Return an array from dll to labview

Hello,
I am using "Call Library Function" where I call a C function from Labview.
Now .. I want to return an 1 dimensional array from C DLL back to Labview.
Can someone provide an example code how to do it.
When I configure parameter, there are options "Array Data Pointer", "Array Handle" and "Array Handle Pointer".
When I take the first (the simple one), so there is no way labview can know how many items are in the array.
But what is the right to take?
Thanks in advance
Kind Regards

You would run into the same problem calling a function that returns an array in C, because you cannot determine the number of items in an array in C solely from the pointer value that a function returns. Also, it's a bad idea to return an array of unknown size as a function's return value, because that makes the calling function responsible for deallocating the memory even though the called function allocated it. If you don't know in advance how large the array will be, then a better approach is to allocate an array of sufficient size in the calling function (or in LabVIEW, in this case) and pass that by reference to the function, then have the function's return value indicate the number of values in the array that are actually filled with data.

Similar Messages

Sending arrays from Excel into Labview

I want to send an array from Excel VBA into a LabView VI.
The Excel example shows how to send individual numbers and return an array into Excel but not send an array.
Everything tried sends blank arrays into LabView, which can then be modified in LabView and returned to Excel.
A VBA code snippit that does not work is:
Sub LoadData()
' LoadData Macro
' Keyboard Shortcut: Ctrl+l
' This is an example to demonstrate LabVIEW's Active-X server capabilities.
' Executing this macro loads a LabVIEW supplied example VI "Frequency Response.vi",
' runs it and plots the result on an Excel Chart.
Dim lvapp As LabVIEW.Application
Dim vi As LabVIEW.VirtualInstrument
Dim paramNames(0)
Dim paramVals As Variant
Set lvapp = CreateObject("LabVIEW.Application")
viPath = lvapp.ApplicationDirectory + "\examples\apps\freqresp.llb\DAK Frequency Response.vi"
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vi.FPWinOpen = True                     'Open front panel
paramNames(0) = "Foo"
paramVals = Sheet1.Range("j1:j1000").Value
Call vi.Call(paramNames, paramVals)
This code generates an error - expecting 1D array or variants.
However, if I supply the correct array, then LabView thinks it is empty
'foo' is a cluster
'Array' is a double array
Neither work to receive the data

Thanks for the reply but that approach will be difficult. The problem to solve is relatively simple IF LabView could read arrays (it writes arrays easily). Here is the problem:
I want to convolute two large arrays. I have written VBA programs to do this but they take too long - over 30 sec whereas the LabView version take <1 sec IF I could get the data into LabView.
The convolute is part of an optimization program that goes though many loops so that it takes hours to run efficiently AND if I manually change cells in the spreadsheet, then it takes 30sec to come back as VBA does not respect clean cells (for some reason).
I was trying to write a function in VBA to do this calculation via LabView rather than VBA. One way to do this is to write a text file in VBA and read in LabView, then pass the results back or maybe the clipboard as a buffer. That is faster but clumsy. You could also have LabView look for dirty cells and then do the calculation as the server rather than the client. Again, time consuming and cumbersome. I have written pure LabView code to do the curve fitting but prefer to use Excel as that is easier to incorporate and work with the data.   You can do convolute using FFTs but Excel does not do that correctly - they CANNOT make their FFTs into a function (VBA functions cannot modify cells in the spreadsheet but only return variables. FFT modifies cells so cannot be called from a function, only a macro, which then needs to be updated manually). Again, I can kluge VBA (real kluge this time) to make FFTs work as a function BUT prefer the LabView solution, if possible, as I am not sure the FFT will actually save time.
I am not sure if the problem is LabView's fault or Excel's (2013) fault that the variables are not set-up properly. LabView claims to be able to do this. Again, you can pass single variables into LabView and read back arrays but try as I might, I cannot get arrays into LabView.
Any help in sending arrays (maybe Labview expects a variant variable and needs to convert it somehow) would be appreciated. Variants are suppose to be able to be converted automatically but maybe there is a bug in LabView (2010) that does not handle input variant arrays correctly (I have tried making them clusters, double arrays, ect). LabView thinks that all the arrays sent by VBA are empty. If LabView modifies the same array, VBA sees that modification so that the addresses appear to be sent correctly i.e. the array "handle" is being sent to LabView or else it could not fill the array to send back to VBA.
If ever this is solved, I will put on-line the solution for others as again marrying both programs will have advantages. Others may find this interesting is marry LabView with Excel so that LabView does some of the heavy calculations that Excel has kluged.

