Date: Thu, 15 May 2008 22:18:53 -0700 From: Xin LI <delphij@delphij.net> To: freebsd-arch@FreeBSD.org Cc: sephe@FreeBSD.org Subject: A couple of bitwise operations Message-ID: <482D193D.2010802@delphij.net>
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This is a multi-part message in MIME format. --------------070905020208020405010806 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, I find the DragonFly macros, __BIT, __BITS, __LOWEST_SET_BIT, __SHIFTOUT, __SHIFTIN and __SHIFTOUT_MASK useful. Any objection adding this as sys/sys/bitops.h? (These macros are found in NetBSD in sys/sys/cdefs.h and DragonFly as sys/sys/bitops.h) Cheers, - -- ** Help China's quake relief at http://www.redcross.org.cn/ |>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Xin LI <delphij@delphij.net> http://www.delphij.net/ FreeBSD - The Power to Serve! -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (FreeBSD) iEYEARECAAYFAkgtGTwACgkQi+vbBBjt66DYYACePxDc5HaOpQXoJVSfttjukSvp bsAAnR61/+vOEaHqVNZjiynQzksLmTix =X14I -----END PGP SIGNATURE----- --------------070905020208020405010806 Content-Type: text/plain; name="bitops.h" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="bitops.h" /* * Copyright (c) 2004, 2005 David Young. All rights reserved. * * Programmed for NetBSD by David Young. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of David Young may not be used to endorse or promote * products derived from this software without specific prior * written permission. * * THIS SOFTWARE IS PROVIDED BY David Young ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL David * Young BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY * OF SUCH DAMAGE. * * $DragonFly: src/sys/sys/bitops.h,v 1.1 2007/10/14 04:15:17 sephe Exp $ * $FreeBSD$ */ #ifndef _SYS_BITOPS_H_ #define _SYS_BITOPS_H_ /* * __BIT(n): Return a bitmask with bit n set, where the least * significant bit is bit 0. * * __BITS(m, n): Return a bitmask with bits m through n, inclusive, * set. It does not matter whether m>n or m<=n. The * least significant bit is bit 0. * * A "bitfield" is a span of consecutive bits defined by a bitmask, * where 1s select the bits in the bitfield. __SHIFTIN, __SHIFTOUT, * and __SHIFTOUT_MASK help read and write bitfields from device * registers. * * __SHIFTIN(v, mask): Left-shift bits `v' into the bitfield * defined by `mask', and return them. No * side-effects. * * __SHIFTOUT(v, mask): Extract and return the bitfield selected * by `mask' from `v', right-shifting the * bits so that the rightmost selected bit * is at bit 0. No side-effects. * * __SHIFTOUT_MASK(mask): Right-shift the bits in `mask' so that * the rightmost non-zero bit is at bit * 0. This is useful for finding the * greatest unsigned value that a bitfield * can hold. No side-effects. Note that * __SHIFTOUT_MASK(m) = __SHIFTOUT(m, m). */ /* __BIT(n): nth bit, where __BIT(0) == 0x1. */ #define __BIT(__n) (((__n) == 32) ? 0 : ((uint32_t)1 << (__n))) /* __BITS(m, n): bits m through n, m < n. */ #define __BITS(__m, __n) \ ((__BIT(MAX((__m), (__n)) + 1) - 1) ^ (__BIT(MIN((__m), (__n))) - 1)) /* Find least significant bit that is set */ #define __LOWEST_SET_BIT(__mask) ((((__mask) - 1) & (__mask)) ^ (__mask)) #define __SHIFTOUT(__x, __mask) (((__x) & (__mask)) / __LOWEST_SET_BIT(__mask)) #define __SHIFTIN(__x, __mask) ((__x) * __LOWEST_SET_BIT(__mask)) #define __SHIFTOUT_MASK(__mask) __SHIFTOUT((__mask), (__mask)) #endif /* !_SYS_BITOPS_H_ */ --------------070905020208020405010806--
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