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Improve CRC computation of ISM
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@ -15,9 +15,7 @@
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*/
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*/
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#include "galileo_ism.h"
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#include "galileo_ism.h"
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#include <boost/dynamic_bitset.hpp>
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#include <algorithm>
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#include <algorithm>
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#include <vector>
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void Galileo_ISM::set_ism_constellation_id(uint8_t const_id)
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void Galileo_ISM::set_ism_constellation_id(uint8_t const_id)
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{
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{
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@ -177,12 +175,27 @@ uint16_t Galileo_ISM::get_Tvalidity_hours() const
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bool Galileo_ISM::check_ism_crc(const std::bitset<GALILEO_DATA_JK_BITS>& bits)
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bool Galileo_ISM::check_ism_crc(const std::bitset<GALILEO_DATA_JK_BITS>& bits)
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{
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{
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boost::dynamic_bitset<unsigned char> frame_bits(bits.to_string().substr(0, GALILEO_ISM_CRC_DATA_BITS));
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std::bitset<96> extracted;
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std::vector<unsigned char> bytes;
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for (int32_t i = 0; i < GALILEO_ISM_CRC_DATA_BITS; ++i)
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boost::to_block_range(frame_bits, std::back_inserter(bytes));
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{
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std::reverse(bytes.begin(), bytes.end());
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extracted[i] = bits[i + 32];
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crc32_ism.process_bytes(bytes.data(), GALILEO_ISM_CRC_DATA_BYTES);
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}
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const uint32_t crc_computed = crc32_ism.checksum();
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std::vector<uint8_t> data_bytes((extracted.size() + 7) / 8);
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for (size_t i = 0; i < extracted.size(); i += 8)
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{
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uint8_t byte = 0;
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for (size_t j = 0; j < 8 && i + j < extracted.size(); ++j)
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{
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byte |= (extracted[i + j] << j);
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}
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data_bytes[i / 8] = byte;
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}
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std::reverse(data_bytes.begin(), data_bytes.end());
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const uint32_t crc_computed = this->compute_crc(data_bytes);
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if (this->ism_crc == crc_computed)
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if (this->ism_crc == crc_computed)
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{
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{
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return true;
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return true;
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@ -69,10 +69,10 @@ public:
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uint16_t get_WN_ISM() const;
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uint16_t get_WN_ISM() const;
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uint16_t get_t0_ISM() const;
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uint16_t get_t0_ISM() const;
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uint16_t get_Tvalidity_hours() const;
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uint16_t get_Tvalidity_hours() const;
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uint32_t compute_crc(const std::vector<uint8_t>& data);
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private:
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private:
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boost::crc_basic<32> crc32_ism;
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boost::crc_basic<32> crc32_ism;
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uint32_t compute_crc(const std::vector<uint8_t>& data);
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// ICD 2.1 Table 97
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// ICD 2.1 Table 97
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std::unordered_map<uint8_t, double> ISM_PCONST_MAP = {
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std::unordered_map<uint8_t, double> ISM_PCONST_MAP = {
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@ -131,7 +131,7 @@ private:
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#include "unit-tests/signal-processing-blocks/tracking/tracking_loop_filter_test.cc"
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#include "unit-tests/signal-processing-blocks/tracking/tracking_loop_filter_test.cc"
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#include "unit-tests/system-parameters/galileo_e1b_reed_solomon_test.cc"
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#include "unit-tests/system-parameters/galileo_e1b_reed_solomon_test.cc"
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#include "unit-tests/system-parameters/galileo_e6b_reed_solomon_test.cc"
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#include "unit-tests/system-parameters/galileo_e6b_reed_solomon_test.cc"
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#include "unit-tests/system-parameters/glonass_gnav_crc_test.cc"
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#include "unit-tests/system-parameters/galileo_ism_test.cc"
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#include "unit-tests/system-parameters/glonass_gnav_ephemeris_test.cc"
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#include "unit-tests/system-parameters/glonass_gnav_ephemeris_test.cc"
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#include "unit-tests/system-parameters/glonass_gnav_nav_message_test.cc"
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#include "unit-tests/system-parameters/glonass_gnav_nav_message_test.cc"
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#include "unit-tests/system-parameters/has_decoding_test.cc"
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#include "unit-tests/system-parameters/has_decoding_test.cc"
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@ -17,27 +17,14 @@
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#include "galileo_ism.h"
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#include "galileo_ism.h"
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#include <gtest/gtest.h>
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#include <gtest/gtest.h>
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#include <algorithm>
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#include <bitset>
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#include <vector>
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TEST(GalileoISMTest, CRC)
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TEST(GalileoISMTest, CRC)
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{
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{
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// Example from ANNEX G Galileo ICD
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Galileo_ISM gal_ism{};
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Galileo_ISM gal_ism{};
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uint32_t expected_crc = 3002390191;
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uint32_t expected_crc = 3002390191;
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std::bitset<96> input{"010110000010101010101010101010101010101010101010101010101010101010101010101010101010101010101010"};
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gal_ism.set_ism_crc(expected_crc);
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std::vector<uint8_t> data_bytes;
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std::bitset<128> input{"01011000001010101010101010101010101010101010101010101010101010101010101010101010101010101010101010110010111101001101011010101111"};
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for (size_t i = 0; i < input.size(); i += 8)
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bool result = gal_ism.check_ism_crc(input);
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{
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EXPECT_TRUE(result);
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std::bitset<8> byte;
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for (size_t j = 0; j < 8; j++)
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{
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byte[j] = input[i + j];
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}
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data_bytes.push_back(static_cast<uint8_t>(byte.to_ulong()));
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}
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std::reverse(data_bytes.begin(), data_bytes.end());
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auto computed_crc = gal_ism.compute_crc(data_bytes);
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EXPECT_TRUE(computed_crc == expected_crc);
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}
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}
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