libgfortran/io/file_pos.c - gcc - Git at Google

 /* Copyright (C) 2002-2019 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 3, or (at your option)
 any later version.

 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.

 Under Section 7 of GPL version 3, you are granted additional
 permissions described in the GCC Runtime Library Exception, version
 3.1, as published by the Free Software Foundation.

 You should have received a copy of the GNU General Public License and
 a copy of the GCC Runtime Library Exception along with this program;
 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 <http://www.gnu.org/licenses/>.  */

 #include "io.h"
 #include "fbuf.h"
 #include "unix.h"
 #include "async.h"
 #include <string.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[READ_CHUNK];
   ssize_t n;

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

   do
     {
       n = (base < READ_CHUNK) ? base : READ_CHUNK;
       base -= n;
       if (sseek (u->s, base, SEEK_SET) < 0)
         goto io_error;
       if (sread (u->s, p, n) != n)
 	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.  */

       while (n > 0)
 	{
           n--;
 	  if (p[n] == '\n')
 	    {
 	      base += n + 1;
 	      goto done;
 	    }
 	}

     }
   while (base != 0);

   /* base is the new pointer.  Seek to it exactly.  */
  done:
   if (sseek (u->s, base, SEEK_SET) < 0)
     goto io_error;
   u->last_record--;
   u->endfile = NO_ENDFILE;
   u->last_char = EOF - 1;
   return;

  io_error:
   generate_error (&fpp->common, LIBERROR_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.  Loop over subrecords.  */

 static void
 unformatted_backspace (st_parameter_filepos *fpp, gfc_unit *u)
 {
   gfc_offset m, slen;
   GFC_INTEGER_4 m4;
   GFC_INTEGER_8 m8;
   ssize_t length;
   int continued;
   char p[sizeof (GFC_INTEGER_8)];

   if (compile_options.record_marker == 0)
     length = sizeof (GFC_INTEGER_4);
   else
     length = compile_options.record_marker;

   do
     {
       slen = - (gfc_offset) length;
       if (sseek (u->s, slen, SEEK_CUR) < 0)
         goto io_error;
       if (sread (u->s, p, length) != length)
         goto io_error;

       /* Only GFC_CONVERT_NATIVE and GFC_CONVERT_SWAP are valid here.  */
       if (likely (u->flags.convert == GFC_CONVERT_NATIVE))
 	{
 	  switch (length)
 	    {
 	    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
 	{
 	  uint32_t u32;
 	  uint64_t u64;
 	  switch (length)
 	    {
 	    case sizeof(GFC_INTEGER_4):
 	      memcpy (&u32, p, sizeof (u32));
 	      u32 = __builtin_bswap32 (u32);
 	      memcpy (&m4, &u32, sizeof (m4));
 	      m = m4;
 	      break;

 	    case sizeof(GFC_INTEGER_8):
 	      memcpy (&u64, p, sizeof (u64));
 	      u64 = __builtin_bswap64 (u64);
 	      memcpy (&m8, &u64, sizeof (m8));
 	      m = m8;
 	      break;

 	    default:
 	      runtime_error ("Illegal value for record marker");
 	      break;
 	    }

 	}

       continued = m < 0;
       if (continued)
 	m = -m;

       if (sseek (u->s, -m -2 * length, SEEK_CUR) < 0)
 	goto io_error;
     } while (continued);

   u->last_record--;
   return;

  io_error:
   generate_error (&fpp->common, LIBERROR_OS, NULL);
 }


 extern void st_backspace (st_parameter_filepos *);
 export_proto(st_backspace);

 void
 st_backspace (st_parameter_filepos *fpp)
 {
   gfc_unit *u;
   bool needs_unlock = false;

   library_start (&fpp->common);

   u = find_unit (fpp->common.unit);
   if (u == NULL)
     {
       generate_error (&fpp->common, LIBERROR_BAD_UNIT, NULL);
       goto done;
     }

