Using External Code
in LabVIEW
Using External Code in LabVIEW
July 2000 Edition
Part Number 370109A-01
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© National Instruments Corporation v Using External Code in LabVIEW
Contents
About This Manual
Conventions ...................................................................................................................xiii
Related Documentation..................................................................................................xiv
Chapter 1
Introduction
Calling Code in Various Platforms................................................................................1-1
Characteristics of the Two Calling Approaches ............................................................1-2
Details of Call Library Function......................................................................1-3
Details of a CIN...............................................................................................1-3
Chapter 2
Shared Libraries (DLLs)
Calling Shared Libraries................................................................................................2-1
Calling Conventions (Windows).....................................................................2-3
Parameters .......................................................................................................2-3
Calling Functions That Expect Other Data Types...........................................2-5
Building a Shared Library (DLL)..................................................................................2-6
Task 1: Build the Function Prototype in LabVIEW........................................2-6
Task 2: Complete the .c File............................................................................2-8
Task 3: Build a Library Project in an External IDE........................................2-10
Calling External APIs....................................................................................................2-14
Common Pitfalls with the Call Library Function............................................2-14
Example 1: Call a Shared Library that You Built ...........................................2-16
Example 2: Call a Hardware Driver API.........................................................2-17
Example 3: Call the Win32 API......................................................................2-19
Additional Examples of LabVIEW Calls to DLLs........................................................2-25
Debugging DLLs and Calls to DLLs.............................................................................2-26
Troubleshooting the Call Library Function.....................................................2-26
Troubleshooting your DLL..............................................................................2-26
Troubleshooting Checklist...............................................................................2-27
Module Definition Files.................................................................................................2-29
Array and String Options...............................................................................................2-30
Arrays of Numeric Data ..................................................................................2-30
String Data.......................................................................................................2-31
Array and String Tip........................................................................................2-33
Contents
Using External Code in LabVIEW vi www.ni.com
Chapter 3
CINs
Supported Languages .................................................................................................... 3-1
Macintosh........................................................................................................ 3-1
Microsoft Windows......................................................................................... 3-1
Solaris, Linux, and HP-UX.............................................................................3-2
Resolving Multithreading Issues................................................................................... 3-2
Making LabVIEW Recognize a CIN as Thread Safe ..................................... 3-2
Using C Code that is Thread Safe...................................................................3-3
Creating a CIN...............................................................................................................3-3
Step 1. Set Up Input and Output Terminals for a CIN....................................3-4
Step 2. Wire the Inputs and Outputs to the CIN .............................................3-6
Step 3. Create a .c File .................................................................................... 3-6
Step 4. Compile the CIN Source Code ........................................................... 3-8
Step 5. Load the CIN Object Code ................................................................. 3-16
LabVIEW Manager Routines........................................................................................ 3-16
Pointers as Parameters ....................................................................................3-17
Debugging External Code .............................................................................................3-18
DbgPrintf......................................................................................................... 3-19
Windows .........................................................................................................3-19
UNIX...............................................................................................................3-21
Chapter 4
Programming Issues for CINs
Passing Parameters........................................................................................................ 4-1
Parameters in the CIN .c File..........................................................................4-1
Passing Fixed-Size Data to CINs.................................................................... 4-2
Return Value for CIN Routines ......................................................................4-3
Examples with Scalars ....................................................................................4-4
Creating a CIN That Multiplies Two Numbers ..............................................4-4
Passing Variably Sized Data to CINs............................................................................ 4-7
Resizing Arrays and Strings............................................................................ 4-9
SetCINArraySize.............................................................................. 4-11
NumericArrayResize ........................................................................ 4-12
Examples with Variably Sized Data ............................................................... 4-14
Manager Overview........................................................................................................ 4-21
Basic Data Types ............................................................................................ 4-23
Memory Manager............................................................................................4-27
File Manager.................................................................................................................. 4-32
Support Manager............................................................................................. 4-36
