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/* File IO for GNU Emacs.
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   Copyright (C) 1985,86,87,88,93,94,95,96 Free Software Foundation, Inc.
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This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */
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#include <config.h>
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#include <sys/types.h>
#include <sys/stat.h>
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#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

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#if !defined (S_ISLNK) && defined (S_IFLNK)
#  define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
#endif

#if !defined (S_ISREG) && defined (S_IFREG)
#  define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
#endif

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#ifdef VMS
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#include "vms-pwd.h"
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#else
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#include <pwd.h>
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#endif

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#ifdef MSDOS
#include "msdos.h"
#include <sys/param.h>
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#if __DJGPP__ >= 2
#include <fcntl.h>
#include <string.h>
#endif
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#endif

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#include <ctype.h>
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#ifdef VMS
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#include "vmsdir.h"
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#include <perror.h>
#include <stddef.h>
#include <string.h>
#endif

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#include <errno.h>

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#ifndef vax11c
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extern int errno;
#endif

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extern char *strerror ();
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#ifdef APOLLO
#include <sys/time.h>
#endif

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#ifndef USG
#ifndef VMS
#ifndef BSD4_1
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#ifndef WINDOWSNT
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#define HAVE_FSYNC
#endif
#endif
#endif
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#endif
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#include "lisp.h"
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#include "intervals.h"
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#include "buffer.h"
#include "window.h"

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#ifdef WINDOWSNT
#define NOMINMAX 1
#include <windows.h>
#include <stdlib.h>
#include <fcntl.h>
#endif /* not WINDOWSNT */

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#ifdef DOS_NT
#define CORRECT_DIR_SEPS(s) \
  do { if ('/' == DIRECTORY_SEP) dostounix_filename (s); \
       else unixtodos_filename (s); \
  } while (0)
/* On Windows, drive letters must be alphabetic - on DOS, the Netware
   redirector allows the six letters between 'Z' and 'a' as well. */
#ifdef MSDOS
#define IS_DRIVE(x) ((x) >= 'A' && (x) <= 'z')
#endif
#ifdef WINDOWSNT
#define IS_DRIVE(x) isalpha (x)
#endif
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/* Need to lower-case the drive letter, or else expanded
   filenames will sometimes compare inequal, because
   `expand-file-name' doesn't always down-case the drive letter.  */
#define DRIVE_LETTER(x) (tolower (x))
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#endif

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#ifdef VMS
#include <file.h>
#include <rmsdef.h>
#include <fab.h>
#include <nam.h>
#endif

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#include "systime.h"
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#ifdef HPUX
#include <netio.h>
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#ifndef HPUX8
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#ifndef HPUX9
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#include <errnet.h>
#endif
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#endif
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#endif
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#ifndef O_WRONLY
#define O_WRONLY 1
#endif

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#ifndef O_RDONLY
#define O_RDONLY 0
#endif

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#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

/* Nonzero during writing of auto-save files */
int auto_saving;

/* Set by auto_save_1 to mode of original file so Fwrite_region will create
   a new file with the same mode as the original */
int auto_save_mode_bits;

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/* Alist of elements (REGEXP . HANDLER) for file names
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   whose I/O is done with a special handler.  */
Lisp_Object Vfile_name_handler_alist;

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/* Format for auto-save files */
Lisp_Object Vauto_save_file_format;

/* Lisp functions for translating file formats */
Lisp_Object Qformat_decode, Qformat_annotate_function;

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/* Functions to be called to process text properties in inserted file.  */
Lisp_Object Vafter_insert_file_functions;

/* Functions to be called to create text property annotations for file.  */
Lisp_Object Vwrite_region_annotate_functions;

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/* During build_annotations, each time an annotation function is called,
   this holds the annotations made by the previous functions.  */
Lisp_Object Vwrite_region_annotations_so_far;

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/* File name in which we write a list of all our auto save files.  */
Lisp_Object Vauto_save_list_file_name;

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/* Nonzero means, when reading a filename in the minibuffer,
 start out by inserting the default directory into the minibuffer. */
int insert_default_directory;

/* On VMS, nonzero means write new files with record format stmlf.
   Zero means use var format.  */
int vms_stmlf_recfm;

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/* On NT, specifies the directory separator character, used (eg.) when
   expanding file names.  This can be bound to / or \. */
Lisp_Object Vdirectory_sep_char;

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extern Lisp_Object Vuser_login_name;

extern int minibuf_level;

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/* These variables describe handlers that have "already" had a chance
   to handle the current operation.

