TweetFollow Us on Twitter

Shared Libraries in CPX
Volume Number:12
Issue Number:8
Column Tag:Programming Workshop

Using Shared Libraries in CPX

Can you really use the Code Fragment Manager and not go crazy?

By John Shackelford

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

Introduction

The Power Mac and upgrades to System 7 harbor many exciting new technologies waiting for application developers to explore. One new technology allows executable code to be shared at run-time. This means you can share code libraries across applications regardless of which development environment you use - or in other words you can finally start using all that code those C++ developers are writing down the hall from you! This technology is provided by a new manager called the Code Fragment Manager (CFM). The CFM is responsible for loading fragments, blocks of executable PowerPC code and data, into memory, and preparing them for execution. Currently the CFM is supported only on Power Macs. However, very soon the CFM will be supported on 68K Macs.

This article describes and demonstrates with some example code one approach to accessing shared libraries from Prograph CPX. It shows a way to wrap a C/C++ library, defining an XPrim that provides the interface to shared libraries and describing in detail a set of CPX classes which encapsulate the use of shared libraries. You’ll receive many benefits from using shared libraries in your applications, including reduced development time (because non-Prograph code no longer has to be ported to the Prograph language) and increased application speed (because of the native Power Mac code). The code described in this article gives you the basic tools for accessing shared libraries, listing export symbols, connecting to shared libraries, and executing functions. The code is shareware, and can be found at Tangent Systems’ Web page.

Figure 1. The main window for the demo app

Shared Library Demo Application

For this article I have created a simple demo application and two shared libraries. The demo application will access the shared libraries. The libraries each contain a different implementation of the same set of functions. One library (OOSharedLib) implements a set of functions using C++ code, while the other library (ExampleCLib) uses all C code.

When the application launches and opens its main window (Figure 1), it also “opens” or “connects to” the two shared libraries. The exported symbols or functions contained in each library are then available for the application to use. The functions or symbols that a library exports are listed in the main window. The functions in each library have been designed to operate on an array of data, and can compute the maximum, minimum, average, variance, or sum of the data.

You can select the desired library by choosing its name in the pop-up menu. The scroll list on the left side of the window lists the exported symbols of the selected shared library. When a symbol is selected in this scrolling list, the Do Function button becomes active. When the Do Function button is pushed, the selected function in the selected library is executed. The results are then listed in the right-hand scroll list.

The pop-up menu in the window lists the two shared libraries the application will work with. These libraries are loaded when the main window opens by a call to the window’s method /loadLibraries (Figure 2). A «Shared Library» instance is created for each shared library and stored in an attribute of the main window for later use.

Figure 2. Test Window has a method which loads
a list of shared libraries

Exported symbols are the items which can be referenced by other code fragments. You can think of exported symbols as the public functions the library supports. Internally there may be a lot of functions that are hidden from the outside world. This provides some measure of control over how the library is used - which can be a nice feature for developers and users. As a developer, I may not always want every function in the library to be exposed, for fear they might not be properly used; and as a user, I may not want to know all the gory details of someone else’s library. The typical Power Mac development environment has a procedure you must follow to define the export symbols. In CodeWarrior, for instance, there is a file (*.exp) you can edit prior to building the shared library, that controls which symbols will be exported (more on this later on).

Now let’s try one function with the demo; then we will dive into more Prograph code. With the application still running, select a function in the function list and click Do Function (or simply double-click a function in the function list).

The demo application on the CPX side of things generates a list of 50 numbers. It then sends this list (embedded in a data structure) as an argument to the chosen function in the shared library. The shared library function then calculates the result and sends it back to the application (Figure 3). For the case where we use OOSharedLib and its get_average function, I did some timing analysis and found that a pure Prograph-coded equivalent using CPX built-in list primitives can be slower (I compared 68K compiled CPX to using a PPC-native shared library). Using 8000 values on a Power Mac 7100/80 (System 7.5), I got these results:

Interpreted CPX 200 Ticks

Compiled CPX 20 Ticks

Using native shared library < 1 Tick

(By the way, in looking at my Prograph code, don’t be put off by the idiosyncracies of my shorthand comments to myself, where I’m reminding myself what data type is being input or output. “<Shared Library>” means «Shared Library», an instance of the Shared Library class; at the time I was writing that comment I didn’t know how to type the '«' character! Use of parentheses generally indicates a list; so, for instance, “():name” means “a list of names”.)

