.. _program_listing_file_data_tai_utc.cc:

Program Listing for File tai_utc.cc
===================================

|exhale_lsh| :ref:`Return to documentation for file <file_data_tai_utc.cc>` (``data/tai_utc.cc``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   
   #include "lupnt/data/tai_utc.h"
   
   #include <fstream>
   #include <iostream>
   #include <memory>
   #include <mutex>
   #include <sstream>
   #include <string>
   
   #include "lupnt/core/constants.h"
   #include "lupnt/core/file.h"
   
   namespace lupnt {
   
     std::mutex tai_utc_mutex;
     UniquePtr<TaiUtcFileData> tai_utc_data;
   
     void LoadTaiUtcFileData(const std::filesystem::path& filepath) {
       std::lock_guard<std::mutex> lock(tai_utc_mutex);
       if (tai_utc_data) return;  // Data already loaded
   
       size_t n_lines = CountLines(filepath.string());
       std::ifstream file = OpenFile<std::ifstream>(filepath);
   
       // Initialize TaiUtcFileData struct
       tai_utc_data = MakeUnique<TaiUtcFileData>();
       tai_utc_data->jd.resize(n_lines);
       tai_utc_data->tai_utc.resize(n_lines);
       tai_utc_data->mjd0.resize(n_lines);
       tai_utc_data->scale.resize(n_lines);
   
       std::string line;
       size_t index = 0;
       while (std::getline(file, line)) {
         if (line.empty()) continue;
   
         double jd, tai_utc, mjd0, scale;
         std::istringstream iss(line);
         std::string year, month, day, eq_jd, tai_utc_eq, s1, plus, paren_mjd, minus, paren, times, s2;
   
         iss >> year >> month >> day >> eq_jd >> jd >> tai_utc_eq >> tai_utc >> s1 >> plus >> paren_mjd
             >> minus >> mjd0 >> paren >> times >> scale >> s2;
   
         tai_utc_data->jd(index) = jd;
         tai_utc_data->tai_utc(index) = tai_utc;
         tai_utc_data->mjd0(index) = mjd0;
         tai_utc_data->scale(index) = scale;
         ++index;
       }
   
       file.close();
       return;
     }
   
     double Evaluate(double mjd, int i) {
       return tai_utc_data->tai_utc(i) + tai_utc_data->scale(i) * (mjd - tai_utc_data->mjd0(i));
     }
   
     double GetTaiUtcDifference(double mjd) {
       if (!tai_utc_data) LoadTaiUtcFileData(GetFilePath(TAI_UTC_FILENAME));
       double jd = mjd + JD_MJD_OFFSET;
       if (jd < tai_utc_data->jd(0)) {
         return 0.0;
       } else if (jd > tai_utc_data->jd(tai_utc_data->jd.size() - 1)) {
         int index = tai_utc_data->jd.size() - 1;
         return Evaluate(mjd, index);
       }
   
       // Find closest MJD for the immediate smaller date
       double* start = tai_utc_data->jd.data();
       double* end = tai_utc_data->jd.data() + tai_utc_data->jd.size();
       auto it = std::upper_bound(start, end, jd);
   
       int index = (it - tai_utc_data->jd.data()) - 1;
       if (index < 0) index = 0;
       return Evaluate(mjd, index);
     }
   }  // namespace lupnt