Returning 2D array from a stored procedure

hi,
i'm trying to return a nested table from a procedure.can any one help me out i'm getting the fallowing error.
SQL> ed
Wrote file afiedt.buf
1 declare
2 TYPE data_t IS TABLE OF NUMBER
3 INDEX BY PLS_INTEGER;
4 TYPE array_t IS TABLE OF data_t
5 INDEX BY PLS_INTEGER;
6 array array_t;
7 begin
8 Sp_test(123,'12-jan-08',array);
9 dbms_output.put_line(array (10) (1));
10* end;
11 /
Sp_test(123,'12-jan-08',array);
ERROR at line 8:
ORA-06550: line 8, column 1:
PLS-00306: wrong number or types of arguments in call to
'SP_TEST
ORA-06550: line 8, column 1:
PL/SQL: Statement ignored
The procedure is
CREATE OR REPLACE PROCEDURE Sp_test(S_KEY NUMBER,V_DATE DATE, array_out OUT array_t) as....

Below is the error i got when using the above suggestion.
SQL> ED
Wrote file afiedt.buf
1 DECLARE
2 TYPE data_t IS TABLE OF NUMBER
3 INDEX BY PLS_INTEGER;
4 TYPE array_t IS TABLE OF data_t
5 INDEX BY PLS_INTEGER;
6 begin
7 Sp_test(123,'12-jan-08',array REPORT.ARRAY_T);
8 dbms_output.put_line(array (10) (1));
9* end;
10 /
Sp_test(123,'12-jan-08',array REPORT.ARRAY_T);
ERROR at line 7:
ORA-06550: line 7, column 32:
PLS-00103: Encountered the symbol "REPORT" when expecting one of the
following:
. ( ) , * @ % & | = - + < / > at in is mod not range rem =>
.. <an exponent (**)> <> or != or ~= >= <= <> and or like
between ||
The symbol "." was substituted for "REPORT" to continue.

C++ do not support JNi && how to return the array from jni?

hi,
1.. I have created the Cpp file to implemement the native method but it seems that the native method can not complie rightly , it tells me follows
error C2819: type 'JNIEnv_' does not have an overloaded member 'operator ->'
c:\program files\microsoft visual studio\vc98\include\jni.h(764) : see declaration of 'JNIEnv_'
c:\users\wangyue\desktop\java_gui\beattrack 5.6 - ��_��_�� 5.7\beattrack.cpp(202) : error C2227: left of '->GetByteArrayRegion' must point to class/struct/union
then I use the c file to paste the same code, it can complie rightly , why? I really need my native method to complie rightly in Cpp file, how to solve it?
2.I want to return a double, for the most simple way, I do the following
#include "RealBeatTrack_BeatTrack.h"
JNIEXPORT jdoubleArray JNICALL Java_playaudio_BeatTrack_BeatTrack
(JNIEnv *env, jobject j, jbyteArray data)
jdouble outdata[4]={1,2,3,4};
return (*env)->NewDoubleArray(env, outdata);
then in the java code, I difine a array to receive it,
say double mydata[] = new double[4];
mydata= BeatTrack(buffedata);
but the java comlier tells me the Exception in thread "Thread-2" java.lang.OutOfMemoryError: Java heap space?
anyone can help me?
Thanks

thanks for your reply
another problem of my!
the jni pass the string, I then convert it to the
const char* filename = env->GetStringUTFChars(fname,NULL);
then I use the filename to opent the file but fails, what is the problem???
FILE *fp= fopen(filename,"w"); // there are some problem here!!!
fprintf(fp, "%s\n","wangyue fighting!");
the error is as follows
# An unexpected error has been detected by Java Runtime Environment:
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x0bfc1a55, pid=7040, tid=11384
# Java VM: Java HotSpot(TM) Client VM (10.0-b19 mixed mode windows-x86)
# Problematic frame:
# C [beattrack.dll+0x1a55]
# An error report file with more information is saved as:
# D:\programs\playAudio\hs_err_pid7040.log
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#

Return 2D array from web service

Hi All,
I am new to web services development and start developing web service using net bean 6.9. I want to create the web service which needs to return the 2-d array. So i created it like this
public Object[][] getData(@WebParam(name = "startDate")
String startDate, @WebParam(name = "endDate")
String endDate) {
HashMap hm= new HashMap();
hm.put("key1", "val1");
hm.put("key2", "val2");
Object[][] twoDarray = new String[hm.size()][2];
Object[] keys = hm.keySet().toArray();
Object[] values = hm.values().toArray();
for (int row = 0; row < twoDarray.length; row++) {
twoDarray[row][0] = keys[row];
twoDarray[row][1] = values[row];
return twoDarray;
But when i test the web service using SOAPui then it did not returning anything. Can anyone guide me where is the problem??
Thanks
Shuja

