lib/lseek.c

   1 /* An lseek() function that detects pipes.
   2    Copyright (C) 2007, 2009-2021 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <unistd.h>
  21
  22 #if defined _WIN32 && ! defined __CYGWIN__
  23 /* Windows platforms.  */
  24 /* Get GetFileType.  */
  25 # include <windows.h>
  26 /* Get _get_osfhandle.  */
  27 # if GNULIB_MSVC_NOTHROW
  28 #  include "msvc-nothrow.h"
  29 # else
  30 #  include <io.h>
  31 # endif
  32 #else
  33 # include <sys/stat.h>
  34 #endif
  35 #include <errno.h>
  36
  37 #undef lseek
  38
  39 off_t
  40 rpl_lseek (int fd, off_t offset, int whence)
  41 {
  42 #if defined _WIN32 && ! defined __CYGWIN__
  43   /* mingw lseek mistakenly succeeds on pipes, sockets, and terminals.  */
  44   HANDLE h = (HANDLE) _get_osfhandle (fd);
  45   if (h == INVALID_HANDLE_VALUE)
  46     {
  47       errno = EBADF;
  48       return -1;
  49     }
  50   if (GetFileType (h) != FILE_TYPE_DISK)
  51     {
  52       errno = ESPIPE;
  53       return -1;
  54     }
  55 #else
  56   /* BeOS lseek mistakenly succeeds on pipes...  */
  57   struct stat statbuf;
  58   if (fstat (fd, &statbuf) < 0)
  59     return -1;
  60   if (!S_ISREG (statbuf.st_mode))
  61     {
  62       errno = ESPIPE;
  63       return -1;
  64     }
  65 #endif
  66 #if _GL_WINDOWS_64_BIT_OFF_T || (defined __MINGW32__ && defined _FILE_OFFSET_BITS && (_FILE_OFFSET_BITS == 64))
  67   return _lseeki64 (fd, offset, whence);
  68 #else
  69   return lseek (fd, offset, whence);
  70 #endif
  71 }