Figure 3. The method /doFunction handles the execution of the selected library function

The local setup data_cache builds up a vector of data in a data structure to be sent off to the shared library. Figure 4 shows the fields of this structure. The functions in the shared library have been designed to return the result in the result field.

Figure 4. The data_cache fields
as shown in the CPX “info” window

SLD Kit CPX interface

On the CPX side of the things, the interface for using shared libraries is handled by a class called Shared Library. For Power Mac-native shared libraries you’ll actually use its subclass Shared Library PPC. When the port to 68K machines is complete, CPX users will use the Shared Library 68K subclass. The purpose of the Shared Library class is to encapsulate all the low-level calls to the CFM and the Mixed Mode Manager when working with shared libraries. The class provides a set of methods to access shared libraries. We will now review the six most significant of these methods.

Figure 5. /getLibrary gets a Connection ID to the shared library

/getLibrary

This method (Figure 5) retrieves a connection identification number using the toolbox call GetSharedLibrary. That call is in the local get shared library. The attribute Connection ID comes into play when using functions in the shared library or listing the exported symbols.

/closeLibrary

This method uses the Connection ID to close the connection (Figure 6).

Figure 6. /closeLibrary closes the connection to the shared library

/executeFunction

This method calls the function in the shared library (Figure 7). Two Shared Library methods are called prior to the final call to the shared library function via the XPrim exec-code-frag. The method /getGlue gets a chunk of embedded code (Shackelford [1994]) that exec-code-frag needs. The method /findSymbol gets a pointer to the function in the shared library. The XPrim exec-code-frag makes the call to the selected function.

Figure 7. /executeFunction encapsulates low-level CFM calls

Figure 8. /listSymbols obtains a list of function pointers

Figure 9. /listSymbolInfos gets basic information for symbols exported by a shared library

Figure 10. /findSymbol gets the function pointer
for a specific symbol by name

/listSymbols

This method can be used to get pointers to the functions exported by the shared library (Figure 8).

/listSymbolInfos

This method can be used to get pointers to the functions exported by the shared library, names of the functions, and SymClass for each function (Figure 9).

/findSymbol

This method can be used to get a specific function pointer. You must pass in the name of the function (Figure 10).

C++ Wrapper

For this article I created a small C++ library. I’ll show a function in that library and the wrapper code that was written to access it from CPX. The wrapper technique is basically the same for each function. I won’t discuss the pure C library (ExampleCLib), since the C++ version is more general as concerns the techniques required to access shared libraries from CPX. The C++ code is a simple class called Tvector. It provides a way to do calculations on a single-dimensional array of data. The next few listings show the declaration file for the shared library (OOSharedLib), the declaration file for the data structure we use to pass data into the shared libraries from CPX, the declaration file for the wrapper functions, the declaration file for the Tvector class, and the implementation files for the wrapper functions and the Tvector class.

Listing 1: OOSharedLib.h
Declaration file for the OOP shared library for this article.

#ifndef OOSHAREDLIB_H
#define OOSHAREDLIB_H
/*
    OOSharedLib.h
    
    Purpose: Header file for OOSharedLib.c
    
    This is the public function interface.
*/

#include "OOSharedLibStructs.h"

#if defined(__cplusplus)
extern "C" {
#endif


void get_average(data_cache *data);
void get_maximum(data_cache *data);
void get_minimum(data_cache *data);
void get_sum(data_cache *data);
void get_variance(data_cache *data);

#if defined(__cplusplus)
}
#endif
#endif

Listing 2: TanLibStructs.h

Declaration file for the data_cache. This is in a separate file so that we can use it with Prograph C Tool to 
“expose” or define the data structures for CPX - i.e. we can allocate the structure and fill the fields.

#ifndef TAN_LIB_STRUCTS_H
#define TAN_LIB_STRUCTS_H
/*
    © 1995 Tangent Systems
    All Rights Reserved.
    
