src/tzwrapper.cc

   1 ///
   2 /// \file       tzwrapper.cc
   3 ///             Timezone adjustment class, wrapping the TZ environment
   4 ///             variable to make struct tm -> time_t conversions easier.
   5 ///
   6
   7 /*
   8     Copyright (C) 2010, Chris Frey <cdfrey@foursquare.net>, To God be the glory
   9     Released to the public domain.
  10 */
  11
  12 #include "tzwrapper.h"
  13 #include <string.h>
  14 #include <stdio.h>
  15
  16 namespace reuse {
  17
  18 time_t utc_mktime(struct tm *utctime)
  19 {
  20         time_t result;
  21         struct tm tmp, check;
  22
  23         // loop, converting "local time" to time_t and back to utc tm,
  24         // and adjusting until there are no differences... this
  25         // automatically takes care of DST issues.
  26
  27         // do first conversion
  28         tmp = *utctime;
  29         tmp.tm_isdst = -1;
  30         result = mktime(&tmp);
  31         if( result == (time_t)-1 )
  32                 return (time_t)-1;
  33         if( gmtime_r(&result, &check) == NULL )
  34                 return (time_t)-1;
  35
  36         // loop until match
  37         while(  check.tm_year != utctime->tm_year ||
  38                 check.tm_mon != utctime->tm_mon ||
  39                 check.tm_mday != utctime->tm_mday ||
  40                 check.tm_hour != utctime->tm_hour ||
  41                 check.tm_min != utctime->tm_min )
  42         {
  43                 tmp.tm_min  += utctime->tm_min - check.tm_min;
  44                 tmp.tm_hour += utctime->tm_hour - check.tm_hour;
  45                 tmp.tm_mday += utctime->tm_mday - check.tm_mday;
  46                 tmp.tm_year += utctime->tm_year - check.tm_year;
  47                 tmp.tm_isdst = -1;
  48
  49                 result = mktime(&tmp);
  50                 if( result == (time_t)-1 )
  51                         return (time_t)-1;
  52                 gmtime_r(&result, &check);
  53                 if( gmtime_r(&result, &check) == NULL )
  54                         return (time_t)-1;
  55         }
  56
  57         return result;
  58 }
  59
  60 struct tm* iso_to_tm(const char *timestamp,
  61                         struct tm *result,
  62                         bool &utc)
  63 {
  64         memset(result, 0, sizeof(struct tm));
  65         char zflag = 0;
  66
  67         int found = sscanf(timestamp, "%04d%02d%02dT%02d%02d%02d%c",
  68                 &(result->tm_year), &(result->tm_mon), &(result->tm_mday),
  69                 &(result->tm_hour), &(result->tm_min), &(result->tm_sec),
  70                 &zflag);
  71
  72         result->tm_year -= 1900;
  73         result->tm_mon -= 1;
  74         result->tm_isdst = -1;
  75
  76         utc = (found == 7 && zflag == 'Z');
  77
  78         return (found >= 6) ? result : 0;
  79 }
  80
  81 time_t TzWrapper::iso_mktime(const char *timestamp)
  82 {
  83         bool utc;
  84         struct tm t;
  85         if( !iso_to_tm(timestamp, &t, utc) )
  86                 return (time_t)-1;
  87         TzWrapper tzw;
  88         if( utc )
  89                 tzw.SetUTC();
  90         return tzw.mktime(&t);
  91 }
  92
  93 } // namespace reuse
  94
  95
  96 #ifdef TZ_TEST_MODE
  97 #include <iostream>
  98 using namespace std;
  99 using namespace reuse;
 100 int main()
 101 {
 102         time_t now = time(NULL);
 103
 104         cout << "TZ:             " << TzWrapper().ctime(&now);
 105         cout << "UTC:            " << TzWrapper("").ctime(&now);
 106         cout << "UTC:            " << TzWrapper().SetUTC().ctime(&now);
 107         cout << "SysLocaltime:   " << TzWrapper().SetUTC().SetSysLocal().ctime(&now);
 108         cout << "TZ:             " << TzWrapper().SetUTC().SetDefault().ctime(&now);
 109         cout << "Canada/Eastern: " << TzWrapper("Canada/Eastern").ctime(&now);
 110         cout << "Canada/Pacific: " << TzWrapper("Canada/Pacific").ctime(&now);
 111
 112         {
 113                 TzWrapper tzw("UTC");
 114                 cout << "UTC:            " << ctime(&now);
 115         }
 116
 117         cout << "TZ:             " << ctime(&now);
 118
 119         // test iso_mktime()... the test values assume a Canada/Eastern TZ
 120         cout << "Using Canada/Eastern:" << endl;
 121         TzWrapper tzw("Canada/Eastern");
 122         const char *iso1 = "20100430T231500";
 123         const char *iso2 = "20100501T031500Z";
 124         time_t t1 = TzWrapper::iso_mktime(iso1);
 125         time_t t2 = TzWrapper::iso_mktime(iso2);
 126         cout << " " << iso1 << ": (" << t1 << ") " << ctime(&t1);
 127         cout        << iso2 << ": (" << t2 << ") " << ctime(&t2);
 128
 129         if( TzWrapper::iso_mktime("20100430") == (time_t)-1 )
 130                 cout << "Fail check: passed" << endl;
 131         else
 132                 cout << "Fail check: ERROR" << endl;
 133 }
 134 #endif
 135