90 lines
3.0 KiB
C
90 lines
3.0 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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* This code is derived from software contributed to Berkeley by
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* Chris Torek.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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/*static char *sccsid = "from: @(#)ftell.c 5.4 (Berkeley) 2/5/91";*/
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static char *rcsid = "$Id: ftell.c,v 1.3 1993/08/26 00:46:58 jtc Exp $";
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#endif /* LIBC_SCCS and not lint */
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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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/*
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* ftell: return current offset.
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*/
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long
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ftell(fp)
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register const FILE *fp;
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{
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register fpos_t pos;
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if (fp->_seek == NULL) {
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errno = ESPIPE; /* historic practice */
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return (-1L);
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}
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/*
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* Find offset of underlying I/O object, then
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* adjust for buffered bytes.
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*/
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if (fp->_flags & __SOFF)
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pos = fp->_offset;
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else {
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pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
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if (pos == -1L)
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return (pos);
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}
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if (fp->_flags & __SRD) {
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/*
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* Reading. Any unread characters (including
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* those from ungetc) cause the position to be
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* smaller than that in the underlying object.
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*/
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pos -= fp->_r;
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if (HASUB(fp))
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pos -= fp->_ur;
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} else if (fp->_flags & __SWR && fp->_p != NULL) {
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/*
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* Writing. Any buffered characters cause the
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* position to be greater than that in the
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* underlying object.
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*/
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pos += fp->_p - fp->_bf._base;
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}
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return (pos);
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}
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