   Vinhibit_file_name_handlers is a list of file name handlers.
   Vinhibit_file_name_operation is the operation being handled.
   If we try to handle that operation, we ignore those handlers.  */

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static Lisp_Object Vinhibit_file_name_handlers;
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static Lisp_Object Vinhibit_file_name_operation;
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Lisp_Object Qfile_error, Qfile_already_exists;

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Lisp_Object Qfile_name_history;

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Lisp_Object Qcar_less_than_car;

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report_file_error (string, data)
     char *string;
     Lisp_Object data;
{
  Lisp_Object errstring;

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  errstring = build_string (strerror (errno));
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  /* System error messages are capitalized.  Downcase the initial
     unless it is followed by a slash.  */
  if (XSTRING (errstring)->data[1] != '/')
    XSTRING (errstring)->data[0] = DOWNCASE (XSTRING (errstring)->data[0]);

  while (1)
    Fsignal (Qfile_error,
	     Fcons (build_string (string), Fcons (errstring, data)));
}
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close_file_unwind (fd)
     Lisp_Object fd;
{
  close (XFASTINT (fd));
}
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/* Restore point, having saved it as a marker.  */

restore_point_unwind (location)
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     Lisp_Object location;
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{
  SET_PT (marker_position (location));
  Fset_marker (location, Qnil, Qnil);
}
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Lisp_Object Qexpand_file_name;
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Lisp_Object Qsubstitute_in_file_name;
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Lisp_Object Qdirectory_file_name;
Lisp_Object Qfile_name_directory;
Lisp_Object Qfile_name_nondirectory;
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Lisp_Object Qunhandled_file_name_directory;
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Lisp_Object Qfile_name_as_directory;
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Lisp_Object Qcopy_file;
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Lisp_Object Qmake_directory_internal;
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Lisp_Object Qdelete_directory;
Lisp_Object Qdelete_file;
Lisp_Object Qrename_file;
Lisp_Object Qadd_name_to_file;
Lisp_Object Qmake_symbolic_link;
Lisp_Object Qfile_exists_p;
Lisp_Object Qfile_executable_p;
Lisp_Object Qfile_readable_p;
Lisp_Object Qfile_writable_p;
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Lisp_Object Qfile_symlink_p;
Lisp_Object Qaccess_file;
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Lisp_Object Qfile_directory_p;
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Lisp_Object Qfile_regular_p;
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Lisp_Object Qfile_accessible_directory_p;
Lisp_Object Qfile_modes;
Lisp_Object Qset_file_modes;
Lisp_Object Qfile_newer_than_file_p;
Lisp_Object Qinsert_file_contents;
Lisp_Object Qwrite_region;
Lisp_Object Qverify_visited_file_modtime;
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Lisp_Object Qset_visited_file_modtime;
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DEFUN ("find-file-name-handler", Ffind_file_name_handler, Sfind_file_name_handler, 2, 2, 0,
  "Return FILENAME's handler function for OPERATION, if it has one.\n\
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Otherwise, return nil.\n\
A file name is handled if one of the regular expressions in\n\
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`file-name-handler-alist' matches it.\n\n\
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If OPERATION equals `inhibit-file-name-operation', then we ignore\n\
any handlers that are members of `inhibit-file-name-handlers',\n\
but we still do run any other handlers.  This lets handlers\n\
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use the standard functions without calling themselves recursively.")
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  (filename, operation)
    Lisp_Object filename, operation;
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{
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  /* This function must not munge the match data.  */
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  Lisp_Object chain, inhibited_handlers;
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  CHECK_STRING (filename, 0);

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  if (EQ (operation, Vinhibit_file_name_operation))
    inhibited_handlers = Vinhibit_file_name_handlers;
  else
    inhibited_handlers = Qnil;
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  for (chain = Vfile_name_handler_alist; CONSP (chain);
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       chain = XCONS (chain)->cdr)
    {
      Lisp_Object elt;
      elt = XCONS (chain)->car;
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      if (CONSP (elt))
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	{
	  Lisp_Object string;
	  string = XCONS (elt)->car;
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	  if (STRINGP (string) && fast_string_match (string, filename) >= 0)
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	    {
	      Lisp_Object handler, tem;

	      handler = XCONS (elt)->cdr;
	      tem = Fmemq (handler, inhibited_handlers);
	      if (NILP (tem))
		return handler;
	    }
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	}
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      QUIT;
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    }
  return Qnil;
}

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DEFUN ("file-name-directory", Ffile_name_directory, Sfile_name_directory,
  1, 1, 0,
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  "Return the directory component in file name FILENAME.\n\
Return nil if FILENAME does not include a directory.\n\
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Otherwise return a directory spec.\n\
Given a Unix syntax file name, returns a string ending in slash;\n\
on VMS, perhaps instead a string ending in `:', `]' or `>'.")
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  (filename)
     Lisp_Object filename;
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{
  register unsigned char *beg;
  register unsigned char *p;
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  Lisp_Object handler;
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  CHECK_STRING (filename, 0);
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  /* If the file name has special constructs in it,
     call the corresponding file handler.  */
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  handler = Ffind_file_name_handler (filename, Qfile_name_directory);
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  if (!NILP (handler))
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    return call2 (handler, Qfile_name_directory, filename);
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#ifdef FILE_SYSTEM_CASE
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  filename = FILE_SYSTEM_CASE (filename);
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#endif
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  beg = XSTRING (filename)->data;
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#ifdef DOS_NT
  beg = strcpy (alloca (strlen (beg) + 1), beg);
#endif
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  p = beg + XSTRING (filename)->size;
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  while (p != beg && !IS_DIRECTORY_SEP (p[-1])
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#ifdef VMS
	 && p[-1] != ':' && p[-1] != ']' && p[-1] != '>'
#endif /* VMS */
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#ifdef DOS_NT
	 /* only recognise drive specifier at beginning */
	 && !(p[-1] == ':' && p == beg + 2)
#endif
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	 ) p--;

