FreeBSD/Linux Kernel Cross Reference
sys/sys/_bitset.h

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2008, Jeffrey Roberson <jeff@freebsd.org>
      * All rights reserved.
      *
      * Copyright (c) 2008 Nokia Corporation
      * All rights reserved.
      *
     * 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 unmodified, 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 THE AUTHOR 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.
     *
     * $FreeBSD$
     */
    
    #ifndef _SYS__BITSET_H_
    #define _SYS__BITSET_H_
    
    /*
     * Macros addressing word and bit within it, tuned to make compiler
     * optimize cases when SETSIZE fits into single machine word.
     */
    #define _BITSET_BITS            (sizeof(long) * 8)
    
    #define __howmany(x, y) (((x) + ((y) - 1)) / (y))
    
    #define __bitset_words(_s)      (__howmany(_s, _BITSET_BITS))
    
    #define __BITSET_DEFINE(_t, _s)                                         \
    struct _t {                                                             \
            long    __bits[__bitset_words((_s))];                           \
    }
    
    /*
     * Helper to declare a bitset without it's size being a constant.
     *
     * Sadly we cannot declare a bitset struct with 'bits[]', because it's
     * the only member of the struct and the compiler complains.
     */
    #define __BITSET_DEFINE_VAR(_t) __BITSET_DEFINE(_t, 1)
    
    /*
     * Define a default type that can be used while manually specifying size
     * to every call.
     */
    
    #if defined(_KERNEL) || defined(_WANT_FREEBSD_BITSET)
    __BITSET_DEFINE(bitset, 1);
    
    #define BITSET_DEFINE(_t, _s)   __BITSET_DEFINE(_t, _s)
    #define BITSET_DEFINE_VAR(_t)   __BITSET_DEFINE_VAR(_t)
    #endif /* defined(_KERNEL) || defined(_WANT_FREEBSD_BITSET) */
    
    #endif /* !_SYS__BITSET_H_ */

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