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strcpy whacking; ci.c and expand.c need more work

/*	$OpenBSD: path.c,v 1.4 1997/09/16 11:01:15 deraadt Exp $	*/

/*
 * Copyright (c) 1991 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator   or   Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the rights
 * to redistribute these changes.
 */
/*  path  --  break filename into directory and file
 *
 *  path (filename,direc,file,filen);
 *  char *filename,*direc,*file;
 *  int filen;
 *  filename is input; direc and file are output (user-supplied).
 *  file will not have any trailing /; direc might.
 *  filen is the length of the file buffer.
 *  Note these rules:
 *  1.  trailing / are ignored (except as first character)
 *  2.  x/y is x;y where y contains no / (x may contain /)
 *  3.  /y  is /;y where y contains no /
 *  4.  y   is .;y where y contains no /
 *  5.      is .;. (null filename)
 *  6.  /   is /;. (the root directory)
 *
 * Algorithm is this:
 *  1.  delete trailing / except in first position
 *  2.  if any /, find last one; change to null; y++
 *      else y = x;		(x is direc; y is file)
 *  3.  if y is null, y = .
 *  4.  if x equals y, x = .
 *      else if x is null, x = /
 *
 *  HISTORY
 * 20-Nov-79  Steven Shafer (sas) at Carnegie-Mellon University
 *	Copied verbatim from PDP-11.  Still as messy as ever.
 *	Some people have asked for a modification (I think that's a better
 *	idea than a new routine) which will change the directory name
 *	into an absolute pathname if it isn't one already.  The change
 *	involves doing a getwd() and prepending that if appropriate, with
 *	a "/" in between that and the directory part of the path.
 *	If you want to be cute, you can also resolve ".."s at that time.
 *
 */
#include "supcdefs.h"
#include "supextern.h"

void
path (original,direc,file, filen)
char *original,*direc,*file;
int filen;
{
	register char *y;
	/* x is direc */
	register char *p;

	/* copy and note the end */
	p = original;
	y = direc;
	while ((*y++ = *p++) != '\0') ;		/* copy string */
	/* y now points to first char after null */
	--y;	/* y now points to null */
	--y;	/* y now points to last char of string before null */

	/* chop off trailing / except as first character */
	while (y>direc && *y == '/') --y;	/* backpedal past / */
	/* y now points to char before first trailing / or null */
	*(++y) = 0;				/* chop off end of string */
	/* y now points to null */

	/* find last /, if any.  If found, change to null and bump y */
	while (y>direc && *y != '/') --y;
	/* y now points to / or direc.  Note *direc may be / */
	if (*y == '/') {
		*y++ = 0;
	}

	/* find file name part */
	if (*y)  strncpy (file,y, filen-1);
	else     strncpy (file,".", filen-1);
	file[filen-1] = '\0';

	/* find directory part */
	if (direc == y)        strcpy (direc,".");
	else if (*direc == 0)  strcpy (direc,"/");
	/* else direc already has proper value */
}