1 /* $OpenBSD: ftell.c,v 1.6 2005/08/08 08:05:36 espie Exp $ */
2 /*-
3 * Copyright (c) 1990, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #include <stdio.h>
35 #include <errno.h>
36 #include "local.h"
37
38 /*
39 * ftello: return current offset.
40 */
41 off_t
ftello(FILE * fp)42 ftello(FILE *fp)
43 {
44 fpos_t pos;
45
46 if (fp->_seek == NULL) {
47 errno = ESPIPE; /* historic practice */
48 return ((off_t)-1);
49 }
50
51 /*
52 * Find offset of underlying I/O object, then
53 * adjust for buffered bytes.
54 */
55 __sflush(fp); /* may adjust seek offset on append stream */
56 if (fp->_flags & __SOFF)
57 pos = fp->_offset;
58 else {
59 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
60 if (pos == -1L)
61 return (pos);
62 }
63 if (fp->_flags & __SRD) {
64 /*
65 * Reading. Any unread characters (including
66 * those from ungetc) cause the position to be
67 * smaller than that in the underlying object.
68 */
69 pos -= fp->_r;
70 if (HASUB(fp))
71 pos -= fp->_ur;
72 } else if (fp->_flags & __SWR && fp->_p != NULL) {
73 /*
74 * Writing. Any buffered characters cause the
75 * position to be greater than that in the
76 * underlying object.
77 */
78 pos += fp->_p - fp->_bf._base;
79 }
80 return (pos);
81 }
82
83 /*
84 * ftell() returns a long and sizeof(off_t) != sizeof(long) on all arches
85 */
86 #if defined(__alpha__) && defined(__indr_reference)
87 __indr_reference(ftello, ftell);
88 #else
89 long
ftell(FILE * fp)90 ftell(FILE *fp)
91 {
92 long pos;
93
94 pos = (long)ftello(fp);
95 return(pos);
96 }
97 #endif
98