cos / third_party / kernel / 5e0cdb245b7c83cfa2939071bf0cb7a2ecd31abe / . / kernel / time / timeconv.c

/* | |

* Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc. | |

* This file is part of the GNU C Library. | |

* Contributed by Paul Eggert (eggert@twinsun.com). | |

* | |

* The GNU C Library is free software; you can redistribute it and/or | |

* modify it under the terms of the GNU Library General Public License as | |

* published by the Free Software Foundation; either version 2 of the | |

* License, or (at your option) any later version. | |

* | |

* The GNU C Library is distributed in the hope that it will be useful, | |

* but WITHOUT ANY WARRANTY; without even the implied warranty of | |

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |

* Library General Public License for more details. | |

* | |

* You should have received a copy of the GNU Library General Public | |

* License along with the GNU C Library; see the file COPYING.LIB. If not, | |

* write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |

* Boston, MA 02111-1307, USA. | |

*/ | |

/* | |

* Converts the calendar time to broken-down time representation | |

* Based on code from glibc-2.6 | |

* | |

* 2009-7-14: | |

* Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com> | |

*/ | |

#include <linux/time.h> | |

#include <linux/module.h> | |

/* | |

* Nonzero if YEAR is a leap year (every 4 years, | |

* except every 100th isn't, and every 400th is). | |

*/ | |

static int __isleap(long year) | |

{ | |

return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0); | |

} | |

/* do a mathdiv for long type */ | |

static long math_div(long a, long b) | |

{ | |

return a / b - (a % b < 0); | |

} | |

/* How many leap years between y1 and y2, y1 must less or equal to y2 */ | |

static long leaps_between(long y1, long y2) | |

{ | |

long leaps1 = math_div(y1 - 1, 4) - math_div(y1 - 1, 100) | |

+ math_div(y1 - 1, 400); | |

long leaps2 = math_div(y2 - 1, 4) - math_div(y2 - 1, 100) | |

+ math_div(y2 - 1, 400); | |

return leaps2 - leaps1; | |

} | |

/* How many days come before each month (0-12). */ | |

static const unsigned short __mon_yday[2][13] = { | |

/* Normal years. */ | |

{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365}, | |

/* Leap years. */ | |

{0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366} | |

}; | |

#define SECS_PER_HOUR (60 * 60) | |

#define SECS_PER_DAY (SECS_PER_HOUR * 24) | |

/** | |

* time64_to_tm - converts the calendar time to local broken-down time | |

* | |

* @totalsecs the number of seconds elapsed since 00:00:00 on January 1, 1970, | |

* Coordinated Universal Time (UTC). | |

* @offset offset seconds adding to totalsecs. | |

* @result pointer to struct tm variable to receive broken-down time | |

*/ | |

void time64_to_tm(time64_t totalsecs, int offset, struct tm *result) | |

{ | |

long days, rem, y; | |

int remainder; | |

const unsigned short *ip; | |

days = div_s64_rem(totalsecs, SECS_PER_DAY, &remainder); | |

rem = remainder; | |

rem += offset; | |

while (rem < 0) { | |

rem += SECS_PER_DAY; | |

--days; | |

} | |

while (rem >= SECS_PER_DAY) { | |

rem -= SECS_PER_DAY; | |

++days; | |

} | |

result->tm_hour = rem / SECS_PER_HOUR; | |

rem %= SECS_PER_HOUR; | |

result->tm_min = rem / 60; | |

result->tm_sec = rem % 60; | |

/* January 1, 1970 was a Thursday. */ | |

result->tm_wday = (4 + days) % 7; | |

if (result->tm_wday < 0) | |

result->tm_wday += 7; | |

y = 1970; | |

while (days < 0 || days >= (__isleap(y) ? 366 : 365)) { | |

/* Guess a corrected year, assuming 365 days per year. */ | |

long yg = y + math_div(days, 365); | |

/* Adjust DAYS and Y to match the guessed year. */ | |

days -= (yg - y) * 365 + leaps_between(y, yg); | |

y = yg; | |

} | |

result->tm_year = y - 1900; | |

result->tm_yday = days; | |

ip = __mon_yday[__isleap(y)]; | |

for (y = 11; days < ip[y]; y--) | |

continue; | |

days -= ip[y]; | |

result->tm_mon = y; | |

result->tm_mday = days + 1; | |

} | |

EXPORT_SYMBOL(time64_to_tm); |