Passing Array to DLL Function

madhatt30 (16)
Ok i'm trying to pass an array to a function inside a DLL. the following is the C++ DLL Function

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	double XPortBarArray(double inArray[][6], int Size)
	{
		/** 
		0 - time,
		1 - open,
		2 - low,
		3 - high,
		4 - close,
		5 - volume.
		**/

		double first = inArray[4][1];

		return first;
	}

any reason why this wouldn't work. I must be missing something because the returned double is not correct.
thanks
Last edited on
LB (13399)
The DLL and main application are compiled separately from each other so your compile-time inArray[][6] will do no good. You must handle it as either a double* and do the width/height math yourself, or pass it as a double** pointer with a width and height and treat it as an array of pointers to doubles.
madhatt30 (16)
Thanks for information am I close

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// the export
__declspec(dllexport) double* XPortBarArray(double* InArray[][6], int szRows, int szCols);


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// the function

	double* XPortBarArray(double* inArray[][6], int szRow, int szCol=6)
	{
		/** 
		0 - time,
		1 - open,
		2 - low,
		3 - high,
		4 - close,
		5 - volume.
		**/

		double* first = inArray[0][4];

		return first;
	}

madhatt30 (16)
Ok, I guess i'm a little confused about the whole double* thing. I want to be able to cycle through the whole array If need be but I need to know that the array is being passed and extract the first double from inArray[0][4] at col 4

still not working
LB (13399)
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double GetAtRow0Col4(double **arr, unsigned rows, unsigned cols)
{
    return arr[0][4];
    //to iterate:
    for(unsigned r = 0; r < rows; ++r)
    {
        for(unsigned c = 0; c < cols; ++c)
        {
            //do stuff with arr[r][c]
        }
    }
}
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//calling code:
const unsigned MyRows (3), MyCols (6);
double **MyArr = new double*[MyRows];
for(unsigned r = 0; r < MyRows; ++r)
{
    MyArr[r] = new double[MyCols];
}
//...
//fill array with data
//...
double first = TheDLLFunc(MyArr, MyRows, MyCols);

Last edited on
madhatt30 (16)
ok now im just confused

<DLL CODE>
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#include <iostream>
#include <string>
#include <cstring>

using namespace std;

namespace MT4_Export
{
    class MyFunctions
    {
    public:
        __declspec(dllexport) int XPortCurBar(double HIGH, double LOW, double OPEN, double CLOSE, int VOLUME);
		__declspec(dllexport) double* XPortBarArray(double* InArr[][6], int szRows, int szCols);
		__declspec(dllexport) char* XPortMsg(string XMsg);
	};

	int XPortCurBar(double High, double Low, double Open, double Close, int Volume)
	{

		return 0;
	}

	double* XPortBarArray(double **inArray[], unsigned szRow, unsigned szCol=6)
	{
		/** 
		0 - time,
		1 - open,
		2 - low,
		3 - high,
		4 - close,
		5 - volume.
		**/
		double* first = inArray[0][4];

		return first; //first;
	}

	char* XPortMsg(char* inmsg)
	{
		char* mHeader = "DLL Received: ";
		// retrieve incoming string and assign to variable
		char* msgHeader = new char[strlen(inmsg)+1];
		memcpy(msgHeader,inmsg,strlen(inmsg)+1);
		msgHeader[strlen( inmsg )] = '\0';

		char* retVal = new char[strlen(mHeader)+strlen(msgHeader)+1];
		*retVal = '\0';
		
		// Assemble the string
		strcat(retVal,mHeader);
		strcat(retVal,msgHeader);

		return retVal;
	}

}

The calling routine is located outside of the DLL. The Function XPortMsg() works just fine and returns what is expected.
Last edited on
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