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