FreeBSD/Linux Kernel Cross Reference
sys/contrib/ck/src/ck_internal.h

     /*
      * Copyright 2011-2015 Samy Al Bahra.
      * Copyright 2011 David Joseph.
      * 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, 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
     */
    
    /*
     * Several of these are from: http://graphics.stanford.edu/~seander/bithacks.html
     */
    
    #define CK_INTERNAL_LOG_0 (0xAAAAAAAA)
    #define CK_INTERNAL_LOG_1 (0xCCCCCCCC)
    #define CK_INTERNAL_LOG_2 (0xF0F0F0F0)
    #define CK_INTERNAL_LOG_3 (0xFF00FF00)
    #define CK_INTERNAL_LOG_4 (0xFFFF0000)
    
    CK_CC_INLINE static uint32_t
    ck_internal_log(uint32_t v)
    {
            uint32_t r = (v & CK_INTERNAL_LOG_0) != 0;
    
            r |= ((v & CK_INTERNAL_LOG_4) != 0) << 4;
            r |= ((v & CK_INTERNAL_LOG_3) != 0) << 3;
            r |= ((v & CK_INTERNAL_LOG_2) != 0) << 2;
            r |= ((v & CK_INTERNAL_LOG_1) != 0) << 1;
            return (r);
    }
    
    CK_CC_INLINE static uint32_t
    ck_internal_power_2(uint32_t v)
    {
    
            --v;
            v |= v >> 1;
            v |= v >> 2;
            v |= v >> 4;
            v |= v >> 8;
            v |= v >> 16;
            return (++v);
    }
    
    CK_CC_INLINE static unsigned long
    ck_internal_max(unsigned long x, unsigned long y)
    {
    
            return x ^ ((x ^ y) & -(x < y));
    }
    
    CK_CC_INLINE static uint64_t
    ck_internal_max_64(uint64_t x, uint64_t y)
    {
    
            return x ^ ((x ^ y) & -(x < y));
    }
    
    CK_CC_INLINE static uint32_t
    ck_internal_max_32(uint32_t x, uint32_t y)
    {
    
            return x ^ ((x ^ y) & -(x < y));
    }

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