Gi,
not sure what you are doing there, but you can build the J2EE WebService from your working POJO, and create a Web Service proxy class from the WSDL description (of the deployed or local WSDL file). Then, using the proxy class, you can access the output of the WebService.
Frank

Returning int array from C to Java as method parameter

Hello,
I've been trying to accomplish this
Java
int[] myArray = ... (filled with some data);
int retCode = myNativeCall(myArray);
if(retCode == 0)
doSomethingWith(myArray); //myArray gets overwritten with new data (with new size also) during the native call...
C
JNIEXPORT jint JNICALL Java_GenChav_rsaEncrypt(JNIEnv *env, jobject obj, jintArray myArray){
jintArray outbuf;
int[] new_array = .. // some function will fill this....
int new_array_length = ...//some function will give me the new size, not big, 512 max...
jint tmp[new_array_length]; //allocate..need something more ??
memcpy(tmp, new_array, new_array_lenght);
outbuf=(*env)->NewIntArray(env, new_array_length);
(*env)->SetIntArrayRegion(env, outbuf, 0, new_array_length, tmp);
myArray=outbuf;
I tought this way I would have a updated myArray ints on the Java program...
Any thought??

user5945780 wrote:
Ok, let's try to be constructive here...
How I do implement a return type for my method like a int array ?First realized it has nothing to do with JNI. So the same question and answer applies to java only.
>
like:
int[] return = myNativeCall();
Yes.
Then I will look for return[0], if it is == to 0, fine, it means a successful calculation by the native code. Not sure what that means. The structure of what you return it up to you.
It can help when you are unsure of what to do in JNI....write a pseudo representation of what you want to do in a java method. Then translate that java method into JNI, everything in the pseudo method must be in the JNI code.

Returning arrays from function

Hi all,
Can u please guide me in how to return an array from function .
Is it possible or not ??
If it is possible please tell me how to declare the function(prototype) that returns string array
and how to return the string array..
Thanks in Advance

Hi all,
Can u please guide me in how to return an array from
function .
Is it possible or not ??
If it is possible please tell me how to declare the
function(prototype) that returns string array
and how to return the string array..
Thanks in Advance
public String [] methodReturnsAnArray()
}

Use a wrapper to build a C++ Dll that calls a C++ .lib and Use the Dll is LabView

Hi All,
I need to access some functions in a C++ .lib within LabView, but has no source code for the library. Can I build a Dll in Visual C++ that calls this library, then have LabView calls the Dll? If so, how different is building this Dll compared to building a Dll from a .cpp file? I am new to C++, could some one suggest how to use the .lib in Visual C++ 6.0 studio to build the Dll?
Thanks for your help.
Bryan

BryanL wrote:
Hi Rolf, thanks for the info. I will try to build a vi to call that function. For a more immediate need, I can use a downloaded vi that calls SetActiveWindow function, then use its output windowshandle to find the window name with a lvwuser32.dll function. The problem is this find window name function vi requires a windows reference input, which does not take the window handle output from the SetActiveWindow vi. How do i convert the window handle into a reference number? Thanks again.
Don't try to write a VI to call that function. That function requires a callback function pointer, something that is more or less impossible (well you can get it done but it is not worth the trouble) to create in LabVIEW. You will need an external DLL that does the enumeration and returns an array of strings to LabVIEW.
The lvwuser32.dll also just uses window handles. Look inside those VIs and you should see that those window references are typecasted into uint32 and then passed to the Call Library Node if I remember correctly. You definitely should be able to typecast the (probably uint32) you get from your other function into the window reference that that VI takes. The window reference of the lvutil library is just a nice trick to make it refnum like so that you can not inadvertly wire something else to it (and confuse/crash Windows).
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