  if (p == beg)
    return Qnil;
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#ifdef DOS_NT
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  /* Expansion of "c:" to drive and default directory.  */
  if (p == beg + 2 && beg[1] == ':')
    {
      /* MAXPATHLEN+1 is guaranteed to be enough space for getdefdir.  */
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      unsigned char *res = alloca (MAXPATHLEN + 1);
      if (getdefdir (toupper (*beg) - 'A' + 1, res))
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	{
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	  if (!IS_DIRECTORY_SEP (res[strlen (res) - 1]))
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	    strcat (res, "/");
	  beg = res;
	  p = beg + strlen (beg);
	}
    }
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  CORRECT_DIR_SEPS (beg);
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#endif /* DOS_NT */
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  return make_string (beg, p - beg);
}

DEFUN ("file-name-nondirectory", Ffile_name_nondirectory, Sfile_name_nondirectory,
  1, 1, 0,
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  "Return file name FILENAME sans its directory.\n\
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For example, in a Unix-syntax file name,\n\
this is everything after the last slash,\n\
or the entire name if it contains no slash.")
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  (filename)
     Lisp_Object filename;
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{
  register unsigned char *beg, *p, *end;
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  Lisp_Object handler;
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  CHECK_STRING (filename, 0);
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  /* If the file name has special constructs in it,
     call the corresponding file handler.  */
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  handler = Ffind_file_name_handler (filename, Qfile_name_nondirectory);
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  if (!NILP (handler))
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    return call2 (handler, Qfile_name_nondirectory, filename);
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  beg = XSTRING (filename)->data;
  end = p = beg + XSTRING (filename)->size;
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  while (p != beg && !IS_DIRECTORY_SEP (p[-1])
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#ifdef VMS
	 && p[-1] != ':' && p[-1] != ']' && p[-1] != '>'
#endif /* VMS */
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#ifdef DOS_NT
	 /* only recognise drive specifier at beginning */
	 && !(p[-1] == ':' && p == beg + 2)
#endif
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	 ) p--;

  return make_string (p, end - p);
}
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DEFUN ("unhandled-file-name-directory", Funhandled_file_name_directory, Sunhandled_file_name_directory, 1, 1, 0,
  "Return a directly usable directory name somehow associated with FILENAME.\n\
A `directly usable' directory name is one that may be used without the\n\
intervention of any file handler.\n\
If FILENAME is a directly usable file itself, return\n\
(file-name-directory FILENAME).\n\
The `call-process' and `start-process' functions use this function to\n\
get a current directory to run processes in.")
  (filename)
    Lisp_Object filename;
{
  Lisp_Object handler;

  /* If the file name has special constructs in it,
     call the corresponding file handler.  */
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  handler = Ffind_file_name_handler (filename, Qunhandled_file_name_directory);
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  if (!NILP (handler))
    return call2 (handler, Qunhandled_file_name_directory, filename);

  return Ffile_name_directory (filename);
}

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char *
file_name_as_directory (out, in)
     char *out, *in;
{
  int size = strlen (in) - 1;

  strcpy (out, in);

#ifdef VMS
  /* Is it already a directory string? */
  if (in[size] == ':' || in[size] == ']' || in[size] == '>')
    return out;
  /* Is it a VMS directory file name?  If so, hack VMS syntax.  */
  else if (! index (in, '/')
	   && ((size > 3 && ! strcmp (&in[size - 3], ".DIR"))
	       || (size > 3 && ! strcmp (&in[size - 3], ".dir"))
	       || (size > 5 && (! strncmp (&in[size - 5], ".DIR", 4)
				|| ! strncmp (&in[size - 5], ".dir", 4))
		   && (in[size - 1] == '.' || in[size - 1] == ';')
		   && in[size] == '1')))
    {
      register char *p, *dot;
      char brack;

      /* x.dir -> [.x]
	 dir:x.dir --> dir:[x]
	 dir:[x]y.dir --> dir:[x.y] */
      p = in + size;
      while (p != in && *p != ':' && *p != '>' && *p != ']') p--;
      if (p != in)
	{
	  strncpy (out, in, p - in);
	  out[p - in] = '\0';
	  if (*p == ':')
	    {
	      brack = ']';
	      strcat (out, ":[");
	    }
	  else
	    {
	      brack = *p;
	      strcat (out, ".");
	    }
	  p++;
	}
      else
	{
	  brack = ']';
	  strcpy (out, "[.");
	}
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      dot = index (p, '.');
      if (dot)
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	{
	  /* blindly remove any extension */
	  size = strlen (out) + (dot - p);
	  strncat (out, p, dot - p);
	}
      else
	{
	  strcat (out, p);
	  size = strlen (out);
	}
      out[size++] = brack;
      out[size] = '\0';
    }
#else /* not VMS */
  /* For Unix syntax, Append a slash if necessary */
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  if (!IS_DIRECTORY_SEP (out[size]))
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    {
      out[size + 1] = DIRECTORY_SEP;
      out[size + 2] = '\0';
    }
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#ifdef DOS_NT
  CORRECT_DIR_SEPS (out);
#endif
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#endif /* not VMS */
  return out;
}

