ftell.c revision 269623 
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 269623 2014-08-06 10:33:43Z 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	int dflags;
92
93	if (fp->_seek == NULL) {
94		errno = ESPIPE;			/* historic practice */
95		return (1);
96	}
97
98	/*
99	 * Find offset of underlying I/O object, then
100	 * adjust for buffered bytes.
101	 */
102	if (fp->_flags & __SOFF)
103		pos = fp->_offset;
104	else {
105		pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
106		if (pos == -1)
107			return (1);
108	}
109	if (fp->_flags & __SRD) {
110		/*
111		 * Reading.  Any unread characters (including
112		 * those from ungetc) cause the position to be
113		 * smaller than that in the underlying object.
114		 */
115		if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
116			fp->_flags |= __SERR;
117			errno = EIO;
118			return (1);
119		}
120		if (HASUB(fp))
121			pos -= fp->_r;  /* Can be negative at this point. */
122	} else if ((fp->_flags & __SWR) && fp->_p != NULL) {
123		dflags = 0;
124		if (fp->_flags & __SAPP)
125			dflags = O_APPEND;
126		else if (fp->_file != -1 &&
127			 (dflags = _fcntl(fp->_file, F_GETFL)) < 0)
128			return (1);
129		if ((dflags & O_APPEND) &&
130		    (pos = _sseek(fp, (fpos_t)0, SEEK_END)) == -1) {
131			if ((fp->_flags & __SOPT) || __sflush(fp) ||
132			    (pos = _sseek(fp, (fpos_t)0, SEEK_CUR)) == -1)
133				return (1);
134			else {
135				*offset = pos;
136				return (0);
137			}
138		}
139		/*
140		 * Writing.  Any buffered characters cause the
141		 * position to be greater than that in the
142		 * underlying object.
143		 */
144		n = fp->_p - fp->_bf._base;
145		if (pos > OFF_MAX - n) {
146			errno = EOVERFLOW;
147			return (1);
148		}
149		pos += n;
150	}
151	*offset = pos;
152	return (0);
153}
154