将文件读取到C中的2D数组

Question

I'm learning C and I decided to make a text game as my learning project . So I'm trying this primitive "parser" that reads a text file into a 2D array, but there's a problem: this map doesn't use 1 character-wide cells, it uses 2 character-wide cells. For instance, the player is represented with a ** , a door is represented like ## and so on.

That means, I need to read 2 characters of the text file and then assign it to the respective cell in the map.

Well, I made a test file that contains

aabbccddee
ffgghhiijj
kkllmmnnoo
ppqqrrsstt
uuvvwwxxyy

And I tried to read it with

#include <stdio.h>

#define ROWS 5 
#define COLS 5

int main() {
    FILE *mapfile = fopen("durr", "r");
    char charbuffer[3], row, col, *map[ROWS][COLS];

    /* Initializing array */
    for (row = 0; row < ROWS; row++) {
        for (col = 0; col < COLS; col++) {
            map[row][col] = "  ";
        }
    }

    /* Reading file into array */
    for (row = 0; row < ROWS; row++) {
        for (col = 0; col < COLS; col++) {
            map[row][col] = fgets(charbuffer, 3, mapfile);
        }
    }

    /* Printing array */
    for (row = 0; row < ROWS; row++) {
        for (col = 0; col < COLS; col++) {
            printf("%s", map[row][col]);
        }
        printf("\n");
    }

    fclose(mapfile);    
    return 0;
}

But when I execute it, I get this

uuuuuuuuuu
uuuuuuuuuu
uuuuuuuuuu
uuuuuuuuuu
uuuuuuuuuu

I think it has something to do with the fact that fgets return a pointer, but I'm not sure. I tried doing it with fgetc but it looks messy and I dropped it after reading about gets.

Answer 1

You should have strdup'ed the contents read from the file. Replace the file reading block with this:

/* Reading file into array */
for (row = 0; row < ROWS; row++) {
    for (col = 0; col < COLS; col++) {
        if (fgets(charbuffer, 3, mapfile))
            map[row][col] = strdup(charbuffer);
    }
}

and don't forget to put this at the beginning of your code too:

#include <string.h>

Answer 2

The main problem is that

char *map[ROWS][COLS];

only allocates space for ROWS x COLS char pointers , it does not allocate space for the strings themselves. So you're continually overwriting charbuffer as you've done it with every iteration, which explains why you end up with the same characters repeated over and over when you read out. You need to dynamically allocate the memory you need, along the lines of

for (row = 0; row < ROWS; row++) {
    for (col = 0; col < COLS; col++) {
        charbuffer = (char*)malloc(sizeof(char) * 3);  //****
        map[row][col] = fgets(charbuffer, 3, mapfile);
    }
}