External java function that should return String array

Hi everyone,
I have a split function in plsql that takes 10 times longer a java tokenizer function that i was written. So, i want to use java external function to split my plsql strings into pieces.
I can write a java external procedure that returns types like int, float and String types. I have no problem about it.
My problem is returning an array of strings. I found a book that has an example about how can we get directory list in plsql with java external procedure.
(code)
import java.io.File;
import java.sql.*;
import oracle.sql.*;
import oracle.jdbc.*;
public class JFile {
public static oracle.sql.ARRAY dirlist (String dir)
throws java.sql.SQLException
Connection conn = new OracleDriver().defaultConnection( );
ArrayDescriptor arraydesc =
ArrayDescriptor.createDescriptor ("DIRLIST_T", conn);
File myDir = new File (dir);
String[] filesList = myDir.list( );
ARRAY dirArray = new ARRAY(arraydesc, conn, filesList);
return dirArray;
CREATE OR REPLACE FUNCTION dirlist (dir IN VARCHAR2)
RETURN dirlist_t
AS
LANGUAGE JAVA
NAME 'myFile.dirlist(java.lang.String) return oracle.sql.ARRARY';
(code)
I could compile this source file in localhost but not remotehost. There are jar files ( import oracle.sql.*; import oracle.jdbc.*; ) that should be added to remote classpath. ( others have already added java classpath ). But, which classpath i should add? Oracle has own JVM and Classpath, probably i should upload these jar files to oracle classpath. Am i wrong? How can i do? Can you explain in detail? How can i return string array from java external function in Oracle ?
I am using Oracle 11.1.0.7 on Solaris Sparc Machine.

Hi,
What do you mean "compile in remote host"
Aren't you using the loadjava tool? - that should be enough, the RDBMS already "has" the jars needed.
[A must read|http://download.oracle.com/docs/cd/B28359_01/java.111/b31225/chone.htm#BABCFIIF]
Regards
Peter

Want to pass 2D integer array from VB 6.0 to LabView (v 8.0) DLL

I was able to pass 1D arrays from VB 6.0 to LabView 8.0 with no problem. I checked the literature for help regarding 2D arrays and found
scant help unless it was for VB.NET, C or single dimensional arrays. Thanks.
I wrote a simple test VB program to pass 2D arrays shown below after which I get a memory crash:
Private Declare Sub Test2D Lib _
    "C:\Documents and Settings\Owner\My Documents\builds\Test2DArray\Test2DArray\Test2DArray.DLL" _
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Private Sub cmdStart_Click()
    On Error GoTo handle_error
    Dim intInArray(8, 8) As Integer
    Dim intOutArray(8, 8) As Integer
    Dim varInArray As Variant, varOutArray As Variant
    Dim i As Long, j As Long, k As Integer
    For i = 0 To 7
        k = i * 8
        For j = 0 To 7
            intInArray(i, j) = k + j
        Next j
    Next i
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handle_error:
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In the Labview DLL I have a definition of the exported function call as:
void Test2darray(TD1Hdl * InArray, TD1Hdl * OutArray)
(in the Labview DLL I take the input array, add 1 to each of the elements and then stuff it into the output)

jd162,
The following discussing forum may help out:Pass array to "Labview 7" DLL in Visual Basic . Let us know if this helps out at all.
Chris C
Chris Cilino
National Instruments
LabVIEW Product Marketing Manager
Certified LabVIEW Architect

How do I return a Boolean array from LabView to TestStand?

I am trying to return a Boolean array from Labview to TestStand and have TS evaluate the results. I can do this for arrays of integers or reals but booleans do not work. I tried copying the PassFailTest step type and adding an array of Bool but I couldn't get it to evaluate the array. It simply always passed. How can this be done?
Bob A.

I have thought about evaluating the Boolean data in TestStand but, as you say, this is a lot of work. What I have been doing is to map the boolean data to integers in LV (very easy) and then use the multiple numeric step type to evaluate the integer array automatically. This feels kludgy and I have tried a couple of times to create a "multiple boolean" step type with little success. I'm surprised TS hasn't anticipated a test returning multiple pass/fail results. I do this all the time for production code.
What I have tried is to copy MultipleNumericLimitsTest data type to a custom type and add a BooleanArray with a data type Array of Boolean[0..empty]. Then when I specify module, I select Step.BooleanArray as the value. The last step (that I know of) is to select Step.BooleanArray as the data source in the edit limits window. At this point if I run the test, I get the error "expect numeric, found boolean" (or something similar). When I look at the properties of my custom step type, the Substeps has DoMultiNumericMeasEvaluation as the Post-Step. I believe this is the root of my problem but I can't figure out how to change this to "DoMultiBooleanMeasEvaluation" or similar. Any Ideas?

