1 | /* |
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2 | * Copyright (c) 1990 The Regents of the University of California. |
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3 | * All rights reserved. |
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4 | * |
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5 | * Redistribution and use in source and binary forms are permitted |
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6 | * provided that the above copyright notice and this paragraph are |
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7 | * duplicated in all such forms and that any documentation, |
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8 | * advertising materials, and other materials related to such |
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9 | * distribution and use acknowledge that the software was developed |
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10 | * by the University of California, Berkeley. The name of the |
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11 | * University may not be used to endorse or promote products derived |
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12 | * from this software without specific prior written permission. |
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13 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR |
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14 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED |
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15 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. |
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16 | */ |
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17 | |
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18 | /* |
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19 | FUNCTION |
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20 | <<fseek>>, <<fseeko>>---set file position |
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21 | |
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22 | INDEX |
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23 | fseek |
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24 | INDEX |
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25 | fseeko |
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26 | INDEX |
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27 | _fseek_r |
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28 | INDEX |
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29 | _fseeko_r |
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30 | |
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31 | SYNOPSIS |
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32 | #include <stdio.h> |
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33 | int fseek(FILE *<[fp]>, long <[offset]>, int <[whence]>); |
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34 | int fseeko(FILE *<[fp]>, off_t <[offset]>, int <[whence]>); |
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35 | int _fseek_r(struct _reent *<[ptr]>, FILE *<[fp]>, |
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36 | long <[offset]>, int <[whence]>); |
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37 | int _fseeko_r(struct _reent *<[ptr]>, FILE *<[fp]>, |
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38 | off_t <[offset]>, int <[whence]>); |
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39 | |
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40 | DESCRIPTION |
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41 | Objects of type <<FILE>> can have a ``position'' that records how much |
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42 | of the file your program has already read. Many of the <<stdio>> functions |
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43 | depend on this position, and many change it as a side effect. |
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44 | |
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45 | You can use <<fseek>>/<<fseeko>> to set the position for the file identified by |
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46 | <[fp]>. The value of <[offset]> determines the new position, in one |
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47 | of three ways selected by the value of <[whence]> (defined as macros |
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48 | in `<<stdio.h>>'): |
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49 | |
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50 | <<SEEK_SET>>---<[offset]> is the absolute file position (an offset |
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51 | from the beginning of the file) desired. <[offset]> must be positive. |
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52 | |
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53 | <<SEEK_CUR>>---<[offset]> is relative to the current file position. |
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54 | <[offset]> can meaningfully be either positive or negative. |
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55 | |
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56 | <<SEEK_END>>---<[offset]> is relative to the current end of file. |
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57 | <[offset]> can meaningfully be either positive (to increase the size |
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58 | of the file) or negative. |
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59 | |
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60 | See <<ftell>>/<<ftello>> to determine the current file position. |
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61 | |
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62 | RETURNS |
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63 | <<fseek>>/<<fseeko>> return <<0>> when successful. On failure, the |
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64 | result is <<EOF>>. The reason for failure is indicated in <<errno>>: |
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65 | either <<ESPIPE>> (the stream identified by <[fp]> doesn't support |
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66 | repositioning) or <<EINVAL>> (invalid file position). |
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67 | |
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68 | PORTABILITY |
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69 | ANSI C requires <<fseek>>. |
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70 | |
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71 | <<fseeko>> is defined by the Single Unix specification. |
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72 | |
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73 | Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>, |
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74 | <<lseek>>, <<read>>, <<sbrk>>, <<write>>. |
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75 | */ |
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76 | |
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77 | #include <_ansi.h> |
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78 | #include <reent.h> |
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79 | #include <stdio.h> |
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80 | #include <errno.h> |
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81 | #include "local.h" |
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82 | |
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83 | int |
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84 | _fseek_r (struct _reent *ptr, |
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85 | register FILE *fp, |
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86 | long offset, |
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87 | int whence) |
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88 | { |
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89 | return _fseeko_r (ptr, fp, offset, whence); |
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90 | } |
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91 | |
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92 | #ifndef _REENT_ONLY |
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93 | |
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94 | int |
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95 | fseek (register FILE *fp, |
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96 | long offset, |
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97 | int whence) |
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98 | { |
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99 | return _fseek_r (_REENT, fp, offset, whence); |
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100 | } |
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101 | |
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102 | #endif /* !_REENT_ONLY */ |
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