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/* Copyright (C) 2002-2003, 2005 Free Software Foundation, Inc.

   Contributed by Andy Vaught and Janne Blomqvist

This file is part of the GNU Fortran runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

In addition to the permissions in the GNU General Public License, the

Free Software Foundation gives you unlimited permission to link the

compiled version of this file into combinations with other programs,

and to distribute those combinations without any restriction coming

from the use of this file.  (The General Public License restrictions

do apply in other respects; for example, they cover modification of

the file, and distribution when not linked into a combine

executable.)

Libgfortran 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 Libgfortran; see the file COPYING.  If not, write to

the Free Software Foundation, 51 Franklin Street, Fifth Floor,

Boston, MA 02110-1301, USA.  */

#include "config.h"

#include <string.h>

#include "libgfortran.h"

#include "io.h"

/* file_pos.c-- Implement the file positioning statements, i.e. BACKSPACE,

   ENDFILE, and REWIND as well as the FLUSH statement.  */

/* formatted_backspace(fpp, u)-- Move the file back one line.  The

   current position is after the newline that terminates the previous

   record, and we have to sift backwards to find the newline before

   that or the start of the file, whichever comes first.  */

#define READ_CHUNK 4096

static void

formatted_backspace (st_parameter_filepos *fpp, gfc_unit *u)

{

  gfc_offset base;

  char *p;

  int n;

  base = file_position (u->s) - 1;

  do

    {

      n = (base < READ_CHUNK) ? base : READ_CHUNK;

      base -= n;

      p = salloc_r_at (u->s, &n, base);

      if (p == NULL)

        goto io_error;

      /* We have moved backwards from the current position, it should

         not be possible to get a short read.  Because it is not

         clear what to do about such thing, we ignore the possibility.  */

      /* There is no memrchr() in the C library, so we have to do it

         ourselves.  */

      n--;

      while (n >= 0)

        {

          if (p[n] == '\n')

            {

              base += n + 1;

              goto done;

            }

          n--;

        }

    }

  while (base != 0);

  /* base is the new pointer.  Seek to it exactly.  */

 done:

  if (sseek (u->s, base) == FAILURE)

    goto io_error;

  u->last_record--;

  u->endfile = NO_ENDFILE;

  return;

 io_error:

  generate_error (&fpp->common, ERROR_OS, NULL);

}

/* unformatted_backspace(fpp) -- Move the file backwards for an unformatted

   sequential file.  We are guaranteed to be between records on entry and

   we have to shift to the previous record.  */

static void

unformatted_backspace (st_parameter_filepos *fpp, gfc_unit *u)

{

  gfc_offset m, new;

  GFC_INTEGER_4 m4;

  GFC_INTEGER_8 m8;

  int length, length_read;

  char *p;

  if (compile_options.record_marker == 0)

    length = sizeof (gfc_offset);

  else

    length = compile_options.record_marker;

  length_read = length;

  p = salloc_r_at (u->s, &length_read,

                   file_position (u->s) - length);

  if (p == NULL || length_read != length)

    goto io_error;

  /* Only CONVERT_NATIVE and CONVERT_SWAP are valid here.  */

  if (u->flags.convert == CONVERT_NATIVE)

    {

      switch (compile_options.record_marker)

        {

        case 0:

          memcpy (&m, p, sizeof(gfc_offset));

          break;

        case sizeof(GFC_INTEGER_4):

          memcpy (&m4, p, sizeof (m4));

          m = m4;

          break;

        case sizeof(GFC_INTEGER_8):

          memcpy (&m8, p, sizeof (m8));

          m = m8;

          break;

        default:

          runtime_error ("Illegal value for record marker");

          break;

        }

    }

  else

    {

      switch (compile_options.record_marker)

        {

        case 0:

          reverse_memcpy (&m, p, sizeof(gfc_offset));

          break;

        case sizeof(GFC_INTEGER_4):

          reverse_memcpy (&m4, p, sizeof (m4));

          m = m4;

          break;

        case sizeof(GFC_INTEGER_8):

          reverse_memcpy (&m8, p, sizeof (m8));

          m = m8;

          break;

        default:

          runtime_error ("Illegal value for record marker");

          break;

