109 lines
3.1 KiB
C
109 lines
3.1 KiB
C
/*
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are permitted
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* provided that the above copyright notice and this paragraph are
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* duplicated in all such forms and that any documentation,
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* advertising materials, and other materials related to such
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* distribution and use acknowledge that the software was developed
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* by the University of California, Berkeley. The name of the
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* University may not be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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/*
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FUNCTION
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<<ftell>>, <<ftello>>---return position in a stream or file
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INDEX
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ftell
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INDEX
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ftello
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INDEX
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_ftell_r
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INDEX
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_ftello_r
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SYNOPSIS
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#include <stdio.h>
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long ftell(FILE *<[fp]>);
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off_t ftello(FILE *<[fp]>);
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long _ftell_r(struct _reent *<[ptr]>, FILE *<[fp]>);
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off_t _ftello_r(struct _reent *<[ptr]>, FILE *<[fp]>);
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DESCRIPTION
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Objects of type <<FILE>> can have a ``position'' that records how much
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of the file your program has already read. Many of the <<stdio>> functions
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depend on this position, and many change it as a side effect.
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The result of <<ftell>>/<<ftello>> is the current position for a file
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identified by <[fp]>. If you record this result, you can later
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use it with <<fseek>>/<<fseeko>> to return the file to this
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position. The difference between <<ftell>> and <<ftello>> is that
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<<ftell>> returns <<long>> and <<ftello>> returns <<off_t>>.
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In the current implementation, <<ftell>>/<<ftello>> simply uses a character
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count to represent the file position; this is the same number that
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would be recorded by <<fgetpos>>.
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RETURNS
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<<ftell>>/<<ftello>> return the file position, if possible. If they cannot do
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this, they return <<-1L>>. Failure occurs on streams that do not support
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positioning; the global <<errno>> indicates this condition with the
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value <<ESPIPE>>.
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PORTABILITY
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<<ftell>> is required by the ANSI C standard, but the meaning of its
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result (when successful) is not specified beyond requiring that it be
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acceptable as an argument to <<fseek>>. In particular, other
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conforming C implementations may return a different result from
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<<ftell>> than what <<fgetpos>> records.
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<<ftello>> is defined by the Single Unix specification.
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No supporting OS subroutines are required.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "%W% (Berkeley) %G%";
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#endif /* LIBC_SCCS and not lint */
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/*
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* ftell: return current offset.
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*/
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#include <_ansi.h>
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#include <reent.h>
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#include <stdio.h>
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#include <errno.h>
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#include "local.h"
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long
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_ftell_r (struct _reent *ptr,
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register FILE * fp)
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{
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_fpos_t pos;
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pos = _ftello_r (ptr, fp);
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if ((long)pos != pos)
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{
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pos = -1;
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ptr->_errno = EOVERFLOW;
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}
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return (long)pos;
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}
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#ifndef _REENT_ONLY
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long
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ftell (register FILE * fp)
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{
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return _ftell_r (_REENT, fp);
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}
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#endif /* !_REENT_ONLY */
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