HELP!! Urgent !!

Hi, can anyone help me ? i dunno how to solve this. Pls help.
Please follow the step to reach the Question.
Thanks a lot!!!

Code:

Step (1): Type structure definition typedef struct menu_item_struct { ros_data_hdr_t data_hdr; /* place holder for ros header */ struct menu_item_struct *next_item; /* next menu item in the list */ UINT8 position; /* menu item position */ struct { uniChar_t uniString[1]; /* place holder for string of Unicode characters */ UINT8 asciiString[1]; /* place holder for string of ASCII characters */ } text; } menu_item_t; typedef struct { UINT8 row; /* start row for menu */ UINT8 max_item; /* largest menu item position */ menu_item_t *first_menu_item; /* pointer to the first menu item in the list */ } menu_item_list_t; Step (2): Global variables declaration menu_item_t * * m_menuitem; UINT8 index=0; Step (3): void setMenuItems( UINT8 index, menu_item_t * menu_item ) { m_menuitem[index] = menu_item; } //First, assume that the above "setMenuItems" was called for 5 times. Therefore, m_menuitem[] should have 5 elements now, and index has been incremented to 5. Step (4): //After that, assume that "process_menuItemfunc()" is called. At this point, m_menuitem[]contains 5 items. void process_menuItemfunc() { //In this function, I have to call "putMenu(menuItem_t *menuItemPtr, uint8_t num_of_items)" as defined below. //Notice that the 1st parameter of the "putMenu()" is a pointer to an array of menu items to be displayed. //The menu item is of class "menuItem_t" as defined below. //So, before I could call "putMenu", I have to populate the 1st parameters. Because the "m_menuitem" and "menuItem_t" are of different types. //Therefore, I cannot pass in "m_menuitem" directly to "putMenu()" as its 1st parameter. //QUESTION : How to populate/construct the 1st parameter, which is the pointer to an array of menu items of class menuItem_t? } //A class called menuItem_t is defined as below class menuItem_t { public: UINT8 position; UINT16 state; UINT16 *uniString; }; //*menuItemPtr - This is a pointer to an array of menu items to be displayed. void putMenu (menuItem_t *menuItemPtr, UINT8 num_of_items) { //some processing here }

From the announcements:

Quote:

3. Do not put URGENT!, or NEED HELP NOW, etc. in your title; it will not make people look at it any faster. Doing this makes many old time helpers on this board not look at the post at all.

Well he did have two exclamation marks instead of just one...

Quote:

Please follow the step to reach the Question.

Doesn't one usually follow the steps of a question to reach an answer, not the other way around? ;)

Assuming that UINT8 is an integer type, probably something like this,

Code:

typedef unsigned char UINT8;

Then this function cannot modify index:

Code:

void setMenuItems( UINT8 index, menu_item_t * menu_item ) { m_menuitem[index] = menu_item; } //First, assume that the above "setMenuItems" was called for 5 times. Therefore, m_menuitem[] should have 5 elements now, and index has been incremented to 5.

Which means that the calling function must modify index, which makes that function pretty much useless. Besides, index is global, isn't it?

That function wouldn't even work unless the calling function also allocated some memory.

Code:

//A class called menuItem_t is defined as below class menuItem_t { public: UINT8 position; UINT16 state; UINT16 *uniString; };

That might as well be a struct.

Yup. There were some mistakes n errors in the code.
Actually I did not include the full code here that's why the code not complete and got some mistakes. Sorry about that.

But put aside the mistakes first.

For this "menuItem_t" class, it should be a structure instead of class.
So, it would look like this:-

Code:

typedef struct { UINT8 position; UINT16 state; UINT16 *uniString; } menuItem_t;

For "setMenuItems(...)", it should not taken "index" as a parameter.
So, it should be like this:-

Code:

void setMenuItems( menu_item_t * menu_item ) { m_menuitem[index] = menu_item; }

Ok, if there is still mistakes or errors , then just put them aside first.

What I actually want to know is, the above "setMenuItems" was called for 5 times. Therefore, m_menuitem[] should have 5 elements now, and index has been incremented to 5. Am I right?
So, what actually contain inside the "m_menuitem[]" now are the 5 pointers to "menu_item_t". Am I right?

I have "m_menuitem" now. You can see the 1st parameter from this function "putMenu (menuItem_t *menuItemPtr, UINT8 num_of_items)", it actually request a pointer to an array of type "menuItem_t, am I right?

So, I need to construct or get this pointer to an array of type "menuItem_t" from "m_menuitem". My question is how to do so? I don't know how to construct it so that I could pass it to "putMenu(..)" for further processing.
Please help.

Quote:

What I actually want to know is, the above "setMenuItems" was called for 5 times. Therefore, m_menuitem[] should have 5 elements now, and index has been incremented to 5. Am I right?
So, what actually contain inside the "m_menuitem[]" now are the 5 pointers to "menu_item_t". Am I right?

Yes, assuming the calling function handled a few things properly, like making sure that enough memory was allocated, and index was incremented.

Quote:

I have "m_menuitem" now. You can see the 1st parameter from this function "putMenu (menuItem_t *menuItemPtr, UINT8 num_of_items)", it actually request a pointer to an array of type "menuItem_t, am I right?

