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 * @(#)ftell.c 8.2 (Berkeley) 5/4/95
33 * $FreeBSD: src/lib/libc/stdio/ftell.c,v 1.27 2007/01/09 00:28:06 imp Exp $
34 */
35
36 #include "namespace.h"
37 #include <sys/types.h>
38 #include <errno.h>
39 #include <limits.h>
40 #include <stdio.h>
41 #include "un-namespace.h"
42 #include "local.h"
43 #include "libc_private.h"
44
45 /*
46 * standard ftell function.
47 */
48 long
ftell(FILE * fp)49 ftell(FILE *fp)
50 {
51 off_t rv;
52
53 rv = ftello(fp);
54 if (rv > LONG_MAX) {
55 errno = EOVERFLOW;
56 return (-1);
57 }
58 return (rv);
59 }
60
61 /*
62 * ftello: return current offset.
63 */
64 off_t
ftello(FILE * fp)65 ftello(FILE *fp)
66 {
67 fpos_t rv;
68 int ret;
69
70 FLOCKFILE(fp);
71 ret = _ftello(fp, &rv);
72 FUNLOCKFILE(fp);
73 if (ret)
74 return (-1);
75 if (rv < 0) { /* Unspecified value because of ungetc() at 0 */
76 errno = ESPIPE;
77 return (-1);
78 }
79 return (rv);
80 }
81
82 int
_ftello(FILE * fp,fpos_t * offset)83 _ftello(FILE *fp, fpos_t *offset)
84 {
85 fpos_t pos;
86 size_t n;
87
88 if (fp->_seek == NULL) {
89 errno = ESPIPE; /* historic practice */
90 return (1);
91 }
92
93 /*
94 * Find offset of underlying I/O object, then
95 * adjust for buffered bytes.
96 */
97 if (fp->pub._flags & __SOFF)
98 pos = fp->_offset;
99 else {
100 pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
101 if (pos == -1)
102 return (1);
103 }
104 if (fp->pub._flags & __SRD) {
105 /*
106 * Reading. Any unread characters (including
107 * those from ungetc) cause the position to be
108 * smaller than that in the underlying object.
109 */
110 if ((pos -= (HASUB(fp) ? fp->_ur : fp->pub._r)) < 0) {
111 fp->pub._flags |= __SERR;
112 errno = EIO;
113 return (1);
114 }
115 if (HASUB(fp))
116 pos -= fp->pub._r; /* Can be negative at this point. */
117 } else if ((fp->pub._flags & __SWR) && fp->pub._p != NULL) {
118 /*
119 * Writing. Any buffered characters cause the
120 * position to be greater than that in the
121 * underlying object.
122 */
123 n = fp->pub._p - fp->_bf._base;
124 if (pos > OFF_MAX - n) {
125 errno = EOVERFLOW;
126 return (1);
127 }
128 pos += n;
129 }
130 *offset = pos;
131 return (0);
132 }
133