Problem with fscanf loop!

Hi all,

Apologies for posting a thread so soon after finding an answer to my last one. This little snippet of my code is driving me crazy.

Soooooo I dont understand the output for my code. Right now my text file is like this.

20010929 0 1
20010929 15 2
20010929 30 3
20010929 45 4
20010929 0 1
20010929 15 2
20010929 30 3
20010929 45 4
20010929 0 1
20010929 15 2
20010929 30 3
20010929 45 4

So with my code I'm hoping to put it into an array. This is just a pratice .txt as the one i will be using is 330770 rows long. When i display the 2nd row, 3rd column. The program displays a 45 instead of a 2. Any help or correction in understanding would be much appreciated. I'll add that it was working fine until I started to use malloc to define my array.

Code:

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  FILE *fr;                                                                                // declare the file pointer
 
  int x, y;                                                                                // Dimensions of .txt data, 3 columsn and 330770 inputs;
 
  //DYNAMIC MEMORY ALLOCATION FOR data ARRAY and finalData ARRAY.
 
  int** data;
  data = (int **) malloc(330770 * sizeof(int*));
  for (int h = 0; h < 330770; h++) 
            data[h] = (int*) malloc(3*sizeof(double));
                                                                                            //determines the placement of the finalData
  fr = fopen ("c:\\blahblah.txt", "r");                                                    /* reads the file */                               
  for(x=0; x<330770; x++){                                                                // loops through the rows
                    y = 0;                                                                //starts at first column during each row loop       
                    while(fscanf(fr,"%d", &data[x][y++]) >0);                            // loops through the columns until each row ends.
  }
 
  cout<<data[1][0];

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You changed from double to int, presumably to simplify things during testing, but now this is wrong:

Code:

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data[h] = (int*) malloc(3*sizeof(double));

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You could have avoided this problem by writing:

Code:

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data = malloc(330770 * sizeof(data[0]));
for (int h = 0; h < 330770; h++) {
    data[h] = malloc(3 * sizeof(data[0][0]));
}

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By the way, since you have a rectangular 2D array for which the inner arrays are of fixed size, this might be better:

Code:

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int (*data)[3] = malloc(330770 * sizeof(data[0]));
/* no need to allocate for each inner array */

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EDIT:
Also, I strongly suggest that you use const or #define to give a name to 330770. It is just too magical.

EDIT #2:
Oh, and this is wrong:

Code:

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while(fscanf(fr,"%d", &data[x][y++]) >0);

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You should be checking that the number of times this loop runs is exactly 3.

You are seriously the most awesome person on the internet <3. I did all the fixes and it works great!

However, if i use...

Code:

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int (*data)[3] = malloc(330770 * sizeof(data[0]));

---

it gives me an error saying invalid conversion from void to int[*][3]

Thank you so much! I understand fscanf a lot more now.

Quote:

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Originally Posted by turkadurka

You are seriously the most awesome person on the internet <3. I did all the fixes and it works great!

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You're welcome!

Quote:

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Originally Posted by turkadurka

it gives me an error saying invalid conversion from void to int[*][3]

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You're probably compiling as C++. Configure your compiler to compile as C and/or use a ".c" extension for your source file(s).

haha yep! That was the problem!

Thank you again, laserlight!