    Public declarations for interface structures.
    Putting these declarations in a separate header makes it easier when it
    comes time to use Prograph C Tool to define these strcutures for use in CPX.
*/

#pragma pgtype double Real8
#pragma pgtype int Int4
#pragma pgtype unsigned Nat4

typedef struct {
 unsigned long length;
 int  success;
 double result;
 double *data;
 } data_cache;
 
#endif

Listing 3: Tvector.h

Declaration file for Tvector class. Defines simple methods for doing calculations on one dimensional arrays 
of doubles. Each Tvector has an array of doubles.

#ifndef TVECTOR_H
#define TVECTOR_H

class Tvector
{
 public:
    // Attributes
 unsigned long length;  // Number of element in this object
 double *theVector;
 
    // Methods
 Tvector(unsigned long length, double *aVector);
 ~Tvector();

 int calc_average(double *result);
 int calc_maximum(double *result);
 int calc_minimum(double *result);
 int calc_sum(double *result);
 int calc_variance(double *result);
 
 protected:
 
 private:
 int ok_vector;
 
};

#endif

As you can see, the class provides a constructor, a destructor, and five “mathematical” methods. Let’s look at get_average, which wraps the method calc_average. One limitation we have is that on the CPX side we will be allowed only one argument when making a call. So each wrapper will be designed to provide one argument - a pointer to a structure. We will handle the allocation and deletion of Tvector objects as needed.

Listing 4: get_average

Wraps method “calc_average” in class Tvector. Uses the Tvector class to calculate the average value of 
an array of doubles buried in data_cache.

/*
Pass in a pointer to data_cache, calculates the average value and returns
the answer in data_cache->result.
*/
void get_average(data_cache *theData)
{
 Tvector* aVector;
 double average = 0;
 TestDebug;
 
 aVector = new Tvector(theData->length, theData->data);
 theData->success = aVector->calc_average(&average);

 theData->result = average;
 delete(aVector);
}

The C function get_average instantiates a Tvector (aVector), passing the data to it (a pointer to data_cache). It then sends the message calc_average to aVector. The function captures the result in a local variable called average. The value of average is then passed back in the data_cache structure. All the wrappers are written so that there is only one calling argument and it is a pointer to a data structure. Here are the Tvector methods used in the wrapper function get_average.

Listing 5: Tvector

Constructor, destructor and method “calc_average” for class Tvector. This is only a partial listing of the 
the file Tvector.c.

Tvector::Tvector(unsigned long theLength, double *aVector)
{
 int i;
 ok_vector = 0;
 if(theLength < 0)
 {
 length = 0;
 return;
 }
 theVector = new double[theLength];

 for(i = 0;i < theLength; i++)
 {
 theVector[i] = aVector[i];
 }

 length = theLength;
 ok_vector = 1;
}
 
Tvector::~Tvector()
{
 delete(theVector);
 ok_vector = 0;
}

int Tvector::calc_average(double *result)
{
 int i;
 double theResult = 0;
 *result = theResult;
 if(ok_vector == 1)
 {
 for(i=0; i<length; i++)
 {
 theResult += theVector[i];
 }
 theResult = theResult/i;
 }
 *result = theResult;
 return ok_vector;
}

Building Shared Libraries

I used CodeWarrior for this article, and now I’ll show the files you’ll need to create a shared library. In general there are some special files you’ll need to include in the project file, there are some preferences you’ll have to set for the project, and then there is an export definition file (the .exp file) that you’ll need to define. According to the CodeWarrior documentation, you’ll need the files listed below under “libraries” and “MW Sources” (Figure 11).

Figure 11. To build a shared library
there are a few required files

Figure 12. Define the name of the shared library
in the PEF preference panel

Figure 13. Define the creator and type attributes of the shared library in the Project preference panel

Before building the shared library there a few preferences you’ll need to set up. See the CodeWarrior documentation for a complete description of the steps. I’ll highlight a few items to get you started. You’ll have to define the name of the library or fragment. That is defined in the “PEF” portion of the preferences in CodeWarrior (Figure 12).

You’ll also define the type and creator attributes, and the fact that the project is going to build a shared library. This is accomplished in the “Project” preferences panel (Figure 13).

One of the final steps before building the shared library is to define the symbols to be exported. If the Project file does not find the appropriate .exp file, it will export all functions. You can control what functions are made publicly available by creating a file with the same name as the project file, plus the .exp extension. When compilation occurs, the exported symbols will be those functions listed in the .exp file. So, for example, the project file for the OOSharedLib is called OOSharedLib.µ. The export file for this project would be named OOSharedLib.µ.exp. Listing 6 shows the content of the file in order to export our functions.

