libio/iofdopen.c

   1 /* Copyright (C) 1993-2017 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 (int fd, const char *mode)
  45 {
  46   int read_write;
  47   struct locked_FILE
  48   {
  49     struct _IO_FILE_plus fp;
  50 #ifdef _IO_MTSAFE_IO
  51     _IO_lock_t lock;
  52 #endif
  53     struct _IO_wide_data wd;
  54   } *new_f;
  55   int i;
  56   int use_mmap = 0;
  57
  58   /* Decide whether we modify the offset of the file we attach to and seek to
  59      the end of file.  We only do this if the mode is 'a' and if the file
  60      descriptor did not have O_APPEND in its flags already.  */
  61   bool do_seek = false;
  62
  63   switch (*mode)
  64     {
  65     case 'r':
  66       read_write = _IO_NO_WRITES;
  67       break;
  68     case 'w':
  69       read_write = _IO_NO_READS;
  70       break;
  71     case 'a':
  72       read_write = _IO_NO_READS|_IO_IS_APPENDING;
  73       break;
  74     default:
  75       MAYBE_SET_EINVAL;
  76       return NULL;
  77   }
  78   for (i = 1; i < 5; ++i)
  79     {
  80       switch (*++mode)
  81         {
  82         case '\0':
  83           break;
  84         case '+':
  85           read_write &= _IO_IS_APPENDING;
  86           break;
  87         case 'm':
  88           use_mmap = 1;
  89           continue;
  90         case 'x':
  91         case 'b':
  92         default:
  93           /* Ignore */
  94           continue;
  95         }
  96       break;
  97     }
  98 #ifdef F_GETFL
  99   int fd_flags = _IO_fcntl (fd, F_GETFL);
 100 #ifndef O_ACCMODE
 101 #define O_ACCMODE (O_RDONLY|O_WRONLY|O_RDWR)
 102 #endif
 103   if (fd_flags == -1)
 104     return NULL;
 105
 106   if (((fd_flags & O_ACCMODE) == O_RDONLY && !(read_write & _IO_NO_WRITES))
 107       || ((fd_flags & O_ACCMODE) == O_WRONLY && !(read_write & _IO_NO_READS)))
 108     {
 109       MAYBE_SET_EINVAL;
 110       return NULL;
 111     }
 112
 113   /* The May 93 draft of P1003.4/D14.1 (redesignated as 1003.1b)
 114      [System Application Program Interface (API) Amendment 1:
 115      Realtime Extensions], Rationale B.8.3.3
 116      Open a Stream on a File Descriptor says:
 117
 118          Although not explicitly required by POSIX.1, a good
 119          implementation of append ("a") mode would cause the
 120          O_APPEND flag to be set.
 121
 122      (Historical implementations [such as Solaris2] do a one-time
 123      seek in fdopen.)
 124
 125      However, we do not turn O_APPEND off if the mode is "w" (even
 126      though that would seem consistent) because that would be more
 127      likely to break historical programs.
 128      */
 129   if ((read_write & _IO_IS_APPENDING) && !(fd_flags & O_APPEND))
 130     {
 131       do_seek = true;
 132 #ifdef F_SETFL
 133       if (_IO_fcntl (fd, F_SETFL, fd_flags | O_APPEND) == -1)
 134 #endif
 135         return NULL;
 136     }
 137 #endif
 138
 139   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
 140   if (new_f == NULL)
 141     return NULL;
 142 #ifdef _IO_MTSAFE_IO
 143   new_f->fp.file._lock = &new_f->lock;
 144 #endif
 145   _IO_no_init (&new_f->fp.file, 0, 0, &new_f->wd,
 146 #ifdef _G_HAVE_MMAP
 147                (use_mmap && (read_write & _IO_NO_WRITES))
 148                ? &_IO_wfile_jumps_maybe_mmap :
 149 #endif
 150                &_IO_wfile_jumps);
 151   _IO_JUMPS (&new_f->fp) =
 152 #ifdef _G_HAVE_MMAP
 153     (use_mmap && (read_write & _IO_NO_WRITES)) ? &_IO_file_jumps_maybe_mmap :
 154 #endif
 155       &_IO_file_jumps;
 156   _IO_new_file_init_internal (&new_f->fp);
 157 #if  !_IO_UNIFIED_JUMPTABLES
 158   new_f->fp.vtable = NULL;
 159 #endif
 160   /* We only need to record the fd because _IO_file_init_internal will
 161      have unset the offset.  It is important to unset the cached
 162      offset because the real offset in the file could change between
 163      now and when the handle is activated and we would then mislead
 164      ftell into believing that we have a valid offset.  */
 165   new_f->fp.file._fileno = fd;
 166   new_f->fp.file._flags &= ~_IO_DELETE_DONT_CLOSE;
 167
 168   _IO_mask_flags (&new_f->fp.file, read_write,
 169                   _IO_NO_READS+_IO_NO_WRITES+_IO_IS_APPENDING);
 170
 171   /* For append mode, set the file offset to the end of the file if we added
 172      O_APPEND to the file descriptor flags.  Don't update the offset cache
 173      though, since the file handle is not active.  */
 174   if (do_seek && ((read_write & (_IO_IS_APPENDING | _IO_NO_READS))
 175                   == (_IO_IS_APPENDING | _IO_NO_READS)))
 176     {
 177       _IO_off64_t new_pos = _IO_SYSSEEK (&new_f->fp.file, 0, _IO_seek_end);
 178       if (new_pos == _IO_pos_BAD && errno != ESPIPE)
 179         return NULL;
 180     }
 181   return &new_f->fp.file;
 182 }
 183 libc_hidden_ver (_IO_new_fdopen, _IO_fdopen)
 184
 185 strong_alias (_IO_new_fdopen, __new_fdopen)
 186 versioned_symbol (libc, _IO_new_fdopen, _IO_fdopen, GLIBC_2_1);
 187 versioned_symbol (libc, __new_fdopen, fdopen, GLIBC_2_1);