glibc/libio/iofdopen.c

/* Copyright (C) 1993, 1994, 1997 Free Software Foundation, Inc.
   This file is part of the GNU IO Library.

   This library 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.

   This library 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 this library; see the file COPYING.  If not, write to
   the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
   MA 02111-1307, USA.

   As a special exception, if you link this library with files
   compiled with a GNU compiler to produce an executable, this does
   not cause the resulting executable to be covered by the GNU General
   Public License.  This exception does not however invalidate any
   other reasons why the executable file might be covered by the GNU
   General Public License.  */

#ifdef __STDC__
#include <stdlib.h>
#endif
#include "libioP.h"
#include <fcntl.h>

#ifndef _IO_fcntl
#define _IO_fcntl fcntl
#endif

_IO_FILE *
_IO_fdopen (fd, mode)
     int fd;
     const char *mode;
{
  int read_write;
  int posix_mode = 0;
  struct locked_FILE
  {
    struct _IO_FILE_plus fp;
#ifdef _IO_MTSAFE_IO
    _IO_lock_t lock;
#endif
  } *new_f;
  int fd_flags;

  switch (*mode++)
    {
    case 'r':
      read_write = _IO_NO_WRITES;
      break;
    case 'w':
      read_write = _IO_NO_READS;
      break;
    case 'a':
      posix_mode = O_APPEND;
      read_write = _IO_NO_READS|_IO_IS_APPENDING;
      break;
    default:
      MAYBE_SET_EINVAL;
      return NULL;
  }
  if (mode[0] == '+' || (mode[0] == 'b' && mode[1] == '+'))
    read_write &= _IO_IS_APPENDING;
#ifdef F_GETFL
  fd_flags = _IO_fcntl (fd, F_GETFL);
#ifndef O_ACCMODE
#define O_ACCMODE (O_RDONLY|O_WRONLY|O_RDWR)
#endif
  if (fd_flags == -1
      || ((fd_flags & O_ACCMODE) == O_RDONLY && !(read_write & _IO_NO_WRITES))
      || ((fd_flags & O_ACCMODE) == O_WRONLY && !(read_write & _IO_NO_READS)))
    return NULL;

  /* The May 93 draft of P1003.4/D14.1 (redesignated as 1003.1b)
     [System Application Program Interface (API) Amendment 1:
     Realtime Extensions], Rationale B.8.3.3
     Open a Stream on a File Descriptor says:

         Although not explicitly required by POSIX.1, a good
         implementation of append ("a") mode would cause the
         O_APPEND flag to be set.

     (Historical implementations [such as Solaris2] do a one-time
     seek in fdopen.)

     However, we do not turn O_APPEND off if the mode is "w" (even
     though that would seem consistent) because that would be more
     likely to break historical programs.
     */
  if ((posix_mode & O_APPEND) && !(fd_flags & O_APPEND))
    {
#ifdef F_SETFL
      if (_IO_fcntl (fd, F_SETFL, fd_flags | O_APPEND) == -1)
#endif
	return NULL;
    }
#endif

  new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
  if (new_f == NULL)
    return NULL;
#ifdef _IO_MTSAFE_IO
  new_f->fp.file._lock = &new_f->lock;
#endif
  _IO_init (&new_f->fp.file, 0);
  _IO_JUMPS (&new_f->fp.file) = &_IO_file_jumps;
  _IO_file_init (&new_f->fp.file);
#if  !_IO_UNIFIED_JUMPTABLES
  new_f->fp.vtable = NULL;
#endif
  if (_IO_file_attach (&new_f->fp.file, fd) == NULL)
    {
      _IO_un_link (&new_f->fp.file);
      free (new_f);
      return NULL;
    }
  new_f->fp.file._flags &= ~_IO_DELETE_DONT_CLOSE;

  new_f->fp.file._IO_file_flags =
    _IO_mask_flags (&new_f->fp.file, read_write,
		    _IO_NO_READS+_IO_NO_WRITES+_IO_IS_APPENDING);

  return (_IO_FILE *) &new_f->fp;
}

#ifdef weak_alias
weak_alias (_IO_fdopen, fdopen)
#endif