4 replies to this topic

[WhiteHouse]

Is ther any file input/output commands that can write and/or read data like below to/from a file.

code:

---

struct MyDataFile {
  char*   lpszEditor;        //String (lp)
  UCHAR** lplpucMapTile;     //2D Array
  UCHAR   Floors        = 1; //Normal UCHAR
}

---

[Melo]

Look at the 'Using File'-Subject.
Everythin' is explained there.

Bye!

[WhiteHouse]

Thanks for the response but what is in there doesn't help me. I have already tried all what all you other GameDev.net members have sugested and it doesn't work.

So, please, be a little bit more precise.
Thanks.

[Sphet]

I think the other post uses a structure defined as such:

typedef struct
{
char string1[1024];
char string2[255];
int posX;
int posY;
} GameData;

If you do a sizeof(GameData), you'll get a value that represents the contents of the data, and a fwrite(fp, pGameData, sizeof(GameData), will work.

In your sample:

struct MyDataFile {
char* lpszEditor; //String (lp)
UCHAR** lplpucMapTile; //2D Array
UCHAR Floors = 1; //Normal UCHAR
}

this will not work, since you are storing strings as pointers with no length.

When you have data stored in a pointer, a sizeof(pointerVariable) will return the size of the pointer, not its contents. So if you have malloc'd 2MBs to a pointer, the pointer will still return 4 if you do a sizeof(pointerVar). If you need to do it this way, you will have to store your data in a different method, most likely using something like this:

For each member of your structure, you will have to save it seperately, and load it seperately, in sequence, as in the following:

SaveBlock(char *data, unsigned long int length)
{
  // first same a number as to how long 
  // the data is
  fwrite(fp, length, sizeof(length));
  // now save the block
  fwrite(fp, data, length);
}

call this function with your data and the length of the data, then when loading it..

fp = fopen(filename, "wb");
SaveBlock(DataFile.lpszEditor, strlen(DataFile.lpszEditor));
SaveBlock(DataFile.lplpucMapTile, mapSize);
fwrite(fp, DataFile.Floors, sizeof(UCHAR)); // not a pointer

Then to load:

LoadData(char **data, int *length)
{
  // find out how long the data chunk is
  fread(fp, *length, sizeof(*length));
  
  // allocate the memory
  *data = malloc(*length);
  
  // read the data
  fread(fp, *data, *length);
}
fp = fopen(filename, "rb");
unsigned int loadLength;
LoadData(*DataFile.lpszEditor, *loadLength);
DataFile.lpszEditor[loadLength] = '\0'; // terminate the string
LoadData(*DataFile.lplpucMapTile, *loadLength);
mapSize = *loadLength; // save this so you know how bit the mapsize was
fread(fp, *DataFile.Floors, sizeof(UCHAR)); // not a pointer

Hope that helps.. it might just be confusing.

[This message has been edited by Sphet (edited October 05, 1999).]

[WhiteHouse]

It does help but I have already created functions that do exactly that but they are so timeconsuming to use and I was hoping that perhaps windows has functions for doing it.

But OK, I'll have to accept reality.

Thanks!