~drizzle-trunk/drizzle/development

/* Copyright (C) 2000 MySQL AB

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

#include "mysys_priv.h"

/* 

  Seek to a position in a file.

  ARGUMENTS

  File fd          The file descriptor

  my_off_t pos     The expected position (absolute or relative)

  int whence       A direction parameter and one of 

                   {SEEK_SET, SEEK_CUR, SEEK_END}

  myf MyFlags      MY_THREADSAFE must be set in case my_seek may be mixed

                   with my_pread/my_pwrite calls and fd is shared among

                   threads.

  DESCRIPTION

    The my_seek  function  is a wrapper around the system call lseek and

    repositions  the  offset of the file descriptor fd to the argument 

    offset according to the directive whence as follows:

      SEEK_SET    The offset is set to offset bytes.

      SEEK_CUR    The offset is set to its current location plus offset bytes

      SEEK_END    The offset is set to the size of the file plus offset bytes

  RETURN VALUE

    my_off_t newpos    The new position in the file.

    MY_FILEPOS_ERROR   An error was encountered while performing 

                       the seek. my_errno is set to indicate the

                       actual error.

*/

my_off_t my_seek(File fd, my_off_t pos, int whence,

		 myf MyFlags __attribute__((unused)))

{

  register off_t newpos= -1;

  assert(pos != MY_FILEPOS_ERROR);		/* safety check */

  /*

      Make sure we are using a valid file descriptor!

  */

  assert(fd != -1);

#if !defined(HAVE_PREAD)

  if (MyFlags & MY_THREADSAFE)

  {

    pthread_mutex_lock(&my_file_info[fd].mutex);

    newpos= lseek(fd, pos, whence);

    pthread_mutex_unlock(&my_file_info[fd].mutex);

  }

  else

#endif

    newpos= lseek(fd, pos, whence);

  if (newpos == (off_t) -1)

  {

    my_errno=errno;

    return(MY_FILEPOS_ERROR);

  }

  return((my_off_t) newpos);

} /* my_seek */

	/* Tell current position of file */

	/* ARGSUSED */

my_off_t my_tell(File fd, myf MyFlags __attribute__((unused)))

{

  off_t pos;

  assert(fd >= 0);

#ifdef HAVE_TELL

  pos=tell(fd);

#else

  pos=lseek(fd, 0L, MY_SEEK_CUR);

#endif

  if (pos == (off_t) -1)

    my_errno=errno;

  return((my_off_t) pos);

} /* my_tell */