Thread: John Conway's Game Of Life

Code:

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>

#define YMAX 25
#define XMAX 80
#define cell fgetc(pFile)

typedef struct cell_t_ {
	struct cell_t_ *neighbours[8];
	int on;
} cell_t;

typedef struct world_t_ {
	cell_t **array;
	int width;
	int height;
	void *mem;
} world_t;
////////////////////
int CopyFile()
{
    char inName[100];
    FILE *pIn, *pOut;
    int c;

    //get file name from user
    printf("Please enter a text file name: ");
    scanf("%s", inName);
        pIn = fopen(inName, "r");
        //test if file exists
        if(pIn == NULL)
        {
            printf("ERROR: cannot open file");
           return 1;
            abort();
        }
        //create new file
        pOut = fopen("board.txt", "w");

        //copy file contents
        while((c = getc(pIn)) != EOF)
                putc(c, pOut);

        //close file
        fclose(pIn);
        fclose(pOut);
        return (0);
    }

void printworld(world_t *world, FILE *pOutput)
{
	int x, y;

	for(y = 0; y < world->height; y++) {
		for(x = 0; x < world->width; x++) {
			fprintf(pOutput, "%c", (world->array[y][x]).on ? 254 : ' ');
		}
		fputc((int)'\n', pOutput);
	}
	fflush(pOutput);
}

void randomizeworld(world_t *world)
{
	int x, y, test;
    FILE *pFile;
    pFile = fopen ("board.txt", "r");

	while (!feof(pFile))
    {
      if((test = (cell)) != 10)
      {
		  (world->array[y][x]).on = 32;
          ++x;
      }
      if(x == XMAX)                       //Move X coordinate back to 0, increment Y (increasing Y ==> moving down on board)
      {
          x = 0;
          ++y;
      }
    }
}

void updateworld(world_t *world)
{
	int x, y, i, neighbours;

	for(y = 0; y < world->height; y++) {
		for(x = 0; x < world->width; x++, neighbours = 0) {
			for(i = 0; i < 8; i++)
				if((world->array[y][x].neighbours[i]) && ((world->array[y][x]).neighbours[i]->on & 1))
					neighbours++;

			if((neighbours < 2) || (neighbours > 3))
				(world->array[y][x]).on |= 2;
			else if(neighbours == 3)
				(world->array[y][x]).on |= 4;
		}
	}

	for(y = 0; y < world->height; y++) {
		for(x = 0; x < world->width; x++) {
			if(world->array[y][x].on & 4)
				world->array[y][x].on = 1;
			else if(world->array[y][x].on & 2)
				world->array[y][x].on = 0;
		}
	}
}

void destroyworld(world_t *world)
{
	free(world->mem);
}

int createworld(world_t *world, int width, int height)
{
	int i, j;
	unsigned long base   = sizeof(cell_t *) * height;
	unsigned long rowlen = sizeof(cell_t)   * width;

	if(!(world->mem = calloc(base + (rowlen * height), 1)))
		return 0;

	world->array  = world->mem;
	world->width  = width;
	world->height = height;

	for(i = 0; i < height; i++) {
		
		world->array[i] = &world->mem + base + (i * rowlen);
	}

	for(i = 0; i < height; i++) {
		for(j = 0; j < width; j++) {
			if(j != 0) {
				(world->array[i][j]).neighbours[3] = &(world->array[i][j - 1]);
			}

			if(i != 0) {
				(world->array[i][j]).neighbours[1] = &(world->array[i - 1][j]);
			}

			if(j != (width - 1)) {
				(world->array[i][j]).neighbours[4] = &(world->array[i][j + 1]);
			}

			if(i != (height - 1)) {
				(world->array[i][j]).neighbours[6] = &(world->array[i + 1][j]);
			}

			if((i != 0) && (j != 0)) {
				(world->array[i][j]).neighbours[0] = &(world->array[i - 1][j - 1]);
			}

			if((i != (height - 1)) && (j != (width - 1))) {
				(world->array[i][j]).neighbours[7] = &(world->array[i + 1][j + 1]);
			}

			if((i != (height - 1)) && (j != 0)) {
				(world->array[i][j]).neighbours[5] = &(world->array[i + 1][j - 1]);
			}

			if((i != 0) && (j != (width - 1))) {
				(world->array[i][j]).neighbours[2] = &(world->array[i - 1][j + 1]);
			}
		}
	}

	return 1;
}

int main(int argc, char *argv[]) {
	world_t gameoflife;

	if(createworld(&gameoflife, 79, 24)) {
		randomizeworld(&gameoflife);
		do {
			printworld(&gameoflife, stdout);
			getchar();
			fflush(stdin);
			updateworld(&gameoflife);
		}while(1);
		destroyworld(&gameoflife);
	}

	return 0;
}

So here's the deal, I am having an issue with compiling this getting message while running it: "Unhandled exception at 0x00d71e1d in HW8.3.exe: 0xC0000005: Access violation writing location 0x00318ef8." I debugged it and can't find out why I am getting.

Thanks in advance for the help.

> (world->array[i][j]).neighbours[1] = &(world->array[i - 1][j]);
Your loops start at zero.
So here you're trying to access element -1
Does that sound like an out of bound access to you?

> I debugged it and can't find out why I am getting this issue resolved.
If you actually ran this in the debugger, it would have been pointing at a line of code.
Telling us "The debugger is at this line of code, but I don't understand" would have been evidence that you has used a debugger.

Sorry, I didn't mean to say getting the issue resolved; it has been a long day. It pointed to line 138:

(world->array[i][j]).neighbours[3] = &(world->array[i][j - 1]);

As for the line you had pointed out, I believe the line before that is: if(i != 0)

OK, so you've fixed all the out of bound array subscripts in that function then?