sysdeps/posix/posix_fallocate.c

   1 /* Copyright (C) 2000 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <unistd.h>
  22 #include <sys/stat.h>
  23 #include <sys/statfs.h>
  24
  25 /* Reserve storage for the data of the file associated with FD.  */
  26
  27 int
  28 posix_fallocate (int fd, __off_t offset, size_t len)
  29 {
  30   struct stat64 st;
  31   struct statfs f;
  32   size_t step;
  33
  34   /* `off_t´ is a signed type.  Therefore we can determine whether
  35      OFFSET + LEN is too large if it is a negative value.  */
  36   if (offset < 0 || len == 0)
  37     return EINVAL;
  38   if (offset + len < 0)
  39     return EFBIG;
  40
  41   /* First thing we have to make sure is that this is really a regular
  42      file.  */
  43   if (__fxstat64 (_STAT_VER, fd, &st) != 0)
  44     return EBADF;
  45   if (S_ISFIFO (st.st_mode))
  46     return ESPIPE;
  47   if (! S_ISREG (st.st_mode))
  48     return ENODEV;
  49
  50   /* We have to know the block size of the filesystem to get at least some
  51      sort of performance.  */
  52   if (__fstatfs (fd, &f) != 0)
  53     return errno;
  54
  55   /* Align OFFSET to block size and adjust LEN.  */
  56   step = (offset + f.f_bsize - 1) % ~f.f_bsize;
  57   offset += step;
  58
  59   /* Write something to every block.  */
  60   while (len > step)
  61     {
  62       len -= step;
  63
  64       if (__pwrite (fd, "", 1, offset) != 1)
  65         return errno;
  66
  67       offset += step;
  68     }
  69
  70   return 0;
  71 }