Drawing a level

octotep

Hello everybody. For my game I'm trying to create a load_level function which loads a config file from disk to get all of the parameters for drawing the level. The problem is I have is in the level struct, where I have a int **, in order to hold the order of tiles to be drawn. The level struct looks like this:

#SelectExpand
  1#include <stdio.h>
  2#include <stdlib.h>
  3#include <string.h>
  4#include <allegro5/allegro.h>
  5
  6#include "player.h"
  7
  8typedef struct level
  9{
 10  int size_x;
 11  int size_y;
 12  float start_x;
 13  float start_y;
 14  int tilesize;
 15  int **tilemap;
 16  ALLEGRO_BITMAP *tile_file;
 17} level;
 18
 19extern level *load_level(int world_num, int level_num);
 20extern void destroy_level(level *my_level);
 21extern void setup_level(level *my_level, player *my_player);

The problem is in the load level function, where I try to assign the values from the config file to int **tilemap

#SelectExpand
  1level *load_level(int world_num, int level_num)
  2{
ALLEGRO_CONFIG *level_file;
level hard_level;
level *tmp_level;
tmp_level = &hard_level;
const char *tile_file_name;    // for the tiles.bmp level.tile_file 31
char level_file_name[27];    // worldxx-levelyy.cfg 27

// Get all of the data from the level cfg file
sprintf(level_file_name, "levels/world%02d-level%02d.cfg", world_num, level_num);
level_file = al_load_config_file(level_file_name);
tmp_level->size_x = atoi(al_get_config_value(level_file, NULL, "size_x"));
tmp_level->size_y = atoi(al_get_config_value(level_file, NULL, "size_y"));
tmp_level->start_x = (float) atof(al_get_config_value(level_file, NULL, "start_x"));
tmp_level->start_y = (float) atof(al_get_config_value(level_file, NULL, "start_y"));
tmp_level->tilesize = atoi(al_get_config_value(level_file, NULL, "tilesize"));

// Get the tile file loaded into the level struct
tile_file_name = al_get_config_value(level_file, NULL, "tile_file");
tmp_level->tile_file = al_load_bitmap(tile_file_name);
 22

// Create the tilemap array
tmp_level->tilemap = malloc(tmp_level->size_y * sizeof(int *));
if(tmp_level->tilemap == NULL)
{
  fprintf(stderr, "Out of memory for the pointer-pointer-int in the level struct!\n");
  return NULL;
}
int i;
for(i = 0; i < tmp_level->size_y; i++)
{
  tmp_level->tilemap[i] = malloc(tmp_level->size_x * sizeof(int));
  if(tmp_level->tilemap[i] == NULL)
  {
    fprintf(stderr, "Out of memory for the **intergers in the level struct!\n");
    return NULL;
  }
}

// Get the tilemap data from the cfg file
char *result = NULL;
const char *tilemap_data;
tilemap_data = al_get_config_value(level_file, NULL, "map_data");
result = strtok((char *)tilemap_data, ",");
int x = 0;
int y = 0;
 49
while (result != NULL)
{
  hard_level.tilemap[y][x] = atoi(result);
  while(x < tmp_level->size_x)
  {
    hard_level.tilemap[y][x] = atoi(result);
    result = strtok(NULL, ",");
    x++;
  }
  x = 0;
  result = strtok(NULL, ",");
  y++;
}
fprintf(stderr, "done the strtok loop\n");

// See if the pointer was filled correctly
      int b, c;
for(b = 0; b < tmp_level->size_y; b++)
{
  for(c = 0; c < tmp_level->size_x; c++)
    fprintf(stderr, "%i,", tmp_level->tilemap[b][c]);
}

al_destroy_config(level_file);
fprintf(stderr, "~~CREATE LEVEL - DONE~~\n");
return tmp_level;
 76}

Inside the function, getting the values from a_level->tilemap[y][x] returns the expected values. Outside the function, a_level->tilemap[y][x] returns garbage values and crashes the program.

