offset.h

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00001 /*
00002  * Copyright (C) 2004, 2005, 2007, 2008  Internet Systems Consortium, Inc. ("ISC")
00003  * Copyright (C) 2000, 2001  Internet Software Consortium.
00004  *
00005  * Permission to use, copy, modify, and/or distribute this software for any
00006  * purpose with or without fee is hereby granted, provided that the above
00007  * copyright notice and this permission notice appear in all copies.
00008  *
00009  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
00010  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
00011  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
00012  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
00013  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
00014  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
00015  * PERFORMANCE OF THIS SOFTWARE.
00016  */
00017 
00018 /* $Id: offset.h,v 1.17 2008/12/01 23:47:45 tbox Exp $ */
00019 
00020 #ifndef ISC_OFFSET_H
00021 #define ISC_OFFSET_H 1
00022 
00023 /*! \file
00024  * \brief
00025  * File offsets are operating-system dependent.
00026  */
00027 #include <limits.h>             /* Required for CHAR_BIT. */
00028 #include <sys/types.h>
00029 #include <stddef.h>             /* For Linux Standard Base. */
00030 
00031 typedef off_t isc_offset_t;
00032 
00033 /*%
00034  * POSIX says "Additionally, blkcnt_t and off_t are extended signed integral
00035  * types", so the maximum value is all 1s except for the high bit.
00036  * This definition is more complex than it really needs to be because it was
00037  * crafted to keep both the SunOS 5.6 and the HP/UX 11 compilers quiet about
00038  * integer overflow.  For example, though this is equivalent to just left
00039  * shifting 1 to the high bit and then inverting the bits, the SunOS compiler
00040  * is unhappy about shifting a positive "1" to negative in a signed integer.
00041  */
00042 #define ISC_OFFSET_MAXIMUM \
00043         (~(((off_t)-1 >> (sizeof(off_t) * CHAR_BIT - 1)) \
00044                       << (sizeof(off_t) * CHAR_BIT - 1)))
00045 
00046 #endif /* ISC_OFFSET_H */

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