IBM Visualization Data Explorer Programmer's Reference

Chapter 3. Module Builder

Partial Table-of-Contents

The Module Builder is a point-and-click interface for creating a module from user-supplied information.

The next several sections describe the general structure of modules built with the Module Builder; its dialog box; and examples of the "worker routine"--the interface between a module and the user-supplied application code.

3.1 Overview

1. a module description file (with the extension .mdf);
2. a C-code framework file that implements the structure of the module; and
3. a makefile.

The C-code framework file itself consists of three major routines:

• The first routine checks input parameters and creates output Objects. It is named by prefixing m_ to the module name (e.g., the entry point for a module named Example is m_Example).
• The second routine traverses hierarchically defined data Objects. When this routine (Traverse) encounters a Data Explorer Field Object, it calls the third routine.
• The third routine (doLeaf) creates a "worker routine" as an interface to the user's application-specific code: it extracts the input arguments, sets up the outputs, and calls the user-supplied code. (See 3.7 , "Worker Routine" and "Worker Routine Examples".). The worker routine appears at the end of the C-code framework file.

To complete a customized module, the user need only:

add the application-specific code to the worker routine (after the line "User's code goes here" at the end of the C-code framework file) by:

using an "include" file, or

adding the application code directly to the framework file.

Using an include file is recommended because (1) if you rerun the module builder, it will overwrite the .c file, and (2) it makes replacing your own code easy.

Notes:

1. The Module Builder is designed to accommodate the most common form of customized module, in which the output Object is a copy of the input, but the data component is modified.
2. Other inputs can be constant parameters or other hierarchically defined data Objects (note that the hierarchy of the data Objects must match exactly).

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