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/*
* lseek() - POSIX 1003.1b 6.5.3 - Reposition Read/Write File Offset
*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.OARcorp.com/rtems/license.html.
*
* $Id$
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdio.h>
#include <rtems/libio_.h>
off_t lseek(
int fd,
off_t offset,
int whence
)
{
rtems_libio_t *iop;
off_t old_offset;
off_t status;
rtems_libio_check_fd( fd );
iop = rtems_libio_iop( fd );
rtems_libio_check_is_open(iop);
/*
* Check as many errors as possible before touching iop->offset.
*/
if ( !iop->handlers->lseek_h )
set_errno_and_return_minus_one( ENOTSUP );
/*
* Now process the lseek().
*/
old_offset = iop->offset;
switch ( whence ) {
case SEEK_SET:
iop->offset = offset;
break;
case SEEK_CUR:
iop->offset += offset;
break;
case SEEK_END:
iop->offset = iop->size + offset;
break;
default:
set_errno_and_return_minus_one( EINVAL );
}
/*
* At this time, handlers assume iop->offset has the desired
* new offset.
*/
status = (*iop->handlers->lseek_h)( iop, offset, whence );
if ( status == (off_t) -1 )
iop->offset = old_offset;
/*
* So if the operation failed, we have to restore iop->offset.
*/
return status;
}
/*
* _lseek_r
*
* This is the Newlib dependent reentrant version of lseek().
*/
#if defined(RTEMS_NEWLIB)
#include <reent.h>
off_t _lseek_r(
struct _reent *ptr,
int fd,
off_t offset,
int whence
)
{
return lseek( fd, offset, whence );
}
#endif
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