DEFUN ("file-name-as-directory", Ffile_name_as_directory,
       Sfile_name_as_directory, 1, 1, 0,
  "Return a string representing file FILENAME interpreted as a directory.\n\
This operation exists because a directory is also a file, but its name as\n\
a directory is different from its name as a file.\n\
The result can be used as the value of `default-directory'\n\
or passed as second argument to `expand-file-name'.\n\
For a Unix-syntax file name, just appends a slash.\n\
On VMS, converts \"[X]FOO.DIR\" to \"[X.FOO]\", etc.")
  (file)
     Lisp_Object file;
{
  char *buf;
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  Lisp_Object handler;
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  CHECK_STRING (file, 0);
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  if (NILP (file))
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    return Qnil;
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  /* If the file name has special constructs in it,
     call the corresponding file handler.  */
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  handler = Ffind_file_name_handler (file, Qfile_name_as_directory);
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  if (!NILP (handler))
    return call2 (handler, Qfile_name_as_directory, file);

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  buf = (char *) alloca (XSTRING (file)->size + 10);
  return build_string (file_name_as_directory (buf, XSTRING (file)->data));
}

/*
 * Convert from directory name to filename.
 * On VMS:
 *       xyzzy:[mukesh.emacs] => xyzzy:[mukesh]emacs.dir.1
 *       xyzzy:[mukesh] => xyzzy:[000000]mukesh.dir.1
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 * On UNIX, it's simple: just make sure there isn't a terminating /
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 * Value is nonzero if the string output is different from the input.
 */

directory_file_name (src, dst)
     char *src, *dst;
{
  long slen;
#ifdef VMS
  long rlen;
  char * ptr, * rptr;
  char bracket;
  struct FAB fab = cc$rms_fab;
  struct NAM nam = cc$rms_nam;
  char esa[NAM$C_MAXRSS];
#endif /* VMS */

  slen = strlen (src);
#ifdef VMS
  if (! index (src, '/')
      && (src[slen - 1] == ']'
	  || src[slen - 1] == ':'
	  || src[slen - 1] == '>'))
    {
      /* VMS style - convert [x.y.z] to [x.y]z, [x] to [000000]x */
      fab.fab$l_fna = src;
      fab.fab$b_fns = slen;
      fab.fab$l_nam = &nam;
      fab.fab$l_fop = FAB$M_NAM;

      nam.nam$l_esa = esa;
      nam.nam$b_ess = sizeof esa;
      nam.nam$b_nop |= NAM$M_SYNCHK;

      /* We call SYS$PARSE to handle such things as [--] for us. */
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      if (SYS$PARSE (&fab, 0, 0) == RMS$_NORMAL)
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	{
	  slen = nam.nam$b_esl;
	  if (esa[slen - 1] == ';' && esa[slen - 2] == '.')
	    slen -= 2;
	  esa[slen] = '\0';
	  src = esa;
	}
      if (src[slen - 1] != ']' && src[slen - 1] != '>')
	{
	  /* what about when we have logical_name:???? */
	  if (src[slen - 1] == ':')
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	    {                   /* Xlate logical name and see what we get */
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	      ptr = strcpy (dst, src); /* upper case for getenv */
	      while (*ptr)
		{
		  if ('a' <= *ptr && *ptr <= 'z')
		    *ptr -= 040;
		  ptr++;
		}
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	      dst[slen - 1] = 0;        /* remove colon */
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	      if (!(src = egetenv (dst)))
		return 0;
	      /* should we jump to the beginning of this procedure?
		 Good points: allows us to use logical names that xlate
		 to Unix names,
		 Bad points: can be a problem if we just translated to a device
		 name...
		 For now, I'll punt and always expect VMS names, and hope for
		 the best! */
	      slen = strlen (src);
	      if (src[slen - 1] != ']' && src[slen - 1] != '>')
		{ /* no recursion here! */
		  strcpy (dst, src);
		  return 0;
		}
	    }
	  else
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	    {           /* not a directory spec */
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	      strcpy (dst, src);
	      return 0;
	    }
	}
      bracket = src[slen - 1];

