Writing/Reading 2D array to Binary File C++

Question

I am trying to write data from a 2D array into a binary file. I am only writing the data that has a value greater than 0. Therefore, if the data is is 0, it will not be written to the file. The data is as follows:

Level       0   1   2   3   4   5

Row 0       4   3   1   0   2   4
Row 1       0   2   4   5   0   0 
Row 2       3   2   1   5   2   0
Row 3       1   3   0   1   2   0

void { 

    // This is what i have for writing to file.

    ofstream outBinFile; 
    ifstream inBinFile; 
    int row; 
    int column; 

    outBinFile.open("BINFILE.BIN", ios::out | ios::binary);

    for (row = 0; row < MAX_ROW; row++){

        for (column = 0; column < MAX_LEVEL; column++){

          if (Array[row][column] != 0){

             outBinFile.write (reinterpret_cast<char*> (&Array[row][column]), sizeof(int)
          }
        }
    } 

    outBinFile.close(); 

    // Reading to file. 

    inBinFile.open("BINFILE.BIN", ios::in | ios::binary);

    for (row = 0; row < MAX_ROW; row++){

        for (column = 0; column < MAX_LEVEL; column++){

          if (Array[row][column] != 0){

             inBinFile.read (reinterpret_cast<char*> (&Array[row][column]), sizeof(int)
          }
        }
    } 

    inBinFile.close();  
}

All the data being read is being inserted into the first row, how can i get the data to load as i exited the program?

user1678413 · Accepted Answer · 2013-04-14 18:39:10Z

2

You are reading only when data is not equal zero, means that it gets locked with first zero. Once it reaches zero it stops reading.

Before "if command" read file to some other varaible then in if (variable != 0) Array[row][column] = variable.

If your Array is initialized with data, maybe take a look into setting position of your reading. So to set ok I have zero, I should read from another position next.

edited Apr 14, 2013 at 18:39

answered Apr 14, 2013 at 18:33

user1678413

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Comments

frood · Accepted Answer · 2017-04-16 20:39:22Z

Binary files take a simple memory dump. I'm on a mac so I had to find a way to calculate the size of the array since sizeof(array name) doesn't return the memory size of the array for some reason (macintosh, netbeans IDE, xCode compiler). The workaround I had to use was: to write the file:

fstream fil;
fil.open("filename.xxx", ios::out | ios::binary);
fil.write(reinterpret_cast<char *>(&name), (rows*COLS)*sizeof(int));
fil.close();
//note: since using a 2D array &name can be replaced with just the array name
//this will write the entire array to the file at once

Reading was the same. Since the examples from the Gaddis book I was using did not work correctly on Macintosh I had to find a different way to accomplish this. Had to use the following code snippet

fstream fil;
fil.open("filename.xxx", ios::in | ios::binary);
fil.read(reinterpret_cast<char *>(&name), (rows*COLS)*sizeof(int));
fil.close();
//note: since using a 2D array &name can be replaced with just the array name
//this will write the entire array to the file at once

Instead of just getting the size of the entire array you need to calculate the size of the entire array by multiplying the rows*columns for a 2d array then multiplying it by the size of the data type (since I used integer array it was int in this case).

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