Annotation of prex-old/usr/lib/libc/stdio/ftell.c, Revision 1.1.1.1
1.1 nbrk 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: #include <stdio.h>
34: #include <errno.h>
35: #include "local.h"
36:
37: /*
38: * ftell: return current offset.
39: */
40: long
41: ftell(fp)
42: FILE *fp;
43: {
44: fpos_t pos;
45:
46: /*
47: * Find offset of underlying I/O object, then
48: * adjust for buffered bytes.
49: */
50: pos = __sseek(fp, (fpos_t)0, SEEK_CUR);
51: if (pos == -(fpos_t)1)
52: return (pos);
53:
54: if (fp->_flags & __SRD) {
55: /*
56: * Reading. Any unread characters (including
57: * those from ungetc) cause the position to be
58: * smaller than that in the underlying object.
59: */
60: pos -= fp->_r;
61: if (HASUB(fp))
62: pos -= fp->_ur;
63: } else if (fp->_flags & __SWR && fp->_p != NULL) {
64: /*
65: * Writing. Any buffered characters cause the
66: * position to be greater than that in the
67: * underlying object.
68: */
69: pos += fp->_p - fp->_bf._base;
70: }
71: return (pos);
72: }
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