198 lines
7.2 KiB
C++
198 lines
7.2 KiB
C++
/**
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* \file Utility.cpp
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* \brief Implementation for GeographicLib::Utility class
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*
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* Copyright (c) Charles Karney (2011-2022) <charles@karney.com> and licensed
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* under the MIT/X11 License. For more information, see
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* https://geographiclib.sourceforge.io/
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**********************************************************************/
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#include <cstdlib>
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#include <GeographicLib/Utility.hpp>
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#if defined(_MSC_VER)
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// Squelch warnings about unsafe use of getenv
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# pragma warning (disable: 4996)
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#endif
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namespace GeographicLib {
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using namespace std;
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int Utility::day(int y, int m, int d) {
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// Convert from date to sequential day and vice versa
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//
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// Here is some code to convert a date to sequential day and vice
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// versa. The sequential day is numbered so that January 1, 1 AD is day 1
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// (a Saturday). So this is offset from the "Julian" day which starts the
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// numbering with 4713 BC.
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//
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// This is inspired by a talk by John Conway at the John von Neumann
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// National Supercomputer Center when he described his Doomsday algorithm
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// for figuring the day of the week. The code avoids explicitly doing ifs
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// (except for the decision of whether to use the Julian or Gregorian
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// calendar). Instead the equivalent result is achieved using integer
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// arithmetic. I got this idea from the routine for the day of the week
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// in MACLisp (I believe that that routine was written by Guy Steele).
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//
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// There are three issues to take care of
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//
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// 1. the rules for leap years,
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// 2. the inconvenient placement of leap days at the end of February,
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// 3. the irregular pattern of month lengths.
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//
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// We deal with these as follows:
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//
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// 1. Leap years are given by simple rules which are straightforward to
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// accommodate.
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//
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// 2. We simplify the calculations by moving January and February to the
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// previous year. Here we internally number the months March–December,
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// January, February as 0–9, 10, 11.
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//
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// 3. The pattern of month lengths from March through January is regular
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// with a 5-month period—31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31. The
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// 5-month period is 153 days long. Since February is now at the end of
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// the year, we don't need to include its length in this part of the
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// calculation.
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bool greg = gregorian(y, m, d);
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y += (m + 9) / 12 - 1; // Move Jan and Feb to previous year,
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m = (m + 9) % 12; // making March month 0.
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return
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(1461 * y) / 4 // Julian years converted to days. Julian year is 365 +
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// 1/4 = 1461/4 days.
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// Gregorian leap year corrections. The 2 offset with respect to the
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// Julian calendar synchronizes the vernal equinox with that at the
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// time of the Council of Nicea (325 AD).
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+ (greg ? (y / 100) / 4 - (y / 100) + 2 : 0)
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+ (153 * m + 2) / 5 // The zero-based start of the m'th month
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+ d - 1 // The zero-based day
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- 305; // The number of days between March 1 and December 31.
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// This makes 0001-01-01 day 1
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}
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int Utility::day(int y, int m, int d, bool check) {
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int s = day(y, m, d);
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if (!check)
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return s;
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int y1, m1, d1;
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date(s, y1, m1, d1);
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if (!(s > 0 && y == y1 && m == m1 && d == d1))
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throw GeographicErr("Invalid date " +
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str(y) + "-" + str(m) + "-" + str(d)
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+ (s > 0 ? "; use " +
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str(y1) + "-" + str(m1) + "-" + str(d1) :
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" before 0001-01-01"));
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return s;
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}
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void Utility::date(int s, int& y, int& m, int& d) {
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int c = 0;
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bool greg = gregorian(s);
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s += 305; // s = 0 on March 1, 1BC
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if (greg) {
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s -= 2; // The 2 day Gregorian offset
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// Determine century with the Gregorian rules for leap years. The
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// Gregorian year is 365 + 1/4 - 1/100 + 1/400 = 146097/400 days.
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c = (4 * s + 3) / 146097;
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s -= (c * 146097) / 4; // s = 0 at beginning of century
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}
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y = (4 * s + 3) / 1461; // Determine the year using Julian rules.
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s -= (1461 * y) / 4; // s = 0 at start of year, i.e., March 1
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y += c * 100; // Assemble full year
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m = (5 * s + 2) / 153; // Determine the month
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s -= (153 * m + 2) / 5; // s = 0 at beginning of month
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d = s + 1; // Determine day of month
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y += (m + 2) / 12; // Move Jan and Feb back to original year
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m = (m + 2) % 12 + 1; // Renumber the months so January = 1
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}
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void Utility::date(const std::string& s, int& y, int& m, int& d) {
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if (s == "now") {
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time_t t = time(0);
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struct tm* now = gmtime(&t);
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y = now->tm_year + 1900;
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m = now->tm_mon + 1;
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d = now->tm_mday;
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return;
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}
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int y1, m1 = 1, d1 = 1;
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const char* digits = "0123456789";
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string::size_type p1 = s.find_first_not_of(digits);
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if (p1 == string::npos)
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y1 = val<int>(s);
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else if (s[p1] != '-')
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throw GeographicErr("Delimiter not hyphen in date " + s);
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else if (p1 == 0)
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throw GeographicErr("Empty year field in date " + s);
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else {
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y1 = val<int>(s.substr(0, p1));
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if (++p1 == s.size())
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throw GeographicErr("Empty month field in date " + s);
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string::size_type p2 = s.find_first_not_of(digits, p1);
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if (p2 == string::npos)
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m1 = val<int>(s.substr(p1));
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else if (s[p2] != '-')
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throw GeographicErr("Delimiter not hyphen in date " + s);
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else if (p2 == p1)
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throw GeographicErr("Empty month field in date " + s);
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else {
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m1 = val<int>(s.substr(p1, p2 - p1));
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if (++p2 == s.size())
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throw GeographicErr("Empty day field in date " + s);
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d1 = val<int>(s.substr(p2));
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}
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}
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y = y1; m = m1; d = d1;
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}
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std::string Utility::trim(const std::string& s) {
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unsigned
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beg = 0,
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end = unsigned(s.size());
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while (beg < end && isspace(s[beg]))
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++beg;
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while (beg < end && isspace(s[end - 1]))
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--end;
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return string(s, beg, end-beg);
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}
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int Utility::lookup(const std::string& s, char c) {
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string::size_type r = s.find(char(toupper(c)));
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return r == string::npos ? -1 : int(r);
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}
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int Utility::lookup(const char* s, char c) {
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const char* p = strchr(s, toupper(c));
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return p != NULL ? int(p - s) : -1;
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}
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bool Utility::ParseLine(const std::string& line,
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std::string& key, std::string& value,
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char equals, char comment) {
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key.clear(); value.clear();
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string::size_type n = comment ? line.find(comment) : line.size();
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string linea = trim(line.substr(0, n));
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if (linea.empty()) return false;
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n = equals ? linea.find(equals) : linea.find_first_of(" \t\n\v\f\r");
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key = trim(linea.substr(0, n));
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if (key.empty()) return false;
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if (n != string::npos) value = trim(linea.substr(n + 1));
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return true;
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}
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int Utility::set_digits(int ndigits) {
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#if GEOGRAPHICLIB_PRECISION == 5
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if (ndigits <= 0) {
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char* digitenv = getenv("GEOGRAPHICLIB_DIGITS");
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if (digitenv)
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ndigits = strtol(digitenv, NULL, 0);
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if (ndigits <= 0)
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ndigits = 256;
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}
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#endif
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return Math::set_digits(ndigits);
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}
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} // namespace GeographicLib
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