libio/iofdopen.c

   1 /* Copyright (C) 1993-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.
  17
  18    As a special exception, if you link the code in this file with
  19    files compiled with a GNU compiler to produce an executable,
  20    that does not cause the resulting executable to be covered by
  21    the GNU Lesser General Public License.  This exception does not
  22    however invalidate any other reasons why the executable file
  23    might be covered by the GNU Lesser General Public License.
  24    This exception applies to code released by its copyright holders
  25    in files containing the exception.  */
  26
  27 #include <stdlib.h>
  28 #include "libioP.h"
  29 #include <fcntl.h>
  30
  31 #ifdef _LIBC
  32 # include <shlib-compat.h>
  33 #endif
  34
  35 #ifndef _IO_fcntl
  36 #ifdef _LIBC
  37 #define _IO_fcntl __fcntl
  38 #else
  39 #define _IO_fcntl fcntl
  40 #endif
  41 #endif
  42
  43 _IO_FILE *
  44 _IO_new_fdopen (fd, mode)
  45      int fd;
  46      const char *mode;
  47 {
  48   int read_write;
  49   int posix_mode = 0;
  50   struct locked_FILE
  51   {
  52     struct _IO_FILE_plus fp;
  53 #ifdef _IO_MTSAFE_IO
  54     _IO_lock_t lock;
  55 #endif
  56     struct _IO_wide_data wd;
  57   } *new_f;
  58   int fd_flags;
  59   int i;
  60   int use_mmap = 0;
  61
  62   /* Decide whether we modify the offset of the file we attach to and seek to
  63      the end of file.  We only do this if the mode is 'a' and if the file
  64      descriptor did not have O_APPEND in its flags already.  */
  65   bool do_seek = false;
  66
  67   switch (*mode)
  68     {
  69     case 'r':
  70       read_write = _IO_NO_WRITES;
  71       break;
  72     case 'w':
  73       read_write = _IO_NO_READS;
  74       break;
  75     case 'a':
  76       posix_mode = O_APPEND;
  77       read_write = _IO_NO_READS|_IO_IS_APPENDING;
  78       break;
  79     default:
  80       MAYBE_SET_EINVAL;
  81       return NULL;
  82   }
  83   for (i = 1; i < 5; ++i)
  84     {
  85       switch (*++mode)
  86         {
  87         case '\0':
  88           break;
  89         case '+':
  90           read_write &= _IO_IS_APPENDING;
  91           break;
  92         case 'm':
  93           use_mmap = 1;
  94           continue;
  95         case 'x':
  96         case 'b':
  97         default:
  98           /* Ignore */
  99           continue;
 100         }
 101       break;
 102     }
 103 #ifdef F_GETFL
 104   fd_flags = _IO_fcntl (fd, F_GETFL);
 105 #ifndef O_ACCMODE
 106 #define O_ACCMODE (O_RDONLY|O_WRONLY|O_RDWR)
 107 #endif
 108   if (fd_flags == -1)
 109     return NULL;
 110
 111   if (((fd_flags & O_ACCMODE) == O_RDONLY && !(read_write & _IO_NO_WRITES))
 112       || ((fd_flags & O_ACCMODE) == O_WRONLY && !(read_write & _IO_NO_READS)))
 113     {
 114       MAYBE_SET_EINVAL;
 115       return NULL;
 116     }
 117
 118   /* The May 93 draft of P1003.4/D14.1 (redesignated as 1003.1b)
 119      [System Application Program Interface (API) Amendment 1:
 120      Realtime Extensions], Rationale B.8.3.3
 121      Open a Stream on a File Descriptor says:
 122
 123          Although not explicitly required by POSIX.1, a good
 124          implementation of append ("a") mode would cause the
 125          O_APPEND flag to be set.
 126
 127      (Historical implementations [such as Solaris2] do a one-time
 128      seek in fdopen.)
 129
 130      However, we do not turn O_APPEND off if the mode is "w" (even
 131      though that would seem consistent) because that would be more
 132      likely to break historical programs.
 133      */
 134   if ((posix_mode & O_APPEND) && !(fd_flags & O_APPEND))
 135     {
 136       do_seek = true;
 137 #ifdef F_SETFL
 138       if (_IO_fcntl (fd, F_SETFL, fd_flags | O_APPEND) == -1)
 139 #endif
 140         return NULL;
 141     }
 142 #endif
 143
 144   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
 145   if (new_f == NULL)
 146     return NULL;
 147 #ifdef _IO_MTSAFE_IO
 148   new_f->fp.file._lock = &new_f->lock;
 149 #endif
 150   _IO_no_init (&new_f->fp.file, 0, 0, &new_f->wd,
 151 #ifdef _G_HAVE_MMAP
 152                (use_mmap && (read_write & _IO_NO_WRITES))
 153                ? &_IO_wfile_jumps_maybe_mmap :
 154 #endif
 155                &_IO_wfile_jumps);
 156   _IO_JUMPS (&new_f->fp) =
 157 #ifdef _G_HAVE_MMAP
 158     (use_mmap && (read_write & _IO_NO_WRITES)) ? &_IO_file_jumps_maybe_mmap :
 159 #endif
 160       &_IO_file_jumps;
 161   _IO_file_init (&new_f->fp);
 162 #if  !_IO_UNIFIED_JUMPTABLES
 163   new_f->fp.vtable = NULL;
 164 #endif
 165   /* We only need to record the fd because _IO_file_init will have unset the
 166      offset.  It is important to unset the cached offset because the real
 167      offset in the file could change between now and when the handle is
 168      activated and we would then mislead ftell into believing that we have a
 169      valid offset.  */
 170   new_f->fp.file._fileno = fd;
 171   new_f->fp.file._flags &= ~_IO_DELETE_DONT_CLOSE;
 172
 173   _IO_mask_flags (&new_f->fp.file, read_write,
 174                   _IO_NO_READS+_IO_NO_WRITES+_IO_IS_APPENDING);
 175
 176   /* For append mode, set the file offset to the end of the file if we added
 177      O_APPEND to the file descriptor flags.  Don't update the offset cache
 178      though, since the file handle is not active.  */
 179   if (do_seek && ((read_write & (_IO_IS_APPENDING | _IO_NO_READS))
 180                   == (_IO_IS_APPENDING | _IO_NO_READS)))
 181     {
 182       _IO_off64_t new_pos = _IO_SYSSEEK (&new_f->fp.file, 0, _IO_seek_end);
 183       if (new_pos == _IO_pos_BAD && errno != ESPIPE)
 184         return NULL;
 185     }
 186   return &new_f->fp.file;
 187 }
 188 libc_hidden_ver (_IO_new_fdopen, _IO_fdopen)
 189
 190 strong_alias (_IO_new_fdopen, __new_fdopen)
 191 versioned_symbol (libc, _IO_new_fdopen, _IO_fdopen, GLIBC_2_1);
 192 versioned_symbol (libc, __new_fdopen, fdopen, GLIBC_2_1);