starting at $849. Apple’s one-year warranty is standard, and shipping is free. The following models are... Read more
2017 13-inch MacBook Airs on sale for $100 of...
B&H Photo new 2017 13″ MacBook Airs on sale today for $100 off MSRP, starting at $899: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off MSRP – 13″ 1.8GHz/256GB MacBook Air (MQD42LL/A... Read more
12-inch MacBooks on sale for $100 off MSRP
Amazon has 2017 12″ Retina MacBooks on sale for $100 off MSRP. Shipping is free: 12″ 1.2GHz Space Gray MacBook: $1199.99 $100 off MSRP 12″ 1.2GHz Silver MacBook: $1198 $101 off MSRP 12″ 1.2GHz Gold... Read more
KuGi Lightweight Stand And Portfolio Case Wit...
This briefcase style embedded keyboard design gives Apple iPad Pro 10.5-inch high-end atmosphere at a low-end price. The ultra-thin lightweight design makes it convenient to carry and provides all-... Read more
2017 15-inch MacBook Pros on sale for up to $...
B&H Photo has the new 2017 15″ MacBook Pros on sale for up to $150 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray: $2249.99, $... Read more
2016 MacBook Pros, Apple refurbished, availab...
Apple has Certified Refurbished 2016 15″ and 13″ MacBook Pros available starting at $1189. An Apple one-year warranty is included with each model, and shipping is free: – 15″ 2.7GHz Touch Bar Space... Read more
Clearance 2016 13-inch MacBook Airs, Apple re...
Apple has Certified Refurbished 2016 13″ MacBook Airs available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is free: – 13″ 1.6GHz/8GB/128GB MacBook Air: $... Read more
Save up to $50 on 9.7-inch 2017 WiFi iPads, p...
B&H Photo has 9.7″ 2017 WiFi iPads on sale for up to $50 off MSRP for a limited time. Shipping is free, and pay sales tax in NY & NJ only: – 32GB iPad WiFi: $299, $30 off – 128GB iPad WiFi: $... Read more

Jobs Board

SW Engineer *Apple* TV - Apple Inc. (United...
Job Summary The Apple TV team is looking for an experienced engineer with a passion for delivering first in class home entertainment solutions. The candidate will Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Frameworks Engineering Manager, *Apple* Wat...
Frameworks Engineering Manager, Apple Watch Job Number: 41632321 Santa Clara Valley, California, United States Posted: Jun. 15, 2017 Weekly Hours: 40.00 Job Summary 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* Solutions Consultant - Apple Inc. (U...
Job Summary As an Apple Solutions Consultant, you'll be the link between our future customers and our products. You'll showcase your entrepreneurial spirit as you Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.