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

     /*      $NetBSD: clock.h,v 1.4 2018/04/19 21:19:07 christos Exp $       */
     
     /*-
      * Copyright (c) 1996 The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * This code is derived from software contributed to The NetBSD Foundation
      * by Gordon W. Ross
      *
     * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
     */
    
    #ifndef _SYS_CLOCK_H_
    #define _SYS_CLOCK_H_
    
    /* Some handy constants. */
    #define SECS_PER_MINUTE         60
    #define SECS_PER_HOUR           3600
    #define SECS_PER_DAY            86400
    #define DAYS_PER_COMMON_YEAR    365
    #define DAYS_PER_LEAP_YEAR      366
    #define SECS_PER_COMMON_YEAR    (SECS_PER_DAY * DAYS_PER_COMMON_YEAR)
    #define SECS_PER_LEAP_YEAR      (SECS_PER_DAY * DAYS_PER_LEAP_YEAR)
    
    /* Traditional POSIX base year */
    #define POSIX_BASE_YEAR 1970
    
    /* Some handy functions */
    static __inline int
    days_in_month(int m)
    {
            switch (m) {
            case 2:
                    return 28;
            case 4: case 6: case 9: case 11:
                    return 30;
            case 1: case 3: case 5: case 7: case 8: case 10: case 12:
                    return 31;
            default:
                    return -1;
            }
    }
    
    /*
     * This inline avoids some unnecessary modulo operations
     * as compared with the usual macro:
     *   ( ((year % 4) == 0 &&
     *      (year % 100) != 0) ||
     *     ((year % 400) == 0) )
     * It is otherwise equivalent.
     */
    static __inline int
    is_leap_year(uint64_t year)
    {
            if ((year & 3) != 0)
                    return 0;
    
            if (__predict_false((year % 100) != 0))
                    return 1;
    
            return __predict_false((year % 400) == 0);
    }
    
    static __inline int
    days_per_year(uint64_t year)
    {
            return is_leap_year(year) ? DAYS_PER_LEAP_YEAR : DAYS_PER_COMMON_YEAR;
    }
    
    #endif /* _SYS_CLOCK_H_ */

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