        }

    }

  if ((new = file_position (u->s) - m - 2*length) < 0)

    new = 0;

  if (sseek (u->s, new) == FAILURE)

    goto io_error;

  u->last_record--;

  return;

 io_error:

  generate_error (&fpp->common, ERROR_OS, NULL);

}

extern void st_backspace (st_parameter_filepos *);

export_proto(st_backspace);

void

st_backspace (st_parameter_filepos *fpp)

{

  gfc_unit *u;

  library_start (&fpp->common);

  u = find_unit (fpp->common.unit);

  if (u == NULL)

    {

      generate_error (&fpp->common, ERROR_BAD_UNIT, NULL);

      goto done;

    }

  /* Ignore direct access.  Non-advancing I/O is only allowed for formatted

     sequential I/O and the next direct access transfer repositions the file

     anyway.  */

  if (u->flags.access == ACCESS_DIRECT)

    goto done;

  /* Check for special cases involving the ENDFILE record first.  */

  if (u->endfile == AFTER_ENDFILE)

    {

      u->endfile = AT_ENDFILE;

      flush (u->s);

      struncate (u->s);

    }

  else

    {

      if (file_position (u->s) == 0)

        goto done;              /* Common special case */

      if (u->mode == WRITING)

        {

          flush (u->s);

          struncate (u->s);

          u->mode = READING;

        }

      if (u->flags.form == FORM_FORMATTED)

        formatted_backspace (fpp, u);

      else

        unformatted_backspace (fpp, u);

      u->endfile = NO_ENDFILE;

      u->current_record = 0;

      u->bytes_left = 0;

    }

 done:

  if (u != NULL)

    unlock_unit (u);

  library_end ();

}

extern void st_endfile (st_parameter_filepos *);

export_proto(st_endfile);

void

st_endfile (st_parameter_filepos *fpp)

{

  gfc_unit *u;

  library_start (&fpp->common);

  u = find_unit (fpp->common.unit);

  if (u != NULL)

    {

      if (u->current_record)

        {

          st_parameter_dt dtp;

          dtp.common = fpp->common;

          memset (&dtp.u.p, 0, sizeof (dtp.u.p));

          dtp.u.p.current_unit = u;

          next_record (&dtp, 1);

        }

      flush (u->s);

      struncate (u->s);

      u->endfile = AFTER_ENDFILE;

      unlock_unit (u);

    }

  library_end ();

}

extern void st_rewind (st_parameter_filepos *);

export_proto(st_rewind);

void

st_rewind (st_parameter_filepos *fpp)

{

  gfc_unit *u;

  library_start (&fpp->common);

  u = find_unit (fpp->common.unit);

  if (u != NULL)

    {

      if (u->flags.access != ACCESS_SEQUENTIAL)

        generate_error (&fpp->common, ERROR_BAD_OPTION,

                        "Cannot REWIND a file opened for DIRECT access");

      else

        {

          /* Flush the buffers.  If we have been writing to the file, the last

               written record is the last record in the file, so truncate the

               file now.  Reset to read mode so two consecutive rewind

               statements do not delete the file contents.  */

          flush (u->s);

          if (u->mode == WRITING)

            struncate (u->s);

          u->mode = READING;

          u->last_record = 0;

          if (sseek (u->s, 0) == FAILURE)

            generate_error (&fpp->common, ERROR_OS, NULL);

          u->endfile = NO_ENDFILE;

          u->current_record = 0;

          u->bytes_left = 0;

          u->read_bad = 0;

          test_endfile (u);

        }

      /* Update position for INQUIRE.  */

      u->flags.position = POSITION_REWIND;

      unlock_unit (u);

    }

  library_end ();

}

extern void st_flush (st_parameter_filepos *);

export_proto(st_flush);

void

st_flush (st_parameter_filepos *fpp)

{

  gfc_unit *u;

  library_start (&fpp->common);

  u = find_unit (fpp->common.unit);

  if (u != NULL)

    {

      flush (u->s);

      unlock_unit (u);

    }

  library_end ();

}