Thread: Binary Read and Writes...

I'm forced to keep an array of 2000 elements on disk for later use..
My program uses this :

struct array //I do the struct to encapsulate -sort of anyway
{
char m_pCodes[1000];
}array;

Now in my program i write let's say 5 codes -at place [0]-1-2-3-4..

I know wanna save them on disk and close the program.
When I open the program i want to see the same codes(offcourse) and then afterwards append the array.. Say know i'll continue writing in element 5-6 and 7.

My program though writes the file... But when reopen -data's smashed !!!!

Please help me on this one.. Since i'm not a huge fan on Console programming -file access has never bin much of intereset...

The Encap... is to categorize the variables... !
So the next programmer who looks might get a quicker overview
of the code.

Well it's still messed up. What if I just wanna write the array ?

like fread(array,array[10000],1,fptr); //???

Should work or ?

It must remember number [3] f.ex.

I use strdup, so the mem alloc problem should be solved..

Since i'm handling a very big chunk of data -it would be sloppy to write it in pure ascii.
Rather in binary... Because i'm able to handle huge amounts of data -while the ascii or single fprintf, fscanf functions don't reach my requirements ;(

> What if I just wanna write the array ?
Do as Kooma showed you

The "rb" and "wb" are important

You mentioned strdup, which involves memory allocation, so, if
struct array //I do the struct to encapsulate -sort of anyway
{
char m_pCodes[1000];
}

contains pointers, you need a different approach

Okay i've studied the code again... And see what you mean.. :=

If I do this:

char array[1000][12];
//String is 12 chars long and there are 1000 of them

I can now do an ordinary strcpy -because the memory is allocated this way...

Now i need to write alle the codes down into a binary file -and shutdown -reopen -place codes into array again (sort of "restore")

Can i then do this ?

while(n<MAX)
fread(array[n][~],sizeof(array[n][~]),1,fptr);

and the same way around with fwrite ?

-> By the way the b in "wb"-"rb" ~well offcourse... it wouldn't be binary else...

> Can i then do this ?
> while(n<MAX)
> fread(array[n][~],sizeof(array[n][~]),1,fptr);

That's one way
But that only does one char at a time, which seems pointlessly inefficient

And in any event, it would need to be
> fread( &array[n][~],sizeof(array[n][~]),1,fptr);


To do the whole array in one go, its
fread( array, sizeof(array), 1, fptr );

Or a line at a time
for ( i = 0 ; i < 1000 ; i++ )
fread( array[i], sizeof(array[i]), 1, fptr );