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Utility.cpp
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/**
* \file Utility.cpp
* \brief Implementation for GeographicLib::Utility class
*
* Copyright (c) Charles Karney (2011-2022) <karney@alum.mit.edu> and licensed
* under the MIT/X11 License. For more information, see
* https://geographiclib.sourceforge.io/
**********************************************************************/
#include <cstdlib>
#include <GeographicLib/Utility.hpp>
#if defined(_MSC_VER)
// Squelch warnings about unsafe use of getenv
# pragma warning (disable: 4996)
#endif
namespace GeographicLib {
using namespace std;
int Utility::day(int y, int m, int d) {
// Convert from date to sequential day and vice versa
//
// Here is some code to convert a date to sequential day and vice
// versa. The sequential day is numbered so that January 1, 1 AD is day 1
// (a Saturday). So this is offset from the "Julian" day which starts the
// numbering with 4713 BC.
//
// This is inspired by a talk by John Conway at the John von Neumann
// National Supercomputer Center when he described his Doomsday algorithm
// for figuring the day of the week. The code avoids explicitly doing ifs
// (except for the decision of whether to use the Julian or Gregorian
// calendar). Instead the equivalent result is achieved using integer
// arithmetic. I got this idea from the routine for the day of the week
// in MACLisp (I believe that that routine was written by Guy Steele).
//
// There are three issues to take care of
//
// 1. the rules for leap years,
// 2. the inconvenient placement of leap days at the end of February,
// 3. the irregular pattern of month lengths.
//
// We deal with these as follows:
//
// 1. Leap years are given by simple rules which are straightforward to
// accommodate.
//
// 2. We simplify the calculations by moving January and February to the
// previous year. Here we internally number the months March-December,
// January, February as 0-9, 10, 11.
//
// 3. The pattern of month lengths from March through January is regular
// with a 5-month period—31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31. The
// 5-month period is 153 days long. Since February is now at the end of
// the year, we don't need to include its length in this part of the
// calculation.
bool greg = gregorian(y, m, d);
y += (m + 9) / 12 - 1; // Move Jan and Feb to previous year,
m = (m + 9) % 12; // making March month 0.
return
(1461 * y) / 4 // Julian years converted to days. Julian year is 365 +
// 1/4 = 1461/4 days.
// Gregorian leap year corrections. The 2 offset with respect to the
// Julian calendar synchronizes the vernal equinox with that at the
// time of the Council of Nicea (325 AD).
+ (greg ? (y / 100) / 4 - (y / 100) + 2 : 0)
+ (153 * m + 2) / 5 // The zero-based start of the m'th month
+ d - 1 // The zero-based day
- 305; // The number of days between March 1 and December 31.
// This makes 0001-01-01 day 1
}
int Utility::day(int y, int m, int d, bool check) {
int s = day(y, m, d);
if (!check)
return s;
int y1, m1, d1;
date(s, y1, m1, d1);
if (!(s > 0 && y == y1 && m == m1 && d == d1))
throw GeographicErr("Invalid date " +
str(y) + "-" + str(m) + "-" + str(d)
+ (s > 0 ? "; use " +
str(y1) + "-" + str(m1) + "-" + str(d1) :
" before 0001-01-01"));
return s;
}
void Utility::date(int s, int& y, int& m, int& d) {
int c = 0;
bool greg = gregorian(s);
s += 305; // s = 0 on March 1, 1BC
if (greg) {
s -= 2; // The 2 day Gregorian offset
// Determine century with the Gregorian rules for leap years. The
// Gregorian year is 365 + 1/4 - 1/100 + 1/400 = 146097/400 days.
c = (4 * s + 3) / 146097;
s -= (c * 146097) / 4; // s = 0 at beginning of century
}
y = (4 * s + 3) / 1461; // Determine the year using Julian rules.
