ftell.c revision 82684 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38#if 0
39static char sccsid[] = "@(#)ftell.c	8.2 (Berkeley) 5/4/95";
40#endif
41static const char rcsid[] =
42  "$FreeBSD: head/lib/libc/stdio/ftell.c 82684 2001-08-31 20:36:19Z ache $";
43#endif /* LIBC_SCCS and not lint */
44
45#include "namespace.h"
46#include <sys/types.h>
47#include <errno.h>
48#include <limits.h>
49#include <stdio.h>
50#include "un-namespace.h"
51#include "local.h"
52#include "libc_private.h"
53
54/*
55 * standard ftell function.
56 */
57long
58ftell(fp)
59	register FILE *fp;
60{
61	register off_t rv;
62
63	rv = ftello(fp);
64	if (rv > LONG_MAX) {
65		errno = EOVERFLOW;
66		return (-1);
67	}
68	return (rv);
69}
70
71/*
72 * ftello: return current offset.
73 */
74off_t
75ftello(fp)
76	register FILE *fp;
77{
78	register off_t rv;
79
80	/* make sure stdio is set up */
81	if (!__sdidinit)
82		__sinit();
83
84	FLOCKFILE(fp);
85	rv = _ftello(fp);
86	FUNLOCKFILE(fp);
87	return (rv);
88}
89
90off_t
91_ftello(fp)
92	register FILE *fp;
93{
94	register fpos_t pos, spos;
95	size_t n;
96
97	if (fp->_seek == NULL) {
98		errno = ESPIPE;			/* historic practice */
99		return (-1);
100	}
101
102	/*
103	 * Find offset of underlying I/O object, then
104	 * adjust for buffered bytes.
105	 */
106	if (fp->_flags & __SOFF) {
107		pos = fp->_offset;
108		spos = -1;
109	} else {
110get_real_pos:
111		spos = pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
112		if (pos == -1)
113			return (-1);
114	}
115	if (fp->_flags & __SRD) {
116		/*
117		 * Reading.  Any unread characters (including
118		 * those from ungetc) cause the position to be
119		 * smaller than that in the underlying object.
120		 */
121		if ((pos -= fp->_r) < 0 ||
122		    (HASUB(fp) && (pos -= fp->_ur) < 0)) {
123			fp->_p = fp->_bf._base;
124			fp->_r = 0;
125			if (HASUB(fp))
126				FREEUB(fp);
127			if (spos == -1)
128				goto get_real_pos;
129			pos = spos;
130		}
131	} else if ((fp->_flags & __SWR) && fp->_p != NULL) {
132		/*
133		 * Writing.  Any buffered characters cause the
134		 * position to be greater than that in the
135		 * underlying object.
136		 */
137		n = fp->_p - fp->_bf._base;
138		if (pos > OFF_MAX - n) {
139			errno = EOVERFLOW;
140			return (-1);
141		}
142		pos += n;
143	}
144	return (pos);
145}
146