From: vern <vern AT iocc DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: writing to a file
Date: Mon, 19 Apr 1999 16:57:08 -0500
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

hi, im having trouble wrintg some variables to a file.  I'm using hte
latest version of DJGPP and allegro.  My program compiles ok, but it
isnt working right.  I put a zillion if statements that output "ERROR!"
whenever something goes wrong, to try to see whats going on.  I can open
the file successfully, but I cannot write to it.  I am trying to write
the following ot the file:  an array of BITMAPS (if u havent used
allegro, a bitmap is a typedef structure), and an array of structures.
here is my code:

#include <stdio.h>
#include <allegro.h>
#include <iostream>
using namespace std;

FILE* save_file;

BITMAP* tile_bmps[2]; //array of all the tile bmps

typedef struct TILE    //basic tile struct
{
   int bmp_number; //the element number for htis tiles bitmap
   int walkable;   //whether this tile can be walked on-0=yes, 1=no,
else=special
   int special;    //any special characteristics the tile has
   int extra;      //extra stuff things might need: whether a door is
open/closed
} TILE;

TILE map[10][10];     //the map, consisting of 100 tile structs.

void draw_tile_bitmaps(void);
void set_up_map(void);
void write_map_to_file(void);

int main()

{
   cout << "Initializing...";
   allegro_init();
   cout << "Done.\n";

   cout << "Drawing tile bitmaps...";
   draw_tile_bitmaps();
   cout << "Done.\n";

   cout << "Creating map...";
   set_up_map();
   cout << "Done.\n";

   cout << "Writing to file demo.map...";
   write_map_to_file();
   cout << "Done.\n";

   cout << "Finished! Shutting down...";
   allegro_exit();
   cout << "Done.\n";

   return 0;
}

void draw_tile_bitmaps(void)
{
int x=0, y=0;

   //create the bmps & clear em.
   tile_bmps[0] = create_bitmap_ex(8, 32, 32);
   tile_bmps[1] = create_bitmap_ex(8, 32, 32);
   clear(tile_bmps[0]);
   clear(tile_bmps[1]);

   //print soem stuff onto em.
   //first tile
   for(x=0; x<33; x++)
      putpixel(tile_bmps[0], x, x, 50);

   x = 32;
   for(y=0; y<33;y++)
   {
      putpixel(tile_bmps[0], x, y, 25);
      x--;
   }
   //second tile.
   rectfill(tile_bmps[0], 0, 0, 32, 32, 150);

   //and thats it!
}

void set_up_map(void)
{
   int y=1;

   //set the edge to all walls
   for(int x=0;x<10;x++)
   {
      map[0][x].bmp_number = 0;
      map[0][x].walkable = 1;
      map[0][x].special = 0;
      map[0][x].extra = 0;
   }

   for(int x=0;x<10;x++)
   {
      map[10][x].bmp_number = 0;
      map[10][x].walkable = 1;
      map[10][x].special = 0;
      map[10][x].extra = 0;
   }

   for(int x=1;x<9;x++)
   {
      map[x][0].bmp_number = 0;
      map[x][0].walkable = 1;
      map[x][0].special = 0;
      map[x][0].extra = 0;
   }

   for(int x=1;x<9;x++)
   {
      map[x][10].bmp_number = 0;
      map[x][10].walkable = 1;
      map[x][10].special = 0;
      map[x][10].extra = 0;
   }

   //fill the inside
   for(y=1;y<9;y++)
   {
      for(int x=1;x<9;x++)
      {
         map[x][y].bmp_number = 1;
         map[x][y].walkable = 0;
         map[x][y].special = 0;
         map[x][y].extra = 0;
      }
      y++;
   }
}


void write_map_to_file(void)
{
   int test;
   cout << "Opening File...";
   save_file = fopen("demo.map", "w");
   if(save_file==NULL)
   {
      cout << "ERROR!" << save_file;
   }
   cout << "Done.\n";

   cout << "Writing ot File...";            //errors start AFTER this
point.
   //write the list of bmps
   test = fwrite(tile_bmps, sizeof(tile_bmps), 1, save_file);
   if(test!=sizeof(tile_bmps)) cout << "ERROR!" << test;       //error
here

   //write the map struct
   test = fwrite(map, sizeof(map), 1, save_file);
   if(test!=sizeof(tile_bmps)) cout << "ERROR!" << test;      //error
here.
   cout << "Done.\n";

}

The error is occuring just after it opens the file, and tries to write.
It opens the file successfully, then gives me 2 error messages.  Ive
spent some time trying to figure this out myself, but no luck.

Thanks,

Andy F.