TweetFollow Us on Twitter

Charting Resource Map
Volume Number:6
Issue Number:9
Column Tag:XCMD Corner

Related Info: Resource Manager

Charting The Resource Map

By Donald Koscheka, Ernst & Young, MacTutor Contributing Editor

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

Fourth Party Developers

If you read this column regularly, you may be a charter member of a new class of programmers that Apple has recently labelled as “Fourth party developers”. This term is used to denote those programmers who add or modify an existing package for a customer. By this token, XCMDs are 4th party programs since you are adding code to an off-the-shelf product (Hypercard) to enhance its capabilities.

4th Party Programming seems to be an interesting way to make a living. First off, the assignments are manageable since most 4th party work tends to be minor additions to existing work. Second, the 4th party developer needs to be a master of all trades. Gone are the days when a programmer could specialize in data base design, or system software or report generation.

If 4th party programming becomes commercially viable, the practitioner will need to be well-versed in many areas but it’s a safe bet that you can focus your expertise on the following: I/O, communications, searching, sorting, report generation, file translators and graphics. The problem is, most programmers don’t have a repertoire that spans this wide a spectrum. If you feel equally comfortable talking LAP as you do discussing the TIFF format, then maybe you should try your hand at becoming a 4th party programmer.

Personally, I think this area can turn out to be very interesting. I remain skeptical as to whether anyone can make a living at it, but I’m willing to consider anything. After all, the most far-fetched ideas are often the ones that lead to innovation.

End of Sermon.

Charting The Resource Map

Although I’ve read just about every page of Inside Macintosh at least twice, there are certain pages that I still find myself glossing over. I don’t skip these pages out of lack of interest, every manager in the Toolbox has some interesting nuance that is just begging to be exploited. I gloss over certain sections of IM solely because I know that reading that section will lead me down a long path that I just never seem to have time for.

One such path for me is decoding the format of the resource fork. I have always looked on pages I-128 through 1-131 as a sort of black hole; the resource forks just seemed too convoluted to ever have to try to understand. Besides, anything one needs to do with the resource fork can be done via the high level resource manager calls. Or so it would seem. But here’s a simple request that cannot be resolved by the resource manager -- give me a list of the type and id of all resources in a particular resource file.

One needs to understand the spirit of the resource manager in order to understand why this seemingly simple problem doesn’t have a simple solution. The resource manager was intended to act as what I call “soft virtual EPROM”. In essence, resources should only be created during the construction of an application. Once the product ships, the resource fork should remain stable. This is exactly how Engineers use EPROM in computer designs. The “soft” nature of resources alludes to the fact that resources are easy to change as one might need to do to internationalize a certain package. This does not mean that the resource fork should be used for storing dynamically altering data. The resource manager is NOT a data base. A lot of early Mac programmers abused the resource fork by using it as a simple sort of data base. The RM doesn’t respond well to constantly changing data -- it is relatively slow for writing and it lacks any inherent compaction scheme. Neither of these are a shortcoming, the resource fork was never meant to be used as a random access data base. Any programmer who uses the resource fork in this way is asking for trouble and is building an inherently unstable program -- if you have data base needs, either buy or develop a data base, but please, keep your paws out of the resource fork.

The next attribute of the resource fork that is significant is its “virtual” nature. The resource manager has a built-in mechanism for searching all open resource files for a given resource. This is good -- it frees the programmer from needing to know how to access the system resources, they just magically appear along with your resources at load time. Of course there is nothing magical about the resource manager develops this virtual behaviour, each file contains a resource map that is loaded into memory when the resource fork is opened. Each resource map stores a handle to the next resource map in the search order. Thus searching all open resource forks becomes straightforward. But herein lies the crux of our problem. The resource manager itself wants to search all open resource files. If we want to get a list of all resources stored in a particular file, then we would first have to close down all open resource files so that they are excluded from the search path. This would be bad and not even worth trying because shutting down your system resource fork and application resource fork would almost certainly be fatal to the application.

Thus, to read all resources from one particular resource file, we are forced to scan the resource map for that file. Listing 1 (GetRsrcList.c) returns a list of all resources by type and id (names will be added in the future, you can use the resource manager to get the name for now). Notice that in order to do this, I needed to reconstruct the structures used in the resource file. I couldn’t find these structures in my libraries so I create my own.