   /* Direct access is prohibited, and so is unformatted stream access.  */


   if (u->flags.access == ACCESS_DIRECT)
     {
       generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
 		      "Cannot BACKSPACE a file opened for DIRECT access");
       goto done;
     }

   if (u->flags.access == ACCESS_STREAM && u->flags.form == FORM_UNFORMATTED)
     {
       generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
                       "Cannot BACKSPACE an unformatted stream file");
       goto done;
     }

   if (ASYNC_IO && u->au)
     {
       if (async_wait (&(fpp->common), u->au))
 	return;
       else
 	{
 	  needs_unlock = true;
 	  LOCK (&u->au->io_lock);
 	}
     }

   /* Make sure format buffer is flushed and reset.  */
   if (u->flags.form == FORM_FORMATTED)
     {
       int pos = fbuf_reset (u);
       if (pos != 0)
         sseek (u->s, pos, SEEK_CUR);
     }


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

   if (u->endfile == AFTER_ENDFILE)
     {
       u->endfile = AT_ENDFILE;
       u->flags.position = POSITION_APPEND;
       sflush (u->s);
     }
   else
     {
       if (stell (u->s) == 0)
 	{
 	  u->flags.position = POSITION_REWIND;
 	  goto done;		/* Common special case */
 	}

       if (u->mode == WRITING)
 	{
 	  /* If there are previously written bytes from a write with
 	     ADVANCE="no", add a record marker before performing the
 	     BACKSPACE.  */

 	  if (u->previous_nonadvancing_write)
 	    finish_last_advance_record (u);

 	  u->previous_nonadvancing_write = 0;

 	  unit_truncate (u, stell (u->s), &fpp->common);
 	  u->mode = READING;
         }

       if (u->flags.form == FORM_FORMATTED)
 	formatted_backspace (fpp, u);
       else
 	unformatted_backspace (fpp, u);

       u->flags.position = POSITION_UNSPECIFIED;
       u->endfile = NO_ENDFILE;
       u->current_record = 0;
       u->bytes_left = 0;
     }

  done:
   if (u != NULL)
     {
       unlock_unit (u);

       if (ASYNC_IO && u->au && needs_unlock)
 	UNLOCK (&u->au->io_lock);
     }

   library_end ();
 }


 extern void st_endfile (st_parameter_filepos *);
 export_proto(st_endfile);

 void
 st_endfile (st_parameter_filepos *fpp)
 {
   gfc_unit *u;
   bool needs_unlock = false;

   library_start (&fpp->common);

   u = find_unit (fpp->common.unit);
   if (u != NULL)
     {
       if (u->flags.access == ACCESS_DIRECT)
 	{
 	  generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
 			  "Cannot perform ENDFILE on a file opened "
 			  "for DIRECT access");
 	  goto done;
 	}

       if (ASYNC_IO && u->au)
 	{
 	  if (async_wait (&(fpp->common), u->au))
 	    return;
 	  else
 	    {
 	      needs_unlock = true;
 	      LOCK (&u->au->io_lock);
 	    }
 	}

       if (u->flags.access == ACCESS_SEQUENTIAL
       	  && u->endfile == AFTER_ENDFILE)
 	{
 	  generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
 			  "Cannot perform ENDFILE on a file already "
 			  "positioned after the EOF marker");
 	  goto done;
 	}

       /* If there are previously written bytes from a write with ADVANCE="no",
 	 add a record marker before performing the ENDFILE.  */

       if (u->previous_nonadvancing_write)
 	finish_last_advance_record (u);

       u->previous_nonadvancing_write = 0;

       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);
 	}

       unit_truncate (u, stell (u->s), &fpp->common);
       u->endfile = AFTER_ENDFILE;
       u->last_char = EOF - 1;
       if (0 == stell (u->s))
         u->flags.position = POSITION_REWIND;
     }
   else
     {
       if (fpp->common.unit < 0)
 	{
 	  generate_error (&fpp->common, LIBERROR_BAD_OPTION,
 			  "Bad unit number in statement");
 	  return;
 	}

       u = find_or_create_unit (fpp->common.unit);
       if (u->s == NULL)
 	{
 	  /* Open the unit with some default flags.  */
 	  st_parameter_open opp;
 	  unit_flags u_flags;

 	  memset (&u_flags, '\0', sizeof (u_flags));
 	  u_flags.access = ACCESS_SEQUENTIAL;
 	  u_flags.action = ACTION_READWRITE;

