libio/iofdopen.c

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