ladybird/AK/Time.cpp

/*
 * Copyright (c) 2020, The SerenityOS developers.
 * 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
 */

#include <AK/Assertions.h>
#include <AK/Time.h>

namespace AK {

int day_of_year(int year, unsigned month, int day)
{
    ASSERT(month >= 1 && month <= 12);

    static const int seek_table[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
    int day_of_year = seek_table[month - 1] + day - 1;

    if (is_leap_year(year) && month >= 3)
        day_of_year++;

    return day_of_year;
}

int days_in_month(int year, unsigned month)
{
    ASSERT(month >= 1 && month <= 12);
    if (month == 2)
        return is_leap_year(year) ? 29 : 28;

    bool is_long_month = (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12);
    return is_long_month ? 31 : 30;
}

unsigned day_of_week(int year, unsigned month, int day)
{
    ASSERT(month >= 1 && month <= 12);
    static const int seek_table[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
    if (month < 3)
        --year;

    return (year + year / 4 - year / 100 + year / 400 + seek_table[month - 1] + day) % 7;
}
}