[RESOLVED] First time using pointers - is this the right way to do this?

[szlamany]

I need to get a pointer to a particular spot in an array - it's an __int64 array. So I googled around and this seems to be what I need to do - please tell me if I'm missing something or doing something wrong.

The array I need a pointer to is passed into this C++ function as cwlayout

	int processCW(WCHAR *strSearch, int *smarkerskt, int *emarkerskt..., __int64 *cwlayout...) {

Comes from VB as Dim cwLayout(cwValue - 1) As Long - but that doesn't really matter...

Back in the C++ I've got this class that I've added cwPointerLayout to - declaring it to be a "pointer to" an "__int64" memory spot (I think I've done that!). I've also initialized the pointer to nullptr - that made it look good while stepping through the code in the debugger...

class cwObject {
	public:
		WCHAR cwR;
.
.
.
		__int64 * cwPointerLayout;
		int dbgS;
		int dbgE;
		bool dbgStarted;
		cwObject () {cwRun = 0...
			cwPointerLayout = nullptr;
			dbgOn = false, dbgStarted = false;
			dbgS = -1, dbgE = -1;
			cwR = L'', cwRXOff = L'';
		};
	};

Back in the function I do this

cwlayout[loopCW] = 0;						// Clear the layout
cwX.cwPointerLayout = & cwlayout[loopCW];	// Get a pointer to that spot

And that seems to load the address of the [loopCW] spot of the array into the cwPointerLayout variable.

And in the immediate window I did this

*cwX.cwPointerLayout = 123

And that seemed to change the value of cwlayout[loopCW].

Is that the way this is supposed to be setup? Am I using the referencing and dereferencing properly?

Thanks!

[Milk]

That looks fine to me.

Another way to write this...

cwlayout[loopCW] = 0;						// Clear the layout
cwX.cwPointerLayout = & cwlayout[loopCW];	// Get a pointer to that spot

is this...

cwx.cwPointerLayout = cwlayout + loopCW; //get a pointer to layout at index loopCW
*cwx.cwPointerLayout = 0 //clear the layout

just another way to do the same thing

[szlamany]

Thanks - I've been using it all day and it's working really well so far.

I would have to have more confidence to do this

cwx.cwPointerLayout = cwlayout + loopCW;

I can see why it works - but would not want to rely on thinking in that syntax.

I'm having a huge pain dealing with the apparent lack of two-dimensional arrays in C++ - I make these arrays in VB and use them in the C++ code.

I've spent hours chasing typo's in offset variables which clobber memory - how can I know it clobbers memory when it actually happens as opposed to many functions later when you get the "you've been a bad boy with your marshaling" error...

When I coded on mainframe/mini's back 30 years ago you were told you touched a bad spot in memory when you did it.

[edit] btw - code like this is allowed - right?

*cwX.cwPointerLayout = *cwX.cwPointerLayout << 1;

*cwX.cwPointerLayout |= (__int64)(1 << (cwX.cwWordCount - cwX.cwLeftWord));

*cwX.cwPointerLayout |= 1;

[/edit]

[Milk]

right