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

Dreii guide - How to play well with othe...
Dreii is a rather stylish and wonderful puzzle game that’s reminiscent of cooperative games like Journey. If that sounds immensely appealing, then you should immediately get cracking and give it a whirl. We can offer you some tips and tricks on... | Read more »
Kill the Plumber World guide - How to ou...
You already know how to hop around like Mario, but do you know how to defeat him? Those are your marching orders in Kill the Plumber, and it's not always as easy as it looks. Here are some tips to get you started. This is not a seasoned platform... | Read more »
Planar Conquest (Games)
Planar Conquest 1.0 Device: iOS Universal Category: Games Price: $12.99, Version: 1.0 (iTunes) Description: IMPORTANT: Planar Conquest is compatible only with iPad 3 & newer devices, iPhone 5 & newer. It’s NOT compatible with... | Read more »
We talk to Cheetah Mobile about its plan...
Piano Tiles 2 is a fast-paced rhythm action high score chaser out now on iOS and Android. You have to tap a series of black tiles that appear on the screen in time to the music, being careful not to accidentally hit anywhere else. Do that and it's... | Read more »
Ultimate Briefcase guide - How to dodge...
Ultimate Briefcase is a simple but tricky game that’s highly dependent on how fast you can react. We can still offer you a few tips and tricks on how to survive though. Guess what? That’s exactly what we’re going to do now. Take it easy [Read more... | Read more »
SoundPrism Link Edition (Music)
SoundPrism Link Edition 1.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0 (iTunes) Description: ***Introductory price for a the first few days after launch - if you're reading this, get it while it's fresh out of... | Read more »
Pre-register now for hack and slasher An...
Fincon, which won Facebook's Studio to Watch award in 2015, has announced that pre-registration is now open for the massive 3.0 update for its award-winning hack and slasher Angel Stone. Angel Stone is a post-apocalyptic action RPG in which the... | Read more »
Google has named Piano Tiles 2 as its Be...
Google has named Piano Tiles 2, which launched back in August last year, as its Best Game of 2015. If you're yet to play it, now's a good time to do so. It's a sequel to the hugely successful viral hit Piano Tiles (Don't Tap the White Tile) but... | Read more »
Sago Mini Trucks and Diggers (Education...
Sago Mini Trucks and Diggers 1.0 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0 (iTunes) Description: Drive a dump truck with Rosie the hamster! Pile dirt high and dig deep in the ground with diggers, cranes and... | Read more »
Day One 2 Journal + Notes (Lifestyle)
Day One 2 Journal + Notes 2.0 Device: iOS Universal Category: Lifestyle Price: $4.99, Version: 2.0 (iTunes) Description: **New Release Sale—50% off for a Limited Time!** Capture life as you live it. From once-in-a-lifetime events to... | Read more »

Price Scanner via MacPrices.net

Watch Super Bowl 50 Live On Your iPad For Fre...
Watch Super Bowl 50 LIVE on the CBS Sports app for iPad and Apple TV. Get the app and then tune in Sunday, February 7, 2016 at 6:30 PM ET to catch every moment of the big game. The CBS Sports app is... Read more
Two-thirds Of All Smart Watches Shipped In 20...
Apple dominated the smart watch market in 2015, accounting for over 12 million units and two-thirds of all shipments according to Canalys market research analysts’ estimates. Samsung returned to... Read more
12-inch 1.2GHz Retina MacBooks on sale for up...
B&H Photo has 12″ 1.2GHz Retina MacBooks on sale for $180 off MSRP. Shipping is free, and B&H charges NY tax only: - 12″ 1.2GHz Gray Retina MacBook: $1499 $100 off MSRP - 12″ 1.2GHz Silver... Read more
12-inch 1.1GHz Gray Retina MacBook on sale fo...
B&H Photo has the 12″ 1.1GHz Gray Retina MacBook on sale for $1199 including free shipping plus NY sales tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model... Read more
Apple now offering full line of Certified Ref...
Apple now has a full line of Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are... Read more
Free GUI Speedometer – The Ultimate Digital D...
Miami, Florida based RMKapps has announced the official release of GUI Speedometer 1.0, their digital dashboard display developed for iOS devices. GUI Speedometer allows users to track their precise... Read more
FutureCalc: Ergonomic iOS Calculator App For...
London, United Kingdom based Independent software developer and entrepreneur, Hovik Melikyan has announced the release and immediate availability of FutureCalc 1.0, his new ergonomic calculator app... 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
Apple’s ‘Next Big Thing’ Drought And Mature M...
Apple’s first fiscal quarter 2016 financial results yielded both good news and bad news. In the positive column, Apple made another boatload of money, reporting record quarterly revenue of $75.9... Read more
Lifeproof NUUD For iPhone 6S, iPhone 6S Plus...
LifeProof NUUD was designed to defy more than the elements. It defies logic itself by combining legendary four-proof protection and screenless technology to survive mountaintop missions and seaside... Read more

Jobs Board

*Apple* Macintosh OSX - Net2Source Inc. (Uni...
…: * Work Authorization : * Contact Number(Best time to reach you) : Skills : Apple Macintosh OSX Location : New York, New York. Duartion : 6+ Months The associate would Read more
Computer Operations Technician ll - *Apple*...
# Web Announcement** Apple Technical Liaison**The George Mason University, Information Technology Services (ITS), Technology Support Services, Desktop Support Read more
Restaurant Manager - Apple Gilroy Inc./Apple...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
Simply Mac *Apple* Specialist- Service Repa...
Simply Mac is the largest premier retailer of Apple products in the nation. In order to support our growing customer base, we are currently looking for a driven Read more
*Apple* IOS / OS X Level 3 Support Analyst -...
Needed: Apple Support Analyst (OS X / IOS); 50k-60k/yr +…Horizon Technology Partners has an immediate opening for an Apple IOS / OS X LEVEL 3 Support Analyst. Your Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.