Problem with FILE in c++

[anhome]

I've tried this code in binary (.bin) file, but it doesn't work on others files such as audio(e.g. .mp3), video (e.g. .avi)
wish somebody could solve this for me.
thanks

#include <stdio.h>
#include <conio.h>
#define length 64000 

void main(){
 FILE *fsrc, *fdes;
 long size;
 char buffer[length];
 clrscr();
 fsrc = fopen("D:\\One.bin","rb+");
 fdes = fopen("D:\\Two.bin","wb+");
 fseek(fsrc,0,2);
 size = ftell(fsrc);
 fseek(fsrc,0,0);
 while ( ftell(fsrc) < size-length ){
   fread(buffer,length,1,fsrc);
   fwrite(buffer,length,1,fdes);
   printf("\nat %ld",ftell(fsrc));
 }

 fclose(fsrc);
 fclose(fdes);
 getch();
}

[ne555]

> it doesn't work
¿what's the error? ¿file corrupted?

> while ( ftell(fsrc) < size-length )
¿wouldn't the last block be omitted?
I suppose that you could

count = fread( buffer, 1, length, fsrc ); //read what remains
fwrite( buffer, 1, count, fdes); //write what you read 

also, main must return int

[Chervil]

Or do this:

    while ( !feof(fsrc) )
    {
        long result = fread(buffer,1, length,fsrc);
        fwrite(buffer, 1, result, fdes);
        printf("\nat %ld",ftell(fsrc));
    }

[anhome]

i've tried ftell before looping and it returns 0 (it's the current position) but after i put looping in it, ftell return -1, what does it mean?an error occurred?

[Chervil]

Please see the reference page for ftell()
http://www.cplusplus.com/reference/cstdio/ftell/
"On failure, -1L is returned, and errno is set to a system-specific positive value."

http://www.cplusplus.com/reference/cerrno/errno/
"The particular error messages associated with values of errno can be obtained using strerror or directly printed using function perror."

[anhome]

thanks Chervil.. i've tried and the error string message is "Bad file number"..
Can someone tell me what does it mean?

[Chervil]

I presume it means the file is not valid, perhaps because the file has been closed.

If you aren't sure, please share your code which gives this error.

[anhome]

#include <stdio.h>
#include <conio.h>
#include <errno.h>
#define length 64000

void main(){
 FILE *fsrc, *fdes;
 long size;
 char buffer[length];
 clrscr();
 fsrc = fopen("D:\\One.bin","rb+");
 fdes = fopen("D:\\Two.bin","wb+");
 fseek(fsrc,0,2);
 size = ftell(fsrc);
 fseek(fsrc,0,0);
 printf("at %ld\n",ftell(fsrc));        // <--ftell return -1 but when i close the 
					            //	looping, ftell return 0

 printf("Error : %s",strerror(errno));

 while ( ftell(fsrc) < size-length ){
// while(!feof(fsrc)){                                          <--same error
//   long result = fread(buffer,length,1,fsrc);
   fread(buffer,length,1,fsrc);
   fwrite(buffer,length,1,fdes);
   printf("\nat %ld",ftell(fsrc));
 }

 fclose(fsrc);
 fclose(fdes);
 getch();
}

i checked the file and it's valid, and i close the file at the end of the code.

[Chervil]

Well, I can make a guess here. I tried the above code with two different compilers.

I had to change a couple of lines:void main() corrected this to int main(),
clrscr(); - removed this line as it is not supported by my compiler.
changed the file paths in fopen() to suit my system.

Result:

at 0
Error : Error 0

But then, having slept on this, I had a hunch. Because of the non-standard use of void main() which does not conform to the standard, main() must always return an int and the use of <conio.h> and clrscr(); I guessed that some old, non-standard compiler was being used. I found an old version of Turbo C and tried this code. Result:

at -1
Error : Bad file number

As far as i can tell, the most likely explanation in this case is the use of an obsolete compiler.

If this is indeed the case, I would strongly recommend the use of something more modern such as Code::Blocks http://www.codeblocks.org/