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