kernel/lib/unistd/lseek.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2009  Tomas 'ZeXx86' Jedrzejek (zexx86@gmail.com)
   4  *
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19
  20 #include <fd.h>
  21 #include <file.h>
  22 #include <stdio.h>
  23 #include <system.h>
  24
  25 long lseek (int fd, long offset, int whence)
  26 {
  27         fd_t *d = fd_get (fd);
  28
  29         if (!d)
  30                 return offset-1;
  31
  32         unsigned l = d->p + d->e;
  33
  34         switch (whence) {
  35                 case SEEK_SET:
  36                         d->p = offset;
  37                         d->e = l;
  38                         break;
  39                 case SEEK_CUR:
  40                         d->p += offset;
  41                         break;
  42                 case SEEK_END:
  43                         d->p = (l + offset);
  44                         d->e = 0;
  45                         break;
  46         }
  47
  48         return d->p;
  49 }