[RESOLVED] Calling a C/C++ string search function from a VB thread

[szlamany]

I created a STRING SEARCH function in C/C++ - and I'm trying to use it in a multi-threaded situation in VB.

I started this problem in a thread in the C/C++ section of the forum - here

http://www.vbforums.com/showthread.php?t=675943

At any rate - my last post shows me getting this error trying to call the function.

Ran the code - got to that point - and in the immediate window I did

?firstIndexOfKeyword("i had fancy italian food for lunch", {"meh", "feh", "italian"}, 3)
{"An exception 'Microsoft.VisualStudio.Debugger.Runtime.CrossThreadMessagingException' occurred"}
    _HResult: -2146232832
    _message: "Error in the application."
    Data: {System.Collections.ListDictionaryInternal}
    HelpLink: Nothing
    HResult: -2146232832
    InnerException: Nothing
    IsTransient: False
    Message: "An exception 'Microsoft.VisualStudio.Debugger.Runtime.CrossThreadMessagingException' occurred"
    Source: "Microsoft.VisualStudio.Debugger.Runtime"
    StackTrace: "   at Microsoft.VisualStudio.Debugger.Runtime.Main.ThrowCrossThreadMessageException(String formatString)     at System.Windows.Forms.SafeNativeMethods.GetWindowTextLength(HandleRef hWnd)     at System.Windows.Forms.Control.get_WindowText()     at System.Windows.Forms.Form.get_WindowText()     at System.Windows.Forms.Control.get_Text()     at System.Windows.Forms.Form.get_Text()     at System.Windows.Forms.Form.ToString()"
    TargetSite: {Void ThrowCrossThreadMessageException(System.String)}

And got a pop-up error about not finding the ENTRY point and this ugly cross threading error...

[jmcilhinney]

So, does the code work correctly when used in a single thread? What about in multiple threads? Is it just when you use the Immediate window that the issue arises? The issue appears to be that ToString is being called on a Form from a background thread, but I'm not 100% sure where that would be occurring.

[szlamany]

Ok - I took this issue out of the immediate window - don't need to add more to my problem then I need

Took the spot where I was doing the breakpoint - and instead of the immediate window I added this code to call the firstIndexOfKeyword() function

    Private Sub ScanFile(ByVal FSObParam As Object)

        Dim x As Object = firstIndexOfKeyword("i had fancy italian food for lunch", {"meh", "feh", "italian"}, 3)

        Dim FSOb As New FSObject
        FSOb = DirectCast(FSObParam, FSObject)

and I am getting this error

System.EntryPointNotFoundException was unhandled
  Message=Unable to find an entry point named 'firstIndexOfKeyword' in DLL 'D:\ACS Desktop\dcx\dcx\Debug\StringLibrary.dll'.
  Source=Librarian
  TypeName=""
  StackTrace:
       at Librarian.Librarian.firstIndexOfKeyword(String s, String[] substr, Int32 substrLength)
       at Librarian.Librarian.ScanFile(Object FSObParam) in D:\ACS Desktop\dcx\dcx\Librarian\Librarian.vb:line 145
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.runTryCode(Object userData)
       at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart(Object obj)
  InnerException:

I am sure I am missing something from the C/C++ project - first time trying to work with C/C++.

This is in a file called StringLibrary.cpp

// StringLibrary.cpp : Defines the exported functions for the DLL application.
//

#include "stdafx.h"

__declspec(dllexport) int firstIndexOfKeyword(char *str, char **keywords, int nKeywords) {
	int i, j, k;
	int keywordlen;
	int len = strlen(str);

	for(k = 0; k < nKeywords; k++)
	{
		keywordlen = strlen(keywords[k]);

		for(i = 0; i <= len - keywordlen; i++)
		{
			for(j = 0; j < keywordlen; j++)
			{
				if(keywords[k][j] != str[i + j])
					j = keywordlen+1;
			}

			if(j == keywordlen)
				return i;
		}
	}

	return -1;
}

[jmcilhinney]

That error message certainly makes it sound like the function is not exported correctly in the C++ project but it's far too long since I wrote any C++ to be able to help in that regard I'm afraid. I see that Atheist got it working so I'm not sure what the issue might be.

[szlamany]

This issue is resolved - refer to the other thread in the first post to see solutuions.