75 lines
2.1 KiB
C++
75 lines
2.1 KiB
C++
#include "engine/polyline_compressor.hpp"
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#include <algorithm>
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#include <boost/assert.hpp>
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#include <climits>
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#include <cmath>
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#include <cstddef>
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#include <cstdlib>
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namespace osrm::engine::detail // anonymous to keep TU local
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{
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std::string encode(int number_to_encode)
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{
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std::string output;
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while (number_to_encode >= 0x20)
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{
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const int next_value = (0x20 | (number_to_encode & 0x1f)) + 63;
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output += static_cast<char>(next_value);
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number_to_encode >>= 5;
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}
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number_to_encode += 63;
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output += static_cast<char>(number_to_encode);
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return output;
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}
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std::string encode(std::vector<int> &numbers)
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{
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std::string output;
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for (auto &number : numbers)
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{
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if (number < 0)
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{
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const unsigned binary = std::llabs(number);
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const unsigned twos = (~binary) + 1u;
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const unsigned shl = twos << 1u;
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number = static_cast<int>(~shl);
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}
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else
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{
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number <<= 1u;
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}
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}
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for (const int number : numbers)
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{
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output += encode(number);
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}
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return output;
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}
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// https://developers.google.com/maps/documentation/utilities/polylinealgorithm
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std::int32_t decode_polyline_integer(std::string::const_iterator &first,
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std::string::const_iterator last)
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{
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// varint coding parameters
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const std::uint32_t bits_in_chunk = 5;
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const std::uint32_t continuation_bit = 1 << bits_in_chunk;
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const std::uint32_t chunk_mask = (1 << bits_in_chunk) - 1;
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std::uint32_t result = 0;
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for (std::uint32_t value = continuation_bit, shift = 0;
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(value & continuation_bit) && (shift < CHAR_BIT * sizeof(result) - 1) && first != last;
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++first, shift += bits_in_chunk)
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{
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value = *first - 63; // convert ASCII coding [?..~] to an integer [0..63]
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result |= (value & chunk_mask) << shift;
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}
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// change "zig-zag" sign coding to two's complement
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result = ((result & 1) == 1) ? ~(result >> 1) : (result >> 1);
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return static_cast<std::int32_t>(result);
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}
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} // namespace osrm
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