fwrite in binary mode

I have a binary file that i am reading in an array and then after doing some processing i want to write it into a new binary file. The reading and the processing is working fine but writing back is not working.

FILE *fptr;

FILE *fptr2;

unsigned short *ds;

unsigned short *ds2;

fptr = fopen("C:\\abc.dat","rb");

fptr2 = fopen("C:\\abs2.dat","wb");

fread((void*)ds, totalSize, sizeof(unsigned short), fptr); // total size is the size of the data and is correct

processds(ds, ds2); // ds is processed and copied into ds2 and works fine

fwrite(ds2, sizeof(unsigned short), totalSize, fptr2); // a new file is created bust has no bytes in there

how can i write it back

thanks in advance

best wishes

Visual C++8

How you open the file for writing And are you sure totalSize does not change between fread and fwrite

hi

i have included the code for opening the files in my first post. yeah total size remains the same

any idea whats going wrong

regards

Although you say you're having success with your code, I see that you haven't allocated any space for ds and ds2. If this isn't the real version of your code, could you please provide it

This is how i am allocating sizes:

ds = new unsigned short [totalSize];

ds2 = new unsigned short [totalSize];

actually this is part of a very lenghty project where i am making changes.

so i am picking code and placing it here.

Reading, and processing of the data works super fine. i have tested ds2 and there is right data in there.

only when i am putting the stuff from ds2 to file, it starts making problems

:(

If its a sneaky bug, then you should give us the benefit of full disclosure of the code. :)

Did you check the return value of fwrite

12 classes and above 4000 lines of code!!

can you give it another try!!

even when i did :

int tt = fwrite(ds2, sizeof(unsigned short), totalSize, fptr2);

tt was equal to totalSize

but the file is still of 0 KB.

now only the following code is there and the problem persists:

FILE *fptr2;

int main (int argc, char** argv){

int abc[] = {1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9};

if((fptr2 = fopen("C:\\work\\datasets\\mine.dac","wb"))==NULL) {

printf("Cannot open file.\n"); // it is not printed

}

int tt = fwrite(abc, sizeof(int), 90, fptr2);

if ( tt != 90)

printf("Cannot open file.\n"); // it is not printed

fclose(fptr2);

}

any ideas

hey the above code executes fine

is there any difference between

unsigned short *ds = ..............;

unsigned short ds[] = .............

are we reaching some solution

Your code looks fine and it works on my machine (after renaming the path). What is the value of errno after fwrite is called

Try:

errno = 0;
int tt = fwrite(abc, sizeof(int), 90, fptr2);
printf("error=%s\n",strerror(errno));

My output: error=No error

it now works fine...believe me the previous code that i earlier had is doing fine now

i did not do any changes

i dont know what is my machine doing

but thanks a lot lot :) :)

Well it's good to know you're out of crisis mode.

I'll mark this thread as answered now.