1 | /* |
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2 | * lseek() - POSIX 1003.1b 6.5.3 - Reposition Read/Write File Offset |
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3 | * |
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4 | * COPYRIGHT (c) 1989-1999. |
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5 | * On-Line Applications Research Corporation (OAR). |
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6 | * |
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7 | * The license and distribution terms for this file may be |
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8 | * found in the file LICENSE in this distribution or at |
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9 | * http://www.OARcorp.com/rtems/license.html. |
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10 | * |
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11 | * $Id$ |
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12 | */ |
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13 | |
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14 | #if HAVE_CONFIG_H |
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15 | #include "config.h" |
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16 | #endif |
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17 | |
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18 | #include <stdio.h> |
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19 | |
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20 | #include <rtems/libio_.h> |
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21 | #include <rtems/seterr.h> |
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22 | |
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23 | off_t lseek( |
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24 | int fd, |
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25 | off_t offset, |
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26 | int whence |
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27 | ) |
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28 | { |
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29 | rtems_libio_t *iop; |
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30 | off_t old_offset; |
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31 | off_t status; |
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32 | |
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33 | rtems_libio_check_fd( fd ); |
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34 | iop = rtems_libio_iop( fd ); |
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35 | rtems_libio_check_is_open(iop); |
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36 | |
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37 | /* |
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38 | * Check as many errors as possible before touching iop->offset. |
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39 | */ |
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40 | |
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41 | if ( !iop->handlers->lseek_h ) |
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42 | rtems_set_errno_and_return_minus_one( ENOTSUP ); |
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43 | |
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44 | /* |
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45 | * Now process the lseek(). |
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46 | */ |
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47 | |
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48 | old_offset = iop->offset; |
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49 | switch ( whence ) { |
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50 | case SEEK_SET: |
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51 | iop->offset = offset; |
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52 | break; |
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53 | |
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54 | case SEEK_CUR: |
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55 | iop->offset += offset; |
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56 | break; |
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57 | |
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58 | case SEEK_END: |
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59 | iop->offset = iop->size + offset; |
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60 | break; |
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61 | |
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62 | default: |
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63 | rtems_set_errno_and_return_minus_one( EINVAL ); |
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64 | } |
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65 | |
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66 | /* |
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67 | * At this time, handlers assume iop->offset has the desired |
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68 | * new offset. |
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69 | */ |
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70 | |
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71 | status = (*iop->handlers->lseek_h)( iop, offset, whence ); |
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72 | if ( status == (off_t) -1 ) |
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73 | iop->offset = old_offset; |
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74 | |
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75 | /* |
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76 | * So if the operation failed, we have to restore iop->offset. |
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77 | */ |
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78 | |
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79 | return status; |
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80 | } |
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81 | |
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82 | /* |
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83 | * _lseek_r |
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84 | * |
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85 | * This is the Newlib dependent reentrant version of lseek(). |
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86 | */ |
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87 | |
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88 | #if defined(RTEMS_NEWLIB) |
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89 | |
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90 | #include <reent.h> |
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91 | |
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92 | off_t _lseek_r( |
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93 | struct _reent *ptr, |
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94 | int fd, |
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95 | off_t offset, |
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96 | int whence |
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97 | ) |
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98 | { |
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99 | return lseek( fd, offset, whence ); |
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100 | } |
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101 | #endif |
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102 | |
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