 	  /* Is it unformatted?  */
 	  if (!(fpp->common.flags & (IOPARM_DT_HAS_FORMAT | IOPARM_DT_LIST_FORMAT
 				     | IOPARM_DT_IONML_SET)))
 	    u_flags.form = FORM_UNFORMATTED;
 	  else
 	    u_flags.form = FORM_UNSPECIFIED;

 	  u_flags.delim = DELIM_UNSPECIFIED;
 	  u_flags.blank = BLANK_UNSPECIFIED;
 	  u_flags.pad = PAD_UNSPECIFIED;
 	  u_flags.decimal = DECIMAL_UNSPECIFIED;
 	  u_flags.encoding = ENCODING_UNSPECIFIED;
 	  u_flags.async = ASYNC_UNSPECIFIED;
 	  u_flags.round = ROUND_UNSPECIFIED;
 	  u_flags.sign = SIGN_UNSPECIFIED;
 	  u_flags.status = STATUS_UNKNOWN;
 	  u_flags.convert = GFC_CONVERT_NATIVE;
 	  u_flags.share = SHARE_UNSPECIFIED;
 	  u_flags.cc = CC_UNSPECIFIED;

 	  opp.common = fpp->common;
 	  opp.common.flags &= IOPARM_COMMON_MASK;
 	  u = new_unit (&opp, u, &u_flags);
 	  if (u == NULL)
 	    return;
 	  u->endfile = AFTER_ENDFILE;
 	  u->last_char = EOF - 1;
 	}
     }

  done:
   if (ASYNC_IO && u->au && needs_unlock)
     UNLOCK (&u->au->io_lock);

   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;
   bool needs_unlock = true;

   library_start (&fpp->common);

   u = find_unit (fpp->common.unit);
   if (u != NULL)
     {
       if (u->flags.access == ACCESS_DIRECT)
 	generate_error (&fpp->common, LIBERROR_BAD_OPTION,
 			"Cannot REWIND a file opened for DIRECT access");
       else
 	{
 	  if (ASYNC_IO && u->au)
 	    {
 	      if (async_wait (&(fpp->common), u->au))
 		return;
 	      else
 		{
 		  needs_unlock = true;
 		  LOCK (&u->au->io_lock);
 		}
 	    }

 	  /* If there are previously written bytes from a write with ADVANCE="no",
 	     add a record marker before performing the ENDFILE.  */

 	  if (u->previous_nonadvancing_write)
 	    finish_last_advance_record (u);

 	  u->previous_nonadvancing_write = 0;

 	  fbuf_reset (u);

 	  u->last_record = 0;

 	  if (sseek (u->s, 0, SEEK_SET) < 0)
 	    {
 	      generate_error (&fpp->common, LIBERROR_OS, NULL);
 	      library_end ();
 	      return;
 	    }

 	  /* Set this for compatibilty with g77 for /dev/null.  */
 	  if (ssize (u->s) == 0)
 	    u->endfile = AT_ENDFILE;
 	  else
 	    {
 	      /* We are rewinding so we are not at the end.  */
 	      u->endfile = NO_ENDFILE;
 	    }

 	  u->current_record = 0;
 	  u->strm_pos = 1;
 	  u->read_bad = 0;
 	  u->last_char = EOF - 1;
 	}
       /* Update position for INQUIRE.  */
       u->flags.position = POSITION_REWIND;

       if (ASYNC_IO && u->au && needs_unlock)
 	UNLOCK (&u->au->io_lock);

       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;
   bool needs_unlock = false;

   library_start (&fpp->common);

   u = find_unit (fpp->common.unit);
   if (u != NULL)
     {
       if (ASYNC_IO && u->au)
 	{
 	  if (async_wait (&(fpp->common), u->au))
 	    return;
 	  else
 	    {
 	      needs_unlock = true;
 	      LOCK (&u->au->io_lock);
 	    }
 	}

       /* Make sure format buffer is flushed.  */
       if (u->flags.form == FORM_FORMATTED)
         fbuf_flush (u, u->mode);

       sflush (u->s);
       u->last_char = EOF - 1;
       unlock_unit (u);
     }
   else
     /* FLUSH on unconnected unit is illegal: F95 std., 9.3.5. */
     generate_error (&fpp->common, LIBERROR_BAD_OPTION,
 			"Specified UNIT in FLUSH is not connected");

   if (needs_unlock)
     UNLOCK (&u->au->io_lock);

   library_end ();
 }
	/* Copyright (C) 2002-2019 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 3, or (at your option)
	any later version.

