libs/port/pread.c

   1 /*
   2  * pread function
   3  *
   4  * Copyright 1996 Alexandre Julliard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  19  */
  20
  21 #include "config.h"
  22 #include "wine/port.h"
  23
  24 #include <errno.h>
  25 #include <stdio.h>
  26 #ifdef HAVE_UNISTD_H
  27 # include <unistd.h>
  28 #endif
  29 #ifdef HAVE_IO_H
  30 # include <io.h>
  31 #endif
  32
  33
  34 /* FIXME: this is not thread-safe */
  35
  36 #ifndef HAVE_PREAD
  37 ssize_t pread( int fd, void *buf, size_t count, off_t offset )
  38 {
  39     ssize_t ret;
  40     off_t old_pos;
  41
  42     if ((old_pos = lseek( fd, 0, SEEK_CUR )) == -1) return -1;
  43     if (lseek( fd, offset, SEEK_SET ) == -1) return -1;
  44     if ((ret = read( fd, buf, count )) == -1)
  45     {
  46         int err = errno;  /* save errno */
  47         lseek( fd, old_pos, SEEK_SET );
  48         errno = err;
  49         return -1;
  50     }
  51     if (lseek( fd, old_pos, SEEK_SET ) == -1) return -1;
  52     return ret;
  53 }
  54 #endif /* HAVE_PREAD */