ftell.c revision 165903 
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 * 4. 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: head/lib/libc/stdio/ftell.c 165903 2007-01-09 00:28:16Z imp $");
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(fp)
53	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(fp)
70	FILE *fp;
71{
72	fpos_t rv;
73	int ret;
74
75	FLOCKFILE(fp);
76	ret = _ftello(fp, &rv);
77	FUNLOCKFILE(fp);
78	if (ret)
79		return (-1);
80	if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
81		errno = ESPIPE;
82		return (-1);
83	}
84	return (rv);
85}
86
87int
88_ftello(fp, offset)
89	FILE *fp;
90	fpos_t *offset;
91{
92	fpos_t pos;
93	size_t n;
94
95	if (fp->_seek == NULL) {
96		errno = ESPIPE;			/* historic practice */
97		return (1);
98	}
99
100	/*
101	 * Find offset of underlying I/O object, then
102	 * adjust for buffered bytes.
103	 */
104	if (fp->_flags & __SOFF)
105		pos = fp->_offset;
106	else {
107		pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
108		if (pos == -1)
109			return (1);
110	}
111	if (fp->_flags & __SRD) {
112		/*
113		 * Reading.  Any unread characters (including
114		 * those from ungetc) cause the position to be
115		 * smaller than that in the underlying object.
116		 */
117		if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
118			fp->_flags |= __SERR;
119			errno = EIO;
120			return (1);
121		}
122		if (HASUB(fp))
123			pos -= fp->_r;  /* Can be negative at this point. */
124	} else if ((fp->_flags & __SWR) && fp->_p != NULL) {
125		/*
126		 * Writing.  Any buffered characters cause the
127		 * position to be greater than that in the
128		 * underlying object.
129		 */
130		n = fp->_p - fp->_bf._base;
131		if (pos > OFF_MAX - n) {
132			errno = EOVERFLOW;
133			return (1);
134		}
135		pos += n;
136	}
137	*offset = pos;
138	return (0);
139}
140