The config file that I am using looks like this:

size_x = 20
size_y = 15
start_x = 32.0
start_y = 416.0
tilesize = 32
tile_file = tiles/tiles.bmp
map_data = 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3,1,2,2,2,2,2,2,3,3,3,2,2,2,2,2,2,2,2,3,1,0,3,3,3,3,3,3,1,1,1,3,3,3,3,3,3,3,3,1,0,0,1,1,1,1,1,1,0,0,0,1,1,1,1,1,1,1,1,0,0,0

How would I need to change my code in order to access the **tilemap pointer and get correct values?

Edgar Reynaldo

octotep said:

  level hard_level;
  level *tmp_level;  tmp_level = &hard_level;
//...return tmp_level;

You are returning the address of a temporary level object. As soon as load_level returns 'hard_level' is no longer a valid object. You have to create a new 'level' using malloc. It crashes because the area in memory where 'hard_level' was has most likely been overwritten or else it causes a segfault.

octotep

Ok, I think I see what the problem is now, but I have one more question.
I now have:
level *tmp_level = malloc(sizeof(level));
instead of
level *tmp_level;
but the program gives the error:
"request for member 'tilemap' in something not a structure or a union", so I don't think what I did was right.

Could you point me in the right direction as to what I need to do to malloc() the level?

Thanks

gnolam

Since you're now dealing with a pointer to a struct instead of a struct itself, you're using the wrong member access operator - "." instead of "->".

octotep

Hrm... I fixed that, but now my main loop always crashes when I try to access the tilemap (even though I allocate memory for that and the level struct pointer), while I can access the other values of the level struct just fine.

#SelectExpand
// In main, before the loop checking for events and after initializing
      // everything
      level *first_level;
first_level = load_level(current_world, current_level);
if(!first_level)
{
  fprintf(stderr, "Couldnt create the level!\n");
              // shutdown everything
  return -1;
}
fprintf(stderr, "Back to main\n");
player *player;
player = create_player();
if(!player)
{
  fprintf(stderr, "Couldnt create the player!\n");
              // shutdown everything
  return -1;
}
fprintf(stderr, "Back to main2\n");
al_set_new_bitmap_flags(0);
printf("Set the flag");
int level_x = SCREEN_W + (2 * first_level->tilesize);
int level_y = SCREEN_H + (2 * first_level->tilesize);
level_bitmap = al_create_bitmap(level_x, level_y);
if(!level_bitmap)
{
  fprintf(stderr, "Couldn't create the level bitmap!\n");
              // shutdown everything
  return -1;
}

//crashes right here 
      int b, c;
for(b = 0; b < first_level->size_y; b++)
{
  for(c = 0; c < first_level->size_x; c++)
                      fprintf(stderr, "%i,", first_level->tilemap[b][c]);
}

I feel bad for asking so many questions, because I feel that there's just one really stupid thing I'm missing...

Edgar Reynaldo

Post your latest load_level function. Either level->size_y or level->size_x is wrong, or you are not allocating level->tilemap correctly.

octotep

Here it is:

#SelectExpand
  1level *load_level(int world_num, int level_num)
  2{
ALLEGRO_CONFIG *level_file;
level *tmp_level = malloc(sizeof(level *));
if(tmp_level == NULL)
{
  fprintf(stderr, "Out of memory for the level struct!\n");
  return NULL;
}
printf("Break here!\n");

const char *tile_file_name;    // for the tiles.bmp level.tile_file 31
char level_file_name[27];    // worldxx-levelyy.cfg 27

// Get all of the data from the level cfg file
sprintf(level_file_name, "levels/world%02d-level%02d.cfg", world_num, level_num);
level_file = al_load_config_file(level_file_name);
tmp_level->size_x = atoi(al_get_config_value(level_file, NULL, "size_x"));
tmp_level->size_y = atoi(al_get_config_value(level_file, NULL, "size_y"));
tmp_level->start_x = (float) atof(al_get_config_value(level_file, NULL, "start_x"));
tmp_level->start_y = (float) atof(al_get_config_value(level_file, NULL, "start_y"));
//without this, I can't access tilesize from outside this function...
tmp_level->tilesize = (int) malloc(sizeof(int));
tmp_level->tilesize = (int) atoi(al_get_config_value(level_file, NULL, "tile_size"));

