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     Included in Barry and Barrified the namespace July 2010
  11 */
  12
  13 #include "tzwrapper.h"
  14 #include <string.h>
  15 #include <stdio.h>
  16
  17 namespace Barry { namespace Sync {
  18
  19 time_t utc_mktime(struct tm *utctime)
  20 {
  21         time_t result;
  22         struct tm tmp, check;
  23
  24         // loop, converting "local time" to time_t and back to utc tm,
  25         // and adjusting until there are no differences... this
  26         // automatically takes care of DST issues.
  27
  28         // do first conversion
  29         tmp = *utctime;
  30         tmp.tm_isdst = -1;
  31         result = mktime(&tmp);
  32         if( result == (time_t)-1 )
  33                 return (time_t)-1;
  34         if( gmtime_r(&result, &check) == NULL )
  35                 return (time_t)-1;
  36
  37         // loop until match
  38         while(  check.tm_year != utctime->tm_year ||
  39                 check.tm_mon != utctime->tm_mon ||
  40                 check.tm_mday != utctime->tm_mday ||
  41                 check.tm_hour != utctime->tm_hour ||
  42                 check.tm_min != utctime->tm_min )
  43         {
  44                 tmp.tm_min  += utctime->tm_min - check.tm_min;
  45                 tmp.tm_hour += utctime->tm_hour - check.tm_hour;
  46                 tmp.tm_mday += utctime->tm_mday - check.tm_mday;
  47                 tmp.tm_year += utctime->tm_year - check.tm_year;
  48                 tmp.tm_isdst = -1;
  49
  50                 result = mktime(&tmp);
  51                 if( result == (time_t)-1 )
  52                         return (time_t)-1;
  53                 gmtime_r(&result, &check);
  54                 if( gmtime_r(&result, &check) == NULL )
  55                         return (time_t)-1;
  56         }
  57
  58         return result;
  59 }
  60
  61 struct tm* iso_to_tm(const char *timestamp,
  62                         struct tm *result,
  63                         bool &utc)
  64 {
  65         memset(result, 0, sizeof(struct tm));
  66         char zflag = 0;
  67
  68         int found = sscanf(timestamp, "%04d%02d%02dT%02d%02d%02d%c",
  69                 &(result->tm_year), &(result->tm_mon), &(result->tm_mday),
  70                 &(result->tm_hour), &(result->tm_min), &(result->tm_sec),
  71                 &zflag);
  72
  73         result->tm_year -= 1900;
  74         result->tm_mon -= 1;
  75         result->tm_isdst = -1;
  76
  77         utc = (found == 7 && zflag == 'Z');
  78
  79         return (found >= 6) ? result : 0;
  80 }
  81
  82 time_t TzWrapper::iso_mktime(const char *timestamp)
  83 {
  84         bool utc;
  85         struct tm t;
  86         if( !iso_to_tm(timestamp, &t, utc) )
  87                 return (time_t)-1;
  88         TzWrapper tzw;
  89         if( utc )
  90                 tzw.SetUTC();
  91         return tzw.mktime(&t);
  92 }
  93
  94 }} // namespace Barry::Sync
  95
  96
  97 #ifdef TZ_TEST_MODE
  98 #include <iostream>
  99 using namespace std;
 100 using namespace Barry::Sync;
 101 int main()
 102 {
 103         time_t now = time(NULL);
 104
 105         cout << "TZ:             " << TzWrapper().ctime(&now);
 106         cout << "UTC:            " << TzWrapper("").ctime(&now);
 107         cout << "UTC:            " << TzWrapper().SetUTC().ctime(&now);
 108         cout << "SysLocaltime:   " << TzWrapper().SetUTC().SetSysLocal().ctime(&now);
 109         cout << "TZ:             " << TzWrapper().SetUTC().SetDefault().ctime(&now);
 110         cout << "Canada/Eastern: " << TzWrapper("Canada/Eastern").ctime(&now);
 111         cout << "Canada/Pacific: " << TzWrapper("Canada/Pacific").ctime(&now);
 112
 113         {
 114                 TzWrapper tzw("UTC");
 115                 cout << "UTC:            " << ctime(&now);
 116         }
 117
 118         cout << "TZ:             " << ctime(&now);
 119
 120         // test iso_mktime()... the test values assume a Canada/Eastern TZ
 121         cout << "Using Canada/Eastern:" << endl;
 122         TzWrapper tzw("Canada/Eastern");
 123         const char *iso1 = "20100430T231500";
 124         const char *iso2 = "20100501T031500Z";
 125         time_t t1 = TzWrapper::iso_mktime(iso1);
 126         time_t t2 = TzWrapper::iso_mktime(iso2);
 127         cout << " " << iso1 << ": (" << t1 << ") " << ctime(&t1);
 128         cout        << iso2 << ": (" << t2 << ") " << ctime(&t2);
 129
 130         if( TzWrapper::iso_mktime("20100430") == (time_t)-1 )
 131                 cout << "Fail check: passed" << endl;
 132         else
 133                 cout << "Fail check: ERROR" << endl;
 134 }
 135 #endif
 136