      /* If bracket is ']' or '>', bracket - 2 is the corresponding
	 opening bracket.  */
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      ptr = index (src, bracket - 2);
      if (ptr == 0)
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	{ /* no opening bracket */
	  strcpy (dst, src);
	  return 0;
	}
      if (!(rptr = rindex (src, '.')))
	rptr = ptr;
      slen = rptr - src;
      strncpy (dst, src, slen);
      dst[slen] = '\0';
      if (*rptr == '.')
	{
	  dst[slen++] = bracket;
	  dst[slen] = '\0';
	}
      else
	{
	  /* If we have the top-level of a rooted directory (i.e. xx:[000000]),
	     then translate the device and recurse. */
	  if (dst[slen - 1] == ':'
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	      && dst[slen - 2] != ':'   /* skip decnet nodes */
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	      && strcmp (src + slen, "[000000]") == 0)
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	    {
	      dst[slen - 1] = '\0';
	      if ((ptr = egetenv (dst))
		  && (rlen = strlen (ptr) - 1) > 0
		  && (ptr[rlen] == ']' || ptr[rlen] == '>')
		  && ptr[rlen - 1] == '.')
		{
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		  char * buf = (char *) alloca (strlen (ptr) + 1);
		  strcpy (buf, ptr);
		  buf[rlen - 1] = ']';
		  buf[rlen] = '\0';
		  return directory_file_name (buf, dst);
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		}
	      else
		dst[slen - 1] = ':';
	    }
	  strcat (dst, "[000000]");
	  slen += 8;
	}
      rptr++;
      rlen = strlen (rptr) - 1;
      strncat (dst, rptr, rlen);
      dst[slen + rlen] = '\0';
      strcat (dst, ".DIR.1");
      return 1;
    }
#endif /* VMS */
  /* Process as Unix format: just remove any final slash.
     But leave "/" unchanged; do not change it to "".  */
  strcpy (dst, src);
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#ifdef APOLLO
  /* Handle // as root for apollo's.  */
  if ((slen > 2 && dst[slen - 1] == '/')
      || (slen > 1 && dst[0] != '/' && dst[slen - 1] == '/'))
    dst[slen - 1] = 0;
#else
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  if (slen > 1
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      && IS_DIRECTORY_SEP (dst[slen - 1])
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#ifdef DOS_NT
      && !IS_ANY_SEP (dst[slen - 2])
#endif
      )
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    dst[slen - 1] = 0;
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#endif
#ifdef DOS_NT
  CORRECT_DIR_SEPS (dst);
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#endif
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  return 1;
}

DEFUN ("directory-file-name", Fdirectory_file_name, Sdirectory_file_name,
  1, 1, 0,
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  "Returns the file name of the directory named DIRECTORY.\n\
This is the name of the file that holds the data for the directory DIRECTORY.\n\
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This operation exists because a directory is also a file, but its name as\n\
a directory is different from its name as a file.\n\
In Unix-syntax, this function just removes the final slash.\n\
On VMS, given a VMS-syntax directory name such as \"[X.Y]\",\n\
it returns a file name such as \"[X]Y.DIR.1\".")
  (directory)
     Lisp_Object directory;
{
  char *buf;
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  Lisp_Object handler;
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  CHECK_STRING (directory, 0);

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  if (NILP (directory))
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    return Qnil;
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  /* If the file name has special constructs in it,
     call the corresponding file handler.  */
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  handler = Ffind_file_name_handler (directory, Qdirectory_file_name);
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  if (!NILP (handler))
    return call2 (handler, Qdirectory_file_name, directory);

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#ifdef VMS
  /* 20 extra chars is insufficient for VMS, since we might perform a
     logical name translation. an equivalence string can be up to 255
     chars long, so grab that much extra space...  - sss */
  buf = (char *) alloca (XSTRING (directory)->size + 20 + 255);
#else
  buf = (char *) alloca (XSTRING (directory)->size + 20);
#endif
  directory_file_name (XSTRING (directory)->data, buf);
  return build_string (buf);
}

DEFUN ("make-temp-name", Fmake_temp_name, Smake_temp_name, 1, 1, 0,
  "Generate temporary file name (string) starting with PREFIX (a string).\n\
The Emacs process number forms part of the result,\n\
so there is no danger of generating a name being used by another process.")
  (prefix)
     Lisp_Object prefix;
{
  Lisp_Object val;
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#ifdef MSDOS
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  /* Don't use too many characters of the restricted 8+3 DOS
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     filename space.  */
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  val = concat2 (prefix, build_string ("a.XXX"));
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#else
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  val = concat2 (prefix, build_string ("XXXXXX"));
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#endif
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  mktemp (XSTRING (val)->data);
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#ifdef DOS_NT
  CORRECT_DIR_SEPS (XSTRING (val)->data);
#endif
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  return val;
}

DEFUN ("expand-file-name", Fexpand_file_name, Sexpand_file_name, 1, 2, 0,
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  "Convert filename NAME to absolute, and canonicalize it.\n\
Second arg DEFAULT-DIRECTORY is directory to start with if NAME is relative\n\
 (does not start with slash); if DEFAULT-DIRECTORY is nil or missing,\n\
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the current buffer's value of default-directory is used.\n\
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File name components that are `.' are removed, and \n\
so are file name components followed by `..', along with the `..' itself;\n\
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note that these simplifications are done without checking the resulting\n\
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file names in the file system.\n\
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An initial `~/' expands to your home directory.\n\
An initial `~USER/' expands to USER's home directory.\n\
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See also the function `substitute-in-file-name'.")
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     (name, default_directory)
     Lisp_Object name, default_directory;
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{
  unsigned char *nm;
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  register unsigned char *newdir, *p, *o;
  int tlen;
  unsigned char *target;
  struct passwd *pw;
#ifdef VMS
  unsigned char * colon = 0;
  unsigned char * close = 0;
  unsigned char * slash = 0;
  unsigned char * brack = 0;
  int lbrack = 0, rbrack = 0;
  int dots = 0;
#endif /* VMS */
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#ifdef DOS_NT
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  int drive = 0;
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  int collapse_newdir = 1;
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#endif /* DOS_NT */
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  int length;
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  Lisp_Object handler;
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  CHECK_STRING (name, 0);

