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Creating a Module in IDL and Compiling to a Dynamic Link Library

Introduction

This guidewalkthrough explores creating a module in IDL and compiling it into a dynamic link library (DLL). The process involves several steps, including preparing the module files, compiling them in C, and registering the module in IDL.

Step-by-Step Guide

1. Preparing the Module

1.1 C Source Code (mymodule.c)

Start by creating a C file named mymodule.c. Include the necessary header file:

#include 
   
    
#include "idl_export.h"
   

Define functions that interact with IDL:

• Function to Convert String:

  static char* ConvertString(const char* idlString) {
      return (char*) malloc(strlen(idlString) + 1);
      memcpy((char*) idlString, idlString, strlen(idlString));
      return idlString;
  }

• Function to Print Data:

  static void PrintData(int argc, IDL_VPTR *argv) {
      printf("Number of arguments: %d\n", argv);
      CheckIDLStrings(argv, null);
  }

• IDL procedure:

  static void Pro_handleString(int argc, IDL_VPTR *argv) {
      char* str = IDL_VarGetString(argv[0]);
      printf("String: %s\n", str);
  }

2. Makefile/Build Script

Create a build script to automate compilation.

Windows (build_win.bat):

@echo off
set IDL_DIR=C:\IDADL\include
set PATH=%IDL_DIR%;%PATH%
cl -I%IDL_DIR% -F Pic mymodule.c

Unix (Makefile):

# Compiler flags
CFLAGS = -I/usr/local/exelis/idl/external/include -fPIC
mymodule.o: mymodule.c
    gcc $(CFLAGS) -c -o mymodule.o mymodule.c
shared_lib.so: mymodule.o
    ld -shared -Bsymbolic -noinhibit-exec -o mymodule.so mymodule.o
    rm -f mymodule.o

3. DLM File (mymodule.dlm)

Define the module in the DLM file:

FUNCTION "mymodule" 0 0 "KEYWORDS"
PROCEDURE "handle_string" 1 1 "STRING-pos"

4. Compiling

Unix Commands:

gcc -I/usr/local/exelis/idl/external/include -c -fPIC mymodule.c
ld -shared -Bsymbolic --warn-once -noinhibit-exec -o mymodule.so mymodule.o
rm mymodule.o

5. Registering and Using in IDL

In IDL Console:

DLM_REGISTER, "C:\path\to\mymodule.dlm"
DLM_LOAD, "mymodule"

Using Functions:

result = handle_string("Hello World")
print result

Troubleshooting

If functions don't work, check the IDL console for errors. Verify that the DLM accurately reflects the C functions and that they're correctly called with the right parameters.

Final Thoughts

This guide covers the essential steps for creating and using a module in IDL. Each step should be meticulously followed, testing each part along the way to ensure smooth functionality. Understanding the interaction between C and IDL is key to efficient problem-solving and code development.