Thread: EOF appears not on end of file?!

Ive wrote a very simple pogram that encrypts a .txt file by reading every char in it , promoting it by 1, and then putting the result in a new .txt file .
then the prog reads the "encrypted "file and decrypts it by substructing 1 from every char.

for example if those chars apear in the file :

Code:

abcd123

after running the program it creats 2 files :
encrypted.txt:

Code:

bcde234

and decrypted.txt

Code:

abcd123

BUT when i run the program on a file with those chars:

Code:

Edֳ$x7ֳ$x7ֳ$x7987ֶ$x7d7ָ$x7ֳ$x7ֲ$x7ֳ$y7D$x79a7־$x7T=7ֲ$x7e7$x79E7ֲ$x7Richֳ$x7                        PE  L
 „};        א 

  (
  ”

the result is :
encrypted.txt:

Code:

Feִ%y8ִ%y8ִ%y8:98ַ%y8e8ֹ%y8ִ%y8ֳ%y8ִ%z8E%y8:b8ֿ%y8U>8ֳ%y8f8א%y8:F8ֳ%y8Sjdiִ%y8!!!!!!!!!!!!!!!!!!!!!!!!QF!!M!…~<!!!!!!!!ב!!!)!!•!

decrypted.txt:

Code:

Edֳ$x7ֳ$x7ֳ$x7987ֶ$x7

this is the code:

Code:

while(ch!=EOF){ /*encryption*/
                                     ch=fgetc(src); /* ch,chr are int  */
                                     chr=ch+1;
                                     fputc(chr,dst);
               }

Code:

while(ch2!=EOF){ /*decryption*/
                                     ch2=fgetc(src); /*  ch2,chr2 are int   */
                                     chr2=ch2 -1;
                                     fputc(chr2,dst);
               }

I think the problem is that for some reason when the chars " "appear the compiler thinks one of them is an EOF and stops.

can that be the problem or is it something else?
plz hlp me fix this BUG!

I think you might want something like this:

Code:

while (EOF != (ch2 = fgetc(src))) {
   chr2 = ch2 - 1;
   fputc (chr2, dst);
}

Otherwise you're putting the decrement of character into the resulting file and then checking it for NULL. Whether this solves your problem, I don't know :-P

Originally Posted by zacs7

You should also limit the encrypted characters to "printable" characters. See isprint() from ctype.h - to make sure you don't get any control characters in there... For example, NUL.

I changed the code so now the promotion and substrucion of chars is done only if the char is printble. ( using isprint() )

that solved many problems including the bug in my first post.
but, still i can find bugs like this:

Code:

source:   ¥־wֵ=־w׃=־w$@־wx־w…־w¿@־w@ֿwL®־w9ˆׁwŒq־wזדׂw..מ׀w    ״¼wץ¼wש׳»wזַ»w־<

Code:

encrypted ¥־xֵ>־x׃>־x%A־xy־x…־x¿A־xAֿxM®־x:ˆׁxŒr־xזדׂx..מ׀x!!!!״

Code:

decrypted ¥־wֵ=־w׃=־w$@־wx־w…־w¿@־w@ֿwL®־w9ˆׁwŒq־wזדׂw..מ׀w    ״

again the programs stops after the '' char which is strange because as you can see in the example, sometimes when '' appears nothing happens, and sometimes when it appears the prog stops .
any idea why is that ? and how to fix it ?
thanks

Originally Posted by Salem

Posting your whole program would really help.

no problem

Code:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include <ctype.h>
int main()
{
 FILE *dst ,*src;
 int ch,ch2;

/**********opppening files**************/

 src=fopen("a.txt" ,"rt");
 if(src==NULL){
               puts("error");
               getchar();
               exit(1);
               }
 dst=fopen("Encrypted.txt" ,"wt");
 if(src==NULL){
               puts("error");
               getchar();
               exit(1);
               }
/************encryption******************/
while (EOF != (ch = fgetc(src))) 
      if(isprint(ch))
         fputc(ch +1, dst);
                                    
      else
        putc(ch, dst);
        
 fclose(dst);
 fclose(src);
 puts("done");
 getchar();
/***************************************/


/************opppening files*************/

 src=fopen("Encrypted.txt" ,"rt");
 if(src==NULL){
               puts("error");
               getchar();
               exit(1);
               }
 dst=fopen("Decrypted.txt" ,"wt");
 if(src==NULL){
               puts("error");
               getchar();
               exit(1);
               }
/**************************************/

/*************decryption****************/
while (EOF != (ch2 = fgetc(src))) 
      if(isprint(ch2))
         fputc(ch2 -1, dst);
      else
         fputc(ch2, dst);

 fclose(dst);
 fclose(src);
 puts("done");
 getchar();
/*************************************/
}

Originally Posted by v01d

Code:

while(ch!=EOF){ /*encryption*/
                                     ch=fgetc(src); /* ch,chr are int  */
                                     chr=ch+1;
                                     fputc(chr,dst);
               }

Code:

while(ch2!=EOF){ /*decryption*/
                                     ch2=fgetc(src); /*  ch2,chr2 are int   */
                                     chr2=ch2 -1;
                                     fputc(chr2,dst);
               }

Why do you process the byte BEFORE you check to see if it's EOF? Your loop is structured wrong.

Also, naming two variables "chr" and "ch" is massively unclear.

Thanks for enlightenment Dave
the code realy works when run in binary mode...