[444] | 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 | <<ftell>>, <<ftello>>---return position in a stream or file |
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| 21 | |
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| 22 | INDEX |
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| 23 | ftell |
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| 24 | INDEX |
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| 25 | ftello |
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| 26 | INDEX |
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| 27 | _ftell_r |
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| 28 | INDEX |
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| 29 | _ftello_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 | long ftell(FILE *<[fp]>); |
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| 34 | off_t ftello(FILE *<[fp]>); |
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| 35 | long _ftell_r(struct _reent *<[ptr]>, FILE *<[fp]>); |
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| 36 | off_t _ftello_r(struct _reent *<[ptr]>, FILE *<[fp]>); |
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| 37 | |
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| 38 | DESCRIPTION |
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| 39 | Objects of type <<FILE>> can have a ``position'' that records how much |
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| 40 | of the file your program has already read. Many of the <<stdio>> functions |
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| 41 | depend on this position, and many change it as a side effect. |
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| 42 | |
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| 43 | The result of <<ftell>>/<<ftello>> is the current position for a file |
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| 44 | identified by <[fp]>. If you record this result, you can later |
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| 45 | use it with <<fseek>>/<<fseeko>> to return the file to this |
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| 46 | position. The difference between <<ftell>> and <<ftello>> is that |
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| 47 | <<ftell>> returns <<long>> and <<ftello>> returns <<off_t>>. |
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| 48 | |
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| 49 | In the current implementation, <<ftell>>/<<ftello>> simply uses a character |
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| 50 | count to represent the file position; this is the same number that |
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| 51 | would be recorded by <<fgetpos>>. |
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| 52 | |
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| 53 | RETURNS |
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| 54 | <<ftell>>/<<ftello>> return the file position, if possible. If they cannot do |
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| 55 | this, they return <<-1L>>. Failure occurs on streams that do not support |
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| 56 | positioning; the global <<errno>> indicates this condition with the |
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| 57 | value <<ESPIPE>>. |
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| 58 | |
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| 59 | PORTABILITY |
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| 60 | <<ftell>> is required by the ANSI C standard, but the meaning of its |
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| 61 | result (when successful) is not specified beyond requiring that it be |
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| 62 | acceptable as an argument to <<fseek>>. In particular, other |
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| 63 | conforming C implementations may return a different result from |
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| 64 | <<ftell>> than what <<fgetpos>> records. |
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| 65 | |
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| 66 | <<ftello>> is defined by the Single Unix specification. |
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| 67 | |
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| 68 | No supporting OS subroutines are required. |
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| 69 | */ |
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| 70 | |
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| 71 | #if defined(LIBC_SCCS) && !defined(lint) |
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| 72 | static char sccsid[] = "%W% (Berkeley) %G%"; |
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| 73 | #endif /* LIBC_SCCS and not lint */ |
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| 74 | |
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| 75 | /* |
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| 76 | * ftell: return current offset. |
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| 77 | */ |
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| 78 | |
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| 79 | #include <_ansi.h> |
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| 80 | #include <reent.h> |
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| 81 | #include <stdio.h> |
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| 82 | #include <errno.h> |
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| 83 | #include "local.h" |
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| 84 | |
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| 85 | long |
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| 86 | _ftell_r (struct _reent *ptr, |
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| 87 | register FILE * fp) |
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| 88 | { |
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| 89 | _fpos_t pos; |
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| 90 | |
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| 91 | pos = _ftello_r (ptr, fp); |
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| 92 | if ((long)pos != pos) |
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| 93 | { |
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| 94 | pos = -1; |
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| 95 | ptr->_errno = EOVERFLOW; |
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| 96 | } |
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| 97 | return (long)pos; |
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| 98 | } |
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| 99 | |
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| 100 | #ifndef _REENT_ONLY |
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| 101 | |
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| 102 | long |
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| 103 | ftell (register FILE * fp) |
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| 104 | { |
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| 105 | return _ftell_r (_REENT, fp); |
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| 106 | } |
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| 107 | |
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| 108 | #endif /* !_REENT_ONLY */ |
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