78579b601d
2004-12-02 Bud Davis <bdavis9659@comcast.net>
PR libfortran/18284
* io/unix.c (fd_alloc_w_at): Update file_length when extending.
* io/backspace.c (formatted_backspace): Reset endfile after backspace.
PR fortran/18284
* gfortran.dg/backspace.f90
From-SVN: r91612
162 lines
3.7 KiB
C
162 lines
3.7 KiB
C
/* Copyright (C) 2002-2003 Free Software Foundation, Inc.
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Contributed by Andy Vaught
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This file is part of the GNU Fortran 95 runtime library (libgfortran).
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Libgfortran is free software; you can redistribute it and/or modify
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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.
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Libgfortran is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Libgfortran; see the file COPYING. If not, write to
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the Free Software Foundation, 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include "config.h"
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#include "libgfortran.h"
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#include "io.h"
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/* backspace.c -- Implement the BACKSPACE statement */
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/* formatted_backspace(void)-- Move the file back one line. The
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* current position is after the newline that terminates the previous
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* record, and we have to sift backwards to find the newline before
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* that or the start of the file, whichever comes first. */
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#define READ_CHUNK 4096
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static void
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formatted_backspace (void)
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{
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gfc_offset base;
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char *p;
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int n;
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base = file_position (current_unit->s) - 1;
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do
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{
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n = (base < READ_CHUNK) ? base : READ_CHUNK;
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base -= n;
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p = salloc_r_at (current_unit->s, &n, base);
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if (p == NULL)
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goto io_error;
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/* Because we've moved backwords from the current position, it
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* should not be possible to get a short read. Because it isn't
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* clear what to do about such thing, we ignore the possibility. */
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/* There is no memrchr() in the C library, so we have to do it
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* ourselves. */
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n--;
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while (n >= 0)
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{
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if (p[n] == '\n')
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{
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base += n + 1;
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goto done;
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}
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n--;
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}
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}
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while (base != 0);
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/* base is the new pointer. Seek to it exactly */
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done:
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if (sseek (current_unit->s, base) == FAILURE)
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goto io_error;
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current_unit->last_record--;
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current_unit->endfile = NO_ENDFILE;
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return;
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io_error:
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generate_error (ERROR_OS, NULL);
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}
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/* unformatted_backspace()-- Move the file backwards for an
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* unformatted sequential file. We are guaranteed to be between
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* records on entry and we have to shift to the previous record. */
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static void
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unformatted_backspace (void)
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{
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gfc_offset *p, new;
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int length;
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length = sizeof (gfc_offset);
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p = (gfc_offset *) salloc_r_at (current_unit->s, &length,
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file_position (current_unit->s) - length);
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if (p == NULL)
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goto io_error;
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new = file_position (current_unit->s) - *p - length;
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if (sseek (current_unit->s, new) == FAILURE)
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goto io_error;
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current_unit->last_record--;
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return;
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io_error:
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generate_error (ERROR_OS, NULL);
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}
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void
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st_backspace (void)
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{
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gfc_unit *u;
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library_start ();
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u = find_unit (ioparm.unit);
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if (u == NULL)
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{
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generate_error (ERROR_BAD_UNIT, NULL);
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goto done;
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}
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current_unit = u;
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/* Ignore direct access. Non-advancing I/O is only allowed for
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* formatted sequential I/O and the next direct access transfer
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* repositions the file anyway. */
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if (u->flags.access == ACCESS_DIRECT)
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goto done;
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/* Check for special cases involving the ENDFILE record first */
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if (u->endfile == AFTER_ENDFILE)
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u->endfile = AT_ENDFILE;
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else
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{
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if (u->current_record)
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next_record (1);
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if (file_position (u->s) == 0)
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goto done; /* Common special case */
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if (u->flags.form == FORM_FORMATTED)
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formatted_backspace ();
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else
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unformatted_backspace ();
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}
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done:
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library_end ();
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}
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