Converting a CSV to 2D Array in C

Question

This is a really fascinating error to me, because literally an hour ago this code was working just fine, but now it's not.

Essentially what is happening is that the first character of first 'block' of the following row is being appended as the last character of the final 'block'

Whereby 'block' I mean the string that is held within that row/col.

For example, let's say that the array is supposed to be something like

1,2,3,Hello
4,5,6,Wonder

It is being read in as

1,2,3,Hello4,
6,Wonder, ,

Here's the logic that I've been using. I really don't know what changed, so any advice would be excellent.

tableFile = fopen(argv[4], "r");


//pulling the table data from the file
char tableArray[30][50][256];
char c;
int i=0, j=0, k=0;
while(c != EOF){

    c = fgetc(tableFile);

    switch(c)
    {
        case ',':
            tableArray[i][j++][k]='\0';
            k=0;
            break;
        case '\n':
            tableArray[i++][j][k]='\0';
            j=0;
            k=0;
            break;
        case '\r':
            break;
        case EOF:
            break;
        default:
            tableArray[i][j][k++] = c;
            break;
    }

} //end file transfer

//Just to display, ignore magic numbers as (mostly) irrelevant
int a, b;

for (a = 0; a < 20; a++)
{
    for (b = 0; b < 47; b++)
    {
        printf ("%s", tableArray[a][b]);
        if (b<46)
            printf (", ");

    }
    printf ("\n");
}

fclose(tableFile);

What changed since it was working? Can't you go back to the working version? Don't you have it under source code control? If not, why not? How else do you keep tabs on working code before you make potentially breaking changes? — Jonathan Leffler
– Jonathan Leffler, Commented Oct 2, 2012 at 16:30
Works fine on my system, apart from outputting a 20x47 matrix and the obvious buffer overflow security vulnerabilites, as well as relying on a random initial value of c in while (c != EOF). — phihag
– phihag, Commented Oct 2, 2012 at 16:37
@phihag Bah.... I was afraid I'd hear that. Is it possible somehow that my csv files are getting corrupted or are malformed somehow?! — Meshach
– Meshach, Commented Oct 2, 2012 at 16:39

Sergey L. · Accepted Answer · 2012-10-02 18:39:31Z

1

You did not initialise your array. It is not guaranteed to come zero filled. add

memset(tableArray, 0, sizeof(tableArray))
case EOF: has to add a NULL terminator to the most recent string.

answered Oct 2, 2012 at 18:39

Sergey L.

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2 Comments

phihag Over a year ago

1. is not a problem (if the correct bounds were stored) because he's writing correctly terminating the strings he writes into it.

Jonathan Leffler Over a year ago

Also, c should not be a char; it should be an int, of course.

Meshach · Accepted Answer · 2012-10-03 00:08:07Z

This is really due to the comments immediately below my original post. But, as disgusting and poor coding form as it is... this is what solved it consistently, not that I'm proud of it... and still open to ideas:

tableFile = fopen(argv[4], "r");

//pulling the table data from the file, lazy magic numbers here... 
char tableArray[30][50][256];
char c;
int i=0, j=0, k=0;

memset(tableArray, 0, sizeof(tableArray));
while(c != EOF){

    c = fgetc(tableFile);

    switch(c)
    {
        case ',':
            tableArray[i][j++][k]='\0';
            k=0;
            break;
        case '\n':
            tableArray[i++][j][k]='\0';
            j=0;
            k=0;
            break;
        case '\r':
            tableArray[i++][j][k]='\0';
            j=0;
            k=0;
            break;
        case EOF:
            tableArray[i][j][k] = '\0';
            break;
        default:
            tableArray[i][j][k++] = c;
            break;
    }

} //end file transfer

/* //Only relevant for displaying the tableArray
int a, b;

for (a = 0; a < 20; a++)
{
    for (b = 0; b < 47; b++)
    {
        printf ("%s", tableArray[a][b]);
        if (b<46)
            printf (", ");

    }
    printf ("\n");
}
 */

fclose(tableFile);

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