Our strategy for scanning the resource file goes like this (refer to page I-131 for a good picture of this strategy). First, we read in the resource header (256 bytes). The resource header contains, among other things, the offset and length of the resource map. I find it noteworthy that the resource map always follows the resource data in the file. This seems reasonable enough. Since we know how big the resource map is, allocate a pointer that contains enough space to read the map into, then move the file mark to the start of the map and read it in. Once the map is read in, we need to move through two levels: the type list and the reference list. The type list immediately follows the map header and tells us how many types of resources the fork contains as well as the resource type (4 bytes), the number of resources of that type and where the reference list starts for that type. Type lists and reference lists are constant-sized structures so we can increment a pointer to sashay nicely through the lists.

Each resource type contains a reference list. This list holds information about each individual resource. There are as many entries as there are resources of a given type (counting from 0 not 1). If your file contains 4 XCMDs then your XCMD reference list will contain 4 contiguous entries, one for each XCMD. Pascal programmers take note -- the count is stored as 1 less than the actual number of items. We walk the reference list thusly:

/* 1 */

 for( i = 0; i <= rTL->r_count; i++ ){
 rRef = (resRefPtr)((long)rTL + (long)rTyp->r_ref );
 for( j = 0; j <= rTyp->r_count; j++ )
 rRef++;

 rTyp++; 
 }

The outer loop (i) walks through the type list (again these are stored contiguously immediately following the the resource map header). If rTyp is a pointer to a type list entry (an 8-byte struct), then all we need to do to move to the next type is increment the pointer. “C” is a natural for this type of work but the equivalent Pascal code looks like this:

/* 2 */

 rTyp = ResTypPtr( ORD4( rTyp ) + LongInt( sizeof( ResTyp) );
       { rTyp++ }

Each type entry contains the offset to the start of the reference list for this type. This offset is relative to the start of the type list itself. Adding this offset to the start of the type list (rTL in the example above) yields the physical location of the reference list. Each resource in the file has a reference list entry. To scan all resources of a given type (eg ‘XCMD’) we can increment the pointer to the reference list entries (rRef).

You may never need to know how to scan a resource map but it does serve two pedantic purposes -- it shows how resource files are created and it absolutely convinces the serious programmer that the resource fork is not intended to be a data base. The 16-bit offsets used throughout the fork should provide some clue as to the limitations on the fork’s capacity. For example, what is the maximum number of resource types that you can have? What is the total number of resources that can be stored safely in the resource fork? Listing 1 provides clues to the answers (hint: study the structures). Understanding limits is an important part of programming. See what you can do with this information.

The resource manager is fun to poke around in and I will visit this theme in the future. In the meantime, if you have an interesting problem that needs solving in an XCMD, drop me a line. I’ll see what I can do.

Listing 1:  GetRsrcList.c

/********************************/
/* File: GetRsrcList.c    */
/* */
/* Given the name of a file,  */
/* return a list of all the */
/* resources in that file.  The */
/* list contains 1 line per */
/* resource with the following  */
/* format:*/
/* */
/* item1 == Resource Type */
/* item2 == Resource ID   */
/* item3 == Resource name */
/* */
/* If the resource fork is empty*/
/* or non-existent, return empty*/
/* */
/* ----------------------------  */
/* ©1990 Donald Koscheka  */
/* All Rights Reserved    */
/********************************/

#define UsingHypercard

#include<MacTypes.h>
#include<OSUtil.h>
#include<MemoryMgr.h>
#include<FileMgr.h>
#include<ResourceMgr.h>
#include<pascal.h>
#include<string.h>
#include<hfs.h>
#include  “HyperXCmd.h”
#include“HyperUtils.h”

#define nil 0L

/*** definition of resource header ***/
typedef struct {
 long r_data_offset;
 long r_map_offset;
 long r_data_size;
 long r_map_size;
 char r_reserved[112];
 char r_application[128];
} resHdr, *resHdrPtr, **resHdrHand;

/*** definition of resource map ***/
typedef struct {
 long   r_header[4];/* duplicates first 16 bytes in header*/
 long   next_map;
 short  f_ref;
 short  attributes;
 short  r_type_list;
 short  r_name_list;
} resMap, *resMapPtr, **resMapHand;

