Reading structure from file

Hello,
I'm learning cpp by trying to translate chunks of my VB6 programs. Of course, I have great missunderstanding of cpp syntax and logic.
Here is example which I cant get to work so please help.

declarations:

Code:

struct n_row
{
    char m_name[27];
    char m_enable[1];
    char m_pointer[6];
    char m_crlf[2];
};
const char *myFile = "names.dat";
const short lenRecord = 36;
char *mbuffer[lenRecord];
int allRecords = 43000;
long lof;
int obi;
int brr;
int stt;

functions:

Code:

bool eVFrame::reloadlist(bool gput, int stt, long lof, char mbuffer[lenRecord])
{
    int i;
    FILE *f;
    n_row r;

    f=fopen(myFile,"r+b");
    if (!f)
        return true;
        fseek(f, 0, SEEK_END);
        lof = ftell(f);

    if (stt<1){stt=1;}
    for (i=stt;i<=stt;i++)
    {
        int sz = sizeof(struct n_row);
        fseek(f,sz*i,SEEK_SET);
     if (!gput)
        {
         fread(&r,sz,1,f);
        }
         else
        {
         fwrite(&r,sz,1,f);
        }
    }
    fclose(f);
    return false;
}

int eVFrame::myitems(int obi, int brr)
{
    for (int i = obi; i < obi + nRows; i++)
    {
     eVFrame::reloadlist(false, i, lof, mbuffer[lenRecord]);
     wxString mystring(*mbuffer, wxConvUTF8);
     wxPuts(mystring);
    }
return 0;
}

I call funcion reloadlist from mytems and i cant get data to mbuffer and mystring.
Problem s that I dont know how to assign data to buffer in reloadlist whish I have in r.
Can I load direct from file to buffer[]?

This depends on how the file was created. If it is a text file this won't work, I think you realize that.

The other problem is this:

Code:

bool eVFrame::reloadlist(bool gput, int stt, long lof, char mbuffer[lenRecord])

You are passing the value of an array (ie, a copy of the entire array) in, which means no changes to it will affect anything outside the function.

To do that you should pass in a pointer to the array, so that changes affect that region of memory and not a copy of it.

Originally Posted by MK27

You are passing the value of an array (ie, a copy of the entire array) in, which means no changes to it will affect anything outside the function.

To do that you should pass in a pointer to the array, so that changes affect that region of memory and not a copy of it.

Actually, that is syntax for a parameter that is a pointer to char. lenRecord is ignored.

No, this is a binary bile.
I try to read fixed length record to mbuffer which I would like read in myitems.
But it is empty.
I dont know yet manipulate with strings and pointers in cpp.

Originally Posted by nime

I dont know yet manipulate with strings and pointers in cpp.

Probably easiest to take a few steps back then and write some short simple demo programs focussed on this, doing the kinds of things you want to do.

That's exaclly what I do.
This sample works but I have data in variable r and I dont know how that put in mbuffer so I can read it in function myitems.
Question is only how to put data (this 36 bytes) from r to mbuffer (in function reloadlist).

Originally Posted by nime

Question is only how to put data (this 36 bytes) from r to mbuffer (in function reloadlist).

But this sounds like something only you can decide, i.e., the format such that you convert an n_row object to a (presumably null terminated) string.

How can I decide when I dont know how to do that!
And second, my strings (in this case) is not null terminated. In file is raw binary data. This is why I read fixed length defined in strucure. To know where is what.
In VB6 this works great. I belive in cpp also.
I see data in function reloadlist by reading variable r.
But I cant get it out (dont know how) in variable mbuffer so I can be able to readi it in function myitems.
OK, I will try further...