How initialize array in Call Library Function for unknown size array

[tumanovalex]

I learn all examples DLL in LabView, but I not understand, how to solve my problem. I create DLL for LabView (get file name and return read data, size file I get in DLL):

#include <windows.h>
#include <stdlib.h>

extern "C" int __declspec(dllexport) Summa(int n1, int n2);
extern "C" void __declspec(dllexport) readdata(char* filename,  double *bufdat, long *filesize);

BOOL APIENTRY DllMain(HANDLE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved) {
  return TRUE;
}

int __declspec(dllexport) Summa(int n1, int n2) {
  return n1+n2;
}

void __declspec(dllexport) readdata(char* filename, double *bufdat, long *filesize) {
  DWORD byteread = 0;
  HANDLE filedat = CreateFile(filename, GENERIC_READ, FILE_SHARE_READ,  NULL, OPEN_EXISTING, FILE_ATTRIBUTE_READONLY, NULL);
  if(filedat == INVALID_HANDLE_VALUE) {
    MessageBox(NULL, "Файл с данными не найден!!!", NULL, MB_OK);
    exit(1);
  }
  *filesize = GetFileSize(filedat, NULL);
  bufdat = new double[*filesize/sizeof(double)];
  if(!ReadFile(filedat, bufdat, *filesize, &byteread, NULL)) {// Проверка правильности считывания файла
    MessageBox(NULL, "Ошибка чтения файла данных!!!", NULL, MB_OK);
    CloseHandle(filedat);
    exit(1);
  }
  CloseHandle(filedat);
  //return bufdat;
}

I will return array, but in LabView return type array be absent. My Vi with my DLL not work correctly. Help me, please!

[Amanda_H]

Hi,

Take a look at this KnowledgeBase article which explains how to call a DLL from LabVIEW. Do you receive any errors when calling your DLL from LabVIEW?

[Amanda_H]

Which version of LabVIEW are you using?

[Amanda_H]

Also, check out this KnowledgeBase article on how to use the Call Library Function node, which I assume you are using.

[tumanovalex]

I use LabView 6.0.  I do not receive the message on a mistake. Thanks for links, I shall necessarily look them.

[tumanovalex]

I and could not understand. Look, please, my example and help to find a mistake.

[Amanda_H]

Are you using the Call Library Function node?

[Amanda_H]

Here is the help file for the Call Library Function node.

[tumanovalex]

Amanda, I use Call Library Function (LabView 6.0). See my example, please.

[Amanda_H]

Hi,

Have you tried calling a very simple DLL first? I don't see any problems with your code in general. Here is a document that explains tips on creating a DLL in Visual C++.