Multiple file access functions

The following group of functions should be the preferred method to access to the library. They allow to access to multiple ephemeris files at the same time, even by multiple threads.

When an error occurs, these functions execute error handlers according to the behavior defined by the function calcephpy.seterrorhandler().

Time notes

The functions calcephpy.CalcephBin.compute(), calcephpy.CalcephBin.compute_unit(), calcephpy.CalcephBin.compute_order(), calcephpy.CalcephBin.orient_unit(), ... only accept a date expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale(). Ephemeris files are generally expressed using the timescale TDB. If a date, expressed in the TT (Terrestrial Time) timescale, is supplied to them, these functions will return an erroneous position of the order of several tens of meters for the planets. If a date, expressed in the Coordinated Universal Time (UTC), is supplied to them, these functions will return a very large erroneous position over several thousand kilometers for the planets.

Thread notes

If the standard I/O functions such as fread are not reentrant then the CALCEPH I/O functions using them will not be reentrant either.

It's not safe for two threads to call the functions with the same object of type CalcephBin if and only if the function calcephpy.CalcephBin.isthreadsafe() returns a non-zero value. A previous call to the function calcephpy.CalcephBin.prefetch() is required for the function calcephpy.CalcephBin.isthreadsafe() to return a non-zero value.

It's safe for two threads to access simultaneously to the same ephemeris file with two different objects of type CalcephBin. In this case, each thread must open the same file.


The following examples, that can be found in the directory examples of the library sources, show the typical usage of this group of functions.

The example in Python language is