offset.h revision 290001 
1/*
2 * Copyright (C) 2004, 2007  Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 2000, 2001  Internet Software Consortium.
4 *
5 * Permission to use, copy, modify, and/or distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15 * PERFORMANCE OF THIS SOFTWARE.
16 */
17
18/* $Id: offset.h,v 1.6 2007/06/19 23:47:20 tbox Exp $ */
19
20#ifndef ISC_OFFSET_H
21#define ISC_OFFSET_H 1
22
23/*
24 * File offsets are operating-system dependent.
25 */
26#include <limits.h>             /* Required for CHAR_BIT. */
27#include <sys/types.h>
28
29typedef _off_t isc_offset_t;
30
31/*
32 * POSIX says "Additionally, blkcnt_t and off_t are extended signed integral
33 * types", so the maximum value is all 1s except for the high bit.
34 * This definition is more complex than it really needs to be because it was
35 * crafted to keep both the SunOS 5.6 and the HP/UX 11 compilers quiet about
36 * integer overflow.  For example, though this is equivalent to just left
37 * shifting 1 to the high bit and then inverting the bits, the SunOS compiler
38 * is unhappy about shifting a positive "1" to negative in a signed integer.
39 */
40#define ISC_OFFSET_MAXIMUM \
41	(~(((off_t)-1 >> (sizeof(off_t) * CHAR_BIT - 1)) \
42		      << (sizeof(off_t) * CHAR_BIT - 1)))
43
44#endif /* ISC_OFFSET_H */
45