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1 /*	$OpenBSD: ftell.c,v 1.6 2005/08/08 08:05:36 espie Exp $ */
2 /*-
3  * Copyright (c) 1990, 1993
4  *	The Regents of the University of California.  All rights reserved.
5  *
6  * This code is derived from software contributed to Berkeley by
7  * Chris Torek.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #include <stdio.h>
35 #include <errno.h>
36 #include "local.h"
37 
38 /*
39  * ftello: return current offset.
40  */
41 off_t
ftello(FILE * fp)42 ftello(FILE *fp)
43 {
44 	fpos_t pos;
45 
46 	if (fp->_seek == NULL) {
47 		errno = ESPIPE;			/* historic practice */
48 		pos = -1;
49                 goto out;
50 	}
51 
52 	/*
53 	 * Find offset of underlying I/O object, then
54 	 * adjust for buffered bytes.
55 	 */
56         FLOCKFILE(fp);
57 	__sflush(fp);		/* may adjust seek offset on append stream */
58 	if (fp->_flags & __SOFF)
59 		pos = fp->_offset;
60 	else {
61 		pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
62 		if (pos == -1)
63 			goto out;
64 	}
65 	if (fp->_flags & __SRD) {
66 		/*
67 		 * Reading.  Any unread characters (including
68 		 * those from ungetc) cause the position to be
69 		 * smaller than that in the underlying object.
70 		 */
71 		pos -= fp->_r;
72 		if (HASUB(fp))
73 			pos -= fp->_ur;
74 	} else if (fp->_flags & __SWR && fp->_p != NULL) {
75 		/*
76 		 * Writing.  Any buffered characters cause the
77 		 * position to be greater than that in the
78 		 * underlying object.
79 		 */
80 		pos += fp->_p - fp->_bf._base;
81 	}
82 out:	FUNLOCKFILE(fp);
83 	return (pos);
84 }
85 
86 /*
87  * ftell() returns a long and sizeof(off_t) != sizeof(long) on all arches
88  */
89 #if defined(__alpha__) && defined(__indr_reference)
90 __indr_reference(ftello, ftell);
91 #else
92 long
ftell(FILE * fp)93 ftell(FILE *fp)
94 {
95 	long pos;
96 
97 	pos = (long)ftello(fp);
98 	return(pos);
99 }
100 #endif
101