s -= (1461 * y) / 4; // s = 0 at start of year, i.e., March 1
y += c * 100; // Assemble full year
m = (5 * s + 2) / 153; // Determine the month
s -= (153 * m + 2) / 5; // s = 0 at beginning of month
d = s + 1; // Determine day of month
y += (m + 2) / 12; // Move Jan and Feb back to original year
m = (m + 2) % 12 + 1; // Renumber the months so January = 1
}
void Utility::date(const std::string& s, int& y, int& m, int& d) {
if (s == "now") {
time_t t = time(0);
struct tm* now = gmtime(&t);
y = now->tm_year + 1900;
m = now->tm_mon + 1;
d = now->tm_mday;
return;
}
int y1, m1 = 1, d1 = 1;
const char* digits = "0123456789";
string::size_type p1 = s.find_first_not_of(digits);
if (p1 == string::npos)
y1 = val<int>(s);
else if (s[p1] != '-')
throw GeographicErr("Delimiter not hyphen in date " + s);
else if (p1 == 0)
throw GeographicErr("Empty year field in date " + s);
else {
y1 = val<int>(s.substr(0, p1));
if (++p1 == s.size())
throw GeographicErr("Empty month field in date " + s);
string::size_type p2 = s.find_first_not_of(digits, p1);
if (p2 == string::npos)
m1 = val<int>(s.substr(p1));
else if (s[p2] != '-')
throw GeographicErr("Delimiter not hyphen in date " + s);
else if (p2 == p1)
throw GeographicErr("Empty month field in date " + s);
else {
m1 = val<int>(s.substr(p1, p2 - p1));
if (++p2 == s.size())
throw GeographicErr("Empty day field in date " + s);
d1 = val<int>(s.substr(p2));
}
}
y = y1; m = m1; d = d1;
}
std::string Utility::trim(const std::string& s) {
unsigned
beg = 0,
end = unsigned(s.size());
while (beg < end && isspace(s[beg]))
++beg;
while (beg < end && isspace(s[end - 1]))
--end;
return string(s, beg, end-beg);
}
int Utility::lookup(const std::string& s, char c) {
string::size_type r = s.find(char(toupper(c)));
return r == string::npos ? -1 : int(r);
}
int Utility::lookup(const char* s, char c) {
const char* p = strchr(s, toupper(c));
return p != NULL ? int(p - s) : -1;
}
bool Utility::ParseLine(const std::string& line,
std::string& key, std::string& value,
char equals, char comment) {
key.clear(); value.clear();
string::size_type n = comment ? line.find(comment) : line.size();
string linea = trim(line.substr(0, n));
if (linea.empty()) return false;
n = equals ? linea.find(equals) : linea.find_first_of(" \t\n\v\f\r");
key = trim(linea.substr(0, n));
if (key.empty()) return false;
if (n != string::npos) value = trim(linea.substr(n + 1));
return true;
}
int Utility::set_digits(int ndigits) {
#if GEOGRAPHICLIB_PRECISION == 5
if (ndigits <= 0) {
char* digitenv = getenv("GEOGRAPHICLIB_DIGITS");
if (digitenv)
ndigits = strtol(digitenv, NULL, 0);
if (ndigits <= 0)
ndigits = 256;
}
#endif
return Math::set_digits(ndigits);
}
} // namespace GeographicLib
Utility.hpp
Header for GeographicLib::Utility class.
GeographicLib::GeographicErr
Exception handling for GeographicLib.
Definition Constants.hpp:344
GeographicLib::Math::set_digits
static int set_digits(int ndigits)
Definition Math.cpp:28
GeographicLib::Utility::date
static void date(int s, int &y, int &m, int &d)
Definition Utility.cpp:89
GeographicLib::Utility::lookup
static int lookup(const std::string &s, char c)
Definition Utility.cpp:160
GeographicLib::Utility::ParseLine
static bool ParseLine(const std::string &line, std::string &key, std::string &value, char equals='\0', char comment='#')
Definition Utility.cpp:170
GeographicLib::Utility::val
static T val(const std::string &s)
Definition Utility.hpp:225
GeographicLib::Utility::set_digits
static int set_digits(int ndigits=0)
Definition Utility.cpp:184
GeographicLib::Utility::trim
static std::string trim(const std::string &s)
Definition Utility.cpp:149
GeographicLib::Utility::day
static int day(int y, int m=1, int d=1)
Definition Utility.cpp:22
GeographicLib::Utility::str
static std::string str(T x, int p=-1)
Definition Utility.hpp:161
GeographicLib
Namespace for GeographicLib.
Definition Accumulator.cpp:12