Xref: news2.mv.net comp.os.msdos.djgpp:8533
From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Binary files and ^C chars-try again
Date: Wed, 11 Sep 1996 19:04:03 -0700
Organization: Three pounds of chaos and a pinch of salt
Lines: 123
Message-ID: <32376F93.7147@cs.com>
References: <3237032D DOT 258A AT ccfsun DOT nrl DOT navy DOT mil>
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To: John Moon <moon2 AT ccfsun DOT nrl DOT navy DOT mil>
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

John Moon wrote:
> 
> Let's try this again,
> 
> This may be a dumb question, but
> when I try to read a ^C char in binary from a
> file I get an EOF condition, no matter if I try
> to read further into the file or not. Is this a
> perversity of the djgpp stdlib? If so, what is the
> standard work-around? I have tried getc, fgetc,
> fscanf, and fread, and they all do the same thing.
> Apparently, the 255 (EOF) char does the same thing so
> even if I get the file size and fseek past the
> offending character I don't know whether it was a
> ^C or EOF.

Okay-- where should I start?

>     if((fp=fopen(argv[1],"w"))!=NULL) {
>     if((fp=fopen(argv[1],"r"))!=NULL) {

1) Your problem is caused by the fact that you are NOT opening
   the file in binary mode.  Under DOS, binary and text modes are
   substantially different in the way they treat special characters
   like ^C and ^Z.  Instead of "w" and "r", use "wb" and "rb" when
   you call fopen().


> I am using go32 v 1.12.maint3

2) The latest version of DJGPP is v2.  There is no problem with
   using older versions, but be aware that they are not supported by
   the DJGPP development team anymore.  The latest version is at:

   ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2, /v2gnu, /v2misc, etc.

   Please download and read the file v2/readme.1st before getting any
   other files, and be sure to obtain the FAQ (v2/faq201b.zip) and read
   it as well for changes from v1.x to v2.


> main(argc,argv)
>     int argc;
>     char *argv[];

3) Why are you writing code for traditional C?  The ANSI standard has
   been around more than long enough for all programmers to adopt it -
   it is easier, more intuitive, and makes it far easier to catch
   errors.

 
Below I have made some recommended changes to your code.  In case you
wonder, I have tested this and it works.

#include <stdio.h>
#include <stdlib.h>
#include <io.h>

#define MAX 256

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

    FILE *fp;
    long size;
    long i = 0;
    int j;
    char buf[MAX];

    if ( argc < 2 )
    {
	fprintf( stderr, "You must specify a filename.\n" );
	exit( 1 );
    }
 
/* this creates a test binary file 0-255 named w/ contents of argv[1] */
 
    if ( ( fp = fopen( argv[1], "wb" ) ) == NULL )
    {
	perror( argv[1] );
	exit( 1 );
    }

    for ( i = 0; i < MAX; ++i )
	fputc( (char) i, fp );
    fclose( fp );


/* this attempts to read it back */

    if ( ( fp = fopen( argv[1], "rb" ) ) == NULL )
    {
	perror( argv[1] );
	exit( 1 );
    }

    size = filelength( fileno( fp ) );
    printf( "\n\n\nFile Size = %ld\n", size );

    for ( i = 0; ( j = fread( buf, (size_t) 1, (size_t) 1, fp ) ) > 0; ++i )
        printf( "%ld %d %d\n", i, j, buf[0] );

/*
 * I don't think this is exactly what you want to do - are you trying to read the
 * characters one by one and fill up buf, or are you just reading them into the first
 * element of buf?  If the former, then here's how you should do it.
 *
 *
 *    for ( i = 0; ( j = fread( buf + i, (size_t) 1, (size_t) 1, fp ) > 0; ++i )
 *        printf( "%ld %d %d\n", i, j, buf[i] );
 */

    return 0;
}

-- 
                      Anything that happens, happens.
    Anything that, in happening, causes something else to happen, causes
                         something else to happen.
 Anything that, in happening, causes itself to happen again, happens again.
        It doesn't necessarily do it in chronological order, though.
 
                                       --- Douglas Adams