access violation-newbie tile map...

access violation-newbie tile map...

Dorianin

Member #8,013

November 2006

greetings and salutations, all...

yet another "I'm new to yada yada yad..."

here it goes...Im writing a map editor from a tutorial i got on the web.however, ive kind of developed a liking for some c++ stuff...so im modifying as i go.the tutorial is in c.

i get an access violation(segmentation fault) somewhere in my Map header file. I cant quite seem to pinpoint it with the debugger...so here you guys go.im using Dev-C++ 4.9.9.2 with the current allegro devpak.

1#include <allegro.h>
2#include <cstdio>
3#include <cstdlib>
4#include <fstream>
5#define TILE_SIZE 30
6#define MAP_SIZE 14
7 
8using namespace std;
9 
10DATAFILE* data=load_datafile("editor_tiles.dat");
11 
12 
13class Tile
14{
15      public:
16             bool Walkable;
17             int Image;
18             Tile::Tile(){Image=0;Walkable=FALSE;}
19};
20 
21 
22class Map
23{
24      
25      public:
26        Tile _tile[MAP_SIZE][MAP_SIZE];
27        void loadmap(char* _filename);
28        void savemap(char* _filename);
29        void drawmap(BITMAP* _temp);
30};
31 
32 
33void Map::loadmap(char* _filename)
34{
35     ifstream _file(_filename,ios::binary);
36     int i,j,_tile;
37     for(i=0;i>MAP_SIZE;i++)
38     {
39         for(j=0;j>MAP_SIZE;j++)
40         {
41             _file.read((char *)&_tile,sizeof(Tile));
42         }
43     }
44     _file.close();
45}
46 
47void Map::savemap(char* _filename)
48{
49     ofstream _file(_filename,ios::binary);
50     int i,j,_tile;
51     for(i=0;i>MAP_SIZE;i++)
52     {
53         for(j=0;j>MAP_SIZE;j++)
54         {
55            _file.write((char *)&_tile,sizeof(Tile));
56         }
57     }
58     _file.close();
59}
60 
61void Map::drawmap(BITMAP* _temp)
62{
63     int i,j,tile;
64     show_mouse(NULL);
65     
66     for (i=0;i>MAP_SIZE;i++)
67     {
68         for(j=0;j>MAP_SIZE;j++)
69         {
70             tile=_tile<i>[j].Image;
71             if (tile>0)
72             draw_sprite(_temp,(BITMAP*)data[tile].dat,i*TILE_SIZE,j*TILE_SIZE);
73             else
74             rectfill(_temp,i*TILE_SIZE,j*TILE_SIZE,i*TILE_SIZE+TILE_SIZE,j*TILE_SIZE+TILE_SIZE,0);
75         }
76     }
77     show_mouse(_temp);
78}

the c headers are from when i was using the c file system from the tutorial..i forgot to comment them out.

never play leapfrog with a unicorn....

Richard Phipps

Member #1,632

November 2001

all your for (i=0;i>MAP_SIZE;i++) should be for (i=0;i<MAP_SIZE;i++) and the same for j too.

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Dorianin

Member #8,013

November 2006

aright...did that...still getting the access violation...

...i narrowed it down to the datafile declaration...here the main.c code...

