libgfortran/io/rewind.c

   1 /* Copyright (C) 2002-2003 Free Software Foundation, Inc.
   2    Contributed by Andy Vaught
   3
   4 This file is part of the GNU Fortran 95 runtime library (libgfortran).
   5
   6 Libgfortran is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 In addition to the permissions in the GNU General Public License, the
  12 Free Software Foundation gives you unlimited permission to link the
  13 compiled version of this file into combinations with other programs,
  14 and to distribute those combinations without any restriction coming
  15 from the use of this file.  (The General Public License restrictions
  16 do apply in other respects; for example, they cover modification of
  17 the file, and distribution when not linked into a combine
  18 executable.)
  19
  20 Libgfortran is distributed in the hope that it will be useful,
  21 but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23 GNU General Public License for more details.
  24
  25 You should have received a copy of the GNU General Public License
  26 along with Libgfortran; see the file COPYING.  If not, write to
  27 the Free Software Foundation, 59 Temple Place - Suite 330,
  28 Boston, MA 02111-1307, USA.  */
  29
  30 #include "config.h"
  31 #include "libgfortran.h"
  32 #include "io.h"
  33
  34 /* rewind.c--  Implement the rewind statement */
  35
  36 extern void st_rewind (void);
  37 export_proto(st_rewind);
  38
  39 void
  40 st_rewind (void)
  41 {
  42   gfc_unit *u;
  43
  44   library_start ();
  45
  46   u = find_unit (ioparm.unit);
  47   if (u != NULL)
  48     {
  49       if (u->flags.access != ACCESS_SEQUENTIAL)
  50         generate_error (ERROR_BAD_OPTION,
  51                         "Cannot REWIND a file opened for DIRECT access");
  52       else
  53         {
  54           /* If we have been writing to the file, the last written record
  55              is the last record in the file, so truncate the file now.
  56              Reset to read mode so two consecutive rewind statements
  57              don't delete the file contents.  */
  58           if (u->mode==WRITING)
  59             struncate(u->s);
  60           u->mode = READING;
  61           u->last_record = 0;
  62           if (sseek (u->s, 0) == FAILURE)
  63             generate_error (ERROR_OS, NULL);
  64
  65           u->endfile = NO_ENDFILE;
  66           u->current_record = 0;
  67           test_endfile (u);
  68         }
  69       /* update position for INQUIRE */
  70       u->flags.position = POSITION_REWIND;
  71     }
  72
  73   library_end ();
  74 }