mono/btls/btls-time64.c

   1 /*
   2
   3 Copyright (c) 2007-2008  Michael G Schwern
   4
   5 This software originally derived from Paul Sheer's pivotal_gmtime_r.c.
   6
   7 The MIT License:
   8
   9 Permission is hereby granted, free of charge, to any person obtaining a copy
  10 of this software and associated documentation files (the "Software"), to deal
  11 in the Software without restriction, including without limitation the rights
  12 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13 copies of the Software, and to permit persons to whom the Software is
  14 furnished to do so, subject to the following conditions:
  15
  16 The above copyright notice and this permission notice shall be included in
  17 all copies or substantial portions of the Software.
  18
  19 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25 THE SOFTWARE.
  26
  27 */
  28
  29 /* See http://code.google.com/p/y2038 for this code's origin */
  30
  31 #include <assert.h>
  32 #include <stdlib.h>
  33 #include <stdio.h>
  34 #include <stdint.h>
  35 #include <string.h>
  36 #include <time.h>
  37 #include <errno.h>
  38
  39 static const int julian_days_by_month[2][12] = {
  40     {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},
  41     {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335},
  42 };
  43
  44 static const int length_of_year[2] = { 365, 366 };
  45
  46 /* Some numbers relating to the gregorian cycle */
  47 #define               days_in_gregorian_cycle      ((365 * 400) + 100 - 4 + 1)
  48
  49 /* Year range we can trust the time funcitons with */
  50 #define MAX_SAFE_YEAR 2037
  51 #define MIN_SAFE_YEAR 1971
  52
  53 /* 28 year Julian calendar cycle */
  54 #define SOLAR_CYCLE_LENGTH 28
  55
  56 /* Let's assume people are going to be looking for dates in the future.
  57    Let's provide some cheats so you can skip ahead.
  58    This has a 4x speed boost when near 2008.
  59 */
  60 /* Number of days since epoch on Jan 1st, 2008 GMT */
  61 #define CHEAT_DAYS  (1199145600 / 24 / 60 / 60)
  62 #define CHEAT_YEARS 108
  63
  64 #define IS_LEAP(n)      ((!(((n) + 1900) % 400) || (!(((n) + 1900) % 4) && (((n) + 1900) % 100))) != 0)
  65 #define WRAP(a,b,m)     ((a) = ((a) <  0  ) ? ((b)--, (a) + (m)) : (a))
  66
  67 /* timegm() is not in the C or POSIX spec, but it is such a useful
  68    extension I would be remiss in leaving it out.  Also I need it
  69    for localtime64()
  70 */
  71 int64_t btls_timegm64(const struct tm *date) {
  72     int64_t days    = 0;
  73     int64_t seconds = 0;
  74     int64_t     year;
  75     int64_t     orig_year = (int64_t)date->tm_year;
  76     int      cycles  = 0;
  77
  78     if( orig_year > 100 ) {
  79         cycles = (orig_year - 100) / 400;
  80         orig_year -= cycles * 400;
  81         days      += (int64_t)cycles * days_in_gregorian_cycle;
  82     }
  83     else if( orig_year < -300 ) {
  84         cycles = (orig_year - 100) / 400;
  85         orig_year -= cycles * 400;
  86         days      += (int64_t)cycles * days_in_gregorian_cycle;
  87     }
  88
  89     if( orig_year > 70 ) {
  90         year = 70;
  91         while( year < orig_year ) {
  92             days += length_of_year[IS_LEAP(year)];
  93             year++;
  94         }
  95     }
  96     else if ( orig_year < 70 ) {
  97         year = 69;
  98         do {
  99             days -= length_of_year[IS_LEAP(year)];
 100             year--;
 101         } while( year >= orig_year );
 102     }
 103
 104
 105     days += julian_days_by_month[IS_LEAP(orig_year)][date->tm_mon];
 106     days += date->tm_mday - 1;
 107
 108     seconds = days * 60 * 60 * 24;
 109
 110     seconds += date->tm_hour * 60 * 60;
 111     seconds += date->tm_min * 60;
 112     seconds += date->tm_sec;
 113
 114     return(seconds);
 115 }