Passing byte array from C++ unmanaged dll to C# unity

Question

I am trying to return the byte array from my unmanaged c++ dll back to c# unity. Thank you very much in advance for taking the time to help >< I\'m really new to DLL in u

Answer 1

There are many ways to return byte arrays from C# and below is one of them. The memory allocation and de-allocation are both done in C++. You must call the function to free the memory from C#. I made the example very simple so that you can easily integrate it in your current code.

IntPtr is the key in this answer.

C++:

char* getByteArray() 
{
    //Create your array(Allocate memory)
    char * arrayTest = new char[2];

    //Do something to the Array
    arrayTest[0]=3;
    arrayTest[1]=5;

    //Return it
    return arrayTest;
}


int freeMem(char* arrayPtr){
    delete[] arrayPtr;
    return 0;
}

C#:

[DllImport("Test.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr getByteArray();

[DllImport("Test.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern int freeMem(IntPtr ptr);

//Test
void Start() {
 //Call and return the pointer
 IntPtr returnedPtr = getIntArray();

 //Create new Variable to Store the result
 byte[] returnedResult = new byte[2];

 //Copy from result pointer to the C# variable
 Marshal.Copy(returnedPtr, returnedResult, 0, 2);

 //Free native memory
 freeMem(returnedPtr);

 //The returned value is saved in the returnedResult variable
 byte val1 = returnedResult[0];
 byte val2 = returnedResult[1];
}

Answer 2

You could pass an extra parameter to the function, let's say another byte array, and then in the adjustBrightnesss function replace that myvector with that array. As far as i know you will get the array with the modified values