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7fed816cb3
* Removing -fsingle-precision-constant This is so that -Wdouble-promotion raises a warning as it should. * Adding -Wunsuffixed-float-constants * Not ideal. * Moving to a named constant * Named constant update * Using M_PIf * Updated following feedback from @ledvinap
69 lines
2.9 KiB
C
69 lines
2.9 KiB
C
/*
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* We place these static definitions on a separate header file so that we can
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* include the file in both the library and the tests.
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*/
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#include <ctype.h>
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#include <float.h>
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#include <math.h>
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#include <memory.h>
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#define OLC_kEncodingBase 20
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#define OLC_kGridCols 4
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#define OLC_kLatMaxDegrees 90
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#define OLC_kLonMaxDegrees 180
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// Separates the first eight digits from the rest of the code.
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static const char kSeparator = '+';
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// Used to indicate null values before the separator.
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static const char kPaddingCharacter = '0';
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// Digits used in the codes.
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static const char kAlphabet[] = "23456789CFGHJMPQRVWX";
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// Number of digits in the alphabet.
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static const size_t kEncodingBase = OLC_kEncodingBase;
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// The max number of digits returned in a plus code. Roughly 1 x 0.5 cm.
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static const size_t kMaximumDigitCount = 15;
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// The number of code characters that are lat/lng pairs.
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static const size_t kPairCodeLength = 10;
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// The number of characters that combine lat and lng into a grid.
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// kMaximumDigitCount - kPairCodeLength
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static const size_t kGridCodeLength = 5;
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// The number of columns in each grid step.
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static const size_t kGridCols = OLC_kGridCols;
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// The number of rows in each grid step.
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static const size_t kGridRows = OLC_kEncodingBase / OLC_kGridCols;
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// The number of digits before the separator.
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static const size_t kSeparatorPosition = 8;
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// Inverse of the precision of the last pair digits (in degrees).
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static const size_t kPairPrecisionInverse = 8000;
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// Inverse (1/) of the precision of the final grid digits in degrees.
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// Latitude is kEncodingBase^3 * kGridRows^kGridCodeLength
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static const size_t kGridLatPrecisionInverse = 2.5e7f;
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// Longitude is kEncodingBase^3 * kGridColumns^kGridCodeLength
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static const size_t kGridLonPrecisionInverse = 8.192e6f;
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// Latitude bounds are -kLatMaxDegrees degrees and +kLatMaxDegrees degrees
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// which we transpose to 0 and 180 degrees.
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static const double kLatMaxDegrees = OLC_kLatMaxDegrees;
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static const double kLatMaxDegreesT2 = 2 * OLC_kLatMaxDegrees;
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// Longitude bounds are -kLonMaxDegrees degrees and +kLonMaxDegrees degrees
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// which we transpose to 0 and 360 degrees.
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static const double kLonMaxDegrees = OLC_kLonMaxDegrees;
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static const double kLonMaxDegreesT2 = 2 * OLC_kLonMaxDegrees;
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// Lookup table of the alphabet positions of characters 'C' through 'X',
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// inclusive. A value of -1 means the character isn't part of the alphabet.
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static const int kPositionLUT['X' - 'C' + 1] = {
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8, -1, -1, 9, 10, 11, -1, 12, -1, -1, 13,
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-1, -1, 14, 15, 16, -1, -1, -1, 17, 18, 19,
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};
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// Returns the position of a char in the encoding alphabet, or -1 if invalid.
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static int get_alphabet_position(char c) {
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char uc = toupper(c);
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// We use a lookup table for performance reasons.
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if (uc >= 'C' && uc <= 'X') return kPositionLUT[uc - 'C'];
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if (uc >= 'c' && uc <= 'x') return kPositionLUT[uc - 'c'];
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if (uc >= '2' && uc <= '9') return uc - '2';
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return -1;
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}
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