/*** definition of type list entry ***/
typedef struct {
 char   r_type[4]; /*** this resource type   ***/
 short  r_count; /*** # of resources of this type ***/
 short  r_ref;   
 /*** offset from start of type list to***/
 /*** reference list for resources of  ***/
 /*** this type (not used here)    ***/
} resTyp, *resTypPtr, **resTypHand;

/*** definition of resource type list ***/
typedef struct {
 short  r_count; /* 0..n */
 resTyp r_typ[]; /* array of type entries */
} resTypeList, *resTypeListPtr, **resTypeListHand;

/*** definition of resource reference list ***/
typedef struct {
 short  r_id;    
 short  r_name;  
 /* offset from start of name list to this name */
 long r_offset;  /* offset to date (hi byte == attributes */
 Handle r_handle;/* handle when resource is in memory */
} resRef, *resRefPtr, **resRefHand;

pascal void main( paramPtr )
 XCmdBlockPtr  paramPtr;
{
 resMapPtrrMap = NIL;
 resTypeListPtr  rTL;
 resTypPtrrTyp;
 resRefPtrrRef;
 Handle rsrcList = NIL; /* the output*/
 resHdr rHdr;
 Str31  fName;   /* name of the file */
 short  ref;
 OSErr  err;
 long   temp;
 short  i,j;/* loop counters*/
 Str255 str;
 
 paramPtr->returnValue = NIL; /* prepare for the worst */
 /* (but plan for the best) */
 
 if( paramPtr->params[0] ){

 HLock( paramPtr->params[0] );
 ZeroToPas( paramPtr, *(paramPtr->params[0]), &fName );
 HUnlock( paramPtr->params[0] );

 err  = (short)OpenRF( &fName, -1, &ref );

 if( !err ) /*** Move to  start of  file & read header ***/
 err = SetFPos( ref, fsFromStart, 0L );
 else
 return;
 
 if( !err ){/*** read in the resource header ***/
 temp = (long)sizeof( resHdr );
 err = FSRead( ref, &temp, &rHdr );
 }
 
 if( !err ) /*** Move to start of map & read it in ***/
 err = SetFPos( ref, fsFromStart, rHdr.r_map_offset );
 
 if( !err ){
 rMap = (resMapPtr)NewPtr( rHdr.r_map_size );
 err = FSRead( ref, &rHdr.r_map_size, rMap);
 }
 
 if( !err ){
 /*** this calculation doesn’t seem correct ***/
 rTL = (resTypeListPtr)((long)rMap + (long)(rMap->r_type_list));

 /*** move to the start of the reference list ***/
 rTyp = (resTypPtr)((long)rTL + (long)sizeof( short )); 
 
 /* Allocate handle for the output list*/
 if( rsrcList = NewHandle( 0L ) ){
 for( i = 0; i <= rTL->r_count; i++ ){
 rRef = (resRefPtr)((long)rTL + (long)rTyp->r_ref );
 for( j = 0; j <= rTyp->r_count; j++ ){
 /*** read the reference list entry int ***/
 
 /*** add this type & id to the output list ***/
 AppendCharToHandle( rsrcList, (char)rTyp->r_type[0]);
 AppendCharToHandle( rsrcList, (char)rTyp->r_type[1]);
 AppendCharToHandle( rsrcList, (char)rTyp->r_type[2]);
 AppendCharToHandle( rsrcList, (char)rTyp->r_type[3]);
 AppendCharToHandle( rsrcList, ‘,’);
 
 /*** convert id to a string & add to list ***/
 NumToStr( paramPtr, (long)rRef->r_id, &str );
 pStrToField( (char *)str, ‘\r’,  rsrcList );
 rRef++;
 }/* for j = 0 to # of resources of this type */
 rTyp++; 
 }/* for i = 0 to the number of resource types */
 