	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.

	Under Section 7 of GPL version 3, you are granted additional
	permissions described in the GCC Runtime Library Exception, version
	3.1, as published by the Free Software Foundation.

	You should have received a copy of the GNU General Public License and
	a copy of the GCC Runtime Library Exception along with this program;
	see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
	<http://www.gnu.org/licenses/>. */

	#include "io.h"
	#include "fbuf.h"
	#include "unix.h"
	#include "async.h"
	#include <string.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[READ_CHUNK];
	ssize_t n;

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

	do
	{
	n = (base < READ_CHUNK) ? base : READ_CHUNK;
	base -= n;
	if (sseek (u->s, base, SEEK_SET) < 0)
	goto io_error;
	if (sread (u->s, p, n) != n)
	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. */

	while (n > 0)
	{
	n--;
	if (p[n] == '\n')
	{
	base += n + 1;
	goto done;
	}
	}

	}
	while (base != 0);

	/* base is the new pointer. Seek to it exactly. */
	done:
	if (sseek (u->s, base, SEEK_SET) < 0)
	goto io_error;
	u->last_record--;
	u->endfile = NO_ENDFILE;
	u->last_char = EOF - 1;
	return;

	io_error:
	generate_error (&fpp->common, LIBERROR_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. Loop over subrecords. */

	static void
	unformatted_backspace (st_parameter_filepos fpp, gfc_unit u)
	{
	gfc_offset m, slen;
	GFC_INTEGER_4 m4;
	GFC_INTEGER_8 m8;
	ssize_t length;
	int continued;
	char p[sizeof (GFC_INTEGER_8)];

	if (compile_options.record_marker == 0)
	length = sizeof (GFC_INTEGER_4);
	else
	length = compile_options.record_marker;

	do
	{
	slen = - (gfc_offset) length;
	if (sseek (u->s, slen, SEEK_CUR) < 0)
	goto io_error;
	if (sread (u->s, p, length) != length)
	goto io_error;

	/* Only GFC_CONVERT_NATIVE and GFC_CONVERT_SWAP are valid here. */
	if (likely (u->flags.convert == GFC_CONVERT_NATIVE))
	{
	switch (length)
	{
	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
	{
	uint32_t u32;
	uint64_t u64;
	switch (length)
	{
	case sizeof(GFC_INTEGER_4):
	memcpy (&u32, p, sizeof (u32));
	u32 = __builtin_bswap32 (u32);
	memcpy (&m4, &u32, sizeof (m4));
	m = m4;
	break;

	case sizeof(GFC_INTEGER_8):
	memcpy (&u64, p, sizeof (u64));
	u64 = __builtin_bswap64 (u64);
	memcpy (&m8, &u64, sizeof (m8));
	m = m8;
	break;

	default:
	runtime_error ("Illegal value for record marker");
	break;
	}

	}

	continued = m < 0;
	if (continued)
	m = -m;

	if (sseek (u->s, -m -2 * length, SEEK_CUR) < 0)
	goto io_error;
	} while (continued);

	u->last_record--;
	return;

	io_error:
	generate_error (&fpp->common, LIBERROR_OS, NULL);
	}


	extern void st_backspace (st_parameter_filepos *);
	export_proto(st_backspace);

	void
	st_backspace (st_parameter_filepos *fpp)
	{
	gfc_unit *u;
	bool needs_unlock = false;

	library_start (&fpp->common);

	u = find_unit (fpp->common.unit);
	if (u == NULL)
	{
	generate_error (&fpp->common, LIBERROR_BAD_UNIT, NULL);
	goto done;
	}

