ftell.c revision 290544 
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/10/lib/libc/stdio/ftell.c 290544 2015-11-08 13:37:16Z ache $");
38
39#include "namespace.h"
40#include <sys/types.h>
41#include <errno.h>
42#include <fcntl.h>
43#include <limits.h>
44#include <stdio.h>
45#include "un-namespace.h"
46#include "local.h"
47#include "libc_private.h"
48
49/*
50 * standard ftell function.
51 */
52long
53ftell(FILE *fp)
54{
55	off_t rv;
56
57	rv = ftello(fp);
58	if (rv > LONG_MAX) {
59		errno = EOVERFLOW;
60		return (-1);
61	}
62	return (rv);
63}
64
65/*
66 * ftello: return current offset.
67 */
68off_t
69ftello(FILE *fp)
70{
71	fpos_t rv;
72	int ret;
73
74	FLOCKFILE(fp);
75	ret = _ftello(fp, &rv);
76	FUNLOCKFILE(fp);
77	if (ret)
78		return (-1);
79	if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
80		errno = ESPIPE;
81		return (-1);
82	}
83	return (rv);
84}
85
86int
87_ftello(FILE *fp, fpos_t *offset)
88{
89	fpos_t pos;
90	size_t n;
91
92	if (fp->_seek == NULL) {
93		errno = ESPIPE;			/* historic practice */
94		return (1);
95	}
96
97	/*
98	 * Find offset of underlying I/O object, then
99	 * adjust for buffered bytes.
100	 */
101	if (fp->_flags & __SOFF)
102		pos = fp->_offset;
103	else {
104		pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
105		if (pos == -1)
106			return (1);
107	}
108	if (fp->_flags & __SRD) {
109		/*
110		 * Reading.  Any unread characters (including
111		 * those from ungetc) cause the position to be
112		 * smaller than that in the underlying object.
113		 */
114		if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
115			fp->_flags |= __SERR;
116			errno = EIO;
117			return (1);
118		}
119		if (HASUB(fp))
120			pos -= fp->_r;  /* Can be negative at this point. */
121	} else if ((fp->_flags & __SWR) && fp->_p != NULL &&
122	    (n = fp->_p - fp->_bf._base) > 0) {
123		/*
124		 * Writing.  Any buffered characters cause the
125		 * position to be greater than that in the
126		 * underlying object.
127		 */
128		if ((fp->_flags & __SAPP) || (fp->_flags2 & __S2OAP)) {
129			int serrno = errno;
130
131			errno = 0;
132			if ((pos = _sseek(fp, (fpos_t)0, SEEK_END)) == -1) {
133				if (errno == ESPIPE ||
134				    (fp->_flags & __SOPT) || __sflush(fp) ||
135				    (pos =
136				    _sseek(fp, (fpos_t)0, SEEK_CUR)) == -1)
137					return (1);
138				else {
139					errno = serrno;
140					*offset = pos;
141					return (0);
142				}
143			}
144			errno = serrno;
145			/* fp->_p can be changed in _sseek(), recalculate. */
146			n = fp->_p - fp->_bf._base;
147		}
148		if (pos > OFF_MAX - n) {
149			errno = EOVERFLOW;
150			return (1);
151		}
152		pos += n;
153	}
154	*offset = pos;
155	return (0);
156}
157