Programming

Hi
I have an fwrite function in my C++ application. It is able to create the files in HP-UX.

cross is one structure
rec2 is another structure within cross.

fwrite_return = fwrite( &cross.rec2,
sizeof(cross.rec2),
1,
FPTR);

When the same applicationo is run in linux, the file that is formed has checksums different from the one formed in UNIX>

Can any one pleas get me the reason. When i debuged normally and i got the ASCII values which is the same in LINUX and UNIX before fwite.

Regards
rkraj

If the compiler pads the structures differently, or the byte order of the underlying architecture is different, the contents of the memory will not be the same. You should really be using some sort of marshaling to save the structures to disk if you want the files to be portable between different machine architectures. A simple textual format is often a good solution.

If you copy the HPUX file to linux (or the other way around) and run diff against the two output files, what do you see?

I am not able to read those files as it is in the binary format.
When i debugged the application using gdb and when i tried to print the structure cross, i am getting the same values in both LINUX and UNIX, but when completing the writing the checksums vary.

REgards
rkraj

You said that already. We cannot debug your code without seeing it. Era is thinking struct packing, I was thinking locale setting, which appears not to be likely, but either way we need code, mainly the declaration of the record (struct).

Here is my program

#include<stdio.h>
#include<string.h>
struct cross_output_entry
{
char stub_descr[80];
int sort_stub_route;
double arr[20];
};
struct cross_output_type
{
union
{
char rec[8088];
struct cross_output_entry rec2;
};
};

struct cross_output_type cross;
int main()
{
int i;
FILE* fptr;
fptr=fopen("temp.text","wb");
for(i=0;i<5;i++)
{

strcpy(cross.rec2.stub_descr,"122");
cross.rec2.arr[0]=1.0;
cross.rec2.arr[1]=343.1019;
cross.rec2.arr[2]=1000.199;
cross.rec2.arr[3]=0.0;
fwrite( &cross.rec2,
sizeof(struct cross_output_type),
1,
fptr);
}
fclose(fptr);
}


The file temp.text produced in UNIX and LInux has different checksums.
Please help me to get the same check sum as i am involving myself to port application from UNIX to Linux.

Regards
rkraj

Check the return code from fwrite() to make sure it's working properly. That could be one of the many reasons why the checksums are different. The ferror() function verifies that the call to fwrite() worked or not.