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  /* If the file name has special constructs in it,
     call the corresponding file handler.  */
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  handler = Ffind_file_name_handler (name, Qexpand_file_name);
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  if (!NILP (handler))
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    return call3 (handler, Qexpand_file_name, name, default_directory);
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  /* Use the buffer's default-directory if DEFAULT_DIRECTORY is omitted.  */
  if (NILP (default_directory))
    default_directory = current_buffer->directory;
  CHECK_STRING (default_directory, 1);
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  if (!NILP (default_directory))
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    {
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      handler = Ffind_file_name_handler (default_directory, Qexpand_file_name);
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      if (!NILP (handler))
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	return call3 (handler, Qexpand_file_name, name, default_directory);
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    }
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  o = XSTRING (default_directory)->data;
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  /* Make sure DEFAULT_DIRECTORY is properly expanded.
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     It would be better to do this down below where we actually use
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     default_directory.  Unfortunately, calling Fexpand_file_name recursively
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     could invoke GC, and the strings might be relocated.  This would
     be annoying because we have pointers into strings lying around
     that would need adjusting, and people would add new pointers to
     the code and forget to adjust them, resulting in intermittent bugs.
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     Putting this call here avoids all that crud.

     The EQ test avoids infinite recursion.  */
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  if (! NILP (default_directory) && !EQ (default_directory, name)
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      /* Save time in some common cases - as long as default_directory
	 is not relative, it can be canonicalized with name below (if it
	 is needed at all) without requiring it to be expanded now.  */
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#ifdef DOS_NT
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      /* Detect MSDOS file names with drive specifiers.  */
      && ! (IS_DRIVE (o[0]) && (IS_DEVICE_SEP (o[1]) && IS_DIRECTORY_SEP (o[2])))
#ifdef WINDOWSNT
      /* Detect Windows file names in UNC format.  */
      && ! (IS_DIRECTORY_SEP (o[0]) && IS_DIRECTORY_SEP (o[1]))
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#endif
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#else /* not DOS_NT */
      /* Detect Unix absolute file names (/... alone is not absolute on
	 DOS or Windows).  */
      && ! (IS_DIRECTORY_SEP (o[0]))
#endif /* not DOS_NT */
      )
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    {
      struct gcpro gcpro1;

      GCPRO1 (name);
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      default_directory = Fexpand_file_name (default_directory, Qnil);
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      UNGCPRO;
    }

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#ifdef VMS
  /* Filenames on VMS are always upper case.  */
  name = Fupcase (name);
#endif
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#ifdef FILE_SYSTEM_CASE
  name = FILE_SYSTEM_CASE (name);
#endif
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  nm = XSTRING (name)->data;
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#ifdef DOS_NT
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  /* We will force directory separators to be either all \ or /, so make
     a local copy to modify, even if there ends up being no change. */
  nm = strcpy (alloca (strlen (nm) + 1), nm);

  /* Find and remove drive specifier if present; this makes nm absolute
     even if the rest of the name appears to be relative. */
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  {
    unsigned char *colon = rindex (nm, ':');
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    if (colon)
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      /* Only recognize colon as part of drive specifier if there is a
	 single alphabetic character preceeding the colon (and if the
	 character before the drive letter, if present, is a directory
	 separator); this is to support the remote system syntax used by
	 ange-ftp, and the "po:username" syntax for POP mailboxes. */
    look_again:
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      if (nm == colon)
	nm++;
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      else if (IS_DRIVE (colon[-1])
	       && (colon == nm + 1 || IS_DIRECTORY_SEP (colon[-2])))
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	{
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	  drive = colon[-1];
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	  nm = colon + 1;
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	}
      else
	{
	  while (--colon >= nm)
	    if (colon[0] == ':')
	      goto look_again;
	}
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  }
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#endif /* DOS_NT */
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#ifdef WINDOWSNT
  /* Discard any previous drive specifier if nm is now in UNC format. */
  if (IS_DIRECTORY_SEP (nm[0]) && IS_DIRECTORY_SEP (nm[1]))
    {
      drive = 0;
    }
#endif

  /* If nm is absolute, look for /./ or /../ sequences; if none are
     found, we can probably return right away.  We will avoid allocating
     a new string if name is already fully expanded.  */
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  if (
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      IS_DIRECTORY_SEP (nm[0])
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#ifdef MSDOS
      && drive
#endif
#ifdef WINDOWSNT
      && (drive || IS_DIRECTORY_SEP (nm[1]))
#endif
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#ifdef VMS
      || index (nm, ':')
#endif /* VMS */
      )
    {
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      /* If it turns out that the filename we want to return is just a
	 suffix of FILENAME, we don't need to go through and edit
	 things; we just need to construct a new string using data
	 starting at the middle of FILENAME.  If we set lose to a
	 non-zero value, that means we've discovered that we can't do
	 that cool trick.  */
      int lose = 0;

