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130 lines
3.6 KiB
C
130 lines
3.6 KiB
C
// SPDX-License-Identifier: LGPL-2.0+
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/*
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* Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
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* This file is part of the GNU C Library.
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* Contributed by Paul Eggert (eggert@twinsun.com).
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*
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* The GNU C Library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* The GNU C Library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with the GNU C Library; see the file COPYING.LIB. If not,
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* write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/*
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* Converts the calendar time to broken-down time representation
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* Based on code from glibc-2.6
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*
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* 2009-7-14:
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* Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com>
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*/
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#include <linux/time.h>
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#include <linux/module.h>
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/*
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* Nonzero if YEAR is a leap year (every 4 years,
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* except every 100th isn't, and every 400th is).
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*/
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static int __isleap(long year)
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{
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return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0);
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}
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/* do a mathdiv for long type */
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static long math_div(long a, long b)
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{
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return a / b - (a % b < 0);
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}
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/* How many leap years between y1 and y2, y1 must less or equal to y2 */
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static long leaps_between(long y1, long y2)
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{
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long leaps1 = math_div(y1 - 1, 4) - math_div(y1 - 1, 100)
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+ math_div(y1 - 1, 400);
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long leaps2 = math_div(y2 - 1, 4) - math_div(y2 - 1, 100)
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+ math_div(y2 - 1, 400);
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return leaps2 - leaps1;
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}
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/* How many days come before each month (0-12). */
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static const unsigned short __mon_yday[2][13] = {
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/* Normal years. */
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{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
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/* Leap years. */
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{0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
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};
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#define SECS_PER_HOUR (60 * 60)
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#define SECS_PER_DAY (SECS_PER_HOUR * 24)
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/**
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* time64_to_tm - converts the calendar time to local broken-down time
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*
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* @totalsecs the number of seconds elapsed since 00:00:00 on January 1, 1970,
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* Coordinated Universal Time (UTC).
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* @offset offset seconds adding to totalsecs.
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* @result pointer to struct tm variable to receive broken-down time
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*/
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void time64_to_tm(time64_t totalsecs, int offset, struct tm *result)
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{
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long days, rem, y;
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int remainder;
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const unsigned short *ip;
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days = div_s64_rem(totalsecs, SECS_PER_DAY, &remainder);
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rem = remainder;
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rem += offset;
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while (rem < 0) {
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rem += SECS_PER_DAY;
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--days;
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}
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while (rem >= SECS_PER_DAY) {
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rem -= SECS_PER_DAY;
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++days;
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}
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result->tm_hour = rem / SECS_PER_HOUR;
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rem %= SECS_PER_HOUR;
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result->tm_min = rem / 60;
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result->tm_sec = rem % 60;
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/* January 1, 1970 was a Thursday. */
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result->tm_wday = (4 + days) % 7;
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if (result->tm_wday < 0)
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result->tm_wday += 7;
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y = 1970;
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while (days < 0 || days >= (__isleap(y) ? 366 : 365)) {
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/* Guess a corrected year, assuming 365 days per year. */
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long yg = y + math_div(days, 365);
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/* Adjust DAYS and Y to match the guessed year. */
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days -= (yg - y) * 365 + leaps_between(y, yg);
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y = yg;
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}
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result->tm_year = y - 1900;
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result->tm_yday = days;
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ip = __mon_yday[__isleap(y)];
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for (y = 11; days < ip[y]; y--)
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continue;
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days -= ip[y];
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result->tm_mon = y;
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result->tm_mday = days + 1;
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}
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EXPORT_SYMBOL(time64_to_tm);
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