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Nested Structures

Started by bower12345 May 14, 2003 at 12:13 AM 5 replies 450+ views

Original Post

May 14, 2003 at 12:13 AM

Hey Folks, Quick Problem...I''m having a problem nesting structures within other structures. Is this allowed? And if so, is there a certain way to access the data inside of the structures. I am doing something like this.

  
struct Square_Wave_One
{
   struct Sound_Reg_4000
   {
      BYTE Yadda1,
           Yadda2,
           Yadda3;
   };
};

Then to access the elements within those structures I am trying something like this:

  
Square_Wave_One.Sound_Reg_4000.Yadda1 = (Value & 0x0F);

I just can''t seem to figure out if I''m doing something wrong. If you folks need me to post full source, please let me know. Regards, Mike

digitec devil

May 14, 2003 at 12:35 AM

  
struct Sound_Reg_4000   {      BYTE Yadda1,           Yadda2,           Yadda3;   };

struct Square_Wave_One{ struct Sound_Reg_4000 sr4;  };

bower12345

Author

bower12345

May 14, 2003 at 12:42 AM

Sorry,

That solution didn''t work for the code.

Any other ideas?

Regards,
Mike

digitec devil

May 14, 2003 at 12:47 AM

    
//given these definitions

struct Sound_Reg_4000   {      
            BYTE Yadda1,
                 Yadda2,
                 Yadda3;   };
struct Square_Wave_One{ struct Sound_Reg_4000 sr4;  };

//declare a struct Square_Wave_One like this

struct Square_Wave_One sw1;

sw1.sr4.Yadda1 = whatever;
sw1.sr4.Yadda2 = whatever;
sw1.sr4.Yadda3 = whatever;

failing that, yes you'll need to post more code.

EDIT: typos

[edited by - digitec devil on May 14, 2003 1:48:00 AM]

Qw3r7yU10p!

May 14, 2003 at 2:34 AM

Nesting a class inside another doesnt make an instance of that class. It just puts it in the scope. You need to add a member which is an instance of the class if you want to store actual data.

  
#include <iostream>

class empty{
public:
    class full {
        int bigThing[1000];
    };
};

int main() {
    using std:: cout;
    using std::endl;

    cout << "sizeof(full) " << sizeof(empty::full) << endl;
    cout << "sizeof(empty) " << sizeof(empty) << endl;
    return 0;
}

On my machine this prints:
sizeof(full) 4000
sizeof(empty) 1

An object has to have size at least 1 to be able to exist at a memory location. But aside from that empty contains no data.

If you were to make empty have a member you''d get very different results:

  
class empty{
public:
    class full {
        int bigThing[1000];
    };
    full noLongerEmpty;
};

sizeof(full) 4000
sizeof(empty) 4000

Hope this helps

rotos

May 14, 2003 at 4:27 AM

    
struct Square_Wave_One
{
   struct
   {
      BYTE Yadda1,
           Yadda2,
           Yadda3;
   } Sound_Reg_4000;
};

Put the name at the end like above, and you can access it just like you wanted to in the first place.

Good luck with your NES APU emulator

bower12345

Author

bower12345

May 15, 2003 at 12:33 PM

Thanks much Rotos, it worked perfectly...do you any good references on DirectSound where I can learn how to play different tones and whatnot I receve from the channels? Thanks in Advance.

Regards,
Mike

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