GeographicLib 2.3

Geohash.cpp
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1/**
2 * \file Geohash.cpp
3 * \brief Implementation for GeographicLib::Geohash class
4 *
5 * Copyright (c) Charles Karney (2012-2022) <karney@alum.mit.edu> and licensed
6 * under the MIT/X11 License. For more information, see
7 * https://geographiclib.sourceforge.io/
8 **********************************************************************/
9
10#include <GeographicLib/Geohash.hpp>
11#include <GeographicLib/Utility.hpp>
12
13#if defined(_MSC_VER)
14// Squelch warnings about enum-float expressions
15# pragma warning (disable: 5055)
16#endif
17
18 namespace GeographicLib {
19
20 using namespace std;
21
22 const char* const Geohash::lcdigits_ = "0123456789bcdefghjkmnpqrstuvwxyz";
23 const char* const Geohash::ucdigits_ = "0123456789BCDEFGHJKMNPQRSTUVWXYZ";
24
25 void Geohash::Forward(real lat, real lon, int len, string& geohash) {
26 using std::isnan; // Needed for Centos 7, ubuntu 14
27 static const real shift = ldexp(real(1), 45);
28 static const real loneps = Math::hd / shift;
29 static const real lateps = Math::qd / shift;
30 if (fabs(lat) > Math::qd)
31 throw GeographicErr("Latitude " + Utility::str(lat)
32 + "d not in [-" + to_string(Math::qd)
33 + "d, " + to_string(Math::qd) + "d]");
34 if (isnan(lat) || isnan(lon)) {
35 geohash = "invalid";
36 return;
37 }
38 if (lat == Math::qd) lat -= lateps / 2;
39 lon = Math::AngNormalize(lon);
40 if (lon == Math::hd) lon = -Math::hd; // lon now in [-180,180)
41 // lon/loneps in [-2^45,2^45); lon/loneps + shift in [0,2^46)
42 // similarly for lat
43 len = max(0, min(int(maxlen_), len));
44 unsigned long long
45 ulon = (unsigned long long)(floor(lon/loneps) + shift),
46 ulat = (unsigned long long)(floor(lat/lateps) + shift);
47 char geohash1[maxlen_];
48 unsigned byte = 0;
49 for (unsigned i = 0; i < 5 * unsigned(len);) {
50 if ((i & 1) == 0) {
51 byte = (byte << 1) + unsigned((ulon & mask_) != 0);
52 ulon <<= 1;
53 } else {
54 byte = (byte << 1) + unsigned((ulat & mask_) != 0);
55 ulat <<= 1;
56 }
57 ++i;
58 if (i % 5 == 0) {
59 geohash1[(i/5)-1] = lcdigits_[byte];
60 byte = 0;
61 }
62 }
63 geohash.resize(len);
64 copy(geohash1, geohash1 + len, geohash.begin());
65 }
66
67 void Geohash::Reverse(const string& geohash, real& lat, real& lon,
68 int& len, bool centerp) {
69 static const real shift = ldexp(real(1), 45);
70 static const real loneps = Math::hd / shift;
71 static const real lateps = Math::qd / shift;
72 int len1 = min(int(maxlen_), int(geohash.length()));
73 if (len1 >= 3 &&
74 ((toupper(geohash[0]) == 'I' &&
75 toupper(geohash[1]) == 'N' &&
76 toupper(geohash[2]) == 'V') ||
77 // Check A first because it is not in a standard geohash
78 (toupper(geohash[1]) == 'A' &&
79 toupper(geohash[0]) == 'N' &&
80 toupper(geohash[2]) == 'N'))) {
81 lat = lon = Math::NaN();
82 return;
83 }
84 unsigned long long ulon = 0, ulat = 0;
85 for (unsigned k = 0, j = 0; k < unsigned(len1); ++k) {
86 int byte = Utility::lookup(ucdigits_, geohash[k]);
87 if (byte < 0)
88 throw GeographicErr("Illegal character in geohash " + geohash);
89 for (unsigned m = 16; m; m >>= 1) {
90 if (j == 0)
91 ulon = (ulon << 1) + unsigned((byte & m) != 0);
92 else
93 ulat = (ulat << 1) + unsigned((byte & m) != 0);
94 j ^= 1;
95 }
96 }
97 ulon <<= 1; ulat <<= 1;
98 if (centerp) {
99 ulon += 1;
100 ulat += 1;
101 }
102 int s = 5 * (maxlen_ - len1);
103 ulon <<= (s / 2);
104 ulat <<= s - (s / 2);
105 lon = ulon * loneps - Math::hd;
106 lat = ulat * lateps - Math::qd;
107 len = len1;
108 }
109
110} // namespace GeographicLib
Geohash.hpp
Header for GeographicLib::Geohash class.
Utility.hpp
Header for GeographicLib::Utility class.
GeographicLib::GeographicErr
Exception handling for GeographicLib.
Definition: Constants.hpp:316
GeographicLib::Geohash::Forward
static void Forward(real lat, real lon, int len, std::string &geohash)
Definition: Geohash.cpp:25
GeographicLib::Geohash::Reverse
static void Reverse(const std::string &geohash, real &lat, real &lon, int &len, bool centerp=true)
Definition: Geohash.cpp:67
GeographicLib::Math::AngNormalize
static T AngNormalize(T x)
Definition: Math.cpp:71
GeographicLib::Math::NaN
static T NaN()
Definition: Math.cpp:250
GeographicLib::Math::hd
@ hd
degrees per half turn
Definition: Math.hpp:141
GeographicLib::Math::qd
@ qd
degrees per quarter turn
Definition: Math.hpp:138
GeographicLib::Utility::lookup
static int lookup(const std::string &s, char c)
Definition: Utility.cpp:160
GeographicLib::Utility::str
static std::string str(T x, int p=-1)
Definition: Utility.hpp:161
GeographicLib
Namespace for GeographicLib.
Definition: Accumulator.cpp:12
std
Definition: NearestNeighbor.hpp:812