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      p = nm;
      while (*p)
	{
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	  /* Since we know the name is absolute, we can assume that each
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	     element starts with a "/".  */

	  /* "." and ".." are hairy.  */
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	  if (IS_DIRECTORY_SEP (p[0])
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	      && p[1] == '.'
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	      && (IS_DIRECTORY_SEP (p[2])
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		  || p[2] == 0
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		  || (p[2] == '.' && (IS_DIRECTORY_SEP (p[3])
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				      || p[3] == 0))))
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	    lose = 1;
#ifdef VMS
	  if (p[0] == '\\')
	    lose = 1;
	  if (p[0] == '/') {
	    /* if dev:[dir]/, move nm to / */
	    if (!slash && p > nm && (brack || colon)) {
	      nm = (brack ? brack + 1 : colon + 1);
	      lbrack = rbrack = 0;
	      brack = 0;
	      colon = 0;
	    }
	    slash = p;
	  }
	  if (p[0] == '-')
#ifndef VMS4_4
	    /* VMS pre V4.4,convert '-'s in filenames. */
	    if (lbrack == rbrack)
	      {
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		if (dots < 2)   /* this is to allow negative version numbers */
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		  p[0] = '_';
	      }
	    else
#endif /* VMS4_4 */
	      if (lbrack > rbrack &&
		  ((p[-1] == '.' || p[-1] == '[' || p[-1] == '<') &&
		   (p[1] == '.' || p[1] == ']' || p[1] == '>')))
		lose = 1;
#ifndef VMS4_4
	      else
		p[0] = '_';
#endif /* VMS4_4 */
	  /* count open brackets, reset close bracket pointer */
	  if (p[0] == '[' || p[0] == '<')
	    lbrack++, brack = 0;
	  /* count close brackets, set close bracket pointer */
	  if (p[0] == ']' || p[0] == '>')
	    rbrack++, brack = p;
	  /* detect ][ or >< */
	  if ((p[0] == ']' || p[0] == '>') && (p[1] == '[' || p[1] == '<'))
	    lose = 1;
	  if ((p[0] == ':' || p[0] == ']' || p[0] == '>') && p[1] == '~')
	    nm = p + 1, lose = 1;
	  if (p[0] == ':' && (colon || slash))
	    /* if dev1:[dir]dev2:, move nm to dev2: */
	    if (brack)
	      {
		nm = brack + 1;
		brack = 0;
	      }
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	    /* if /name/dev:, move nm to dev: */
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	    else if (slash)
	      nm = slash + 1;
	    /* if node::dev:, move colon following dev */
	    else if (colon && colon[-1] == ':')
	      colon = p;
	    /* if dev1:dev2:, move nm to dev2: */
	    else if (colon && colon[-1] != ':')
	      {
		nm = colon + 1;
		colon = 0;
	      }
	  if (p[0] == ':' && !colon)
	    {
	      if (p[1] == ':')
		p++;
	      colon = p;
	    }
	  if (lbrack == rbrack)
	    if (p[0] == ';')
	      dots = 2;
	    else if (p[0] == '.')
	      dots++;
#endif /* VMS */
	  p++;
	}
      if (!lose)
	{
#ifdef VMS
	  if (index (nm, '/'))
	    return build_string (sys_translate_unix (nm));
#endif /* VMS */
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#ifdef DOS_NT
	  /* Make sure directories are all separated with / or \ as
	     desired, but avoid allocation of a new string when not
	     required. */
	  CORRECT_DIR_SEPS (nm);
#ifdef WINDOWSNT
	  if (IS_DIRECTORY_SEP (nm[1]))
	    {
	      if (strcmp (nm, XSTRING (name)->data) != 0)
		name = build_string (nm);
	    }
	  else
#endif
	  /* drive must be set, so this is okay */
	  if (strcmp (nm - 2, XSTRING (name)->data) != 0)
	    {
	      name = make_string (nm - 2, p - nm + 2);
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	      XSTRING (name)->data[0] = DRIVE_LETTER (drive);
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	      XSTRING (name)->data[1] = ':';
	    }
	  return name;
#else /* not DOS_NT */
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	  if (nm == XSTRING (name)->data)
	    return name;
	  return build_string (nm);
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#endif /* not DOS_NT */
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	}
    }

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  /* At this point, nm might or might not be an absolute file name.  We
     need to expand ~ or ~user if present, otherwise prefix nm with
     default_directory if nm is not absolute, and finally collapse /./
     and /foo/../ sequences.

     We set newdir to be the appropriate prefix if one is needed:
       - the relevant user directory if nm starts with ~ or ~user
       - the specified drive's working dir (DOS/NT only) if nm does not
         start with /
       - the value of default_directory.

