xref: /freebsd/lib/libc/stdio/ftell.c (revision 4a4e32a81de722e6dc702b0f6eec980f2e07ca4a)
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)
34 static char sccsid[] = "@(#)ftell.c	8.2 (Berkeley) 5/4/95";
35 #endif /* LIBC_SCCS and not lint */
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
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  */
51 long
52 ftell(FILE *fp)
53 {
54 	off_t rv;
55 
56 	rv = ftello(fp);
57 	if (rv > LONG_MAX) {
58 		errno = EOVERFLOW;
59 		return (-1);
60 	}
61 	return (rv);
62 }
63 
64 /*
65  * ftello: return current offset.
66  */
67 off_t
68 ftello(FILE *fp)
69 {
70 	fpos_t rv;
71 	int ret;
72 
73 	FLOCKFILE(fp);
74 	ret = _ftello(fp, &rv);
75 	FUNLOCKFILE(fp);
76 	if (ret)
77 		return (-1);
78 	if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
79 		errno = ESPIPE;
80 		return (-1);
81 	}
82 	return (rv);
83 }
84 
85 int
86 _ftello(FILE *fp, fpos_t *offset)
87 {
88 	fpos_t pos;
89 	size_t n;
90 
91 	if (fp->_seek == NULL) {
92 		errno = ESPIPE;			/* historic practice */
93 		return (1);
94 	}
95 
96 	/*
97 	 * Find offset of underlying I/O object, then
98 	 * adjust for buffered bytes.
99 	 */
100 	if (__sflush(fp))	/* may adjust seek offset on append stream */
101 		return (1);
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 		/*
124 		 * Writing.  Any buffered characters cause the
125 		 * position to be greater than that in the
126 		 * underlying object.
127 		 */
128 		n = fp->_p - fp->_bf._base;
129 		if (pos > OFF_MAX - n) {
130 			errno = EOVERFLOW;
131 			return (1);
132 		}
133 		pos += n;
134 	}
135 	*offset = pos;
136 	return (0);
137 }
138