rwsf::TimeZoneSimple
rwsf::TimeZoneSimplerwsf::TimeZone
Local Index
Members
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altZoneName() altZoneOffset() daylightObserved() |
getBeginDaylight() getEndDaylight() isDaylight() |
timeZoneName() timeZoneOffset() TimeZoneSimple() |
Header File
#include rwsf/core/TimeZone.h
Description
rwsf::TimeZoneSimple is an implementation of the abstract interface defined by class rwsf::TimeZone. It implements a simple Daylight Saving Time rule sufficient to represent all historical U.S. conventions and many European and Asian conventions. It is table-driven and depends on parameters given by the struct DaylightRule, which is discussed later in this class.
Daylight saving-time rules are volatile, often reflecting geographical and political changes. In some cases, the hard-coded table-driven struct DaylightRule does not accurately reflect the locale installed on your machine. TimeZone::os() creates a new rwsf::TimeZoneSimple containing the daylight rule discovered from the underlying operating system. The onus of correctness for this DST rule is on the operating system itself.
In many cases, you may want more explicit control of the DST rule for the intended rwsf::TimeZoneSimple. If so, you can build a DST rule with arbitrary begin and end times (see the DaylightRule below), and provide it as a parameter to rwsf::TimeZoneSimple.
Direct use of DaylightRule affords the most general interface to rwsf::TimeZoneSimple. However, a much simpler programmatic interface is offered, as illustrated by the examples below.
Three instances of rwsf::TimeZoneSimple are automatically constructed at program startup, to represent GMT, Standard, and local time. They are available via calls to the static member functions TimeZone::utc(), TimeZone::standard(), and TimeZone::local(), respectively.
These member functions are set up according to the time zone facilities provided in the execution environment (typically defined by the environment variable TZ). By default, if DST is observed at all, then the local zone instance will use U.S. (TimeZone::NoAm) Daylight Saving Time rules.
Note for developers outside North America: for some time zones this default will not be correct because these time zones rely on the C standard global variable _daylight. This variable is set whenever any alternate time zone rule is available, whether it represents Daylight Saving Time or not. Also the periods of history affected by Daylight Saving Time may be different in your time zone from those in North America, causing the North American rule to be erroneously invoked. The best way to ensure that these default time zones are correct is to construct an rwsf::TimeZoneSimple using an appropriate DaylightRule and initialize TimeZone::local() and TimeZone::std() with this value.
Other instances of rwsf::TimeZoneSimple may be constructed to represent other time zones, and may be installed globally using rwsf::TimeZone static member functions TimeZone::local(const TimeZone*) and TimeZone::standard(const TimeZone*).
Public Constructors
TimeZoneSimple(const DaylightRule * rule,
long tzoff,
const std::string & tz_name,
long altoff,
const std::string & altname);
Constructs an rwsf::TimeZoneSimple instance which Daylight Saving Time is computed according to the rule specified. Variables tzoff and tzname are the offset from GMT (in seconds, positive if west of 0 degrees longitude) and the name of standard time. Arguments altoff and altname are the offset (typically equal to tzoff-3600) and name when Daylight Saving Time is in effect. If rule is zero, Daylight Saving Time is not observed.
TimeZoneSimple(long tzoff,
const std::string & tz_name);
Constructs an rwsf::TimeZoneSimple instance in which Daylight Saving Time is not observed. Argument tzoff is the offset from GMT (in seconds, positive if west of 0 degrees longitude) and tzname is the name of the zone.
TimeZoneSimple(StdZone zone,
const DaylightRule * rule);
Constructs an rwsf::TimeZoneSimple instance in which offsets and names are specified by the StdZone argument. Daylight Saving Time is computed according to the rule argument, if non-zero; otherwise, DST is not observed.
TimeZoneSimple(StdZone zone,
DstRule = NoAm);
Constructs an rwsf::TimeZoneSimple instance using internally held DaylightRules. This is the simplest interface to rwsf::TimeZoneSimple. The first argument is the time zone for which an rwsf::TimeZoneSimple is to be constructed. The second argument is the Daylight Saving Time rule which is to be followed.
Public Member Functions
std::string altZoneName() const;
Implements method in rwsf::TimeZone
Base class documentation:
Return the name of, respectively, the standard and Daylight Saving Time zones represented, such as PST and PDT. Note that the current date and time have no effect on the return values of these functions.
long altZoneOffset() const;
Implements method in rwsf::TimeZone
Base class documentation:
Returns the number of seconds west of GMT for Daylight Saving Time in this zone.
bool daylightObserved() const;
Implements method in rwsf::TimeZone
Base class documentation:
Returns true if Daylight Saving Time is observed for this zone.
void getBeginDaylight(struct tm *) const;
Implements method in rwsf::TimeZone
Base class documentation:
Return with the structtm argument set to the local time that Daylight Saving Time begins, or ends, for the year indicated by the tm_year member passed in. If Daylight Saving Time is not observed, the structtm members are all set to a negative value. Note that in the southern hemisphere, Daylight Saving Time ends at an earlier date than it begins.
void getEndDaylight(struct tm *) const;
Implements method in rwsf::TimeZone
Base class documentation:
Return with the structtm argument set to the local time that Daylight Saving Time begins, or ends, for the year indicated by the tm_year member passed in. If Daylight Saving Time is not observed, the structtm members are all set to a negative value. Note that in the southern hemisphere, Daylight Saving Time ends at an earlier date than it begins.
bool isDaylight(const struct tm * tmbuf) const;
Implements method in rwsf::TimeZone
Base class documentation:
Returns true if the time and date represented in the structtm argument is in the range of Daylight Saving Time for this zone. The elements of the tm argument must all be self-consistent; in particular, the tm_wday member must agree with the tm_year, tm_mon, and tm_day members.
std::string timeZoneName() const;
Implements method in rwsf::TimeZone
Base class documentation:
Return the name of, respectively, the standard and Daylight Saving Time zones represented, such as PST and PDT. Note that the current date and time have no effect on the return values of these functions.
long timeZoneOffset() const;
Implements method in rwsf::TimeZone
Base class documentation:
Returns the number of seconds west of GMT for standard time in this zone. The number is negative for zones east of Greenwich, England.
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