Listing 6: Export file

The export file defines the symbols that are made available for external use.

get_average
get_maximum
get_minimum
get_sum
get_variance

Conclusion and Future Plans

With the information in this article, CPX developers can now start planning, designing, and experimenting with shared libraries on the Power Mac. This powerful new feature of the Mac OS offers exciting possibilities to CPX developers, and the code in this article provides a mechanism to unleash that power.

We view the SLD Kit as another tool for CPX developers to use. We are developing a suite of high-performance technically-oriented shared libraries. The first commercial shared library we are releasing for CPX developers will be a Wavelet packet library. The core of the library is written in C++ and currently runs on DOS, Windows and UNIX. A CPX class will be developed to encapsulate the calls to the shared library. The class will provide basic data compression and Wavelet packet analysis functions. Potential application areas for such a library include voice compression, speech recognition, and digital communications.

Bibliography and References

Shackelford, John H. “You Can Have Your ‘C’ and Call It Too!”, Visual News 15 (November 1994) 9-12.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Paragraphs 1.0.1 - Writing tool just for...
Paragraphs is an app just for writers. It was built for one thing and one thing only: writing. It gives you everything you need to create brilliant prose and does away with the rest. Everything in... Read more
BlueStacks App Player 0.9.21 - Run Andro...
BlueStacks App Player lets you run your Android apps fast and fullscreen on your Mac. Version 0.9.21: Note: Now requires OS X 10.8 or later running on a 64-bit Intel processor. Initial stable... Read more
Apple iTunes 12.2 - Play Apple Music...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Apple Security Update 2015-005 - For OS...
Apple Security Update 2015-005 is recommended for all users and improves the security of OS X. For detailed information about the security content of this update, please visit: http://support.apple.... Read more
Apple HP Printer Drivers 3.1 - For OS X...
Apple HP Printer Drivers includes the latest HP printing and scanning software for OS X Lion or later. For information about supported printer models, see this page. Version 3.1: The latest printing... Read more
Epson Printer Drivers 3.1 - For OS X 10....
Epson Printer Drivers installs the latest software for your EPSON printer or scanner for OS X Yosemite, OS X Mavericks, OS X Mountain Lion, and OS X Lion. For more information about printing and... Read more
Xcode 6.4 - Integrated development envir...
Xcode provides everything developers need to create great applications for Mac, iPhone, and iPad. Xcode brings user interface design, coding, testing, and debugging into a united workflow. The Xcode... Read more
OS X Yosemite 10.10.4 - Apple's lat...
OS X Yosemite is Apple's newest operating system for Mac. An elegant design that feels entirely fresh, yet inherently familiar. The apps you use every day, enhanced with new features. And a... Read more
Dash 3.0.2 - Instant search and offline...
Dash is an API Documentation Browser and Code Snippet Manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
FontExplorer X Pro 5.0 - Font management...
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

Heroki (Games)
Heroki 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: CLEAR THE SKIES FOR A NEW HERO!The peaceful sky village of Levantia is in danger! The dastardly Dr. N. Forchin and his accomplice,... | Read more »
Hands-On With Raceline CC
Set for release soon, Rebellion’s motorbike racing game, Raceline CC certainly looks stylish. But how does it play? I got my hands on a preview build to answer exactly that. | Read more »
Siegefall - Tips, Tricks, and Strategies...
So, you fancy establishing a base and ruling the world again. Siegefall is a convenient place to do that, but how about some great tips and tricks on how best to go about it? Here are a few ideas on how to get ahead as a beginner to this medieval... | Read more »
The WWE Comes to Racing Rivals - Because...
Racing Rivals is a racing game that's all about, well, rivalry. And who knows rivalry better than WWE superstars (shhhh, that was rhetorical)? [Read more] | Read more »
Hey, Who Put Apple Music in My SoundHoun...
One of the App Store's popular music discovery sources - SoundHound - has already been updated to include Apple's own music discovery source - Apple Music. That was fast! [Read more] | Read more »
Arcane Legends has a New Expansion Calle...
Arcane Legends has been going strong since it debuted at the tail end of 2012. So well, in fact, that it's already up to its sixth expansion. [Read more] | Read more »
Vector 2 is Officially a Thing and it...
Vector is a pretty cool parkour-driven runner that's gotten a pretty decent following since it first came out - although personally I think more people could stand to show it some love. Anyway, Nekki has announced that a sequel isofficially on its... | Read more »
Get Ready to Trucksform and Roll Out (an...
It looks like NuOxygen is bringing the truck-transforming racer Trucksform (get it?) to iOS in a couple of weeks. Although really it's more of an auto-driver than a racer. But still, transforming trucks! [Read more] | Read more »
This Week at 148Apps:June 22-26, 2015
June's Summer Journey Continues With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice,... | Read more »
LEGO® Minifigures Online (Games)
LEGO® Minifigures Online 1.0.1 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

