1/*	$NetBSD: ftello.c,v 1.6 2012/03/15 18:22:30 christos Exp $	*/
2
3/*-
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/cdefs.h>
36#if defined(LIBC_SCCS) && !defined(lint)
37__RCSID("$NetBSD: ftello.c,v 1.6 2012/03/15 18:22:30 christos Exp $");
38#endif /* LIBC_SCCS and not lint */
39
40#include "namespace.h"
41#include <assert.h>
42#include <errno.h>
43#include <stdio.h>
44#include "reentrant.h"
45#include "local.h"
46
47#ifdef __weak_alias
48__weak_alias(ftello, _ftello)
49#endif
50
51/*
52 * ftell: return current offset.
53 */
54off_t
55ftello(FILE *fp)
56{
57	off_t pos;
58
59
60	FLOCKFILE(fp);
61
62	if (fp->_seek == NULL) {
63		FUNLOCKFILE(fp);
64		errno = ESPIPE;			/* historic practice */
65		return (off_t)-1;
66	}
67
68	/*
69	 * Find offset of underlying I/O object, then
70	 * adjust for buffered bytes.
71	 */
72	(void)__sflush(fp); /* may adjust seek offset on append stream */
73	if (fp->_flags & __SOFF)
74		pos = fp->_offset;
75	else {
76		pos = (*fp->_seek)(fp->_cookie, (off_t)0, SEEK_CUR);
77		if (pos == (off_t)-1) {
78			FUNLOCKFILE(fp);
79			return pos;
80		}
81	}
82	if (fp->_flags & __SRD) {
83		/*
84		 * Reading.  Any unread characters (including
85		 * those from ungetc) cause the position to be
86		 * smaller than that in the underlying object.
87		 */
88		pos -= fp->_r;
89		if (HASUB(fp))
90			pos -= fp->_ur;
91	} else if (fp->_flags & __SWR && fp->_p != NULL) {
92		/*
93		 * Writing.  Any buffered characters cause the
94		 * position to be greater than that in the
95		 * underlying object.
96		 */
97		pos += fp->_p - fp->_bf._base;
98	}
99	FUNLOCKFILE(fp);
100	return pos;
101}
102