	/* Direct access is prohibited, and so is unformatted stream access. */


	if (u->flags.access == ACCESS_DIRECT)
	{
	generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
	"Cannot BACKSPACE a file opened for DIRECT access");
	goto done;
	}

	if (u->flags.access == ACCESS_STREAM && u->flags.form == FORM_UNFORMATTED)
	{
	generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
	"Cannot BACKSPACE an unformatted stream file");
	goto done;
	}

	if (ASYNC_IO && u->au)
	{
	if (async_wait (&(fpp->common), u->au))
	return;
	else
	{
	needs_unlock = true;
	LOCK (&u->au->io_lock);
	}
	}

	/* Make sure format buffer is flushed and reset. */
	if (u->flags.form == FORM_FORMATTED)
	{
	int pos = fbuf_reset (u);
	if (pos != 0)
	sseek (u->s, pos, SEEK_CUR);
	}


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

	if (u->endfile == AFTER_ENDFILE)
	{
	u->endfile = AT_ENDFILE;
	u->flags.position = POSITION_APPEND;
	sflush (u->s);
	}
	else
	{
	if (stell (u->s) == 0)
	{
	u->flags.position = POSITION_REWIND;
	goto done; /* Common special case */
	}

	if (u->mode == WRITING)
	{
	/* If there are previously written bytes from a write with
	ADVANCE="no", add a record marker before performing the
	BACKSPACE. */

	if (u->previous_nonadvancing_write)
	finish_last_advance_record (u);

	u->previous_nonadvancing_write = 0;

	unit_truncate (u, stell (u->s), &fpp->common);
	u->mode = READING;
	}

	if (u->flags.form == FORM_FORMATTED)
	formatted_backspace (fpp, u);
	else
	unformatted_backspace (fpp, u);

	u->flags.position = POSITION_UNSPECIFIED;
	u->endfile = NO_ENDFILE;
	u->current_record = 0;
	u->bytes_left = 0;
	}

	done:
	if (u != NULL)
	{
	unlock_unit (u);

	if (ASYNC_IO && u->au && needs_unlock)
	UNLOCK (&u->au->io_lock);
	}

	library_end ();
	}


	extern void st_endfile (st_parameter_filepos *);
	export_proto(st_endfile);

	void
	st_endfile (st_parameter_filepos *fpp)
	{
	gfc_unit *u;
	bool needs_unlock = false;

	library_start (&fpp->common);

	u = find_unit (fpp->common.unit);
	if (u != NULL)
	{
	if (u->flags.access == ACCESS_DIRECT)
	{
	generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
	"Cannot perform ENDFILE on a file opened "
	"for DIRECT access");
	goto done;
	}

	if (ASYNC_IO && u->au)
	{
	if (async_wait (&(fpp->common), u->au))
	return;
	else
	{
	needs_unlock = true;
	LOCK (&u->au->io_lock);
	}
	}

	if (u->flags.access == ACCESS_SEQUENTIAL
	&& u->endfile == AFTER_ENDFILE)
	{
	generate_error (&fpp->common, LIBERROR_OPTION_CONFLICT,
	"Cannot perform ENDFILE on a file already "
	"positioned after the EOF marker");
	goto done;
	}

	/* If there are previously written bytes from a write with ADVANCE="no",
	add a record marker before performing the ENDFILE. */

	if (u->previous_nonadvancing_write)
	finish_last_advance_record (u);

	u->previous_nonadvancing_write = 0;

	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);
	}

	unit_truncate (u, stell (u->s), &fpp->common);
	u->endfile = AFTER_ENDFILE;
	u->last_char = EOF - 1;
	if (0 == stell (u->s))
	u->flags.position = POSITION_REWIND;
	}
	else
	{
	if (fpp->common.unit < 0)
	{
	generate_error (&fpp->common, LIBERROR_BAD_OPTION,
	"Bad unit number in statement");
	return;
	}

	u = find_or_create_unit (fpp->common.unit);
	if (u->s == NULL)
	{
	/* Open the unit with some default flags. */
	st_parameter_open opp;
	unit_flags u_flags;

	memset (&u_flags, '\0', sizeof (u_flags));
	u_flags.access = ACCESS_SEQUENTIAL;
	u_flags.action = ACTION_READWRITE;