So, I need to construct or get this pointer to an array of type "menuItem_t" from "m_menuitem". My question is how to do so? I don't know how to construct it so that I could pass it to "putMenu(..)" for further processing.

So basically your problem simplifies down to converting this

Code:

typedef struct menu_item_struct { ros_data_hdr_t data_hdr; /* place holder for ros header */ struct menu_item_struct *next_item; /* next menu item in the list */ UINT8 position; /* menu item position */ struct { uniChar_t uniString[1]; /* place holder for string of Unicode characters */ UINT8 asciiString[1]; /* place holder for string of ASCII characters */ } text; } menu_item_t; menu_item_t * * m_menuitem;

to this:

Code:

class menuItem_t { public: UINT8 position; UINT16 state; UINT16 *uniString; }; //*menuItemPtr - This is a pointer to an array of menu items to be displayed. void putMenu (menuItem_t *menuItemPtr, UINT8 num_of_items)

Is that right?

Well, you'll probably need a conversion function of some kind. Perhaps the best way to implement this would be to create a menuItem_t(menu_item_t&) constructor. Something like this.

Code:

class menuItem_t { public: UINT8 position; UINT16 state; UINT16 *uniString; menuItem_t(menu_item_t &other); }; menuItem_t::menuItem_t(menu_item_t &other) { position = other.position; }

I don't know how you'd create the state and uniString members of menuItem_t out of the members of menu_item_t, but however you do it, do it in that function, in the same place I set position.

(To other C++ programmers: I didn't feel like explaining initializers.)

Using constructors is very easy. You can basically do this:

Code:

menu_item_t from; menuItem_t to = from; // now you have to

BTW, try to make your variable and type names different. If two variables are different but you pronounce them the same way (or nearly so), then consider renaming them.

Basically you got what I meant.
But, menuItem_t is not a class anymore.
It is a structure like this:-

Code:

typedef struct { UINT8 position; UINT16 state; UINT16 *uniString; } menuItem_t;

Please help. Thanks a lot.

In C++, you can have constructors in structs as well. But perhaps the best thing to do would be to have a conversion function.

Code:

menuItem_t convert(menu_item_t &other) { menuItem_t m; m.position = other.position; return m; }

Something like that.

Can you show me the complete code?
I still couldn't catch the solution you provided.

Lazy bastard. Ask questions, but do not ask us to do the whole damn job for you.

While your waiting for him to write the code, *cough*. You could read the rules perhaps?

oops!! I m sory.

Anyway, someone who declared the below stuff has just informed me, there was a mistake in the previous declarations.
Check the below declaration:-

Code:

menu_item_t * * m_menuitem; should be declared as :- menu_item_t *m_menuitem[5]; //Array of pointers

Well, it seems much easier to me to handle Array of pointers in this case.

Really thanks a lot to everyone.

Mmm, that makes more sense. With the [5] declaration your program doesn't have to mess around with dynamic memory allocation.

Tell whoever wrote that code that they should think up some better names. :)

Anyway, good luck.

Yeah. The naming is kinda confusing. We will correct them.

1 quick question:

Code:

menuItem_t **ptr_1; and menuItem_t *ptr_1[]; Are they the same?

And where do you compile the second line?

Compile with Visual C++.

At compile time, we may not know how many elements are need to be allocated.
So, we would not know what array size to be defined. If that is the case, how are we going to dynamically allocate the array of pointers?

Why do you need an array? use vectors

Code:

int* someData; //at one point you know how many elements you need someData = new int[ELEMENTS]; //fill the array delete [] someData;

There are few if any reasons to use the dynamic array in indigo0086's example over a vector. This does basically the same thing as that. You can also use functions like push_back or resize to make things easier on yourself.

Code:

vector<int> someData(ELEMENTS);

Quote:

1 quick question:

Code:

menuItem_t **ptr_1;

and

Code:

menuItem_t *ptr_1[];

Are they the same?

As you might have guessed, but no one's actually said, the second one shouldn't compile. Unless it's a parameter to a function, in which case both of those code samples are the same. After all, this

Code:

int main(int argc, char *argv[])

is the same as this

Code:

int main(int argc, char **argv);

Quote:

Originally Posted by indigo0086

Code:

int* someData; //at one point you know how many elements you need someData = new int[ELEMENTS]; //fill the array delete [] someData;

What if the data type is a structure?for eg: menuItem_t
Is the below definition correct?

Code:

menuItem_t **someData; someData = new (*menuItem_t)[MAXSIZE]; delete [] someData;

There are still few if any good reasons to go this route rather than use a vector, but if you are more comfortable with it (or the other person is making the decision) then the syntax would be:

Code:

menuItem_t **someData; someData = new menuItem_t*[MAXSIZE]; // later, when you are done: delete [] someData;

However, using MAXSIZE for the size of the array is something you usually do with static arrays, not dynamic ones. You would use the same code you had above with the 5, but instead of 5 you would use a constant like MAXSIZE.

If MAXSIZE is not constant, then the code I just posted would work. Remember also that the pointers aren't initialized, so you'll have to do that yourself.