 }/* if( rsrcList allocated */
 
 AppendCharToHandle( rsrcList, ‘\0’ );
 } 
 
 if( rMap )
 DisposPtr( (Ptr)rMap );
 /*** Only reach here if file was opened     ***/
 err = FSClose( ref );
 }
 
 paramPtr->returnValue = rsrcList;
}

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Adobe Illustrator 24.0.3 - Professional...
You can download Adobe Illustrator for Mac as a part of Creative Cloud for only $20.99/month (or $9.99/month if you have also purchased an earlier software version). Adobe Illustrator for Mac is the... Read more
Adobe Dreamweaver CC 2020 20.1 - Build w...
Dreamweaver CC 2020 is available as part of Adobe Creative Cloud for as little as $20.99/month (or $9.99/month if you're a previous Dreamweaver customer). Adobe Dreamweaver CC 2020 allows you to... Read more
Adobe Audition 13.0.3 - Professional pos...
Audition is available as part of Adobe Creative Cloud for as little as $20.99/month (or $9.99/month if you're a previous Audition customer). Adobe Audition empowers you to create and deliver... Read more
Adobe After Effects 17.0.3 - Create prof...
After Effects is available as part of Adobe Creative Cloud for $52.99/month (or $20.99/month for a single app license). The new, more connected After Effects can make the impossible possible. Get... Read more
Audio Hijack 3.6.4 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
Eye Candy 7.2.3.96 - 30 professional Pho...
Eye Candy renders realistic effects that are difficult or impossible to achieve in Photoshop alone, such as Fire, Chrome, and the new Lightning. Effects like Animal Fur, Smoke, and Reptile Skin are... Read more
Notability 4.2.2 - Note-taking and annot...
Notability is a powerful note-taker to annotate documents, sketch ideas, record lectures, take notes and more. It combines, typing, handwriting, audio recording, and photos so you can create notes... Read more
Adobe Acrobat Reader 20.006.20034 - View...
Adobe Acrobat Reader allows users to view PDF documents. You may not know what a PDF file is, but you've probably come across one at some point. PDF files are used by companies and even the IRS to... Read more
Adobe Acrobat DC 20.006.20034 - Powerful...
Acrobat DC is available only as a part of Adobe Creative Cloud, and can only be installed and/or updated through Adobe's Creative Cloud app. Adobe Acrobat DC with Adobe Document Cloud services is... Read more
Day One 4.8 - Maintain a daily journal.
Day One is an easy, great-looking way to use a journal / diary / text-logging application. Day One is well designed and extremely focused to encourage you to write more through quick Menu Bar entry,... Read more

Latest Forum Discussions

See All

Marvel Strike Force introduces new brawl...
FoxNext's squad-based RPG Marvel Strike Force is set to receive some fresh characters from the X-Men and Iron Man series. They'll arrive as part of the game's latest update, which follows a sizable spending boycott on the title due to complaints... | Read more »
Speed Dating for Ghosts is a narrative a...
Speed Dating for Ghosts originally released on Steam back 2018, since then it has received honourable mentions for narrative during the Independent Games Festival. Now it's made its way over to iOS devices where it's available as a premium title... | Read more »
Fast-paced multiplayer title Tennis Star...
Tennis Stars: Ultimate Clash is the latest free-to-play tennis title to hit iOS and Android. It's said to be a fairly casual experience, offering easy-to-learn controls and fast-paced, mobile-friendly matches. [Read more] | Read more »
Super Mecha Champions' latest updat...
Super Mecha Champions' latest update sees the addition of a brand new character called R.E.D. Alongside that, there's news about the current season and a series of Emojis that have been added to the game. [Read more] | Read more »
Isle Escape: The House is an upcoming pu...
Isle Escape: The House is an upcoming puzzle game from Simeon Angelov that's intended to serve as an introduction to a saga they're planning on releasing in an episodic fashion. The first chapter is set to release for both iOS and Android on 29th... | Read more »
Company of Heroes, the classic RTS, is n...
Feral Interactive has finally released their highly anticipated iOS version of the strategy classic Company of Heroes. It's available now for iPad as a premium title and has had various tweaks to ensure that it's optimised for touch controls. [... | Read more »
Mario Kart Tour's Vancouver Tour ha...
With Mario Kart Tour's Valentine's Tour now at an end (suspiciously before Valentine's Day has even arrived), it's now time to move on to the all-new and exciting Vancouver Tour. This time around, the featured drivers are Hiker Wario and Aurora... | Read more »
A new PictoQuest update makes it a much...
PictoQuest is a charming little puzzle game, but it left us a little disappointed. The game just didn’t seem to use screen space effectively, to the point that using the touch controls (as opposed to the default virtual d-pad) could lead to errant... | Read more »
Alley is an atmospheric adventure game a...
Alley is an atmospheric adventure game that sees you playing as a young girl trapped in an inescapable nightmare. Surrounded by her worst fears, every step forward for her is a huge challenge that you'll help guide her through using some simple... | Read more »
Fight monsters and collect heroes in Cry...
From Final Fantasy to Chaos Rings, Japanese roleplaying games have found a large and loyal fanbase on mobile devices. If you’re seeking a more under-the-radar JRPG to escape into, Lionsfilm’s Cryptract could be the one. The game has been around... | Read more »