How to remove the "int len" of my return string on the DLLS header when building a DLL on LabVIEW 8.5

Hi all.
I'm building a DLL on LabVIEW and I choose a string as an output on the terminals connectors.
But LabVIEW creates another output, the lenght of the return string.
This is a problem because I have other DLLs and I need them to be compatible.
How do I remove this length from the header? What is the difference between Pascal String and C string and String Handle Pointer?
String Handle Pointer removes the length from the header but I don't know the difference between this data types.
Thanks in advance for the help.
Daniel Coelho
Portugal
Daniel Coelho
VISToolkit - http://www.vistoolkit.com - Your Real Virtual Instrument Solution
Controlar - Electronica Industrial e Sistemas, Lda

Daniel Coelho wrote:
Hi all.
I'm building a DLL on LabVIEW and I choose a string as an output on the terminals connectors.
But LabVIEW creates another output, the lenght of the return string.
This is a problem because I have other DLLs and I need them to be compatible.
How do I remove this length from the header? What is the difference between Pascal String and C string and String Handle Pointer?
String Handle Pointer removes the length from the header but I don't know the difference between this data types.
Thanks in advance for the help.
Daniel Coelho
Portugal
C string pointer is a pointer to a memory location whose string information is terminated by a 0 byte. Pascal String Pointer is a pointer to a memory location where the first byte specifies the number of bytes to follow. This obviously allows only for strings up to 255 character length.
LabVIEW String Handle is a pointer to a pointer to a memory location where the first 4 bytes are an int32 value indicating the number of characters to follow. You can read such a String handle in a function without many problems, but you can only create, resize and delete such a handle by using LabVIEW memory manager functions. So this makes only sense if the caller of such a DLL is LabVIEW too as another caller would have to go through several hoops and tricks in order to gain access to the correct LabVIEW kernel that could provide the memory manager functions to deal with such handles.
Last but not least output strings whose allocated length is not passed to the funciton as additional parameter are a huge secerity risk (talk about buffer overrun errors). LabVIEW DLL Builder does not support the creation of DLLs with output string (or array parameters) without the explicit passing of an additional parameter telling the DLL function how large the allocated size is (so that the DLL function can make sure to never write over the end of the buffer).
The additional length parameter only disappears for String Handles because LabVIEW will simply resize them to whatever length is necessary and that is also the reason why those handles need to be allocated by the same memory manager instance that is also going to execute the DLL function.
Resizing of memory pointers is non-standardized and in normal circumstances not suited for passed function parameters at all.
Rolf Kalbermatter
Message Edited by rolfk on 06-13-2008 12:28 PM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

How to create a dll in LabVIEW with a 2D array

I'm attempting to create a dll in LabVIEW with the following parameters from Test DLL.vi:
Inputs:
IN1 - Word
Buffer - 2D array of Unsigned Byte
Output:
OUT1 - Unsigned Byte
The prototype is constructed as follows in the Build Specifications of the Project:
uint8_t TestDLL(int16_t IN1, TD1Hdl *Buffer)
The dll builds successfully but when I attempt to use it in another VI (using the Call Library Function block) the prototype appears but it does not look like what was defined from the Build Specifications. Instead it looks like the following:
void TestDll(void );
I attached some screen shots of all the settings as described above.
Attachments:
Test DLL Front Panel.JPG ‏85 KB
DLL Prototype Before.JPG ‏84 KB
DLL Prototype After.JPG ‏54 KB

The Test DLL.vi is what I used to create dll prototype with in the Build Specifications in the project.
Note: There is no logic implemented yet.
Attachments:
Test DLL.vi ‏7 KB

Returning structure from dll to pl/sql

hi
we have a problem regarding how to return structure of arrays from c dll. It may be possible with oci programing . Is it possible with simple c program using oracle object types or by pl/sql records .
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Thanks,
Zuber
null

Oracle9 i JDBC Developers Guide and Reference(page 21-16):
It is not feasible for Oracle JDBC drivers to support calling arguments or return
values of the PL/SQL RECORD, BOOLEAN, or table with non-scalar element types.
However, Oracle JDBC drivers support PL/SQL index-by table of scalar element
types. For a complete description of this, see "Accessing PL/SQL Index-by Tables"
on page 16-21.
As a workaround to PL/SQL RECORD, BOOLEAN, or non-scalar table types, create
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that takes a character or number from JDBC and passes it to the original procedure
as BOOLEAN or, for an output parameter, accepts a BOOLEAN argument from the
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a record in its individual components (such as CHAR and NUMBER) or in a structured
object type. To wrap a stored procedure that uses PL/SQL tables, break the data
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Array output of a Labview dll

Hi all,
I haven´t found the solution in the posts of this forum, if somebody has, please inform me.
I want to output an array from a dll compiled in LV7.1. It doesn´t work. I have tried all the combinations of Array Data Pointer & Array Handle Pointer, and the two calling conventions, and it doesn´t work. My output array (Y) is always the unchanged input array. Any idea?

Whithout having your DLL it's difficult to say why your code is not working. There are different ways to pass array data, please also have a look at the examples that are contained in LabVIEW.
You can also find a pretty good tutorial here

Return an array from dll to labview

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