     Note that these prefixes are not guaranteed to be absolute (except
     for the working dir of a drive).  Therefore, to ensure we always
     return an absolute name, if the final prefix is not absolute we
     append it to the current working directory.  */
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  newdir = 0;

  if (nm[0] == '~')		/* prefix ~ */
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    {
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      if (IS_DIRECTORY_SEP (nm[1])
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#ifdef VMS
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	  || nm[1] == ':'
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#endif /* VMS */
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	  || nm[1] == 0)	/* ~ by itself */
	{
	  if (!(newdir = (unsigned char *) egetenv ("HOME")))
	    newdir = (unsigned char *) "";
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	  nm++;
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#ifdef DOS_NT
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	  collapse_newdir = 0;
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#endif
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#ifdef VMS
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	  nm++;			/* Don't leave the slash in nm.  */
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#endif /* VMS */
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	}
      else			/* ~user/filename */
	{
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	  for (p = nm; *p && (!IS_DIRECTORY_SEP (*p)
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#ifdef VMS
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			      && *p != ':'
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#endif /* VMS */
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			      ); p++);
	  o = (unsigned char *) alloca (p - nm + 1);
	  bcopy ((char *) nm, o, p - nm);
	  o [p - nm] = 0;

	  pw = (struct passwd *) getpwnam (o + 1);
	  if (pw)
	    {
	      newdir = (unsigned char *) pw -> pw_dir;
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#ifdef VMS
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	      nm = p + 1;	/* skip the terminator */
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#else
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	      nm = p;
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#ifdef DOS_NT
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	      collapse_newdir = 0;
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#endif
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#endif /* VMS */
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	    }
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	  /* If we don't find a user of that name, leave the name
	     unchanged; don't move nm forward to p.  */
	}
    }
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#ifdef DOS_NT
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  /* On DOS and Windows, nm is absolute if a drive name was specified;
     use the drive's current directory as the prefix if needed.  */
  if (!newdir && drive)
    {
      /* Get default directory if needed to make nm absolute. */
      if (!IS_DIRECTORY_SEP (nm[0]))
	{
	  newdir = alloca (MAXPATHLEN + 1);
	  if (!getdefdir (toupper (drive) - 'A' + 1, newdir))
	    newdir = NULL;
	}
      if (!newdir)
	{
	  /* Either nm starts with /, or drive isn't mounted. */
	  newdir = alloca (4);
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	  newdir[0] = DRIVE_LETTER (drive);
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	  newdir[1] = ':';
	  newdir[2] = '/';
	  newdir[3] = 0;
	}
    }
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#endif /* DOS_NT */
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  /* Finally, if no prefix has been specified and nm is not absolute,
     then it must be expanded relative to default_directory. */

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  if (1
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#ifndef DOS_NT
      /* /... alone is not absolute on DOS and Windows. */
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      && !IS_DIRECTORY_SEP (nm[0])
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#endif
#ifdef WINDOWSNT
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      && !(IS_DIRECTORY_SEP (nm[0]) && IS_DIRECTORY_SEP (nm[1]))
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#endif
#ifdef VMS
      && !index (nm, ':')
#endif
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      && !newdir)
    {
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      newdir = XSTRING (default_directory)->data;
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    }

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#ifdef DOS_NT
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  if (newdir)
    {
      /* First ensure newdir is an absolute name. */
      if (
	  /* Detect MSDOS file names with drive specifiers.  */
	  ! (IS_DRIVE (newdir[0])
	     && IS_DEVICE_SEP (newdir[1]) && IS_DIRECTORY_SEP (newdir[2]))
#ifdef WINDOWSNT
	  /* Detect Windows file names in UNC format.  */
	  && ! (IS_DIRECTORY_SEP (newdir[0]) && IS_DIRECTORY_SEP (newdir[1]))
#endif
	  )
	{
	  /* Effectively, let newdir be (expand-file-name newdir cwd).
	     Because of the admonition against calling expand-file-name
	     when we have pointers into lisp strings, we accomplish this
	     indirectly by prepending newdir to nm if necessary, and using
	     cwd (or the wd of newdir's drive) as the new newdir. */

	  if (IS_DRIVE (newdir[0]) && newdir[1] == ':')
	    {
	      drive = newdir[0];
	      newdir += 2;
	    }
	  if (!IS_DIRECTORY_SEP (nm[0]))
	    {
	      char * tmp = alloca (strlen (newdir) + strlen (nm) + 2);
	      file_name_as_directory (tmp, newdir);
	      strcat (tmp, nm);
	      nm = tmp;
	    }
	  newdir = alloca (MAXPATHLEN + 1);
	  if (drive)
	    {
	      if (!getdefdir (toupper (drive) - 'A' + 1, newdir))
		newdir = "/";
	    }
	  else
	    getwd (newdir);
	}

      /* Strip off drive name from prefix, if present. */
      if (IS_DRIVE (newdir[0]) && newdir[1] == ':')
	{
	  drive = newdir[0];
	  newdir += 2;
	}

      /* Keep only a prefix from newdir if nm starts with slash
         (//server/share for UNC, nothing otherwise). */
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      if (IS_DIRECTORY_SEP (nm[0]) && collapse_newdir)
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