#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# @Author: José Sánchez-Gallego (gallegoj@uw.edu)
# @Date: 2020-08-16
# @Filename: sofa_bindings.py
# @License: BSD 3-clause (http://www.opensource.org/licenses/BSD-3-Clause)
# Bindings for SOFA procedures. This does not intent to be a comprehensive
# wrapping of the library, just of those functions that are needed for our
# purposes.
import ctypes
import datetime
import importlib
import os
from ctypes import POINTER, c_char_p, c_double, c_int
# List of argument times for some of the SOFA functions.
ARGTYPES = [
# const char *scale, int iy, int im, int id,
# int ihr, int imn, double sec,
# double *d1, double *d2
('iauDtf2d', (c_char_p, c_int, c_int, c_int,
c_int, c_int, c_double,
POINTER(c_double), POINTER(c_double))),
# double utc1, double utc2, double *tai1, double *tai2
('iauUtctai', (c_double, c_double, POINTER(c_double), POINTER(c_double))),
# double tai1, double tai2, double dta, double *ut11, double *ut12
('iauTaiut1', (c_double, c_double, c_double,
POINTER(c_double), POINTER(c_double))),
# double tai1, double tai2, double *utc1, double *utc2
('iauTaiutc', (c_double, c_double, POINTER(c_double), POINTER(c_double))),
# int iy, int im, int id, double fd, double *deltat
('iauDat', (c_int, c_int, c_int, c_double, POINTER(c_double))),
# double rc, double dc, double pr, double pd, double px, double rv,
# double utc1, double utc2, double dut1,
# double elong, double phi, double hm, double xp, double yp,
# double phpa, double tc, double rh, double wl,
# double *aob, double *zob, double *hob,
# double *dob, double *rob, double *eo
('iauAtco13', (c_double, c_double, c_double, c_double, c_double, c_double,
c_double, c_double, c_double,
c_double, c_double, c_double, c_double, c_double,
c_double, c_double, c_double, c_double,
POINTER(c_double), POINTER(c_double), POINTER(c_double),
POINTER(c_double), POINTER(c_double), POINTER(c_double))),
('iauAtoc13', (c_char_p, c_double, c_double, c_double, c_double, c_double,
c_double, c_double, c_double, c_double, c_double, c_double,
c_double, c_double, c_double, POINTER(c_double), POINTER(c_double))),
# double date1, double date2, double ut, double elong, double u, double v
('iauDtdb', (c_double, c_double, c_double, c_double, c_double, c_double)),
# double ra1, double dec1, double pmr1, double pmd1,
# double px1, double rv1,
# double ep1a, double ep1b, double ep2a, double ep2b,
# double *ra2, double *dec2, double *pmr2, double *pmd2,
# double *px2, double *rv2
('iauPmsafe', (c_double, c_double, c_double, c_double, c_double, c_double,
c_double, c_double, c_double, c_double,
POINTER(c_double), POINTER(c_double), POINTER(c_double),
POINTER(c_double), POINTER(c_double), POINTER(c_double))),
# compute position angle http://www.iausofa.org/2019_0722_C/sofa/hd2pa.c
# args: hour angle, declination, site latitude (radians)
('iauHd2pa', (c_double, c_double, c_double)),
# Horizon to equatorial coordinates: transform azimuth and altitude
# to hour angle and declination.
# args: double az, double alt, double latitude, double *ha, double *dec
('iauAe2hd', (c_double, c_double, c_double,
POINTER(c_double), POINTER(c_double))),
# Earth rotation angle
# sum of the arguments should be jd in the UT1 scale
# args: double jd, double 0
('iauEra00', (c_double, c_double)),
# Determine the constants A and B in the atmospheric refraction model
# dZ = A tan Z + B tan^3 Z.
# args: double phpa, double tc, double rh, double wl, double *refa, double *refb
('iauRefco', (c_double, c_double, c_double, c_double,
POINTER(c_double), POINTER(c_double))),
# Greenwich mean sidereal time (model consistent with IAU 2000 resolutions).
# args: double uta, double utb, double tta, double ttb
('iauGmst00', (c_double, c_double, c_double, c_double))
]
[docs]
class SOFA(ctypes.CDLL):
"""Load the SOFA C extension.
Parameters
----------
name : str
The path to the shared object. If `None`, will try the standard
variants of ``libsofa`` for this architecture. If the library is not
in a standard location the path needs to be added to
``LD_LIBRARY_PATHS``.
"""
def __init__(self, name=None):
if name is None:
# Try all the usual suffixes.
success = False
mod_path = os.path.join(os.path.dirname(__file__), 'libsofa')
for suffix in importlib.machinery.EXTENSION_SUFFIXES:
try:
super().__init__(mod_path + suffix)
success = True
break
except OSError:
pass
if success is False:
raise OSError('Could not find a valid libsofa extension.')
else:
super().__init__(name)
# Assign argtypes. This also adds the functions to the class dir().
for func_name, argtypes in ARGTYPES:
func = self.__getattr__(func_name)
func.argtypes = argtypes
# Some special cases of function that do not return
# an integer error check.
self.iauDtdb.restype = c_double
self.iauHd2pa.restype = c_double
self.iauEra00.restype = c_double
self.iauGmst00.restype = c_double
[docs]
def get_internal_date(self, date=None, scale='UTC'):
"""Returns the internal representation of a date.
Parameters
----------
date : ~datetime.datetime
The date to convert. If `None`, `~datetime.datetime.utcnow` will
be used and ``scale`` will be ignored.
scale : str
The scale of the date.
Returns
-------
d1, d2 : `float`
The two-part Julian date.
"""
if date is None:
date = datetime.datetime.now(datetime.timezone.utc)
scale = 'UTC'
d1 = c_double()
d2 = c_double()
res = self.iauDtf2d(scale.upper().encode(), date.year, date.month,
date.day, date.hour, date.minute,
date.second + date.microsecond / 1e6,
d1, d2)
if res != 0:
raise ValueError(f'iauDtf2d return with error code {res}.')
return d1.value, d2.value