// Get the tile file loaded into the level struct
tile_file_name = al_get_config_value(level_file, NULL, "tile_file");
tmp_level->tile_file = al_load_bitmap(tile_file_name);
if(!tmp_level->tile_file)
{
  printf("TILE FILE NOT LOADED!\n");
  return NULL;
}
 34
 35
// Create the tilemap array
tmp_level->tilemap = malloc(tmp_level->size_y * sizeof(int *));
if(tmp_level->tilemap == NULL)
{
  fprintf(stderr, "Out of memory for the pointer-pointer-int in the level struct!\n");
  return NULL;
}
int i;
for(i = 0; i < tmp_level->size_y; i++)
{
  tmp_level->tilemap[i] = malloc(tmp_level->size_x * sizeof(int));
  if(tmp_level->tilemap[i] == NULL)
  {
    fprintf(stderr, "Out of memory for the **intergers in the level struct!\n");
    return NULL;
  }
}
 53

// Get the tilemap data from the cfg file
char *result = NULL;
const char *tilemap_data;
tilemap_data = al_get_config_value(level_file, NULL, "map_data");
result = strtok((char *)tilemap_data, ",");
int x = 0;
int y = 0;
 62
while (result != NULL)
{
  tmp_level->tilemap[y][x] = atoi(result);
  while(x < tmp_level->size_x)
  {
    tmp_level->tilemap[y][x] = atoi(result);
    result = strtok(NULL, ",");
    x++;
  }
  x = 0;
  result = strtok(NULL, ",");
  y++;
}

int b, c;
for(b = 0; b < tmp_level->size_y; b++)
{
  for(c = 0; c < tmp_level->size_x; c++)
    fprintf(stderr, "%i,", tmp_level->tilemap[b][c]);
}

al_destroy_config(level_file);
printf("%i\n", tmp_level->tilesize);
fprintf(stderr, "~~CREATE LEVEL - DONE~~\n");
return tmp_level;
 88}

Edgar Reynaldo

octotep said:

  level *tmp_level = malloc(sizeof(level *));

That should be level* tmp_level = malloc(sizeof(level));, like you had it before. You're only allocating enough memory to hold a pointer.

octotep said:

  //without this, I can't access tilesize from outside this function...
//  tmp_level->tilesize = (int) malloc(sizeof(int));
  tmp_level->tilesize = atoi(al_get_config_value(level_file, NULL, "tile_size"));

The line I commented out (the second one) is not good C. You allocate an integer's worth of memory and then cast that address to an integer - it's value would likely be huge, and totally incorrect. The third line there is correct.

octotep said:

#SelectExpand
tilemap_data = al_get_config_value(level_file, NULL, "map_data");
result = strtok((char *)tilemap_data, ",");
int x = 0;
int y = 0;
  5
while (result != NULL)
{
  8//    tmp_level->tilemap[y][x] = atoi(result);// this is not necessary
  while(x < tmp_level->size_x)
  {
    tmp_level->tilemap[y][x] = atoi(result);
    result = strtok(NULL, ",");
    x++;
  }
  x = 0;
 16//    result = strtok(NULL, ",");// You're skipping a token here
  y++;
}

I commented out two lines - the first commented line is unnecessary and is overwritten by your second assignment, and the second commented line is a mistake, because it would skip one of your values.

octotep

Thank you, it works perfectly!

Edgar Reynaldo

Glad to hear it. Got a screenshot you could show us?

octotep

Here's one. Unfortunately I'm not the best artist, so all I have right now is a stick figure for testing purposes.
{"name":"screenshot.jpg","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/0\/6\/069bfb2e47ac9abeeb5ce934152edd50.jpg","w":646,"h":512,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/0\/6\/069bfb2e47ac9abeeb5ce934152edd50"}

Edgar Reynaldo

Well, your basic ground tile looks good. It blends perfectly with the tiles next to it.

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