	/* Is it unformatted? */
	if (!(fpp->common.flags & (IOPARM_DT_HAS_FORMAT \| IOPARM_DT_LIST_FORMAT
	\| IOPARM_DT_IONML_SET)))
	u_flags.form = FORM_UNFORMATTED;
	else
	u_flags.form = FORM_UNSPECIFIED;

	u_flags.delim = DELIM_UNSPECIFIED;
	u_flags.blank = BLANK_UNSPECIFIED;
	u_flags.pad = PAD_UNSPECIFIED;
	u_flags.decimal = DECIMAL_UNSPECIFIED;
	u_flags.encoding = ENCODING_UNSPECIFIED;
	u_flags.async = ASYNC_UNSPECIFIED;
	u_flags.round = ROUND_UNSPECIFIED;
	u_flags.sign = SIGN_UNSPECIFIED;
	u_flags.status = STATUS_UNKNOWN;
	u_flags.convert = GFC_CONVERT_NATIVE;
	u_flags.share = SHARE_UNSPECIFIED;
	u_flags.cc = CC_UNSPECIFIED;

	opp.common = fpp->common;
	opp.common.flags &= IOPARM_COMMON_MASK;
	u = new_unit (&opp, u, &u_flags);
	if (u == NULL)
	return;
	u->endfile = AFTER_ENDFILE;
	u->last_char = EOF - 1;
	}
	}

	done:
	if (ASYNC_IO && u->au && needs_unlock)
	UNLOCK (&u->au->io_lock);

	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;
	bool needs_unlock = true;

	library_start (&fpp->common);

	u = find_unit (fpp->common.unit);
	if (u != NULL)
	{
	if (u->flags.access == ACCESS_DIRECT)
	generate_error (&fpp->common, LIBERROR_BAD_OPTION,
	"Cannot REWIND a file opened for DIRECT access");
	else
	{
	if (ASYNC_IO && u->au)
	{
	if (async_wait (&(fpp->common), u->au))
	return;
	else
	{
	needs_unlock = true;
	LOCK (&u->au->io_lock);
	}
	}

	/* If there are previously written bytes from a write with ADVANCE="no",
	add a record marker before performing the ENDFILE. */

	if (u->previous_nonadvancing_write)
	finish_last_advance_record (u);

	u->previous_nonadvancing_write = 0;

	fbuf_reset (u);

	u->last_record = 0;

	if (sseek (u->s, 0, SEEK_SET) < 0)
	{
	generate_error (&fpp->common, LIBERROR_OS, NULL);
	library_end ();
	return;
	}

	/* Set this for compatibilty with g77 for /dev/null. */
	if (ssize (u->s) == 0)
	u->endfile = AT_ENDFILE;
	else
	{
	/* We are rewinding so we are not at the end. */
	u->endfile = NO_ENDFILE;
	}

	u->current_record = 0;
	u->strm_pos = 1;
	u->read_bad = 0;
	u->last_char = EOF - 1;
	}
	/* Update position for INQUIRE. */
	u->flags.position = POSITION_REWIND;

	if (ASYNC_IO && u->au && needs_unlock)
	UNLOCK (&u->au->io_lock);

	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;
	bool needs_unlock = false;

	library_start (&fpp->common);

	u = find_unit (fpp->common.unit);
	if (u != NULL)
	{
	if (ASYNC_IO && u->au)
	{
	if (async_wait (&(fpp->common), u->au))
	return;
	else
	{
	needs_unlock = true;
	LOCK (&u->au->io_lock);
	}
	}

	/* Make sure format buffer is flushed. */
	if (u->flags.form == FORM_FORMATTED)
	fbuf_flush (u, u->mode);

	sflush (u->s);
	u->last_char = EOF - 1;
	unlock_unit (u);
	}
	else
	/* FLUSH on unconnected unit is illegal: F95 std., 9.3.5. */
	generate_error (&fpp->common, LIBERROR_BAD_OPTION,
	"Specified UNIT in FLUSH is not connected");

	if (needs_unlock)
	UNLOCK (&u->au->io_lock);

	library_end ();
	}