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Array problem

Started by Jaxks Jun 29, 2000 at 6:02 AM 4 replies 400+ views

Original Post

Jun 29, 2000 at 6:02 AM

    
class someclass
{
public:
   int Give_me_integer()const{return integer;}
   void LoadFile(char *);
private:
   int integer;
};
void Someclass::LoadFile(char * file)
{
  //opens filee...

  unsigned char array[integer][integer];

Defination of Array makes some errors because integer doesn´t have no value. I´ve following situation in my Bmp loader which loads height and widht from file. How make such array or this unsigned char * data; data=new unsigned char[width][heihgt]; Edited by - Jaxks on 6/29/00 6:04:32 AM Edited by - Jaxks on 6/29/00 6:05:30 AM Edited by - Jaxks on 6/29/00 6:06:01 AM

Armitage

Jun 29, 2000 at 6:43 AM

You'll have to initialize it dynamically, yes.

        
unsigned char **data;
data = new unsigned char*[width];
for (int i = 0; i < width; i++)
{
   data<i> = new unsigned char[height];
}

I've probably mixed some things up, I usually check my manual for this, but I'm at work.
But why not use "new unsigned char[width * height]" and manage the offsets yourself?

Edited by - Armitage on June 29, 2000 7:45:24 AM

gavcc

Jun 29, 2000 at 6:46 AM

The reason you are getting errors is beacuase you can only define an array using constant values.

Simple using


int i = 100
char array


char array[(const int )i]

will not do. One way around this is to allocate memory to your array, then you can use your variable Integer:


char* array = new char[Integer][Integer]

You could always declate Integer as const int Integer, but you will not be able to change the value.

Regards
Michael

Edited by - gavcc on June 29, 2000 7:49:01 AM

Jeranon

Jun 29, 2000 at 7:08 AM

I''m making a stab in the dark here...

Vectors?

MikeD

Jun 29, 2000 at 12:03 PM

You could write your own dynamic unsigned char array class and do all the data allocation, manipulation and extraction in internal member functions.

Kinda like

class myarray
{
public:
myarray(int width, int height);
getelement(int x, int y);

private:
unsigned char* array;
int width, height;
}

myarray* myarray::myarray(int newwidth, int newheight)
{
malloc(sizeof(unsigned char) * newwidth * newheight);
width = newwidth;
height = newheight;
return this;
}

unsigned char myarray::getelement(int x, int y)
{
return (unsigned char) *(array + (x * width) + y);
}

Obviously you can override the new operator to make it more c++ like but that''s ''a'' way of doing it.

Mike

Jaxks

Author

Jaxks

Jun 30, 2000 at 1:48 AM

Can´t do constants because information is red from file.
And armitage if I make two dimensional dynamical array how to initialize via two fors? my book is so old so i haven´t heard anything about it.

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