Function returns BYTE array

Question

I want my function to return a BYTE array. The function is as follows.

BYTE sendRecieveData(BYTE control, unsigned int value){

//Open connection to LAC
HANDLE LACOutpipe;
HANDLE LACInpipe;
LACOutpipe=openConnection(MP_WRITE);
LACInpipe=openConnection(MP_READ);

//declare variables
BYTE bufDataOut[3];
BYTE bufDataIn[3];
DWORD bufInProcess;
DWORD bufOutProcess;


//sets CONTROL
bufDataOut[0]=control;

//sets DATA to be sent to LAC
BYTE low_byte = 0xff & value;
BYTE high_byte = value >> 8;
bufDataOut[1]=low_byte;
bufDataOut[2]=high_byte;

MPUSBWrite(LACOutpipe,bufDataOut,3,&bufOutProcess,1000);
MPUSBRead(LACInpipe,bufDataIn,3,&bufInProcess,1000);
MPUSBClose(LACOutpipe);
MPUSBClose(LACInpipe);

return bufDataIn[3];
}

It doesn't return a byte array and when I change BYTE to BYTE[] or BYTE[3] it gives me an error.

Ben Voigt · Accepted Answer · 2012-02-27 19:02:08Z

10

return bufDataIn[3]; means "return 4th element of bufDataIn array" and in this case it leads to undefined behaviour since the size of this array is 3.

You can allocate memory for this new array in the body of your function and return pointer to its first element:

BYTE* createArray(...)
{
    BYTE* bufDataOut = new BYTE[3];
    ....
    return bufDataOut;
}

Don't forget to delete it when you finish with it:

{
    BYTE* myArray = createArray(...);
    ...
    delete[] myArray;
}

Even better, use std::vector<BYTE> and get rid of this ugly memory management with it ;) This ensures that the memory is properly freed on any return path, even when exceptions are thrown.

edited Feb 27, 2012 at 19:02

Ben Voigt

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answered Feb 27, 2012 at 18:26

LihO

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1 Comment

Ben Voigt Over a year ago

Please swap "you should" with "you can"... very good answer overall. +1

Igor Chornous · Accepted Answer · 2012-02-27 18:57:17Z

4

Since your array is relatively small I'd recommend to pass your buffer as a function argument.

void sendRecieveData(BYTE control, unsigned int value, BYTE (&buffdataIn)[3] ).

Now, one will use this function as follows:

BYTE result[3] = {0};
sendRecieveData(3, 0, result);

This way you may avoid usage of dynamic memory allocation and make your code safer.

answered Feb 27, 2012 at 18:57

Igor Chornous

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