[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 | * ftello: 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 | _off_t |
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| 86 | _ftello_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 | /* Ensure stdio is set up. */ |
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| 92 | |
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| 93 | CHECK_INIT (ptr, fp); |
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| 94 | |
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| 95 | _newlib_flockfile_start (fp); |
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| 96 | |
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| 97 | if (fp->_seek == NULL) |
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| 98 | { |
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| 99 | ptr->_errno = ESPIPE; |
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| 100 | _newlib_flockfile_exit (fp); |
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| 101 | return (_off_t) -1; |
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| 102 | } |
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| 103 | |
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| 104 | /* Find offset of underlying I/O object, then adjust for buffered bytes. */ |
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| 105 | if (!(fp->_flags & __SRD) && (fp->_flags & __SWR) && |
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| 106 | fp->_p != NULL && fp->_p - fp->_bf._base > 0 && |
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| 107 | (fp->_flags & __SAPP)) |
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| 108 | { |
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| 109 | pos = fp->_seek (ptr, fp->_cookie, (_fpos_t) 0, SEEK_END); |
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| 110 | if (pos == (_fpos_t) -1) |
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| 111 | { |
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| 112 | _newlib_flockfile_exit (fp); |
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| 113 | return (_off_t) -1; |
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| 114 | } |
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| 115 | } |
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| 116 | else if (fp->_flags & __SOFF) |
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| 117 | pos = fp->_offset; |
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| 118 | else |
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| 119 | { |
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| 120 | pos = fp->_seek (ptr, fp->_cookie, (_fpos_t) 0, SEEK_CUR); |
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| 121 | if (pos == (_fpos_t) -1) |
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| 122 | { |
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| 123 | _newlib_flockfile_exit (fp); |
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| 124 | return (_off_t) -1; |
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| 125 | } |
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| 126 | } |
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| 127 | if (fp->_flags & __SRD) |
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| 128 | { |
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| 129 | /* |
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| 130 | * Reading. Any unread characters (including |
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| 131 | * those from ungetc) cause the position to be |
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| 132 | * smaller than that in the underlying object. |
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| 133 | */ |
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| 134 | pos -= fp->_r; |
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| 135 | if (HASUB (fp)) |
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| 136 | pos -= fp->_ur; |
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| 137 | } |
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| 138 | else if ((fp->_flags & __SWR) && fp->_p != NULL) |
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| 139 | { |
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| 140 | /* |
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| 141 | * Writing. Any buffered characters cause the |
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| 142 | * position to be greater than that in the |
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| 143 | * underlying object. |
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| 144 | */ |
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| 145 | pos += fp->_p - fp->_bf._base; |
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| 146 | } |
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| 147 | |
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| 148 | _newlib_flockfile_end (fp); |
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| 149 | return (_off_t) pos; |
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| 150 | } |
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| 151 | |
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| 152 | #ifndef _REENT_ONLY |
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| 153 | |
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| 154 | _off_t |
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| 155 | ftello (register FILE * fp) |
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| 156 | { |
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| 157 | return _ftello_r (_REENT, fp); |
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| 158 | } |
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| 159 | |
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| 160 | #endif /* !_REENT_ONLY */ |
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