Logo Pop Free Vector Logo Design App For OS X...
128bit Technologies has released of Logo Pop Free 1.2 for Mac OS X, a vector based, full-fledged, logo design app available exclusively on the Mac App Store for the agreeable price of absolutely free... Read more
21-inch 1.4GHz iMac on sale for $999, save $1...
B&H Photo has new 21″ 1.4GHz iMac on sale for $999 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Best Buy has the 21″ 1.4GHz iMac on sale for $999.99 on their... Read more
16GB iPad mini 3 on sale for $339, save $60
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $339 including free shipping plus NY tax only. Their price is $60 off MSRP. Read more
Save up to $40 on iPad Air 2, NY tax only, fr...
B&H Photo has iPad Air 2s on sale for up to $40 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $489 $10 off - 64GB iPad Air 2 WiFi: $559 $40 off - 128GB iPad Air... Read more
Apple Releases OS X 10.10.4 With WIFi Fix, iO...
On Tuesday, Apple released final versions of OS X 10.10.4 and iOS 8.4, as well as updates for the Safari browser for OS X Yosemite, Mavericks, and Mountain Lion. The OS X 10.10.4 update focuses on... Read more
Dual-Band High-Gain Antennas for Home Wi-Fi N...
Linksys has announced what it claims are the first dual-band, omni-directional high-gain antennas for the consumer market. The new Linksys high-gain antennas available in a 2- and 4-pack (WRT004ANT... Read more
Apple refurbished 2014 15-inch Retina MacBook...
The Apple Store has Apple Certified Refurbished 2014 15″ 2.2GHz Retina MacBook Pros available for $1609, $390 off original MSRP. Apple’s one-year warranty is included, and shipping is free. They have... Read more
Clearance 2014 MacBook Airs available for up...
Adorama has 2014 MacBook Airs on sale for up to $301 off original MSRP including NY + NJ sales tax and free shipping: - 11″ 256GB MacBook Air: $798 $301 off original MSRP - 13″ 128GB MacBook Air: $... Read more
5K iMacs on sale for $100 off MSRP, free ship...
B&H Photo has the new 27″ 3.3GHz 5K iMac on sale for $1899.99 including free shipping plus NY tax only. Their price is $100 off MSRP. They have the 27″ 3.5GHz 5K iMac on sale for $2199, also $100... Read more
27-inch 3.2GHz iMac on sale for $1679, save $...
B&H Photo has the 27″ 3.2GHz iMac on sale for $1679.99 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Read more

Jobs Board

Senior Payments Security Manager - *Apple*...
**Job Summary** Apple , Inc. is looking for a highly motivated, innovative and hands-on senior payments security manager to join the Apple Pay security team. You will Read more
Project Manager - *Apple* Pay Security - Ap...
**Job Summary** The Apple Pay Security team is seeking a highly organized, results-driven Project Manager to drive the development of Apple Pay Security. If you are Read more
Web Developer, *Apple* Online Store Innovat...
**Job Summary** The Apple Online Store Innovation Lab team is seeking a talented individual with strong web development and design skills to prototype future Apple Read more
*Apple* TV Live Streaming Frameworks Test En...
**Job Summary** Work and contribute towards the engineering of Apple 's state-of-the-art products involving video, audio, and graphics in Interactive Media Group (IMG) at Read more
Project Manager, WW *Apple* Fulfillment Ope...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.