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Date: Fri, 21 Sep 2007 02:04:58 -0400
From: CBFalconer <cbfalconer AT yahoo DOT com>
Organization: Ched Research http://cbfalconer.home.att.net
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Newsgroups: comp.os.msdos.djgpp
Subject: Re: How to copy a file?
References: <B1EIi.52071$rr5 DOT 11613 AT newsfe1-win DOT ntli DOT net>
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

MikeC wrote:
> 
> I know this is probably a C question, but I'm asking it here
> because DJGPP is DOS-centric, and I'm trying to execute a system
> call.  My question: What's the best way to copy a file?
> 
> The file I want to copy is on a Unix server.  Under DOS, if I try
> to cd to it, it gives an error message "UNC paths are not
> supported".  I find that I can sense it OK with findfirst(), and
> I can do what I want, but I have a performance problem.

The slowest thing is the external network link, so you needn't
worry about the actual copying speed.  Thus use a simple mechanism
(untested):

int fcopy(FILE *ffrom, FILE *fto) {
   int ch;

   while (EOF != (ch = getc(ffrom)) putc(ch);
   return ch;
}

Now you can isolate the file opening in a controlling routine:

void pathcopy(char *infile, char *outfile) {
   FILE *ffrom, *fto;

   if (ffrom = fopen(infile, "r") {
      if (fto = fopen(outfile, "w") fcopy(ffrom, fto); /* work */
      else  /* some error message about outfile */;
   }
   else {
      /* some error message about infile */
      fto = null;
   }
   if (ffrom) fclose(ffrom);
   if (fto)   
      if (fclose(fto)) /* error message on fclose */;
}

All totally untested code.  No buffers needed.  The file system
does all necessary buffering automatically.  The only thing needed
is the ability to describe the file paths.

-- 
 Chuck F (cbfalconer at maineline dot net)
   Available for consulting/temporary embedded and systems.
   <http://cbfalconer.home.att.net>



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