ftell.c revision 82709 
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 82709 2001-09-01 01:56:54Z 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	fpos_t rv;
79	int ret;
80
81	/* make sure stdio is set up */
82	if (!__sdidinit)
83		__sinit();
84
85	FLOCKFILE(fp);
86	ret = _ftello(fp, &rv);
87	FUNLOCKFILE(fp);
88	if (ret)
89		return (-1);
90	if (rv < 0)     /* Unspecified value because of ungetc() at 0 */
91		rv = 0;
92	return (rv);
93}
94
95int
96_ftello(fp, offset)
97	register FILE *fp;
98	fpos_t *offset;
99{
100	register fpos_t pos, spos;
101	size_t n;
102
103	if (fp->_seek == NULL) {
104		errno = ESPIPE;			/* historic practice */
105		return (1);
106	}
107
108	/*
109	 * Find offset of underlying I/O object, then
110	 * adjust for buffered bytes.
111	 */
112	if (fp->_flags & __SOFF) {
113		pos = fp->_offset;
114		spos = -1;
115	} else {
116get_real_pos:
117		spos = pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
118		if (pos == -1)
119			return (1);
120	}
121	if (fp->_flags & __SRD) {
122		/*
123		 * Reading.  Any unread characters (including
124		 * those from ungetc) cause the position to be
125		 * smaller than that in the underlying object.
126		 */
127		if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
128			/* Lost position, resync. */
129			if (HASUB(fp)) {
130				fp->_extra->_up = fp->_bf._base;
131				fp->_ur = 0;
132			} else {
133				fp->_p = fp->_bf._base;
134				fp->_r = 0;
135			}
136			if (spos == -1)
137				goto get_real_pos;
138			pos = spos;
139		}
140		if (HASUB(fp))
141			pos -= fp->_r;  /* Can be negative at this point. */
142	} else if ((fp->_flags & __SWR) && fp->_p != NULL) {
143		/*
144		 * Writing.  Any buffered characters cause the
145		 * position to be greater than that in the
146		 * underlying object.
147		 */
148		n = fp->_p - fp->_bf._base;
149		if (pos > OFF_MAX - n) {
150			errno = EOVERFLOW;
151			return (1);
152		}
153		pos += n;
154	}
155	*offset = pos;
156	return (0);
157}
158