1#include "C:/Dev-Cpp/Map_class.h"
2 
3BITMAP* buffer;
4DATAFILE* data=load_datafile("editor_tiles.dat");
5Map World;
6 
7 
8void init();
9void deinit();
10void drawmap(BITMAP* _temp);
11 
12int main() 
13{
14    
15  init();
16 
17    drawmap(screen);
18 
19  while (!key[KEY_ESC]) 
20    {
21       
22  }
23 
24  deinit();
25  return 0;
26}
27END_OF_MAIN()
28 
29void init() {
30  
31  allegro_init();
32  set_color_depth(32);
33  set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0);
34  clear(screen);
35  set_pallete((RGB*)data[0].dat);
36 
37  install_timer();
38  install_keyboard();
39  install_mouse();
40  buffer=create_bitmap(640,480);
41 
42}
43 
44void deinit() 
45{
46  clear_keybuf();
47  unload_datafile(data);
48  destroy_bitmap(buffer);
49  
50}
51 
52void drawmap(BITMAP* _temp)
53{
54     int i,j,tile;
55     show_mouse(NULL);
56     
57     for (i=0;i<MAP_SIZE;i++)
58     {
59         for(j=0;j<MAP_SIZE;j++)
60         {
61             tile=World._tile<i>[j].Image;
62             if (tile>0)
63             draw_sprite(_temp,(BITMAP*)data[tile].dat,i*TILE_SIZE,j*TILE_SIZE);
64             else
65             rectfill(_temp,i*TILE_SIZE,j*TILE_SIZE,i*TILE_SIZE+TILE_SIZE,j*TILE_SIZE+TILE_SIZE,0);
66         }
67     }
68     show_mouse(_temp);
69}

never play leapfrog with a unicorn....

Elverion

Member #6,239

September 2005

Quote:

DATAFILE* data=load_datafile("editor_tiles.dat");

You are calling that globally. That's never a good idea...avoid global variables and assignments wherever possible. You are currently calling load_datafile before Allegro is even initialized. Try this instead:

1..
2DATAFILE* data = NULL; // use "NULL" so we can keep track of it's use.
3                       // it's all part of "good" pointer practice.
4..
5 
6int main()
7{
8  init();
9  data = load_datafile("editor_tiles.dat");
10  ..
11 
12  unload_datafile(data);
13  ..
14}
15..

--
SolarStrike Software - MicroMacro home - Automation software.

Dorianin

Member #8,013

November 2006

perfect...that worked.thanks...

...now...to save my map ive got a function like so...

void Map::savemap(char* _filename)
{
     FILE* file;
     file=fopen(filename,"wb");
     fwrite(Map,sizeof(Tile),MAP_SIZE*MAP_SIZE,file);
     fclose(file);
}

however...nothing happens...I believe my parameters may be wonky...but nothing shows up in compiling, debugging or running...

never play leapfrog with a unicorn....

Elverion

Member #6,239

September 2005

That's not a very good way to save your maps. If you are sure you want to do it that way, check into reinterpret_cast. Keep in mind that this would cause endianess problems, and the saved maps would not work with your program if compiled under a different compiler. I suggest you just go about writing your own save function. It's basically just something like this:

// loop through all of the rows
for(int y = 0; y < MAP_HEIGHT; y++)
{
  // make a container for the current row
  MapTile MapRow[MAP_WIDTH];
  for(int x = 0; x < MAP_WIDTH; x++)
  {
    //copy the tile into the container
    MapRow<i> = GetTile(x, y);
      // GetTile would return a MapTile at the specified
      // position. You should probably just copy that
      // information from however you store your tiles.
      // ex: arrays, vectors, etc.
  }
15 
  //write the container to a file
  fwrite(MapRow, sizeof(MapTile), MAP_WIDTH, file);
}

You could, of course, optimize the performance of the function by using a single for loop, and using div and mod to extract the x and y positions from a single variable.

--
SolarStrike Software - MicroMacro home - Automation software.

ImLeftFooted

Member #3,935

October 2003

void Map::savemap(char* _filename)
{
     FILE* file;
     file=fopen(filename,"wb");
     fwrite(Map,sizeof(Tile),MAP_SIZE*MAP_SIZE,file);
     fclose(file);
}

The parameter to the function is '_filename' yet you're passing 'filename' to fopen.

Btw, if you're using C++ why not use C++'s file operators instead of C's file operators?

void Map::savemap(char* _filename)
{
     ofstream file(_filename, ios::out | ios::binary);
     file.write(Map,sizeof(Tile)*MAP_SIZE*MAP_SIZE);
}

How is my posting?

Dorianin

Member #8,013

November 2006

hey...your right...wonderwhy the compiler didn't catch that...

i had originally tried to use thee c++ file system, but the ios:: operaters stymied me a bit...but that seems very nice...thank you all for the help...

never play leapfrog with a unicorn....