sizeof and pointers

This is a discussion on sizeof and pointers within the C++ Programming forums, part of the General Programming Boards category; I have a class Item Code: class Item { public: DWORD originalValue; DWORD changedValue; DWORD offset; Options *optionSwap; int optionCount; ...

  1. #1
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    Nov 2003
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    3

    sizeof and pointers

    I have a class Item
    Code:
    class Item
    {
    public:
    	DWORD originalValue;
    	DWORD changedValue;
    	DWORD offset;
    	Options *optionSwap; 
    	int optionCount;
    	WCHAR *originalName;
    	WCHAR *changedName;
    	ItemType itemType;
    	Item();
    	Item(const Item&);
    	virtual ~Item();
    };
    I know it's not good to make them all public

    then we have the class Page which uses the items
    Code:
    class Page  
    {
    private:
    	//BYTESWAP
    	bool AddItem(WCHAR* itemName, DWORD itemValue, DWORD itemOffset);
    	bool ChangeItem(int itemNumber, WCHAR* itemNewName, DWORD itemNewValue); //by Number
    	//OPTIONSWAP
    	bool AddItem(WCHAR* itemName, DWORD itemOffset);
    	bool AddOption(int itemNumber, WCHAR* optionName, DWORD optionValue );
    	bool ChangeItem(int itemNumber, int optionNumber);
    public:
    	Item *items;
    	int itemCount;
    	bool ParseItem(WCHAR* itemLine); //AUTO CHECKS BETWEEN BYTE/OPTION
    	WCHAR* ItemName(int itemNumber);
    	DWORD ItemValue(int itemNumber);
    	WCHAR* ItemCurrentName(int itemNumber);
    	DWORD ItemCurrentValue(int itemNumber);
    	Page()
    	{
    		itemCount = 0;
    		items = (Item*) malloc(sizeof(Item));
    	}
    	virtual ~Page();
    };
    and finally the AddItem function
    Code:
    bool Page::AddItem(WCHAR *itemName, DWORD itemValue, DWORD itemOffset) //BYTESWAP
    {
    	itemCount++;
    	if ( realloc(items, itemCount * sizeof(Item)) == NULL )
    	{
    		itemCount--; //MEMORY FULL
    		return false;
    	}
    	swprintf( items[itemCount-1].originalName, itemName );
    	swprintf( items[itemCount-1].changedName, itemName );
    	items[itemCount-1].originalValue = itemValue;
    	items[itemCount-1].changedValue = itemValue;
    	items[itemCount-1].offset = itemOffset;
    	items[itemCount-1].itemType = BYTESWAP;
    	return true;
    }
    my question was, will there be any problems when reallocating items and in the program I have an array of the Pages type which gets realloced too

    if page1 has 3 items
    page2 has 5 items
    etc
    wont there be problems with the sizeof thing?
    or should I use instead of

    Code:
    itemCount * sizeof(Item)
    use something like

    Code:
    sizeof(items) + sizeof(Item)
    and then for the pages the same

    Code:
    realloc(pages, sizeof(pages) + sizeof(Page))

    if you need any extra information just lemme know

  2. #2
    Registered User Codeplug's Avatar
    Join Date
    Mar 2003
    Posts
    4,676
    - Just use "<count> * <sizeof object>" to allocate space for count objects (like you have it).
    - This is wrong: swprintf(items[itemCount-1].originalName, itemName ); originalName is an uninitialized pointer (that goes for all your pointers in Item).
    - Make your life alot easier and use std::wstring instead of WCHAR*
    - Make your life alot easier and use STL containers instead of fixed arrays that have to be realloc'ed over and over.

    gg

  3. #3
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    Nov 2003
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    3
    1) thx
    2) the WCHARs are made in the Constructor part
    3) I use them because the print function uses WCHAR* otherwise I have to conver them before I print them
    4) could you give some more information about the last one?
    like a tutorial or something :)

    btw this is an xbox application and can only use DirectX
    this is the DrawText thingy
    Code:
    HRESULT CXBFont::DrawText( FLOAT fOriginX, FLOAT fOriginY, DWORD dwColor,
                               const WCHAR* strText, DWORD dwFlags )

  4. #4
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    Nov 2003
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    3
    about answer 4, searched for it and found lots of stuff about vector, it's looking so cool

    thx alot will try the code with vectors and lett you know

    thx again

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