ftell.c revision 331722 
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. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)ftell.c	8.2 (Berkeley) 5/4/95";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/11/lib/libc/stdio/ftell.c 331722 2018-03-29 02:50:57Z eadler $");
38
39#include "namespace.h"
40#include <sys/types.h>
41#include <errno.h>
42#include <limits.h>
43#include <stdio.h>
44#include "un-namespace.h"
45#include "local.h"
46#include "libc_private.h"
47
48/*
49 * standard ftell function.
50 */
51long
52ftell(FILE *fp)
53{
54	off_t rv;
55
56	rv = ftello(fp);
57	if (rv > LONG_MAX) {
58		errno = EOVERFLOW;
59		return (-1);
60	}
61	return (rv);
62}
63
64/*
65 * ftello: return current offset.
66 */
67off_t
68ftello(FILE *fp)
69{
70	fpos_t rv;
71	int ret;
72
73	FLOCKFILE(fp);
74	ret = _ftello(fp, &rv);
75	FUNLOCKFILE(fp);
76	if (ret)
77		return (-1);
78	if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
79		errno = ESPIPE;
80		return (-1);
81	}
82	return (rv);
83}
84
85int
86_ftello(FILE *fp, fpos_t *offset)
87{
88	fpos_t pos;
89	size_t n;
90
91	if (fp->_seek == NULL) {
92		errno = ESPIPE;			/* historic practice */
93		return (1);
94	}
95
96	/*
97	 * Find offset of underlying I/O object, then
98	 * adjust for buffered bytes.
99	 */
100	if (!(fp->_flags & __SRD) && (fp->_flags & __SWR) &&
101	    fp->_p != NULL && fp->_p - fp->_bf._base > 0 &&
102	    ((fp->_flags & __SAPP) || (fp->_flags2 & __S2OAP))) {
103		pos = _sseek(fp, (fpos_t)0, SEEK_END);
104		if (pos == -1)
105			return (1);
106	} else if (fp->_flags & __SOFF)
107		pos = fp->_offset;
108	else {
109		pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
110		if (pos == -1)
111			return (1);
112	}
113	if (fp->_flags & __SRD) {
114		/*
115		 * Reading.  Any unread characters (including
116		 * those from ungetc) cause the position to be
117		 * smaller than that in the underlying object.
118		 */
119		if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
120			fp->_flags |= __SERR;
121			errno = EIO;
122			return (1);
123		}
124		if (HASUB(fp))
125			pos -= fp->_r;  /* Can be negative at this point. */
126	} else if ((fp->_flags & __SWR) && fp->_p != NULL &&
127	    (n = fp->_p - fp->_bf._base) > 0) {
128		/*
129		 * Writing.  Any buffered characters cause the
130		 * position to be greater than that in the
131		 * underlying object.
132		 */
133		if (pos > OFF_MAX - n) {
134			errno = EOVERFLOW;
135			return (1);
136		}
137		pos += n;
138	}
139	*offset = pos;
140	return (0);
141}
142