Pointers to variables inside a struct

Pointers to variables inside a struct

aeger

Member #5,769

April 2005

I have no idea how to use pack_fread() with variables inside a struct.

The code below illustrates one of my tries on how to do that, however it does not work :/

void vsp_map_load(char *filename)
{
    PACKFILE *rFile;
    rFile = pack_fopen(filename, "r");
    int name_len, tileset_len;
    pack_fread(&name_len, sizeof(int), rFile);
    pack_fread(&(vsp_map.name), name_len * sizeof(char), rFile);
    pack_fread(&tileset_len, sizeof(int), rFile);
    pack_fread(&(vsp_map.tileset), tileset_len * sizeof(char), rFile);
    pack_fread(&(vsp_map.w), sizeof(int), rFile);
    pack_fread(&(vsp_map.h), sizeof(int), rFile);
    pack_fread(&(vsp_map.tile), (vsp_map.w * vsp_map.h) * sizeof(TILE), rFile);
    pack_fclose(rFile);
}

Could somebody please tell me the right way of doing this?

CGamesPlay

Member #2,559

July 2002

Take off all of the &, and it should work.

[append]
Hmm, on second thought... maybe that isn't the problem...

[append]
Yes, it is. Take the &s off of the variables which are arrays or pointers, and it will work. Leave them on the others.

--
Tomasu: Every time you read this: hugging!

Ryan Patterson - <http://cgamesplay.com/>

Synapse Jumps

Member #3,073

December 2002

What type is vsp_map? Is it a pointer?
EDIT:
CGames: if that were the case, he should DEFINATELY be getting values for things like w and h

CGamesPlay

Member #2,559

July 2002

He didn't say he wasn't getting values for things like name_len, w, and h. He just said "does not work"

--
Tomasu: Every time you read this: hugging!

Ryan Patterson - <http://cgamesplay.com/>

aeger

Member #5,769

April 2005

It still errors ;_;

void vsp_map_load(char *filename)
{
    PACKFILE *rFile;
    rFile = pack_fopen(filename, "r");
    int name_len, tileset_len;
    pack_fread(&name_len, sizeof(int), rFile);
    pack_fread(vsp_map.name, name_len * sizeof(char), rFile);
    pack_fread(&tileset_len, sizeof(int), rFile);
    pack_fread(vsp_map.tileset, tileset_len * sizeof(char), rFile);
    pack_fread(&(vsp_map.w), sizeof(int), rFile);
    pack_fread(&(vsp_map.h), sizeof(int), rFile);
    pack_fread(vsp_map.tile, (vsp_map.w * vsp_map.h) * sizeof(TILE), rFile);
    pack_fclose(rFile);
}

When I only read the first int it works alright but when I try to read the string it crashes.

EDIT:

This is vsp_map:

typedef struct MAP
{
    char *name;
    char *tileset;
    int w;
    int h;
    struct TILE * tile;
}MAP;

MAP vsp_map;

CGamesPlay

Member #2,559

July 2002

You forgot to allocate memory for the variables

--
Tomasu: Every time you read this: hugging!

Ryan Patterson - <http://cgamesplay.com/>

Synapse Jumps

Member #3,073

December 2002

Heh. You need to read up on Pointers, my young friend. For things like name and tileset and tile you need to do things first:
FIRST you need to find out how long the saved "name" is, then you need to allocate memory for it, then you can read/copy it. Here's an example:
EDIT: Oops, didn't see you read in the length of the name, new code:

vsp_map.name = new char [ name_len + 1 ]; //+1 to allow for null-character
pack_fread(vsp_map.name, name_len * sizeof(char), rFile);

You need to do equivalent stuff for your other pointers.

Your other data SHOULD be fine. Check everything that ISN'T a pointer and see if you're getting correct data.

aeger

Member #5,769

April 2005

-_-

I can't believe it was that simple. Sad thing is, this is the second time this happened to me this week.

Oh well, hopefully I won't do it again

Thanks guys