Thread: Passing Arrays of Unknown Size

Hey guys...

I'm looping through a file and creating arrays of unknown size depending on the data in the file. I'm having trouble passing the array to another function for more processing. I did a google but each method I tried just seemed to make the compiler go crazy with error messages.

Is there a quick an easy way I can do this

If I just try to pass it like was an Int I get a "error: ‘ex_data’ undeclared (first use in this function)"

You'll need to show some code that illustrates your problems if you want any help.

Jim

The code is kind of long but I can try to give a look... Im reading opcodes and operands from a file.

So at the end of this if tree I have created an array "ex_data[i]" with a size dependant on the opcoade read from the file.

Code:

  if (opcode == 0) {
          f_dx(&numbers, operand);
        }
        else if (opcode == 1) {
          f_dy(d, &numbers, operand);
        }
        else if (opcode == 2) {
          f_dt(d, &numbers, operand);
        }
        else if(opcode == 3){
          int hold;
          //dectect extended dx dy dt
          if (  ((operand & 0x30) >> 4) != 0 ) {
            hold = ((operand & 0x30) >> 4);
            //convert 3 to 4
            if (hold == 3) hold = 4;


            //printf("%d\n", hold);
            unsigned char ex_data[hold];


            //get bytes
            for (int i = 0; i < hold; i++) {
              c = fgetc(in);
              ex_data[i] = c;
              printf("%02x\n", ex_data[i]);
            }
          }




          ex_handler(operand, &numbers);
        }

I need to pass this array to the function ex_handeler at the bottom so it can be processed. I havent written the code yet... I have just done a little house keeping.

here is the ex_handeler function:

Code:

void ex_handler(int op, Numbers *numbers){


  //check for pen
  if (  ((op & 0x30) >> 4) == 0 && ((op & 0x0c) >> 2) == 0){
    //printf("Pen Working\n");
    f_pen(numbers);
  }

  //printf("ex workng\n");


}

How are operand and numbers defined, and what exactly is a Numbers?

Look at this snippet:

Code:

        if (hold == 3) hold = 4;
 
 
          //printf("%d\n", hold);
          unsigned char ex_data[hold];

Do you realize that that last line is creating a VLA?


Jim

I just want to have an array "ex_data [ ]" of unknown size that I can pass around to my functions.

Since you don't know what a VLA is you should be using dynamic memory allocation with malloc() and free().

I want to pass it to ex_handler() at the bottom.

But ex_handler() seems to expect an int and a pointer to a Number, ex_data[] is an array of char not a Number.

Jim

Oh yeah I didnt know how to define the array in the function so I just left it out. Could you give me a short example please? Just showing how I would allocate the space and then pass the array.