Time and Date Utilities
The utilities library provides time and date handling capabilities via the
date library (developed by H. Hinnant, see <hops_src>/extern/date). This date
library has been adopted into the CXX20 STL standard, so it is expected that
eventually the captured copy of this library will be eliminated in favor of the
compiler implementation. The internal time point representation of the hops_clock class is
a 64-bit integer (int64_t) count of the number of UTC nanoseconds since
the J2000 epoch (January 1, 2000, 11:58:55.816 UTC). This provides nanosecond
accurate precision for scan-epoch time stamps until 2292. For in-memory
manipulation of time and dates, time points are represented by:
std::chrono::time_point<hops_clock>;
When a time point is stored as a object tag (either in memory, or on disk) for a data container, the time point class will be converted to a string representation (see below for supported types), generally speaking this will be a VEX style time stamp.
hops_clock
Class |
|
Category |
Time and Date Utilities |
Template Parameters |
Duration-based template parameters for time_point operations |
Primary Functionality |
Custom clock based on J2000 epoch (UTC nanoseconds since J2000) |
Key Features |
Conversion between UTC, TAI, GPS, system, and local time
Support for ISO8601, VEX, VDIF, MJD, and legacy HOPS formats
Leap second handling and timezone support
|
The hops_clock class provides a specialized clock implementation that measures time in UTC nanoseconds since the J2000 epoch. It offers conversion capabilities between different time systems and formats. It is the basis for most time-related operations in HOPS4. The available time_point conversion routines (betwen clock types) are implemented by the functions below:
to_utc(const std::chrono::time_point< hops_clock, Duration >&)
from_utc(const std::chrono::time_point< date::utc_clock, Duration >&)
to_tai(const std::chrono::time_point< hops_clock, Duration >&)
from_tai(const std::chrono::time_point< date::tai_clock, Duration >&)
to_gps(const std::chrono::time_point< hops_clock, Duration >&)
from_gps(const std::chrono::time_point< date::gps_clock, Duration >&)
to_sys(const std::chrono::time_point< hops_clock, Duration >&)
from_sys(const std::chrono::time_point< std::chrono::system_clock, Duration >&)
to_local(const std::chrono::time_point< hops_clock, Duration >&)
from_local(const std::chrono::time_point< date::local_t, Duration >&)
Additional routines are available that handle the conversion of hops_clock time_point objects to/from time stamps with the following formats:
ISO8601
VEX
MJD
(year,floating-point-day)
legacy HOPS3 date struct
The conversion routines are implemented by the associated functions listed below:
static time_point from_iso8601_format(const std::string& timestamp);
static std::string to_iso8601_format(const time_point& tp);
static time_point from_hops_format(const std::string& timestamp);
static std::string to_hops_format(const time_point& tp);
static time_point from_legacy_hops_date(legacy_hops_date& ldate);
static legacy_hops_date to_legacy_hops_date(const time_point& tp);
static time_point from_vdif_format(int& vdif_epoch, int& vdif_seconds);
static void to_vdif_format(const time_point& tp, int& vdif_epoch, int& vdif_second);
static time_point from_mjd(const time_point& mjd_epoch, const double& epoch_offset, const double& mjd);
static double to_mjd(const time_point& mjd_epoch, const double& epoch_offset, const time_point& tp);
static time_point from_vex_format(const std::string& timestamp);
static std::string to_vex_format(const time_point& tp, bool truncate_to_nearest_second = false);
static time_point from_year_fpday(int year, double floating_point_days);
MHO_TimeStampConverter
Class |
|
Category |
Time and Date Utilities |
Primary Functionality |
Converts between Unix epoch and human-readable timestamps |
Key Features |
Unix epoch to ISO8601 format conversion
Nanosecond precision handling
Bidirectional conversion support
|
The MHO_TimeStampConverter class handles conversion between Unix epoch seconds (with fractional parts) and human-readable ISO8601 formatted date strings. This utility is only used by the MHO_DirectoryInterface for reading/converting file modification times.
MHO_LegacyDateConverter
Class |
|
Category |
Time and Date Utilities |
Template Parameters |
None |
Configuration Parameters |
None |
Primary Functionality |
Converts between legacy HOPS3 date formats and modern formats |
Key Features |
Legacy HOPS3 date struct conversion
ISO8601 and VEX format support
Current time and epoch retrieval
|
The MHO_LegacyDateConverter class provides conversion utilities for
the legacy HOPS3 date struct:
typedef struct date
{
short year;
short day;
short hour;
short minute;
float second;
} date_struct;
Conversion is done indirectly through the legacy_hops_date struct in order to prevent a name collision with the external date library.