libio/iofdopen.c

   1 /* Copyright (C) 1993, 1994, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU IO Library.
   3
   4    This library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License as
   6    published by the Free Software Foundation; either version 2, or (at
   7    your option) any later version.
   8
   9    This library is distributed in the hope that it will be useful, but
  10    WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this library; see the file COPYING.  If not, write to
  16    the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  17    MA 02111-1307, USA.
  18
  19    As a special exception, if you link this library with files
  20    compiled with a GNU compiler to produce an executable, this does
  21    not cause the resulting executable to be covered by the GNU General
  22    Public License.  This exception does not however invalidate any
  23    other reasons why the executable file might be covered by the GNU
  24    General Public License.  */
  25
  26 #ifdef __STDC__
  27 #include <stdlib.h>
  28 #endif
  29 #include "libioP.h"
  30 #include <fcntl.h>
  31
  32 #ifndef _IO_fcntl
  33 #define _IO_fcntl fcntl
  34 #endif
  35
  36 _IO_FILE *
  37 _IO_fdopen (fd, mode)
  38      int fd;
  39      const char *mode;
  40 {
  41   int read_write;
  42   int posix_mode = 0;
  43   struct locked_FILE
  44   {
  45     struct _IO_FILE_plus fp;
  46 #ifdef _IO_MTSAFE_IO
  47     _IO_lock_t lock;
  48 #endif
  49   } *new_f;
  50   int fd_flags;
  51
  52   switch (*mode++)
  53     {
  54     case 'r':
  55       read_write = _IO_NO_WRITES;
  56       break;
  57     case 'w':
  58       read_write = _IO_NO_READS;
  59       break;
  60     case 'a':
  61       posix_mode = O_APPEND;
  62       read_write = _IO_NO_READS|_IO_IS_APPENDING;
  63       break;
  64     default:
  65       MAYBE_SET_EINVAL;
  66       return NULL;
  67   }
  68   if (mode[0] == '+' || (mode[0] == 'b' && mode[1] == '+'))
  69     read_write &= _IO_IS_APPENDING;
  70 #ifdef F_GETFL
  71   fd_flags = _IO_fcntl (fd, F_GETFL);
  72 #ifndef O_ACCMODE
  73 #define O_ACCMODE (O_RDONLY|O_WRONLY|O_RDWR)
  74 #endif
  75   if (fd_flags == -1
  76       || ((fd_flags & O_ACCMODE) == O_RDONLY && !(read_write & _IO_NO_WRITES))
  77       || ((fd_flags & O_ACCMODE) == O_WRONLY && !(read_write & _IO_NO_READS)))
  78     return NULL;
  79
  80   /* The May 93 draft of P1003.4/D14.1 (redesignated as 1003.1b)
  81      [System Application Program Interface (API) Amendment 1:
  82      Realtime Extensions], Rationale B.8.3.3
  83      Open a Stream on a File Descriptor says:
  84
  85          Although not explicitly required by POSIX.1, a good
  86          implementation of append ("a") mode would cause the
  87          O_APPEND flag to be set.
  88
  89      (Historical implementations [such as Solaris2] do a one-time
  90      seek in fdopen.)
  91
  92      However, we do not turn O_APPEND off if the mode is "w" (even
  93      though that would seem consistent) because that would be more
  94      likely to break historical programs.
  95      */
  96   if ((posix_mode & O_APPEND) && !(fd_flags & O_APPEND))
  97     {
  98 #ifdef F_SETFL
  99       if (_IO_fcntl (fd, F_SETFL, fd_flags | O_APPEND) == -1)
 100 #endif
 101         return NULL;
 102     }
 103 #endif
 104
 105   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
 106   if (new_f == NULL)
 107     return NULL;
 108 #ifdef _IO_MTSAFE_IO
 109   new_f->fp.file._lock = &new_f->lock;
 110 #endif
 111   _IO_init (&new_f->fp.file, 0);
 112   _IO_JUMPS (&new_f->fp.file) = &_IO_file_jumps;
 113   _IO_file_init (&new_f->fp.file);
 114 #if  !_IO_UNIFIED_JUMPTABLES
 115   new_f->fp.vtable = NULL;
 116 #endif
 117   if (_IO_file_attach (&new_f->fp.file, fd) == NULL)
 118     {
 119       _IO_un_link (&new_f->fp.file);
 120       free (new_f);
 121       return NULL;
 122     }
 123   new_f->fp.file._flags &= ~_IO_DELETE_DONT_CLOSE;
 124
 125   new_f->fp.file._IO_file_flags =
 126     _IO_mask_flags (&new_f->fp.file, read_write,
 127                     _IO_NO_READS+_IO_NO_WRITES+_IO_IS_APPENDING);
 128
 129   return (_IO_FILE *) &new_f->fp;
 130 }
 131
 132 #ifdef weak_alias
 133 weak_alias (_IO_fdopen, fdopen)
 134 #endif