Price Scanner via MacPrices.net

Apple AirPods are on sale for $30 off today
Amazon has new 2019 Apple AirPods (non-Pro models) on sale today for $30 off MSRP, starting at $129. Shipping is free: – AirPods with Wireless Charging Case: $169 $30 off MSRP – AirPods with Charging... Read more
27″ 3.7GHz 6-Core 5K iMac on sale for $2099,...
B&H Photo has the 2019 27″ 3.7GHz 6-Core 5K iMac in stock today and on sale for $200 off Apple’s MSRP. Overnight shipping is free to many locations in the US: – 27″ 3.7GHz 6-Core 5K iMac: $2099 $... Read more
Save up to $250 on a 12.9″ iPad Pros with the...
Apple has Certified Refurbished 12.9″ iPad Pros available on their online store for up to $250 off the cost of new models. Prices start at $849. Each iPad comes with a standard Apple one-year... Read more
Save up to $220 on 11″ iPad Pros with these r...
Apple has Certified Refurbished 11″ iPad Pros available on their online store for up to $220 off the cost of new models. Prices start at $679. Each iPad comes with a standard Apple one-year warranty... Read more
8-Core 27″ iMac Pro available for $4249, Cert...
Apple has Certified Refurbished 27″ 3.2GHz 8-Core iMac Pros available for $4249 including free shipping. Their price is $750 off the cost of new models. A standard Apple one-year warranty is included... Read more
$749 MacBook Airs continue to be available on...
Amazon has the 2017 13″ 1.8GHz/128GB MacBook Air on sale today for only $749 shipped. That’s $250 off Apple’s original MSRP for this model and the cheapest new MacBook available from any Apple... Read more
HomePods on sale for $204 at Other World Comp...
Other World Computing has discounted, new, Apple HomePods on sale for up to $95 off Apple’s MSRP: – HomePod Space Gray: $207.99 $92 off MSRP – HomePod White: $204.99 $95 off MSRP These are the same... Read more
Get a Certified Refurbished iMac at Apple for...
Apple has Certified Refurbished 2019 21″ & 27″ iMacs available starting at $929 and up to $350 off the cost of new models. Apple’s one-year warranty is standard, shipping is free, and each iMac... Read more
A Look Back At The Top 5 Most Read Stories Of...
FEATURE: 02.21.20 The best of the best are now history and we’re not talking about Super Bowl LIV from earlier this month but rather, coverage from the past year (its second and first full one at... Read more
Apple offers wide range of discounted custom...
Save up to $610 on a custom-configured 21″ or 27″ iMac with these Certified Refurbished models available at Apple. Each iMac features a new outer case, free shipping, and includes Apple’s standard 1-... Read more

Jobs Board

Medical Assistant - *Apple* Valley Clinic -...
…professional, quality care to patients in the ambulatory setting at the M Health Fairview Apple Valley Clinic, located in Apple Valley, MN. Join the **M Health Read more
Geek Squad *Apple* Consultation Professiona...
**762475BR** **Job Title:** Geek Squad Apple Consultation Professional **Job Category:** Store Associates **Store NUmber or Department:** 001423-San Jose-Store **Job Read more
Medical Assistant - *Apple* Valley Clinic -...
…professional, quality care to patients in the ambulatory setting at the M Health Fairview Apple Valley Clinic, located in Apple Valley, MN. Join the **M Health Read more
Geek Squad *Apple* Consultation Professiona...
**756636BR** **Job Title:** Geek Squad Apple Consultation Professional **Job Category:** Store Associates **Store NUmber or Department:** 001053-Arundel Mills-Store Read more
Medical Assistant - *Apple* Valley Clinic -...
…professional, quality care to patients in the ambulatory setting at the M Health Fairview Apple Valley Clinic, located in Apple Valley, MN. Join the **M Health Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.